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Environmental changes around the Jurassic/Cretaceous transition: New nannofossil, chemostratigraphic and stable isotope data from the Lókút section (Transdanubian Range, Hungary)
Abstract
New biostratigraphical, chemical and stable isotope (C, O) data are presented from the Lókút section (Transdanubian Range, Hungary) representing a ca. 13 m thick continuous succession of Lower Tithonian–Lower Berriasian pelagic limestones. The study is conducted to verify timing of nannofossil events and major palaeoenvironmental changes at the Jurassic/Cretaceous transition including lithogenic input, palaeoredox and palaeoproductivity variations. Nannofossil zones from NJT 16b to NKT have been identified in the Lókút section and correlated with magnetostratigraphy, covering an interval from polarity zone M21r to M18r. The nannofossil Zone NJT 16b spans the interval from the upper part of M21r to lowermost part of M19n2n but its lower limit is poorly defined due to large diachronism in first occurrence (FO) of Nannoconus infans in various Tethyan sections. FOs of N. kamptneri minor and N. steinmannii minor are situated in the topmost part of the M19n2n and lowermost part of M19n1r magnetozones, respectively. They are located ca. 2–2.5 m above the J/K boundary defined as Intermedia/Alpina subzonal boundary, which falls within the lower half of magnetozone M19n2n. The position of first occurrences of these taxa is similar to that from the Puerto Escaño section (southern Spain) and slightly lower than in Italian sections (Southern Alps). Concentrations of chemical element proxies of terrigenous transport (Al, K, Rb, Th) decrease towards the top of the Lókút section, which suggests a decrease in input of terrigenous material and increasing carbonate productivity during the Early Tithonian and the Berriasian. Slight oxygen depletion at the sea bottom (decrease of Th/U ratio), and large increase in concentrations of productive elements (P, Ba, Ni, Cu) is observed upsection. Nutrients supply via upwelling seems to be the most likely explanation. Increase in phosphorus accumulation rate and a microfacies change from Saccocoma to calpionellid dominated took place in the polarity chron M19r, which apparently coincided with the worldwide Nannofossil Calcification Event, related to a bloom of strongly calcified calcareous nannoplankton taxa. Deposition in the Lókút area was probably affected by long-term climatic trends: aridization and warming. Decreasing δ¹³C values of bulk carbonates throughout the Tithonian and the Berriasian are interpreted as a result of a global trend of accelerated carbonate productivity supported by local factors such as increased upwelling intensity, and a possible change in the composition of carbonate mud.
... They record different palaeobathymetric zones, with the Hárskút composite section (HK-12 and HK-12/a) being deposited on a submarine elevation and the Lókút sections (LO-I and LO-II) recording a more basinal setting of the Bakony Basin (Fig. 1) Valanginian Biancone/Maiolica facies; characteristic of the Hárskút sections is also one of the youngest so-far known appearances of the red nodular limestone, late Berriasian-earliest Valanginian in age. In recent years a detailed biostratigraphic, chemostratigraphic and magnetostratigraphic framework of the Hárskút and Lókút sections was established by Főzy et al. (2010), Grabowski et al. (2010Grabowski et al. ( , 2017, Price et al. (2016), Lodowski et al. (2022) and Szives & Főzy (2022) (Fig. 2). The most characteristic sedimentary features of the Hárskút and the Lókút successions are visualized in Appendix S1. ...
... All of the smear slides were prepared, investigated and are reposited in the Department of Collections, Geological Survey, Supervisory Authority for Regulatory Affairs, Budapest. This study incorporates also the data of Stoykova (Grabowski et al., 2017), collected in the Lókút succession. ...
... Chemical analyses of 86 whole-rock samples were performed at the Bureau Veritas Minerals Laboratories, Canada, using the multi-acid MA250 method (for details see Bureau Veritas Minerals Schedule of Service & Fees, 2020). For the Tithonian-lowermost Berriasian of the Lókút succession this study adopts the data of Grabowski et al. (2017). ...
The Jurassic/Cretaceous transition was characterized by several distinct palaeoenvironmental processes and events, amongst which some of the best known are the late Tithonian-early Berriasian aridization and the late Berriasian tectonic reactivation in the Neotethyan Collision Belt. This study aims to reconstruct the latest Jurassic-earliest Cretaceous palaeoenvironment and its evolution in the area of the Transdanubian Range (Hárskút and Lókút successions, Hungary), and provide new data on the relation between climate changes, palaeoceanography and marine ecosystems. Herein, calcareous nannofossil and geochemical data are presented and put into a geochronological framework in order to evaluate and compare palaeoenvironmental signals recorded in the two studied successions; the resultant scenario is compared with published literature data from both the western Tethyan region and northern Europe. Accordingly , in the Transdanubian Range, the relatively humid climate of the early Tithonian was followed by the late Tithonian-early Berriasian arid phase and the late Berriasian humidification. Besides, two intervals of palaeoceanographic perturbations were documented in the upper Tithonian-lowermost Berriasian (OD I), and the lower/upper Berriasian transition beds (OD II); these are manifested by the record of seafloor hypoxia and elevated accumulations of micronu-trients, as well as changes in calcareous nannofossil assemblages. In the view of this study, the most probable trigger of the late Tithonian-early Berriasian aridi-zation was a restriction in the atmospheric circulation (including monsoons), which was forced by climate cooling and lowering thermal gradient between landmasses and the ocean. Under such conditions, the mechanism of a wind-induced water mixing might become less efficient, driving seawater strati-fication, seafloor hypoxia and increased burial of nutrients. Although the humid climate of the late Berriasian likely resumed the monsoon-type circulation, the tectonic reactivation and uplift in the NeoTethyan Collision Belt might have effectively separated the Bakony Basin from the 'open' NeoTethys, which hampered the marine circulation and efficient water mixing in the former.
... In most cases, MS in carbonate rocks may be interpreted as a proxy of terrigenous admixture (e.g. Da Silva et al. 2015;Grabowski et al. 2017). Nevertheless, in the Giewont series a correlation between MS and the contribution of the clastic fraction is not obvious; for the entire studied succession, the PCC of Al and MS (laboratory measured) is only 0.3. ...
... So far, humid pulses during the mid-Tithonian have been recognized only in northwest France (Deconinck et al. 1983), England (Hesselbo et al. 2009), and the Polish Basin (Grabowski et al. 2021a), but their correlation is not well constrained. In the case of the western Tethyan sections, traces of mid-Tithonian humidification might be followed in the Lókút succession of the Transdanubian Range (Grabowski et al. 2017). There, a sharp increase in the relative abundances of the genus Watznaueria near the base of magnetozone M20n, combined with the temporal disappearance of Nannoconus, may point to increased fertility of surface waters, hence a better mixed water column (e.g. ...
... It is intriguing to note that a decline in lithogenic influx is observed within the Tithonian of numerous Western Tethyan successions, for example in the Lower Sub-Tatric (Grabowski et al. 2013), the Pieniny Klippen Belt (Grabowski et al. 2019;cf. Michalík et al. 2016), and the Transdanubian Range (Grabowski et al. 2017;Lodowski et al. 2022a), as well as in southern England (cf. Morgans-Bell et al. 2001) and in the Polish Basin (Grabowski et al. 2021a) (Text- fig. ...
This paper presents an interpretation of sedimentologic, paleomagnetic, and geochemical data collected in the upper Kimmeridgian–Valanginian carbonates of the Giewont series (Giewont and Mały Giewont sections, High-Tatric succession, Western Tatra Mountains, Poland). The studied succession provides insight into the sedimentary conditions prevailing in the South Tatric Ridge (Tatricum), a submarine elevation located between the Zliechov Basin (Fatricum) and the Vahic (=South Penninic) Ocean. The sedimentary sequence includes micrites, pseudonodular limestones, cyanoid packstones, lithoclastic packstone, and encrinites. The results are discussed with regards to their significance for detrital input, paleoclimate, and paleoproductivity, which in turn are considered in the context of both local and regional paleoenvironmental trends and events. The greatest depositional depths during the latest Kimmeridgian–earliest Tithonian are documented by the occurrence of pseudonodular limestones. A Tithonian shallowing trend is demonstrated via the increasing size and roundness of cyanoids, while the final (?)emergence and erosion in the South Tatric Ridge is documented by earliest Cretaceous disconformities. This process might have been related to both falling sea-level during the major eustatic regressive cycle and tectonic uplift caused by the mutually related (re)activation in the Neotethyan Collision Belt and rifting in the Ligurian-Penninic-Vahic Oceans. The highest lithogenic influx (although still low; max 0.5% of Al content) during the late Kimmeridgian is considered as associated with relatively humid climate conditions, whereas a subsequent decreasing trend is thought to result from aridification during the latest Kimmeridgian–earliest Tithonian. Ultimately, deposition in the High-Tatric zone was affected by both large-scale environmental perturbations characteristic of the latest Jurassic (climate changes, variations in seawater pH, monsoonal upwelling, lithogenic input, etc.), as well as local sedimentary controls, predominantly the oxygenation state of bottom waters and tectonic movements.
... Furthermore, the magnetic susceptibility-a function of concentration and mineralogy of magnetic fraction-can also reflect environmental changes occurring during and after deposition. Magnetic susceptibility is affected by detrital input, water depth, weathering, and diagenesis (Da Silva et al., 2015;Grabowski et al., 2017). Hence, magnetic properties (especially magnetic susceptibility) are increasingly used as a proxy for paleoenvironmental changes. ...
... The increasing sedimentation rate from the middle Tithonian to the early Berriasian in Kurovice (Elbra et al., 2018) supports this interpretation, as the increasing trend can be attributed to increased carbonate productivity related to aridization (e.g. Grabowski et al., 2017). Furthermore, a decrease in terrigenous detritus due to aridization and warming or sea level changes is suggested by magnetic susceptibility in beds −2 to 17 ( Figure 8D). ...
... Furthermore, a decrease in terrigenous detritus due to aridization and warming or sea level changes is suggested by magnetic susceptibility in beds −2 to 17 ( Figure 8D). A decrease in susceptibility because of aridization was reported by Grabowski et al. (2017). These authors suggested that weakening of continental weathering decreased detrital input. ...
... As a consequence, the TR was subdivided into two basins -the proximal Gerecse Basin to the northeast and the distal Bakony Basin to the southwest -which were separated by a relatively elevated submarine plateau. The Gerecse Basin was subjected to fine-grained siliciclastic and argillite sedimentation, the submarine plateau was characterized by limited and condensed carbonate deposition, whilst in the Bakony Basin maiolica/biancone-type pelagic carbonates and siliceous oozes were deposited (Fülöp 1964, Tari 1994, Szederkényi et al. 2013, Grabowski et al. 2017, Lodowski et al. 2022. ...
... In the former Hungarian Geology Survey reports, some sections were investigated for nannofossil studies, but those were preliminary data with taxon lists and mostly lacking photographic illustrations or taxonomic descriptions. Recently, Kristallina Stoykowa (Grabowski et al. 2017) and Ottilia Szives (Lodowski et al. 2022) contributed to the nannofossil researches of Hungary. ...
... In recent years, stratigraphic and paleoenvironmental investigations were focused on the J/K transition interval in the Bakony Mountains by Főzy et al. (2011), Grabowski et al. (2010Grabowski et al. ( , 2017, Price et al. (2016), Vörös et al. (2019Vörös et al. ( , 2020 and Lodowski et al. (2022). From the localities mentioned in this book, HK-II pro parte, Szilas Ravine pro parte and Hárskút Édesvíz Key (HEK) sections nannofossil age constrain was established for the first time for the J/K boundary interval. ...
The position of the Jurassic/Cretaceous (J/K) boundary is a longstanding problem as it is the last system boundary which is still not fixed. Since 1975 (Énay 2020), the base of the Berriasian stage is nominated as the boundary between the Jurassic and Cretaceous
systems. In the past decades, the Berriasian Working Group led by W. Wimbledon added outstanding scientific achievements to place the J/K boundary to the base of the Berriasian. In 2016, the group voted the acme event of Calpionella alpina, as a marker of the base of Alpina Subzone to be the primary marker for the Tithonian/Berriasian (T/B) boundary (Wimbledon et al. 2020). However, even in the Tethys, calpionellids are not the only critical faunal elements of this interval: ammonites, calcareous dinocysts and nannofossils also have historical and significant role in the characterization of this period (Reháková & Michalík 1997, Frau et al. 2016a,b,c, Casellato & Erba 2021). In addition to the classical paleontological definition criteria on placing a stage or system boundary, independent methods as magneto-, chemo-, climate and cyclostratigraphy may provide important data to achieve supraregional correlation (see Grabowski et al. 2010, 2016, Schnabl et al. 2015, Manikin et al. 2019, Price et al. 2016, Deconick 1993, Schnyder et al. 2006, Galloway et al. 2020). The J/K boundary interval of the Transdanubian Range (TR) manifests a distinct lithologic succession, depending on paleogeographic and paleobathymetric position of a particular section. The Late Jurassic was characterized by a large-scale basin-and-horst architecture, with pelagic sedimentation between the basins and non-deposition or condensation zones on horsts (Vörös & Galácz 1998). In addition, during the earliest Cretaceous the marginal zones of the Neotethys were uplifted (e.g. Gawlick et al. 2009, Missoni & Gawlick 2010a,b), what affected also the TR. As a consequence, the TR was subdivided into two basins – the proximal Gerecse Basin to the northeast and the distal Bakony Basin to the southwest – which were separated by a relatively elevated submarine plateau. The Gerecse Basin was subjected to fine-grained siliciclastic and argillite sedimentation, the submarine plateau was characterized by limited and condensed carbonate deposition, whilst in the Bakony Basin maiolica/biancone-
type pelagic carbonates and siliceous oozes were deposited (Fülöp 1964, Tari 1994, Szederkényi et al. 2013, Grabowski et al. 2017,
Lodowski et al. 2022). Recently, new magnetostratigraphic and
geochemical investigations were carried out on some Hungarian sections, namely Lókút (Grabowski et al. 2010, 2017, Lodowski et al.
2022) and Hárskút composite (HK-12 and HK-12/a) sections (Lodowski et al. 2022), and also from Szilas Ravine. Geochemical research is previously performed on HK-12 by Főzy et al. (2010) and on HK-II and Lókút LH-I by Price et al. (2016). A very recent ammonite collecting was done at HK-12/a which clarified the ammonite biostratigraphy of the section, as well as new stable carbon and oxygen isotope data is published here (Főzy et al. 2022a, this volume)
from Szilas Ravine and Hárskút Édesvíz Key (HEK) sections. In this chapter we summarize our new and already published integrated data in order to outline the J/K transition of the Bakony Mountains. Geochemical evidences are summarized and paleoenvironmental reconstruction is concluded, also new perspectives.
... In the J/K boundary time interval, the area is part of the western Tethyan oceanic belt (Fig. 1B). Its complex geologic history has been detailed by several authors (Vörös and Galácz 1998, Gawlick et al. 2009, Szederkényi et al. 2013, Grabowski et al. 2017); its structural geology and Early Cretaceous evolution have recently been summarized by Fodor and Főzy (2013). Szives et al. (2018) drew together details indicating that the TR represents a particular unit within the Alpine-Carpathian-Dinaridic orogen, as its tectono-sedimentary evolution is related to both Dinaric and Austroalpine domains (Tari 1994, Schmid et al. 2008 (Fig. 1B). ...
... The respective positions of the Fallauxi, Volanense and Microcanthum Zones could be located exactly by their ammonite assemblage, on the basis of their bed thicknesses and lithology (as given by Vígh 1984). Recently, complex sedimentologic, microbiostratigraphic, magnetostratigraphic and geochemic research projects were carried out by Grabowski et al. (2010Grabowski et al. ( , 2017 and Lodowski et al. (2021). The Jurassic ammonite fauna of LH-II was re-evaluated by Főzy et al. (2011), material from LH-I and LH-II/I is first published. ...
... 2021), there is no evidence of Lopeziceras in the Crimea, and the age the of T/B deposits is under debate (Bakhmutov et al. 2018, Arkadiev et al. 2019, Wimbledon et al. 2020b). As magneto-and biostratigraphic framework is given at the Le Chouet section (Wimbledon et al. 2013), and the HK-12/a, Lókút LH-II/I sections (Grabowski et al. 2010, Grabowski et al. 2017, Lodowski et al. 2021, the occurrence of L. chaperi can be calibrated as a chronozone if its FO is synchronous from place to place. Fortunately, a single specimen of Lopeziceras appeared at the Hárskút HK-12/a section in Bed 142 of Lodowski et al (2021), where detailed magnetostratigraphy was also carried out (Lodowski et al. 2021), so its presence can be calibrated to the integrated framework. ...
This paper focuses on the heavily debated Mediterranean late Tithonian–early Berriasian
ammonite taxonomy and stratigraphy; therefore it also has implications for the still undefined Jurassic/
Cretaceous boundary. The content of the study presented here is based mostly on a large, typical Mediterranean
ammonite fauna, which was collected several decades ago, bed-by-bed from four ammonitico rosso/biancone
sections of the Bakony Mountains (Hungary). Besides, a new collecting campaign provided additional
ammonite material. Details of some of the stratigraphically important ammonite taxa are summarised from a
critical perspective. Stratigraphic distributions of the observed ammonite species are given section by section
and the taxonomical background of the fauna is described in Supplementary Materials. Previous results from
recent literature of reliable ammonite data were also taken into consideration, thus putting the Hungarian data
in broader context. As a result, an updated ammonite zonal scheme for the late Tithonian–early Berriasian time
interval for the Mediterranean region is suggested herein.
... In turn, in the distal Bakony Basin, Maiolica-type pelagic carbonates and siliceous oozes were deposited. The basins were separated by a relatively elevated submarine plateau (forebulge), characterized by limited and condensed carbonate deposition ( Fig. 1) (Fülöp 1964, Tari 1994, Szederkényi et al. 2013, Grabowski et al. 2017). ...
... The ammonites of the Lókút succession were studied by Vígh (1984). In recent years, stratigraphic and paleoenvironmental investigations focused on the Jurassic-Cretaceous transition interval in the Bakony Mountains were conducted by Főzy et al. (2010), Grabowski et al. (2010Grabowski et al. ( , 2017, Price et al. (2016) and Vörös et al. (2020). Ammonites collected from the Bakony Mts. are under current revision and will be published separately. ...
... The studied sections of the Hárskút (47°9'58"N; 17°47'11"E) and Lókút (47° 12'15"N; 17°52'54"E) hills record the Jurassic-Cretaceous boundary interval of the Bakony Basin. At the time of deposition, both successions were located in the transitional zone between the submarine plateaus and the Bakony Basin (Grabowski et al. 2017). ...
A high-resolution stratigraphic calibration is presented using biostratigraphic (calpionellids, calcareous dinoflagellates, calcareous nannofossils), magnetostratigraphic and chemostratigraphic (δ13C, Al) techniques on the uppermost Jurassic–lowermost Cretaceous sedimentary successions from Hárskút and Lókút in the Bakony Mountains (Transdanubian Range, Hungary). These localities are characterized by noticeably distinct facies developments, despite their geographic proximity. Relatively condensed deposits of early Tithonian–early Valanginian age (ca. 15 m thick; M22r–M13r magnetozones) in the Hárskút succession revealed stratigraphic discontinuities; however, our methodology allowed us to identify hiatuses and condensation levels within the magnetostratigraphic record. The Tithonian–Berriasian boundary, marked by the base of the Alpina calpionellid Subzone, falls in the M19n magnetozone, below the base of the NC0 calcareous nannofossil Zone. In turn, the Berriasian–Valanginian boundary, marked by the base of the Calpionellites darderi calpionellid Subzone, is located in magnetozone M14r, below the base of the NC3 nannofossil Zone. A continuous record of Maiolica-type lower Berriasian limestone is exposed in the Lókút succession, between magnetozones M21r–M17n. A consistently decreasing lithogenic influx throughout the Tithonian–lower Berriasian is correlated with a Tithonian trend of climate aridization, while elevated upper Berriasian influxes primarily correspond to tectonic activity within the Neotethyan Collision Belt. The demise of the Saccocoma microfacies and the timing of Nannofossil Calcification Events are interpreted as both mutually related to paleoceanographic changes.
... Typical upwards decreasing trend of d 13 C values from þ1.75‰ to þ1.20‰ between Malmica Zone and middle part of Calpionella Zone (Ferasini Subzone) is present in the Brodno section ( Fig. 9): it is correlatable with other sections (both in the West Carpathian area or elsewhere in the Tethyan Realm: Weissert and Channell, 1989;Weissert and Mohr, 1996;Erba and Tremolada, 2004;F€ ollmi et al., 2006;Michalík et al., 2009;Jenkyns, 2010;Lukeneder et al., 2010;Z ak et al., 2011;F€ ollmi, 2012;Coimbra et al., 2014;Wierzbowski et al., 2013, Wierzbowski, 2015Price et al., 2016;Grabowski et al., 2017Grabowski et al., , 2019. The d 13 C variation (bed to bed amplitude locally exceeding 0.20‰) could be confronted with distribution of microplankton quantity (Figs. 2 vs 9). ...
... The trend apparently occurs also in the Strapkova section, however the interval is not callibrated magnetostratigraphically. It is worthy to note that the negative shift in magnetozone M20n1n (lower part of Intermedia Subzone) coincides with the major microfacies change between the Saccocoma and calpionellid dominated microfacies (Grabowski et al., 2017. It coincides with a demise of the Polycostella event (Tremolada et al., 2006;Michalík et al., 2009Michalík et al., , 2016 and the beginning of the Nannofossil Calcification Event (Bornemann et al., 2003;Grabowski et al., 2019). ...
... 35% of M19n e the Crassicollaria/Calpionella zonal boundary) reveals a positive feature with values rising to more than 1.66‰ in Velikyi Kamianets and 1.48‰ in Brodno. The trend terminates with a negative shift slightly above (Grabowski et al., 2017) as well as some sections in the Boreal Realm (e.g. Dzyuba et al., 2013;Turner et al., 2019). ...
An integrated study of micro- and nannoplankton distribution, O and C isotopes and palaeomagnetic record of nine Carpathian sections provided a key interpretation tool to characterize the Jurassic–Cretaceous (J/K) boundary transition. Biostratigraphy supported by saccocomids, radiolarians, calpionellids, dinoflagellates and nannofossils helped to distinguish biostratigraphic zones which could have been correlated both with stable isotopes and with magnetostratigraphy. The Alpina Event (lorica size change) accompanied by Nannoconus wintereri and N. steinmannii minor FO's designates the J/K boundary.
Sedimentary model in N Mediterranean Tethys margin consists of elevated blocks with slow (1–2 mm/ka) Rosso Ammonitico carbonate sedimentation separated by dysoxic depressions. Tectonic instability has been indicated by Upper Jurassic fluxoturbidites.
Late early Tithonian (M21n to M20r) saccocomid abundance increases with positive δ¹⁸O isotope ratios, similar excursion between M20n and M19r accompanied late Tithonian crassicollarian boom. The δ¹³C variation (>0.2‰) confronted with microplankton quantity variations: positive excursion occurred both during early Tithonian Saccocoma sp., and during late Tithonian calpionellid and nannoconid blooms. Higher up in the Berriasian “Maiolica” sequence, lighter δ¹³C values prevailed.
During late Tithonian (Praetintinnopsella-to earliest Crassicollaria zones; M20n1n to M19r), Saccocoma microfacies has been substituted by a calpionellid one. Reorganization of Tethyan oceanic currents during opening of the Hispanic corridor started planktonic carbonate particle „rain“ resulting in the Maiolica facies dominance. Sedimentary rate raised ten times. Calpionella alpina lorica size change event was synchronneous with FO's of Nannoconus wintereri and N. steinmannii minor and with negative δ¹⁸O trend of latest Tithonian (Colomi Subzone) warming. Expressiveness of eccentricity and obliquity cycles indicates climatic optimum conditions.
... An age estimate of individual nannofossil events against magnetic chrons was proposed for the first time by Casellato (2010, fig. 15), implemented and modified by Grabowski et al. (2017) and Lakova et al. (2017), and further extended in this study (Fig. 9). Recently, several Authors (Wimbledon, 2017;Bakhmutov et al., 2018;Arkadiev et al., 2019;Wimbledon et al., 2020) proposed a reduced and modified version of such integrated scheme for the CM20neCM17n sequence against calpionellid and ammonite zones. ...
... These plots report only a few calcareous nannofossil events (FOs) selected from limited stratigraphic sections, but it is not clear if the nannofossil data are plotted according to magnetostratigraphy, calpionellid or ammonite biostratigraphies. Therefore, even if these diagrams resemble, and partially overlap the ones previously proposed (Casellato, 2010;Grabowski et al., 2017;Lakova et al., 2017) due to incompleteness of information, they are not directly comparable to the review presented here (Fig. 9). ...
... The FAD of L. carniolensis was found at much older level at Lokut and Xausa, in the middle part of magnetochron CM20r, instead of upper CM20n-2n as at DSDP Site 534 and Torre de' Busi: further investigations are needed to confirm this datum. A note of mention goes to the FAD of H. geometricus, regarded by Grabowski et al. (2017) as a highly reliable event and proposed as potential tool for correlations on the basis of its very short time variability. The FAD of H. geometricus results, here, moderately reliable since its reproducibility is less than 50%. ...
The latest Jurassic was a crucial time for calcareous nannoplankton as a major speciation episode took place with the appearance and rapid evolution of several new genera and species, particularly of highly calcified nannoliths at low latitudes: this origination pulse provides the opportunity to achieve high-resolution biostratigraphic data amplifying the possibility of dating and correlating.
A thorough revision of published as well as newly updated nannofossil biostratigraphies across the Tithonian-lowermost Berriasian interval was achieved to quantitatively evaluate the reliability of individual nannofossil events. Our database comprises 95 land and oceanic sites from different paleogeographic settings and latitudes (Europe, Atlantic Ocean, America, South Asia). We excluded sections with hiatuses or characterized by uncertain calcareous nannofossil biostratigraphy due to scarcity of data and/or poor preservation, as well as taxonomic incongruities. For each stratigraphic section, the critical assessment took into account sampling rates, nannofossil preservation, abundance and taxonomy: biohorizons based on single samples, questionably determined, or based on ambiguous/mismatching taxonomic concepts were excluded. We first performed calibration of nannofossil events against magnetostratigraphy to highlight reproducibility and time variability through the CM22–CM17 interval. The time uncertainties of individual nannofossil events were calculated, considering sampling and sedimentation rates derived from magnetostratigraphy. The reproducibility and variability of nannofossil events were also estimated relative to calpionellid biostratigraphy, as the latter is the primary tool selected by the Berriasian Working Group (ICS) for the definition of the Cretaceous base.
We distinguished highly reliable events characterized by maximum reproducibility, shorter time variability, common and continuous occurrence; moderately reliable events are distinguished by intermediate reproducibility and time variability; unreliable events have minimum reproducibility and longest time variability.
The quantitative evaluation of 37 events against magnetostratigraphy in the CM22–CM17 interval allowed to discriminate among 9 highly reliable first occurrences, 4 reliable first occurrences, 10 moderately reliable events (7 first occurrences, 2 last occurrences and 1 last common occurrence), 6 poorly reliable events (5 first occurrences and 1 last occurrence) and 8 unreliable first occurrences. The evaluation of 18 events against the calpionellid zonation resulted in 4 highly reliable first occurrences.
The revisited taxonomy and reliability assessment of calcareous nannofossil events were used to revise the calcareous nannofossil zonation of the Tithonian–early Berriasian time interval: one zone (NC 0 Zone) and four subzones (NC 0a, NC 0b, NJT 14a, NJT 14b Subzones) are newly defined here. Moreover, one zonal definition is emended (NJT 17 Zone) and the age of top/bases of four zones (NJT 14, NJT 15; NJT 16, NC 1 Zones) are revised. The first appearance datum of Nannoconus wintereri, showing the highest reproducibility and lowest time variability, correlates with magnetochron 19n-2n and results to be the calcareous nannofossil event best approximating the base of the Calpionella alpina Zone equated to the Jurassic/Cretaceous boundary.
... As the last remaining undefined boundary between two systems, the Tithonian-Berriasian stage boundary has been studied intensively over the last three decades ( Michalík et al., 1990;Remane, 1991;Houša et al., 1996Houša et al., , 1999aGrabowski and Pszczółkowski, 2006;Wimbledon, 2008;Michalík et al., 2009;Grabowski et al., 2010aGrabowski et al., , 2010bCasellato, 2010;Lukeneder et al., 2010;Pruner et al., 2010;Michalík and Reháková, 2011;Grabowski, 2011;Grabowski et al., 2013;Wimbledon et al., 2011Wimbledon et al., , 2013Man et al., 2012;López-Martínez et al., 2015aLópez-Martínez et al., , 2015bSchnabl et al., 2015;Michalík et al., 2016;Skupien et al., 2016;Svobodová and Košťák, 2016;Frau et al., 2016aFrau et al., , 2016bGrabowski et al., 2017;Lakova et al., 2017;Wimbledon et al., 2017). The main focus has been to document the largest possible number of key profiles as potential GSSP candidates for the Berriasian stage, to correlate them using multi-proxy methods (i.e. ...
... The Tithonian-Berriasian boundary interval (i.e., Crassicollaria and Calpionella Zones) is generally characterised by no significant regional variations in δ 13 C carb ( Price et al., 2016;Grabowski et al., 2017). However, in some bio-and magnetostratigraphically well-calibrated sections, especially in Tethys, a slight carbon isotopic negative excursion is observed directly at the Jurassic-Cretaceous boundary interval ( Košťák et al., 2018), a pattern has not been seen in the studied sections. ...
... However, in some bio-and magnetostratigraphically well-calibrated sections, especially in Tethys, a slight carbon isotopic negative excursion is observed directly at the Jurassic-Cretaceous boundary interval ( Košťák et al., 2018), a pattern has not been seen in the studied sections. Lower δ 13 C carb values (~1.5‰) are generally characteristic of the lower Berriasian ( Weissert and Channel, 1989;Weissert and Erba, 2004;Michalík et al., 2009;Grabowski et al., 2010b;Coimbra and Olóriz, 2012;Price et al., 2016;Grabowski et al., 2017;and Grabowski et al., 2017) and Valle del Mis ( Tremolada et al., 2006). δ 13 C carb and δ 18 O carb values are generally affected by numerous factors, including diagenetic processes, sediment reworking, primary bioproductivity, salinity, pH, vital effects, temperature etc. ( Montañez et al., 2000;Tremolada et al., 2006). ...
A high-resolution multidisciplinary study of two profiles in the Kotouč Quarry at Štramberk was carried out to define the age and palaeoenvironmental setting of the peri-reefal Štramberk Limestone. Calpionellids of the Alpina and Ferasini subzones of the standard Calpionella Zone confirm an early Berriasian age for both studied sequences. The presence of the calcareous nannofossils Nannoconus kamptneri minor and ?Speetonia colligata supports this stratigraphic interpretation. An ammonite assemblage with Pseudosubplanites grandis was found corresponding to the upper part of the lower Berriasian (Grandis Subzone). Foraminiferan assemblages contain several taxa previously reported from the Valanginian. Magnetostratigraphy verifies that the studied sections span the magnetozones M18r to M18n. Rock magnetic measurements indicate magnetite as the carrier of characteristic remanent magnetization. A palaeolatitude suggested location at 36°N. Microfacies indicate palaeoenvironments of slope (FZ 4), platform margin reefs, sand shoals (FZ 5, FZ 6) and possibly patch-reefs in the inner platform (FZ 7). The presence of calpionellids and the polychaete Terebella lapilloides suggests deposition within the deeper parts of the outer ramp of a platform slope, with redeposited clasts derived from nearby reef slopes and/or talus. This research contributes to the Berriasian Working Group's efforts to define the Tithonian–Berriasian boundary.
... Upper Tithonian -Berriasian pelagic sediments are very well stratigraphically calibrated due to the integration of calpionellid, calcareous nannofossil and magnetic stratigraphy (e.g. Bralower et al., 1989;Ogg et al., 1991;Channell et al., 2010;Grabowski, 2011;Wimbledon et al., 2011;Schnabl et al., 2015;Grabowski et al., 2017). Stage boundaries and magnetic chrons from M21r (late Early Tithonian) to M14r (Berriasian/Valanginian boundary) are well constrained by calpionellid zones. ...
... Thus, although the record of Zliechov event is expressed mostly in the PKB and Central Carpathians basins it can be traced also beyond this area. However, it can not be regarded as global correlation marker as it has not been observed e.g. in the Outer West Carpathians (Kurovice section - Elbra et al., 2018a), Transdanubian Mountains (Lókút section; Grabowski et al., 2010bGrabowski et al., , 2017 and the Vocontian Basin (Wimbledon et al., 2013 -Le Chouet section;Elbra et al., 2018b -St. Bertrand section). ...
... The sedimentation rate suddenly rises between the magneto(sub)zones M19r and M19n2n just above the transition from the Saccocoma to calpionellid microfacies (Fig. 16H). The increase of sedimentation rate correlates with relative decrease of terrigenous influx which is a common feature in the Carpathian sections (Grabowski et al., 2010b(Grabowski et al., , 2017Grabowski et al., 2013;Michalík et al., 2016;Elbra et al., 2018a) related to dilution of detrital clay minerals in carbonate matrix. It is also reflected in other areas from the Western Tethyan domain where a decrease of MS between Kimmeridgian and Lower Berriasian is well documented: Apennines (Bosso Valley and Salto del Cieco sections; Houša et al., 2004;Satolli et al., 2015;Satolli and Turtù, 2016), eastern Alps (Lukeneder et al., 2010) and Sub-Betics Svobodová and Košťák, 2016). ...
A continuous sedimentary and stratigraphic record of Late Kimmeridgian – Early Berriasian age is presented from the pelagic succession from the eastern part of the Pieniny Klippen Belt (Velykyi Kamianets section, Ukraine). The studied section, 26-m-thick, was calibrated using biostratigraphy (calpionellids, calcareous dinocysts, calcareous nannofossils), magnetostratigraphy, stable isotope stratigraphy (δ¹³C and δ¹⁸O) and gamma ray spectrometry. Magnetic polarity zones from M23r to M18n were identified. The magnetostratigraphic calibration of calcareous dinocysts zonation around the Kimmeridgian/Tithonian boundary has been performed for the first time. The Carpistomiosphaera borzai/Committosphaera pulla calcareous dinocyst zonal boundary is situated at the bottom of magnetozone M22n, slightly lower than first occurrence of calcareous nannofossil Conusphaera mexicana minor and higher than the standard Kimmeridgian/Tithonian boundary (M22Ar/M22An; Hybonoticeras beckeri/Hybonoticeras hybonotum Ammonite Zone boundary). The position of the Tithonian/Berriasian boundary in the magnetosubzone M19n2n (Crassicollaria/Calpionella Calpionellid zonal boundary) has been confirmed. A decrease of terrigenous input and an increase of carbonate productivity correlate with increasing sedimentation rates from 0.7 to 1.1 m/Myr in the Upper Kimmeridgian (M23r to M22r) to 5–7 m/Myr in the uppermost Tithonian and Lower Berriasian (M19n to M18n). Transition between the Saccocoma and calpionellid microfacies occurs in a narrow time interval, mostly within polarity subchron M20n1r. This event is traceable in similar stratigraphic position in several Western Tethyan sections and correlates perfectly with Nannofossil Calcification Event of the early Late Tithonian.
... However, the Remaniella ferasini Subzone was not proved due to the missing index species at used sampling density. In addition to the biostratigraphic studies, the stable isotopic record (d 13 C and d 18 O) has been studied in the Tethyan carbonate sections across the J/K boundary (including NCA), and is characterised by only minor fluctuations of values (Grabowski et al., 2017(Grabowski et al., , 2019Price et al., 2013Price et al., , 2016Weissert and Erba, 2004;among others). A negative carbon isotopic excursion close to the J/K boundary (Crassicollaria/Calpionella zones boundary) is recorded at numerous Tethyan section (Michalík et al., 2009(Michalík et al., , 2021Grabowski et al., 2019) and it may represent a promising marker (Ko s 0 t ak et al., 2023). ...
... The negative peaks recorded herein are used for interregional and also intercontinental correlations. The peak at 103.90 m probably represents a peak which should be referred as the "negative shift 2" sensu Michalík et al. (2021), however, it is represented only by a single sample (which might be a misleading and needing further investigation; see also Grabowski et al., 2017). This negative peak closely the J/K boundary is well documented from numerous Tethyan sections including also Mexico (Adatte et al., 1996) and South-east Pacific (Neuqu en Basin; Blanco et al., 2022;Kietzmann et al., 2021). ...
... The carbon and oxygen stable isotope record of the J/K boundary interval has been investigated by many authors in numerous sections (e.g. Weissert and Channell, 1989;Weissert and Erba, 2004;Grabowski et al., 2010aGrabowski et al., , 2017Grabowski et al., , 2019Michalík and Reh akov a, 2011;Price et al., 2013Price et al., , 2016Michalík et al., 2021;and others). ...
... We assume the predominance of the monospecific association of smaller globular forms of C. alpina, as well as the accompanying negative shift in d 13 C carb values, to be isochronous within the Tethys Ocean in different facies/environments (Fig. 1). For instance, Puerto Escaño represents the environment at the Subbetic Cordillera plateau (Pruner et al., 2010), the Kurovice sequence shows the strong influence of allodapic limestone slumps deposited on lower slopes (Ko s 0 t ak et al., 2018), Tr e Maroua is considered to have been deposited in the upper to middle slope environment (Wimbledon et al., 2020b) and L okút is regarded as a transitional sedimentary space between a deep pelagic basin and a shallower plateau (Grabowski et al., 2010b(Grabowski et al., , 2017. Similar or identical trends of stable isotope curves have been observed in other sites (and in different environments) e Brodno, Hlbo ca and Strapkov a (Michalík et al., 2009(Michalík et al., , 2016Grabowski et al., 2010a), Borzav ar , Frisoni (Weissert and Channell, 1989) and Velykyi Kamianets (Grabowski et al., 2019), among numerous studied sections. ...
... In addition, they are also calibrated using floating timescales (Huang 2018). However, the Boreal sections provide consistent palaeoclimatic trends with humid/arid intervals (Abbink et al. 2001;Schnyder et al. 2006;Hesselbo et al. 2009;Schneider et al. 2018), which may also be identified in the Tethyan realm (Schnyder et al. 2005;Grabowski et al. 2017). ...
... The positioning of the Lower and Upper Tithonian boundary at the base of Microcanthum ammonite Zone and near the base of M20n magnetochron was applied according to uppermost Jurassic biostratigraphical correlations of Wierzbowski et al. (2017) and Hesselbo et al. (2021). ...
New microfossil and magnetostratigraphical data as well as geochemical and clay mineral weathering indices are documented from the uppermost Jurassic Owadów-Brzezinki palaeontological site in central Poland. The newly discovered chitinoidellid assemblage of the lowermost part of the section and the previously documented assemblage from the middle part of the section are assigned, respectively, to the uppermost Dobeni and Boneti subzones of the Chitinoidellidae Zone. The same part of the succession is correlated to the magnetosubzone M20n.2n. The new data allow refinement of the Tithonian stratigraphical scheme including an assignment of the upper part of the Boreal Zarajskites Subzone of the Scythicus (Panderi) ammonite Zone to the Upper Tithonian and its correlation with the lowermost part of Tethyan Microcanthum ammonite Zone and the lower portion of the M20n.2n magnetosubzone. The data show that the Fittoni/Albani ammonite zone boundary (constituting a boundary of the informal Bolonian and Portlandian stages) should likely be placed within the Boneti Subzone. The geochemical data show decreasing chemical weathering intensity during the earliest Late Tithonian in central Poland, which is linked to aridification of the latest Jurassic climate. The same trend is observed in coeval sections of NW and NE Europe.
Supplementary material: https://doi.org/10.6084/m9.figshare.c.6299266
... By now the Upper Jurassic-Lower Cretaceous section of Lókút Hill is well studied; the most relevant papers in chronological order are the following: Wein (1934), Fülöp (1964), Vígh (1984, Vörös (1989), Grabowski et al. (2010), Főzy et al. (2011), Price et al. (2016, Grabowski et al. (2017) and Lodowski et al. (2021). ...
... The section off ered a good opportunity for stable isotope and also for magneto-and chemostratigraphic studies. Sampling for stable isotope measurements were completed by Price et al. (2016) and Price in Főzy et al. (2011) and subsequently by Grabowski et al. (2017). Results were correlated with the supposed bed numbers LH-II given by Vígh (1984). ...
The present paper gives an overview of the most important Late Jurassic–Early Cretaceous fossil sites of the Bakony Mountains which have yielded large invertebrate fossil assemblages. The lithological features, the fauna, the stratigraphy as well as the importance of the sites are given below, section by section. The study is based on numerous previous works and also on the latest results, including those which are published herein in this edited volume. For the sake of completeness some repetition of earlier results was inevitable; however the author’s intention was to give concise overview only. The overwhelming part of the studied Upper Jurassic–Lower Cretaceous fossils, which has provided a firm base for the biostratigraphical subdivision of the sections, was collected systematically from the late 50s to the mid 80s of the last century by the team of the Geological Institute of Hungary (GIH, later known as: Mining and Geological Survey of Hungary). Twelve sections scattered along the Bakony Mountains were sampled, most of them bed by bed. Together with additional sections and grab sampling points of less importance, altogether 18 fossil localities were studied and sampled – all of them are plotted on the locality map (Figure 1). The sites are discussed approximately from southwest to northeast. Many of the sections – if it was possible – were measured and testsampled; most of them were already published previously by Fülöp (1964) and subsequently briefly by Császár et al. (2012), Főzy (2017) and also in different journal articles and field trip guides. Details of previous geological studies are given section by section. Those localities which served as grab sample points are only briefly described. The description of many sections is accompanied by an updated list of cephalopods as well as a brief characterisation of benthic faunal elements. The faunal lists contain not only the stratigraphically important taxa, which were collected bed by bed and usually given in separate range charts or listed herein, but they also contain many other taxa which were found in museum collections from the given locality. Systematic descriptions of the studied fossils are published in the second part of this edited monograph. Revision and biostratigraphic evaluation of the ammonite fauna was done by I. Főzy, A. Scherzinger and O. Szives (Főzy et al. 2022, this volume). Nannofossil studies were carried out by O. Szives. The nonammonite fauna is also described herein, in this volume: belemnites were determined and elaborated by N.M.M. Janssen; bivalves and the very rare gastropods by I. Szente; brachiopods by A. Vörös; crinoids by M. Salamon; corals by H. Löser, and the rare fish remains by M. Szabó. T. Koči studied the calcareous worms encountered at a few localities. Stable isotope data were provided by G. Price and by J. Grabowski, and magnetostratigraphic investigations at the Lókút and Hárskút sections were carried out by J. Grabowski and by D. Lodowski. The stratigraphic subdivision of the sections are principally based on ammonites, but nannofossils, calpionellids and magnetostratigraphic data and in some cases microfacies studies – carried outed by B. Szinger – provided also useful information. Some of the Hungarian geographic names were translated into English, e.g. instead of the Hungarian terms “hegy” or “tető”, “árok”, “kőfejtő” the English equivalents, Hill, Ravine and Quarry were used, respectively.
... Subchron), as proposed by Leanza (1996). Important nannofossil bioevents were reported by Vennari et al. (2014) at Las Loicas section, including the FOs of N. wintereri (M19r Subchron, see Grabowski et al. 2017, Wimbledon 2017, and N. kamptneri minor and N. steinmannii steinmannii (M19nSubchron, see Grabowski et al. 2017, Wimbledon 2017 in the uppermost S. koeneni Zone. However, new data from Vennari et al. (2017) locate the FOs of N. kamptneri minor and N. steinmannii steinmannii at the basal part of the S. koeneni Zone in Sierra de la Cara Cura section, which are also very consistent with the M19 Chron at the base of the S. koeneni Zone. ...
... Subchron), as proposed by Leanza (1996). Important nannofossil bioevents were reported by Vennari et al. (2014) at Las Loicas section, including the FOs of N. wintereri (M19r Subchron, see Grabowski et al. 2017, Wimbledon 2017, and N. kamptneri minor and N. steinmannii steinmannii (M19nSubchron, see Grabowski et al. 2017, Wimbledon 2017 in the uppermost S. koeneni Zone. However, new data from Vennari et al. (2017) locate the FOs of N. kamptneri minor and N. steinmannii steinmannii at the basal part of the S. koeneni Zone in Sierra de la Cara Cura section, which are also very consistent with the M19 Chron at the base of the S. koeneni Zone. ...
Detailed systematic studies have been carried out in the Vaca Muerta Formation in order to achieve an integrated multidisciplinary calibration of the Jurassic/Cretaceous transition in the Neuquén Basin. Although this unit has a very well-established ammonite biostratigraphy, the temporal distribution of biozones is yet a matter of hot debate. In this contribution we present the results of a well constrained integrated data from the Arroyo Loncoche section (southern Mendoza), where comprehensive cyclostratigraphic, paleomagnetic and biostratigraphic sampling/data allowed us to elaborate a very strong chronostratigraphic scheme for the Titho-nian-Berriasian interval. The proposed stratigraphic calibration of the Tithonian-Berriasian Andean succession brings foward two key points: 1) The base of the Vaca Muerta Formation shows a polarities pattern which would only be compatible to the uppermost part of Hybonotum Zone (lowermost Lower Tithonian). 2) The position of the Jurassic-Cretaceous boundary is located within the lower third of the S. koeneni Zone. RESUMEN Calibración estratigráfica multidisciplinaria de la transición Jurásico-Cretácico en la Cuenca Neuquina Se realizaron estudios sistemáticos de detalle en la Formación Vaca Muerta con el fin de lograr una calibración multidisciplinaria integrada de la transición jurásico/cretácica en la Cuenca Neuquina. Aunque esta unidad se caracteriza por presentar una bioestra-tigrafía basada en amonites, la distribución temporal de las biozonas es todavía un tema de importante debate. En esta contribución se presentan los resultados integrados de la sección Arroyo Loncoche (sur de Mendoza), en donde exhaustivos estudios cicloestra-tigráficos, paleomagnéticos y bioestratigráficos han permitido elaborar un robusto esquema de correlación cronoestratigráfico para el intervalo Tithoniano-Berriasiano. La calibración estratigráfica propuesta para la sucesión tithoniano-berriasiana andina presenta dos puntos clave: 1) La base de la Formación Vaca Muerta muestra un patrón de polaridades que solo sería compatible con la parte superior de la Zona de Hybonotum (Tithoniano Inferior bajo). 2) La posición del límite Jurásico-Cretáceo está ubicada dentro del tercio inferior de la Zona de S. koeneni.
... Determining the Global Boundary Stratotype Section and Point (GSSP) for the Berriasian Stage in the Tethys has been the objective of elaborate research and discussions of the Berriasian Working Group during the past several years. Tethys was the largest depositional area during Tithonian and Berriasian times that is available for study by diverse stratigraphic methods, namely lithostratigraphy, biostratigraphy (based on calpionellids, nannofossils, dinoflagellates, radiolarians, foraminifers, ammonites and belemnites), as well as by magnetostratigraphy, geochemistry and sequence stratigraphy (Andreini et al. 2007;Houša et al. 2007;Michalík et al. 2009Michalík et al. , 2016Casellato 2010;Lukeneder et al. 2010;Pruner et al. 2010;Grabowski et al. 2010a, b;Grabowski 2011;Michalík & Reháková 2011;Wimbledon et al. 2011Wimbledon et al. , 2013Petrova et al. 2012;Guzhikov et al. 2012;Lakova & Petrova 2013;López-Martínez et al. 2013Schnabl et al. 2015;Svobodová & Košťák 2016;Hoedemaeker et al. 2016;Grabowski et al. 2017;Kietzmann 2017;Lakova et al. 2017;Wimbledon 2017;Elbra et al. 2018a, b, Kowal-Kasprzyk & Reháková 2019. ...
... The calcareous dinoflagellate Malmica Zone corresponds in the Kurovice sequence to magnetozone M 21r, as at Brodno (Central Western Carpathians; Michalík et al. 2009) and Lokút (Transdanubian range; Grabowski et al. 2010aGrabowski et al. , 2017. Even though aragonite shells did not survive sedimentation and early diagenesis of Kurovice limestones, magnetozones M 20r to M 17r in the upper part of the section may also be used to approximate the ammonite zones from Micracanthoceras microcanthum to Subthurmannia occitanica in the Vocontian Basin (Wimbledon et al. 2013;Frau et al. 2016a, b, c;Elbra et al. 2018b). ...
Microfacies and high resolution studies at the Kurovice quarry (Czech Republic, Outer Western Carpathians) on calpionellids, calcareous and non-calcareous dinoflagellate cysts, sporomorphs and calcareous nannofossils, aligned with paleomagnetism, allow construction of a detailed stratigraphy and paleoenvironmental interpretation across the Jurassic/Cretaceous (J/K) boundary. The Kurovice section consists of allodapic and micrite limestones and marlstones. Identified standard microfacies types SMF 2, SMF 3 and SMF 4 indicate that sediments were deposited on a deep shelf margin (FZ 3), with a change, later, into distal basin conditions and sediments (FZ 1). The sequence spans a stratigraphic range from the Early Tithonian calcareous dinoflagellate Malmica Zone, nannoplankton zone NJT 15 and magnetozone M 21r to the late Early Berriasian calpionellid Elliptica Subzone of the Calpionella Zone, nannoplankton NK-1 Zone and M 17r magnetozone. The J/K boundary is marked by a quantitative increase of small forms of Calpionella alpina, the base of the Alpina Subzone (that corresponds to NJT 17b and M 19n.2n) and by the rare occurrence of Nannoconus wintereri. Palynomorphs include Early Berriasian terrestrial elements — non-calcareous dinoflagellate cysts Achomosphaera neptunii, Prolixosphaeridium sp. A and Tehamadinium evittii. The depositional area for Kurovice was situated at the margin of the NW Tethys. The influence of cold waters from northern latitudes and potential upwellings is highlighted by: 1) the high proportion of radiolarians and sponge spicules, 2) rare calpionellids represented mostly by hyaline forms, 3) the absence of microgranular calpionellids — chitinoidellids, 4) the small percentage of the genera Nannoconus, Polycostella and Conusphaera in nannofossil assemblages, as compared to other sites in Tethys, 5) scarce Nannoconus compressus, which has otherwise been mentioned from the Atlantic area.
... Subchron), as proposed by Leanza (1996). Important nannofossil bioevents were reported by Vennari et al. (2014) at Las Loicas section, including the FOs of N. wintereri (M19r Subchron, see Grabowski et al. 2017, Wimbledon 2017, and N. kamptneri minor and N. steinmannii steinmannii (M19nSubchron, see Grabowski et al. 2017, Wimbledon 2017 in the uppermost S. koeneni Zone. However, new data from Vennari et al. (2017) locate the FOs of N. kamptneri minor and N. steinmannii steinmannii at the basal part of the S. koeneni Zone in Sierra de la Cara Cura section, which are also very consistent with the M19 Chron at the base of the S. koeneni Zone. ...
... Subchron), as proposed by Leanza (1996). Important nannofossil bioevents were reported by Vennari et al. (2014) at Las Loicas section, including the FOs of N. wintereri (M19r Subchron, see Grabowski et al. 2017, Wimbledon 2017, and N. kamptneri minor and N. steinmannii steinmannii (M19nSubchron, see Grabowski et al. 2017, Wimbledon 2017 in the uppermost S. koeneni Zone. However, new data from Vennari et al. (2017) locate the FOs of N. kamptneri minor and N. steinmannii steinmannii at the basal part of the S. koeneni Zone in Sierra de la Cara Cura section, which are also very consistent with the M19 Chron at the base of the S. koeneni Zone. ...
Detailed systematic studies have been carried out in the Vaca Muerta Formation in order to achieve an integrated multidisciplinary calibration of the Jurassic/Cretaceous transition in the Neuquén Basin. Although this unit has a very well-established ammonite biostratigraphy, the temporal distribution of biozones is yet a matter of hot debate. In this contribution we present the results of a well constrained integrated data from the Arroyo Loncoche section (southern Mendoza), where comprehensive cyclostratigraphic, paleomagnetic and biostratigraphic sampling/data allowed us to elaborate a very strong chronostratigraphic scheme for the Titho-nian-Berriasian interval. The proposed stratigraphic calibration of the Tithonian-Berriasian Andean succession brings foward two key points: 1) The base of the Vaca Muerta Formation shows a polarities pattern which would only be compatible to the uppermost part of Hybonotum Zone (lowermost Lower Tithonian). 2) The position of the Jurassic-Cretaceous boundary is located within the lower third of the S. koeneni Zone.
... Over the last several years, variety of sections have been studied intensively by the members of the former and current Berriasian Working Group to determine the final selection of the Global Boundary Stratotype Section and Point (GSSP) of the Berriasian Stage. Calpionellids, nannofossils, radiolarians, foraminifers, ammonites, belemnites, as well as magnetostratigraphy, geochemistry and sequence stratigraphy have been used for correlations within Tithonian-Berriasian rocks in the Tethyan realm (Casellato, 2010;Casellato and Erba 2021;Elbra et al., 2018a, b;Grabowski, 2011;Grabowski et al., 2017;Lakova et al., 2017;Lukeneder et al., 2010;Michalík and Reh akov a, 2011;Pruner et al., 2010;Remane, 1991;Schnabl et al., 2015;Skupien and Doupovcov a, 2019;Kowal-Kasprzyk, 2018;Svobodov a and Ko st' ak, 2016;Svobodov a et al., 2019;Va nkov a et al., 2019;Wimbledon, 2014Wimbledon, , 2017Wimbledon et al., 2011Wimbledon et al., , 2013Wimbledon et al., , 2020aetc.). On the other hand, the non-calcareous dinoflagellates are not widespread in all Tethyan limestone facies, as dark claystones suitable for palynological study are missing. ...
Microfacies and high-resolution studies at the Silesian Unit (OuterWestern Carpathians, Czech Republic) on calpionellids, calcareous and non-calcareous dinoflagellate cysts, foraminifers and calcareous nannofossils, aligned with paleomagnetism, d13Ccarb and d18Ocarb, allow construction of a detailed stratigraphy and palaeoenvironmental interpretations across the Jurassic-Cretaceous (J/K) boundary. Two studied sections consist of allodapic and biomicritic limestones and marlstones. Ropice section spans the stratigraphic range from the upper Tithonian calpionellid Chitinoidella Zone, nannoplankton zone NJT16 to the lower Berriasian calpionellid Alpina Subzone of the Calpionella Zone, nannoplankton NC1 Zone. The J/K boundary is marked by the dominance of small forms of Calpionella alpina, rare occurrence of Nannoconus wintereri, and the first occurrence of organic-walled dinoflagellate cysts Dichadogonyaulax bensonii and Muderongia longicorna. A negative shift in the d13Ccarb values corresponds to the Tithonian/Berriasian boundary, the base of the Calpionella Zone (Alpina Subzone). Karpentn�a section is represented by upper Tithonian calpionellid Chitinoidella to Crassicollaria zones. Remagnetization was documented in both sections.
... Pioneering thin-section investigations of some Upper Jurassic rocks of the Bakony Mountains were carried out by Géczy (1961) and Szabó-Drubina (1962) and fundamental sedimentological and microfacies studies of Upper Jurassic and Lower Cretaceous formations were conducted by János Haas (e. g. Haas 1985a, b, Grabowski et al. 2010, 2017 and Géza Császár (e.g. Császár 1996, Császár et al. 2008), among others. ...
... According to Bruno et al. [11] (see also Henriques et al. [13]), this type includes unique trace fossil localities, and the special ichnological subtype of this type is distinguished. Moreover, the Berriasian was a time of global palaeoenvironmental and biotic stress [42][43][44][45][46], which was registered, particularly, in the Greater Caucasus [47]. If so, the event (catastrophic) subtype of the palaeogeographical type exists potentially in these geosites, although detailed palaeontological and geochemical investigations of the sections are required to prove its presence. ...
Field investigations in the northwestern segment of the Greater Caucasus, a Late Cenozoic orogen, have permitted the establishment of two new geosites, namely the Ubin and Bezeps geosites. Both represent Berriasian–Middle Valanginian (Early Cretaceous) marine deposits with abundant trace fossils. The latter are attributed to the Nereites ichnofacies and indicate on deep marine palaeoenvironments (this interpretation challenges previous reconstructions). The geosites represent the palaeogeographical type of geoheritage. They are characterized, particularly, by high scientific and aesthetic importance, but restricted accessibility. Further geoheritage inventory in the central Northwestern Caucasus seems to be promising.
... However, a positive correlation between palaeoredox proxies, (like U/Th ratio or Co EF ) and sea-level rise in a pelagic carbonate succession is not always observed (e.g. Wieczorek, 1988;Grabowski et al. 2017Grabowski et al. , 2019Bąk et al., 2020). Moreover, recent estimations of sea-level variations indicate their very low magnitude in the Berriasian (10 m, according to Ray et al., 2019), which could have hardly affected the geochemistry of deep marine Maiolica-type sediments (Weissert, 1981;Wieczorek, 1988). ...
Upper Berriasian chemostratigraphic, clay mineral and calcareous nanofossil data are presented from a precisely dated hemipelagic section of Barlya (Western Balkan, Bulgaria). The section covers an interval from the upper part of the lower Berriasian (Calpionella elliptica Subzone, magnetozone M17r) to the lowermost Valanginian (Calpionellites darderi Subzone, magnetozone M14r). The study aims to reconstruct the major palaeoenvironmental changes (variations in lithogenic input, palaeoredox and palaeoproductivity) and their relation to palaeoclimate and regional tectonic regime, as well as their application to stratigraphic correlations with the Vocontian Basin and Jura Mts. A long-term increase in terrigenous input during the late Berriasian was controlled mostly by the orogenic activity in the NeoTethyan Collision Zone and to a lesser degree by climate humidification, as revealed by variations in kaolinite content and in lithogenic proxies (Ti/K, Th/K, Ti/Al and Zr/Rb ratios). A good correlation is observed between geochemical palaeoproductivity proxies (sedimentation rates of non-detrital (excess or authigenic) portions of P, Zn and Cd) and nannofossil fluxes, determined as the total abundance and species richness. Major calcareous nannofossil peaks, represented by high-diversity and high-abundance nannofossil assemblages, fall within the low-productivity intervals. A smaller peak formed by a low-diversity and high-abundance assemblage, dominated by Watznaueria barnesiae/fossacincta, coincides with the variable, but mostly high-productivity interval, which indicates high plasticity of Watznaueria concerning to environmental conditions. Additionally, trophic changes seem to correspond to bulk rock carbon-isotopic composition, with rising δ¹³Ccarb values in more oligotrophic intervals. This offers perspectives for long-distance chemostratigraphic correlations between pelagic and platform sections, supplementing traditional schemes based on bio- and sequence stratigraphy. A holostratigraphic correlation is proposed between the Western Balkan (Barlya section), Vocontian Basin (Berrias and Monclus sections) and Jura Mts (La Chambotte section) based on bio-, magnetic and carbon-isotope stratigraphy, as well as climatic and palaeoproductivity proxies.
... Unfortunately, this approach, with ever-changing and contradictory interpretations, is not congruent with other data on Crimea that has been published (Bakhmutov et al. 2018;Svobodová et al. 2019b), nor is it consistent with data from other regions, where the calibration of markers has been accurately determined at numerous sites (e.g. Michalík et al. 2009Michalík et al. , 2016Channell et al. 2010;Lukeneder et al. 2010;Pruner et al. 2010;Wimbledon et al. 2013;Svobodová & Košťák 2016;Hoedemaeker et al. 2016;Grabowski et al. 2017Grabowski et al. , 2019Stoykova et al. 2018;Svobodová et al. 2019a;Wimbledon et al. 2020a). The best correlative framework for the late Tithonian to Berriasian is based on a calpionellid biozonation tied to magnetostratigraphy, supported by nannofossils and ammonites. ...
Here we assess the evidence for the placing of magnetic and fossil biozonal boundaries in Upper Tithonian to lower Berriasian (Jurassic-Cretaceous boundary) sedimentary rocks on the Black Sea coast south of Theodosia (Ukraine): that is, in magnetozones M19n to M17r. We consider our earlier-published results from these sections in relation to the correlative pattern that has become well established further west in Tethys. Additionally, this is compared and contrasted with other, alternative, results from Crimea that have been published in recent times.
... Calibration of selected nannofossil FOs with magnetozones and calpionellid biozones (revised from Wimbledon 2017; Lokut -afterGrabowski et al. 2017; Kopanitsa -after Stoykova et al. 2018). ...
Abstract: This work summarises the results of ten years of study of the palaeomagnetism and biostratigraphy of Tithonian–Berriasian profiles in the middle Vocontian Basin: at Le Chouet, Le Ravin de Font de Saint Bertrand, Charens, Belvedere (Haute Beaume) and Tré Maroua. This study has thus focussed on the “Calcaires Blancs vocontiens”, a predominantly micritic formation developed locally in microfacies categories SMF 2, SMF 3 and SMF 4. Facies zones FZ 3 and FZ 4 indicate deposition in upper to mid slope environments. We record key biotic markers across the J/K boundary, notably the primary marker Calpionella alpina, and supporting secondary datums founded on calpionellid, calcareous nannofossil, calcareous dinoflagellate and ammonite occurrences. All this is keyed to the Global Polarity Time Scale. Here we recognise the Tithonian/Berriasian boundary as coincident with the base of the Alpina Subzone (Calpionella Zone). Geographically, this is the most widespread correlatable datum in the traditional boundary interval, and it can be calibrated with other widespread fossil markers in magnetozone M19n.
... Additionally, recent data published by Ivanova and Kietzmann (2017) suggest the correlation of the Argentiniceras noduliferum ammonite Zone with the uppermost part of Stomiosphaerina proxima and the lower part of Stomiosphaera wanneri calcareous dinoflagellate Zones, which would indicate a Late Berriasian age (Fig. 2a). More recently, Vennari et al. (2017) reported the FOs of N. kamptneri minor and N. steinmannii steinmannii at the lower part of the Substeueroceras koeneni Zone (uppermost M19n Subchron, see Svobodov a and Ko st ak, 2016; Ogg et al., 2016;Grabowski et al., 2017), which is in agreement with our data (see Fig. 2; Kietzmann et al., 2015;Iglesia Llanos et al., 2017). ...
DOI: 10.1016/j.jsames.2017.10.002
In this contribution, Lopez-Martínez et al. (2017) state that they achieved to define the position of the Jurassic- Cretaceous (J-K) boundary from the finding of Tethyan calpionellids in the Vaca Muerta Formation at Las Loicas section, Neuquen Basin. The authors analyzed ten samples in a reduced interval of the Vaca Muerta Formation where the boundary would lie.
... Calpionellids are an example of such group, owing to their uniform occurrence and diversification; as a result they are widely used in biostratigraphic analyses of the Late Jurassic and Early Cretaceous pelagic sequences throughout the Tethyan Realm (Allemann et al., 1971;Remane, 1971;Remane et al., 1986;Pop, 1974Pop, , 1994Reháková & Michalík, 1997;Lakova, et al., 1999;Boughdiri et al., 2006;Houša et al., 2007). From the point of view of calpionellid biostratigraphic potential, we note that alongside Calpionellites darderi, the index marker for the Berriasian/Valanginian stage boundary (Bulot, 1996), Calpionella alpina is considered to be most useful marker for determination of the Jurassic/Cretaceous boundary (Andreini et al., 2007;Houša et al., 2007;Wimbledon, 2008;Michalík et al., 2009;Grabowski et al., 2010a,b;Lukeneder et al., 2010;Pruner et al., 2010;Michalík & Reháková, 2011;Petrova et al., 2012;Guzhikov et al., 2012;Lakova & Petrova, 2013;López-Martínez et al., 2013, 2015Wimbledon et al., 2013Wimbledon et al., , 2017Hoedemaeker et al., 2016;Michalík et al., 2016;Svobodová & Košťák, 2016;Grabowski et al., 2017;Elbra et al., 2018 a,b;Kowal-Kasprzyk & Reháková, 2019). ...
Mt Rudnica in eastern Slovenia structurally belongs to the Sava Folds. The mountain itself is an exposure of the Mesozoic core of the Rudnica Anticline. The major part of the core is composed of Triassic rocks deposited on the NE margin of the Dinaric (Adriatic) Carbonate Platform, overlain locally by deep-marine Berriasian Biancone limestone. The latter formation was logged in a newly discovered section on the northern slopes of Mt Rudnica near the village of Loka pri Žusmu. The Biancone limestone of Mt Rudnica is mostly monotonous, calpionellid-bearing limestone with only minor up-section differences in colour, chert presence, and clay content. It is characteristic pelagic facies for the entire Tethyan Realm of the time. Using calpionellid as well as dinocyst biostratigraphy, the formation was subdivided into Early Berriasian Calpionella Zone - Alpina and Ferasini Subzones, Middle Berriasian Calpionella Zone - Elliptica Subzone and upper Berriasian Calpionellopsis Zone - Oblonga Subzone. Within the Early Berriasian part of the formation a synsedimentary slump was documented, whereas the largest increase in clay content is observed in the topmost, i.e. Late Berriasian part of the formation.
... Sediments are generally well oxi dized, however a long term decrease of Th/U ratio is observed from 7-8 in the uppermost Kimmeridgian/lowermost Tithonian to 4-5 in the upper Tithonian. Comparing to the Lókút section (Transdanubian Mts, Grabowski et al. 2017) the section in Lejowa Valley is much more affected by terrigenous input -the maxi mum Al content in the Lower Tithonian in Lókút is less than 0.5 %. It suggested that, in the Krížna Basin, the terrigenous input was controlled mostly by progradation and proxi mity of the NeoTethyan Collisonal Belt (e.g. ...
Today in the course of active updating and
development (on the basis of the GSSP and
GSSA concept) International Chronostratigraphic Chart in general and, the Mesozoic in
a particular, among the most relevant and
sharp stratigraphy problems still there is
a level division of a Cretaceous system
(GTS–2012) and J/K boundary in particular.
For almost 200 years, an attempt to solve this
problem has been raised by researchers at
the regional and global levels, discussed at
numerous symposiums, colloquiums, meetings, conferences and covered in a number
of publications by several generations of
stratigraphs around the world. In the last
three decades Subcommission on Cretaceous
Stratigraphy (SCS) with the Working Groups
that make important decisions on global
questions of level division, carrying out
boundaries between systems, series, stages
and making GSSP. It was not succeeded to
solve this problem at the regional and global
level yet (Hoedemaeker 1987; Grabowski
2011; Schnabl et al. 2015; Wimbledon et al.
2017). But it is nearing completion (Wimbledon 2017). At the present stage more than
300 section are studied worldwide, more than
3500 taxons and the marking layers are established, but making decision on the choice of
GSSP for unratified stages of the Jurassic and
Cretaceous systems remains the Working
Groups relevant (Granier et al. 2019). Considering emergence of new actual material
and new researches techniques the problem
remains unresolved. It is as follows. Despite
almost 200-year history of studying of a Сretaceous system, stages of lower department
and partially top (except for Cenomanian,
Turonian, Santonian and Maastrichtian) have
the status of unratified. It concerns also
stages of the Upper Jurassic (Oxfordian,
Tithonian). Boundaries Lower Cretaceous
and partially the Upper Cretaceous of stages
have no approved stratotype. Stages and substages of Cretaceous systems as the main
subdivisions of International Chronostratigraphic Chart have the status of unratified.
There is debatable a boundary problem between Jurassic and Cretaceous systems and
also the provision of a Berriassian stage in
International Chronostratigraphic Chart
(System boundary has to correspond to
boundary of the lower stage).
... Sediments are generally well oxi dized, however a long term decrease of Th/U ratio is observed from 7-8 in the uppermost Kimmeridgian/lowermost Tithonian to 4-5 in the upper Tithonian. Comparing to the Lókút section (Transdanubian Mts, Grabowski et al. 2017) the section in Lejowa Valley is much more affected by terrigenous input -the maxi mum Al content in the Lower Tithonian in Lókút is less than 0.5 %. It suggested that, in the Krížna Basin, the terrigenous input was controlled mostly by progradation and proxi mity of the NeoTethyan Collisonal Belt (e.g. ...
... The platy limestones bear a strong resemblance to the basinal pelagic carbonates of the same age that are widespread in the Alpine-Mediterranean Tethys (e.g., Martire et al., 2006;Donatelli and Tramontana, 2014;Grabowski et al., 2017, see also reviews by Jenkyns, 1974 andWieczorek, 1988). Carbonate bioclasts of planktonic organisms are significant components of this facies, which clearly reflects the increasing role of calcareous plankton as carbonate producers in the Tithonian (e.g., Erba, 1989;Reháková, 2000;Bornemann et al., 2003). ...
The Jurassic of the Alpine-Mediterranean Tethys was characterized by the formation of several interconnected basins, which underwent gradual deepening and oceanization. Sedimentation in each basin was influenced by a specific set of interrelated factors, such as tectonic activity, seawater circulation, climate, chemistry and trophic state of seawater as well as evolutionary changes of the marine biota. This paper deals with the Fatricum Domain (Central Carpathians, Poland and Slovakia), which in the Jurassic was a pull-apart basin on a thinned continental crust. The sedimentation history of this domain during the Bajocian-Tithonian and its governing factors have been revealed. Facies analysis of the Bajocian-Oxfordian deposits evidences considerable relief of the basin-floor topography. Deposits in the Western Tatra Mts represent sedimentation on a submarine intrabasinal high, whereas the coeval deposits of the eastern part of the Tatra Mts accumulated in a deeper basin. The basin succession began with Bajocian bioturbated "spotted" limestones and siliciclastic mudstones (Fleckenmergel facies). These were succeeded by uppermost Bajocian-middle Bathonian grey nodular limestones, affected by synsedimentary grav-itational bulk creep. The coeval deposits of the intrabasinal high are represented by well-washed Bositra-crinoidal limestones with condensed horizons. Uniform radiolarite sedimentation commenced in the late Bathonian and persisted until the early late Kimmeridgian. The basal ribbon radiolarites (upper Bathonian-lower Oxfordian), which consist of alternating chert beds and shale partings, are a record of seawater eutrophication, a related crisis in carbonate production and the rise of the CCD, which collectively resulted in biosiliceous sedimentation. The overlying calcareous radiolarites (middle Oxfordian-lowermost upper Kimmeridgian) marked a gradual return to carbonate sedimentation. The return of conditions that were favourable for carbonate sedimentation took place in the late Kimmeridgian, when the red nodular limestones were deposited. They are partly replaced by basinal platy limestones (uppermost Kimmeridgian-Tithonian) in the Western Tatra Mts. This lateral variation in facies reflects a change in the sedimentary conditions governed by a bathymetric reversal of the seafloor configuration, attributed to a further stage in the pull-apart transcurrent tectonics of the Fatricum Domain.
... Over the last few years sections have been studied intensively by the members of the Berriasian Working Group to determine the final selection of the Global Boundary Stratotype Section and Point (GSSP) of the Berriasian Stage in Tethys. Calpionellids, nannofossils, radiolarians, foraminifers, ammonites, belemnites, as well as magnetostratigraphy, geochemistry and sequence stratigraph were used for correlations within Tithonian-Berriasian rocks in the Tethyan realm (Casellato, 2010;Elbra et al., 2018 a,b;Grabowski, 2011;Grabowski et al., 2017;Hou sa and Va sí cek, 2004;Lakova et al., 2017;Lukeneder et al., 2010;Michalík and Reh akov a, 2011;Pruner et al., 2010;Remane, 1991;Schnabl et al., 2015; Svobodov a and Ko s 0 t ak, 2016; Wimbledon et al., 2011Wimbledon et al., , 2013Wimbledon, 2014Wimbledon, , 2017Wimbledon et al., 2017 etc)., Microfossils, such as non-calcareous dinoflagellates are not widespread in all Tethyan limestone facies, as the deposits are unsuitable for the preservation of palynomorphs. Suitable sections are missing due to the absence of dark claystones suitable for palynological study. ...
A palynological analysis and study of calpionellids and calcareous dinoflagellate cysts across the Jurassic–Cretaceous (J/K) boundary succession in the Outer Western Carpathians, Bruzovice section is presented. It is a one of few sections of the Tethyan Realm suitable for the palynological study. The lower part of the section is formed by anoxic deposits consisting of dark grey calcareous claystones. The upper part of the profile is represented by flysch-like alternation of grey limestones, spotted claystones and marlstones. The section spans the stratigraphic range from the upper Tithonian, Cadosina semiradiata calcareous dinoflagellate Zone to the lower Berriasian, calpionellid Calpionella elliptica Subzone. The J/K boundary is marked by a high abundance of small forms of Calpionella alpina. The Tithonian–Berriasian succession of non–calcareous dinoflagellates is as follows: the base of the section is correlated with the dinocyst Semiradiata Zone along with the presence of Glossodinium dimorphum. The first occurrence (FO) of Amphorula metaelliptica and the last occurrence (LO) of Prolixosphaeridium anasillum are recorded in the Cadosina semiradiata Zone followed by the Cadosina tenuis–Colomisphaera fortis Zone. An aboudance of the spherical C. alpina indicates the onset of the Calpionella Zone and the Calpionella alpina Subzone at the base of the Berriasian Stage. The FO of Diacanthum hollisteri is situated in the lower part of the Calpionella alpina Subzone. The FO of Dichadogonyaulax bensonii coincides approximately with the base of the calpionellid Remaniella ferasini Subzone, and the FO's of Muderongia longicorna, M. tabulata and Spiniferites cf. ramosus were found in the upper part of the calpionellid Remaniella ferasini Subzone. The FO of Achomosphaera neptunii was found in the lower part of the Calpionella elliptica Subzone. The work is a contribution to the ICS Berriasian Working Group.
... She underlined two issues. Firstly, the definition of the base of Berriasian Stage, as the J/K boundary by mean of ammonites, is highly problematic: a) it is still being resolved by the Berriasian Working Group, where an ammonite marker was not depicted as a primary but only considered as a secondary marker in 2016 voting; b) it is difficult due to a widespread hiatus related to sea-level lowstand around the boundary, and it is not marked by a significant faunal turnover; in addition, interprovincial correlation is not well established and there is urgent need of systematic revision of certain groups; c) some recent revisions have been made on Perisphinctoidea (Bulot et al., 2014a;Frau et al., 2015Frau et al., , 2016a, and on Berriasella jacobi (Frau et al., 2016b); the B. jacobi Zone and its subdivision was discussed in details by the Group (see Frau's talk, point 1); d) different systematic approaches of different research groups are highly problematic; e) several new ammonitiferous sections were published recently related to the J/K boundary from Antarctica (Dochev et al., 2017), Argentina (Parent et al., 2015;Riccardi, 2015;Vennari and Aguirre-Urreta, 2017), Chile (Salazar and Stinnesbeck, 2015), Crimea (Platonov et al., 2014;Arkadiev et al., 2015a;; boreal Russia (Guzhikov et al., 2016;Rogov and Mironenko, 2016), subboreal Russia (Mitta, 2017), Hungary (Grabowski et al., 2017), Czech Republik (Va sí cek and Skupien, 2016), France (Frau et al., 2016a), and Central Tunisia Zargouni, 2016a, b, 2017). The second issue is the problem of standard TethyaneBoreal correlation caused by ammonite faunal provincialism. ...
The 6th Kilian Group meeting of the IUGS Lower Cretaceous Ammonite Working Group (the Kilian Group) was held in Vienna, Austria, 20th August 2017. The Group mainly discussed the standard zonation
that is suitable for and based mainly on ammonite data of the Mediterranean Province of the MediterraneaneCaucasian Subrealm (Tethyan Realm). Some changes have been made on three stages.
The uppermost part of the Berriasian is now characterised by the Tirnovella alpillensis Zone, that is subdivided into a lower T. alpillensis Subzone and an upper “Thurmanniceras” otopeta Subzone; the
T. alpillensis (Sub-)Zone is here defined by the first appearance datum (FAD) of the index-species. For the Valanginian, the Neocomites premolicus Subzone is introduced in the lower part of the “Thurmanniceras” pertransiens Zone. The FAD of N. premolicus occurs at the base of the “T.” pertransiens Zone. So this subzone starts at the base of the “T.” pertransiens Zone and provisionally ends at the last occurrence of N. premolicus as the upper part of the zone is not characterised by a subzone for the moment. For the Barremian, the former Holcodiscus fallax, Nicklesia didayana, Heinzia communis, Subtorcapella defayae, Coronites darsi, Heinzia caicedi and Anglesites puzosianum horizons have been abandoned. In agreement
with systematic positions, the term “auctorum” is deleted for Taveraidiscus hugii, the index-species of the first zone of this stage. The Kotetishvilia compressissima Zone is subdivided into a lower Holcodiscus fallax Subzone and an upper Holcodiscus caillaudianus Subzone. The Barrancyloceras barremense Subzone (upper subzone of the Toxancyloceras vandenheckii Zone) is replaced by the Gassendiceras alpinum Subzone. The Imerites giraudi Zone is kept but its base should be now defined by the FAD of I. dichotomus,
which marks the inception of the genus Imerites. For certain stratigraphic intervals the Group discussed and in some cases strengthened the previous correlations between the standard Mediterranean zonation with the different ammonite zonal schemes of other provinces and realms. Some members of the Group
presented the possibility of using regional stages as secondary standards, in accordance with the recommendations of the International Commission on Stratigraphy. The report concludes with an appreciation of the French ammonitologist Jean-Pierre Thieuloy deceased in 2017, the nomination of a vicechair, membership, future work and next meeting of the Kilian Group.
... Ogg et al., 1991;Grabowski and Pszcz ołkowski, 2006;Michalík et al., 2009). Grabowski et al. (2017) explained this raising trend as an increased paleoproductivity related to aridization of the climate, decreased detrital input, and increased upwelling in Carpathian part of Tethyan realm. The average Tithonian sedimentation rate in Kurovice section is higher (M21n:~8 m/Myr e M19n: 17 m/Myr) than recorded for other Carpathian (localities 2e4 in Fig. 6) or Alpine Trento Plateau (7e11 in Fig. 6) sections. ...
An integrated magneto- and biostratigraphic study of the Jurassic-Cretaceous (J-K) boundary section at Kurovice, Czech Republic was carried out. The acquired paleomagnetic data showed dual polarity characteristic remanent magnetization (ChRM) with counter-clockwise rotation direction. Rock magnetic data indicated magnetite as the principal carrier of remanent magnetization as well as presence of e.g. hematite and goethite. Magnetozones from M21n up to M17r were identified and dated as early Tithonian (dinoflagellate Semiradiata and nannofossil NJT15b zones) to late early Berriasian (Calpionella Elliptica and nannofossil NK-1 (sub)zones).
... The nannofossil events recognized in the Barlya section have been compared with previous nannofos- Fig. 3. Selected calpionellid and calcareous nannofossil events from the Tithonian/Berriasian boundary interval, directly correlated to magnetostratigraphy (for sources see references in Tables 1, 2). M19n Bralower et al. (1989) sil-magnetostratigraphy relationships mainly in Italy (Casellato, 2010;Channell et al., 2010), as well as in Spain (Svobodová and Košt'ák, 2016), Austria (Lukeneder et al., 2010), Slovakia (Michalík et al., 2009(Michalík et al., , 2016, France (Wimbledon et al., 2013) and Hungary (Grabowski et al., 2017) (see Table 2). A comprehensive review of the available data on nannofossil and magnetostratigraphy correlation has clearly shown two distinct groups of nannofossil taxa: the first one, with rather scattered and diachronous FOs, and the second one, which displays more or less consistent FO record amongst different sections (Fig. 3). ...
Magnetostratigraphy, calpionellid and calcareous nannofossil biostratigraphy of the upper Tithonian and lower Berriasian of section Barlya in the West Balkan Mts are herein presented. The studied interval comprises the magnetozones from M21r to M17r, with a large interval of partial remagnetization. It has been directly correlated with a continuous succession of the calpionellid Chitinoidella, Praetintinnopsella, Crassicollaria and Calpionella zones, and with the nannofossil zones from NJT 15b to NK-1. The accumulated evidence in the last twenty years on the magnetostratigraphy, calpionellid and calcareous nannofossil biostratigraphy and events across the J/K boundary in the European Tethys has provoked the authors to plot the main micropalaeontological events against magnetostratigraphic column in order to assess the extent of diachronism of these events. Data from Slovakia, Poland, Italy, Austria, Hungary, France, Spain and Bulgaria has shown specific behaviour of different calpionellid and nannofossil events with respect to the column of the magnetic polarity chrons, which have been considered as ‘isochronous’ or at least less diachronous than the microfossil events. Thus, some rather consistent events have appeared, such as the first occurrences (FOs) of calpionellids Calpionella grandalpina, Crassicollaria brevis, Calpionella minuta and Remaniella ferasini, and the FOs of calcareous nannofossils Nannoconus globulus minor, Hexalithus geometricus, Nannoconus wintereri, Nannoconus steinmannii minor and Nannoconus kamptneri minor. The J/K boundary, as widely accepted, has been traced in section Barlya at the base of the Calpionella alpina Subzone.
... Additionally, recent data published by Ivanova and Kietzmann (2017) suggest the correlation of the Argentiniceras noduliferum ammonite Zone with the uppermost part of Stomiosphaerina proxima and the lower part of Stomiosphaera wanneri calcareous dinoflagellate Zones, which would indicate a Late Berriasian age (Fig. 2a). More recently, Vennari et al. (2017) reported the FOs of N. kamptneri minor and N. steinmannii steinmannii at the lower part of the Substeueroceras koeneni Zone (uppermost M19n Subchron, see Svobodov a and Ko st ak, 2016; Ogg et al., 2016;Grabowski et al., 2017), which is in agreement with our data (see Fig. 2; Kietzmann et al., 2015;Iglesia Llanos et al., 2017). ...
In this contribution, López-Martínez et al. (2017) state that they achieved to define the position of the Jurassic- Cretaceous (J-K) boundary from the finding of Tethyan calpionellids in the Vaca Muerta Formation at Las Loicas section, Neuquén Basin. In this contribution, the authors analyzed ten samples in a reduced interval of the Vaca Muerta Formation where the boundary would lie. Las Loicas section represents a basinal section of c. 270 m with large covered intervals (c. 90 m) bearing ammonites of the Lower Tithonian Virgatosphinctes mendozanus Zone to at least the Upper Berriasian Spiticeras damesi Zone (Aguirre-Urreta et al. 2014). The upper part is covered.We do consider that the data presented by López-Martínez et al. are important for the discussion on the J-K boundary in Argentina, provided that the knowledge of calpionellids in the Neuquén basin is very poor. The aim of this Comment is to better explain some data derived from previous biostratigraphic and magnetostratigraphic studies (i.e. Fernandez Carmona and Riccardi 1999, Kietzmann et al. 2011a, Kietzmann 2017, Iglesia Llanos et al. 2017) that López-Martínez et al. (2017) failed to interpret correctly.
The key aspect for evaluation of potential effects of ongoing environmental changes is identification of their controls on one hand, and understanding of their mutual relations on other. In this context, the best source of information about medium and long term consequences of various environmental processes is the geologic record. Numerous different-scale palaeoenvironmental events took place during the Jurassic/Cretaceous transition;
amongst them, the best documented so far are: long term marine regression during the Tithonian–early Berriasian, climate aridization during the late Tithonian–early Berriasian, and tectonic activity in western parts of the NeoTethys Ocean during the late Berriasian–Valanginian. This study, which is based on the PhD dissertation of Damian Gerard Lodowski, attempts to reconstruct the latest Jurassic–earliest Cretaceous paleoenvironment and its evolution in the area of the Western Tethys, with special attention paid to cause-and-effect relationships between climate changes, tectonic activity and oceanographic conditions (perturbations in marine circulation and bioproductivity). Here are presented the basic results of high-resolution geochemical investigations performed in the Transdanubian Range (Hárskút and Lókút, Hungary), High-Tatric (Giewont, Poland) and Lower Sub-Tatric (Pooerednie III, Poland) series, Pieniny Klippen Belt (Brodno and Snežnica, Slovakia; Velykyi Kamianets, Ukraine) and Western Balkan (Barlya, Bulgaria) sections. The sections were correlated and compared in terms of paleoredox conditions (authigenic U), accumulation of micronutrient-type element (Zn) and climate changes (chemical index of alteration, CIA), providing a consistent scenario of the Tithonian–Berriasian palaeoenvironment evolution in various western Tethyan basins. Amongst the first-order trends and events, characteristic of studied sections are the two intervals recording an oxygen deficient at the seafloor: 1) the upper Tithonian–lowermost Berriasian (OD I); and 2) at the lower/upper Berriasian transition (OD II). Noteworthy, this phenomena ooccurred with elevated accumulations of nutrient-type elements (i.e. enrichment factor of Zn). Besides, collected data document the late Tithonian–early Berriasian trend of climate aridization, as well as the late Berriasian humidification. Such record is explained by a model, in which decreasing intensity of atmospheric circulation during the late Tithonian–early Berriasian was directly connected with climate cooling and aridization. This process resulted in lesser efficiency of up- and/or downwelling currents, which induced seawater stratification, seafloor hypoxia and perturbations in the nutrient-shuttle process during the OD I. On the other hand, the OD II interval may correspond to tectonic reactivation in the NeoTethyan Collision Belt. This process might have led to physical cutoff of Alpine Tethys basins from the NeoTethyan circulation (both atmospheric and oceanic), driving the limited stratification in the former, and limiting the effect of gradual humidification of global climate (i.e. due to increasing strength of monsoons and monsoonal upwellings).
Relevance of the work. Black shale horizons may reflect abrupt paleoclimate changes. In the northeast of the Ulyanovsk-Saratov Trough (UST), two black shale horizons widely occur, the Middle Volgian Promzino Formation and the Lower Aptian Ulyanovsk Formation. Despite years of research, the role of paleoclimate in their accumulation is still under discussion. The aim of the research was to assess the climate as a factor of the accumulation of the Middle Volgian and Lower Aptian organic carbon-rich deposits in the northeastern UST. Methods. To reconstruct paleoclimate and to evaluate its impact on the black shale deposition, a comprehensive isotope study of calcitic and aragonitic shells of several groups of benthic and pelagic organisms was performed. Besides, the lithological and geochemical features of organic carbon-rich and host deposits were studied using optical microscopy, XRD, and pyrolysis. Results. Isotope study allowed to construct benthic and pelagic palaeotemperature curves and to reconstruct paleoclimate in the UST during the formation of black shales. Based on these data and data on lithological and geochemical features of sediments, the depositional mechanisms of the Promzino and Ulyanovsk Formations were clarified. Conclusions. No causal link has been revealed between climate changes and the deposition of the Middle Volgian black shales. At the end of the Middle Volgian, a short-term cooling has been recorded, probably related to the volcanic activity of the northern Tethyan margin. The Lower Aptian black shales were formed during the hyperthermal. This hyperthermal controlled the accumulation of organic carbon-rich sediments by increasing the input of nutrients and/or providing conditions for its stratification and stagnation.
An Upper Jurassic succession of deep-marine limestones, marls and claystones preserved in the Ambo section of the Qiangtang Basin (Tibet) contains information concerning the response of the eastern Tethys Ocean to multiple carbon cycle perturbations and to palaeoceanographic changes. Three positive δ¹³C excursions (P-CIE 1–3), dated as latest Callovian, middle Oxfordian and early Late Kimmeridgian, respectively, are observed in our section and related to high organic carbon burial episodes; they are correlatable with profiles from the Atlantic, western Tethys and western Paleo-Pacific regions. A significant decrease in δ¹³C values in our section in late Oxfordian to early Kimmeridgian times is attributed to the onset of upwelling of ¹³C-depleted watermasses caused by the opening of new seaways during the progressive collapse of Pangaea. A fourth positive δ¹³C excursions (P-CIE 4), dated as Late Kimmeridgian-Early Tithonian, is unlikely to be due to accelerated burial of organic carbon, but may be associated with the establishment of a stable low-latitude thermohaline circulation that replaced the upwelling zones. Due to the oceanic changes linked to the breakup of Pangaea, incursions of cold Arctic waters and associated changes in water mass density triggered a collapse in thermohaline circulation in the Tethys Ocean during the middle Early Tithonian (ca. ~151–150 Ma). As a consequence, an upwelling cold bottom current was formed, triggering global cooling and a significant reduction in the δ¹³C values. This study is the first to show continuous carbon isotope profiles for the eastern Tethys Ocean, and provides an inter-regional correlation and new paleoceanographic information.
In part 1 of this work we discussed the possibilities for the selection of a GSSP for the Berriasian Stage of the Cretaceous System, based on prevailing practical methods for correlation in that J/K interval, traditional usage and the consensus over the best boundary markers that had developed in the last forty years. This consensus has developed further, based on the results of multidisciplinary studies on numerous sites over the last decade. Here in Part 2 we give an account of the application of those results by the Berriasian Working Group (ISCS), and present the stratigraphic evidence that justifies the selection of the locality of Tré Maroua (Hautes-Alpes, SE France) as the proposed GSSP. We describe a 45 m-thick section in the Calcaires Blancs vocontiens – that part of the formation covering the calpionellid Chitinoidella, Remanei. Intermedia, Colomi, Alpina, Ferasini, Elliptica and Simplex biozones. The stratigraphic data collected here has been compiled as part of a wider comparative study of complementary Vocontian Basin sites (with localities at Charens, St Bertrand, Belvedere and Le Chouet). Evidence from Tré Maroua thus sits in this substantial regional biostratigraphic and magnetostratigraphic con- text. For the purposes of the GSSP definition, here we particularly concentrate on the unbroken sequence and biotic markers in the interval immediately below the boundary, the Colomi Subzone (covering circa 675,000 years), and immediately above, the Alpina Subzone (covering circa 725,000 years). Particularly significant fossil datums identified in the Tré Maroua profile are the primary basal Berriasian marker, the base of the Alpina Subzone (a widespread event marked by dominance of small Calpionella alpina, with rare Crassicollaria parvula and Tintinopsella carpathica): the base of the Berriasian Stage is placed at the base of bed 14, which coincides with the base of the Alpina Subzone. Secondary markers bracketing the base of the Calpionella Zone are the FOs of the calcareous nannofossil species Nannoconus wintereri, close below the boundary, and the FO of Nannoconus steinmannii minor, close above. The Tithonian/Berriasian boundary level occurs within M19n.2n, in common with many documented sites, and is just below the distinctive reversed magnetic subzone M19n.1r (the so-called Brodno reversal). We present data which is congruent with magnetostratigraphic and biostratigraphic data from other key localities in France and in wider regions (Le Chouet, Saint Bertrand, Puerto Escaño, Rio Argos, Bosso, Brodno, Kurovice, Theodosia...), and thus the characteristics and datums identified at Tré Maroua are key for correlation and, in general, they typify the J/K boundary interval in Tethys and connected seas.
STATUS OF THIS PROPOSAL: After more than ten years of work the Berriasian WG completed its discussions and arrived at what was considered to be the best possible proposal for the Berriasian GSSP. The work has demanded important effort, time and financial input from the WG members, with considerable diversion from their everyday aims, functions and duties. The informed specialists of the WG overwhelmingly voted, firstly to choose a primary marker (by 75%) and then to choose a GSSP (by 73%). These decisions were based on sound correlations, founded on documentation of many sites and their fossil, magnetic and other characters. The derived data for the GSSP compares well and in some cases are even superior to those used to define other ratified Cretaceous GSSP's. The approved proposal was first submitted to the Cretaceous Subcommission on 1st December 2019, and during the following six weeks the WG received some negative comments produced by three members of the Subcommission. On that basis the proposal was reviewed and most observations and criticisms were answered with a direct written reply and/or by inserting explanations and improvements into the original text. Regrettably, the WG never got back any comment on its detailed revision. The revised proposal covered all the limitations and positives for correlation in the J/K interval and all that is correlatively possible and useful was described, and what is less possible was discussed, even at some length. Its conclusions have already been cited (Gradstein et al., 2020). Finally, in September 2020 the reviewed proposal was resubmitted and was the subject of a vote by the Cretaceous Subcommission. Of the twenty-two persons in the Subcommission, eight (32%) voted against the proposal, eight voted “Yes”, four did not vote, and two abstained. When the Subcommission Chairperson was asked for the concrete reasons that justified the negative votes the only reply was that “the voting members of the Subcommission are free to express their opinions and provide explanations if they are willing to do so”. Clearly, an unexpected answer within a scientific organization like ICS/IUGS. Although, as here explained, this proposal has not been approved and its final status remains open, the authors continue with research on the site and with publication of Part 2, as it contains a wealth of information that could be useful for future research.
GRADSTEIN F.M., OGG J.G., SCHMITZ M.D., OGG G.M. (Eds.), 2020 – Geologic time scale. Elsevier.
Abstract. In part 1 of this work we discussed the possibilities for the selection of a GSSP for the Berriasian Stage of the Cretaceous System, based on prevailing practical methods for correlation in that J/K interval, traditional usage and the consensus over the best boundary markers that had developed in the last forty years. This consensus has developed further, based on the results of multidisciplinary studies on numerous sites over the last decade. Here in Part 2 we give an account of the application of those results by the Berriasian Working Group (ISCS), and present the stratigraphic evidence that justifies the selection of the locality of Tré Maroua (Hautes-Alpes, SE France) as the proposed GSSP. We describe a 45 m-thick section in the Calcaires Blancs vocontiens – that part of the formation covering the calpionellid Chitinoidella, Remanei. Intermedia, Colomi, Alpina, Ferasini, Elliptica and Simplex biozones. The stratigraphic data collected here has been compiled as part of a wider comparative study of complementary Vocontian Basin sites (with localities at Charens, St Bertrand, Belvedere and Le Chouet). Evidence from Tré Maroua thus sits in this substantial regional biostratigraphic and magnetostratigraphic context. For the purposes of the GSSP definition, here we particularly concentrate on the unbroken sequence and biotic markers in the interval immediately below the boundary, the Colomi Subzone (covering circa 675,000 years), and immediately above, the Alpina Subzone (covering circa 725,000 years). Particularly significant fossil datums identified in the Tré Maroua profile are the primary basal Berriasian marker, the base of the Alpina Subzone (a widespread event marked by dominance of small Calpionella alpina, with rare Crassicollaria parvula and Tintinopsella carpathica): the base of the Berriasian Stage is placed at the base of bed 14, which coincides with the base of the Alpina Subzone. Secondary markers bracketing the base of the Calpionella Zone are the FOs of the calcareous nannofossil species Nannoconus wintereri, close below the boundary, and the FO of Nannoconus steinmannii minor, close above. The Tithonian/Berriasian bound-ary level occurs within M19n.2n, in common with many documented sites, and is just below the distinctive reversed magnetic subzone M19n.1r (the so-called Brodno reversal). We present data which is congruent with magnetostratigraphic and biostratigraphic data from other key localities in France and in wider regions (Le Chouet, Saint Bertrand, Puerto Escaño, Rio Argos, Bosso, Brodno, Kurovice, Theo-dosia...), and thus the characteristics and datums identified at Tré Maroua are key for correlation and, in general, they typify the J/K boundary interval in Tethys and connected seas.
Here in the first part of this publication we discuss the possibilities for the selection of a GSSP for the Berriasian Stage of the Cretaceous System, based on the established methods for correlation in the Tithonian/Berriasian interval. This will be followed, in the second part, by an account of the stratigraphic evidence that justifies the locality of Tré Maroua (Hautes-Alpes, SE France) as the proposed GSSP. Here we discuss the possibilities for correlation in the historical J/K boundary interval, and the evolution of thinking on the positioning of the boundary over recent generations, and in relation to research in the last ten years. The Tithonian/Berriasian boundary level is accepted as occurring within magnetosubzone M19n.2n. The detailed distribution of calpionellids has been recorded at numerous sites, tied to magnetostratigraphy, and the base of the calpionellid Alpina Zone is taken to define the base of the Berriasian Stage. This is at a level just below the distinctive reversed magnetic subzone M19n.1r (the so-called Brodno reversal). We discuss a wide range of magnetostratigraphic and biostratigraphic data from key localities globally, in the type Berriasian areas of France and wider regions (Le Chouet, Saint Bertrand, Puerto Escaño, Rio Argos, Bosso, Brodno, Kurovice, Theodosia etc.). The characteristic datums that typify the J/K boundary interval in Tethys and its extensions are detailed, and the correlative viability of various fossil groups is discussed. The boundary level is correlated to well-known J/K sections globally, and a series of secondary markers and proxies are indicated which assist wider correlation. Particularly significant are the primary basal Berriasian marker, the base of the Alpina Subzone (marked by dominance of small Calpionella alpina, Crassicollaria parvula and Tintinopsella carpathica) and secondary markers bracketing the base of the Calpionella Zone, notably the FOs of the calcareous nannofossil species Nannoconus wintereri (just below the boundary) and the FO of Nannoconus steinmannii minor (just above). Notable proxies for the boundary are: 1) the base of the Arctoteuthis tehamaensis Zone in boreal and subboreal regions, 2) the dated base of the Alpina Subzone at 140.22 ± 0.14 Ma, which also gives a precise age estimate for the system boundary; and 3) the base of radiolarian “unitary zone” 14, which is situated just above the base of the Alpina Subzone.
In the comment on our paper (this issue), Zatoń (2020) questions the conclusions reported in Błażejowski et al. (2019). We present further arguments defending our theses. Late Jurassic horseshoe crabs preserved in sediments of the Kcynia Formation, (Owadów-Brzezinki Quarry), lived in a restricted lagoon repeatedly subjected to dysoxia/anoxia, which promoted their excellent state of preservation. The palaeobiological interpretation of the traces visible on horseshoe crab exoskeletons is consistent with the occurrence of temporal oxygen deficiency.
An unusual and very important macrofauna has been recorded in the deep water environment (i.e. below the aragonite CCD) of the uppermost Tithonian – lower Berriasian carbonate calpionellid-bearing sequence of the Kurovice section (Czechia). Rhyncholites, belemnites, and small vertebrate fauna of elasmobranchians (Neoselachii) are reported herein from a submarine slump probably resulting from a tsunami-like event. The Jurassic – Cretaceous (J/K) boundary interval is well demarcated by the occurrence of small globular Calpionella alpina, the J/K boundary marker established by the Berriasian Working Group. Rhyncholites, belemnites, and elasmobranchians are re-evaluated herein within the modern taxonomic concept, and they are stratigraphically investigated. High resolution sampling provided new data on the stable isotope record (δ13C and δ18O) from the uppermost part of the Crassicollaria through the Calpionella Zones. The stable isotope record shows only minor excursions of the δ13C, with values below 0.5‰, and typically varying from 0.7‰ to 1.2‰ V-PDB; the most negative peak δ13C = 0.2‰ V-PDB is recorded in the uppermost Crassicollaria Zone. A slightly negative shift of carbon isotope values exceeds about 0.2‰ at the J/K boundary. A similar trend at the critical J/K boundary interval (base of the Calpionella Zone) is seen in several Tethyan sections. The δ18O curve shows larger excursions varying between -1.4 to -4.3‰ V-PDB in the J/K boundary interval.
New biostratigraphical and carbon isotope data are presented for the Upper Jurassic limestones of the Raptawicka Turnia Limestone Formation (High Tatric unit, Western Tatra Mountains, Poland) from the Mały Giewont area. The Kimmeridgian, lower Tithonian and lower part of the upper Tithonian have been identified on the basis of calcareous dinocysts and calpionellids. Eight microfossil biozones are distinguished: acme-Fibrata,-acme-Parvula, Moluccana, Borzai, Tithonica-acme-Pulla(?), Malmica, Chitinoidella and Crassicollaria (pars). The Kimmeridgian/Tithonian boundary is indicated at the top of the Borzai Zone 76 m above the base of the Raptawicka Turnia Limestone Formation. The microfossil stratigraphy suggests the late Early Kimmeridgian age (acme-Parvula Zone) of the ammonites described by Passendorfer (1928). The taxon-Taramelliceras ex gr. compsum found 14 m above those ammonites is Late Kimmeridgian in age. Seven microfacies types (MF) are identified in the Upper Jurassic limestones of the Mały Giewont area. The-Bositra-Saccocomidae MF occurs across the Lower-Upper Kimmeridgian boundary. The planktonic and benthic foraminifera occur in the Upper Jurassic deposits of the Raptawicka Turnia Limestone Formation. The genera-Lenticulina-Lamarck and Spirillina Ehrenberg are common in the Kimmeridgian and Tithonian limestones. The palaeobathymetric evolution of the Kimmeridgian-Tithonian deposition recorded in the Mały Giewont sections reveals: the transgressive episode at the Lower/Upper Kimmeridgian boundary interval, the transgression peak during the Early Tithonian (Malmica Zone) and gradual shallowing of the High-Tatric swell in the Late Tithonian. Integrated isotope stratigraphy and biostratigraphy enabled correlation with the pelagic section of the Sub-Tatric succession in the Długa Valley section. The middle part of the Raptawicka Turnia Limestone Formation (Upper Kimmeridgian) might be correlated with the upper part of the Czajakowa Radiolarite Formation (red radiolarites) and Czorsztyn Formation in the Długa Valley section. The upper part of the Raptawicka Turnia Limestone Formation of Early Tithonian age corresponds mostly to the Jasenina Formation. The overall similarity of the δ¹³C decreasing values recorded in the Kimmeridgian–earliest Tithonian interval of the Mały Giewont (this study) and Długa Valley sections indicates that the generally shallow-water deposits of the Raptawicka Turnia Limestone Formation accumulated below the zone influenced by changes in the composition of marine water caused, for instance, by intense rainfall.
Carbon isotope chemostratigraphy and calpionellid biostratigraphy were used in this study to improve the stratigraphic resolution of the Upper Jurassic–Lower Cretaceous Rayda Formation and examine the expression of the Valanginian C-isotope event in the SE-Tethys. This integrated stratigraphic framework allows for a better correlation between south-eastern and western Tethys records and to obtain a better understanding of the oceanographic system on a regional scale. During the Late Jurassic, a major transgression induced a fast flooding of the Arabian Platform and lead to the deposition of the Rayda Formation. Red crinoidal limestones and submarine hardgrounds at the base of the formation are signs of condensed sedimentation influenced by changing current systems along the passive margin shelf. The following deposition of Maiolicatype micritic limestones with chert nodules recorded the establishment of pelagic conditions which presumed during the earliest Cretaceous and ended with the onset of the hemipelagic sediments of the Salil Formation. The upper part of the Rayda Formation, so far considered as Berriasian-earliest Valanginian in age, is here ascribed to the Upper Valanginian. The established δ13C-curve records the distinct Valanginian C-isotope event (CIE) in the uppermost part of the Rayda Formation and the lowermost part of the Salil Formation. The age of the excursion is underpinned by calpionellid biostratigraphy.
The Owadów-Brzezinki quarry is one of the most important paleontological sites in Poland, known for its exceptionally well-preserved Upper Jurassic (Middle Volgian = uppermost Lower Tithonian) fossils. Carbonate deposits of the section record a transition from an offshore to coastal and lagoonal settings and have been studied based on microfacies, micropalaeontological, isotope and chemical proxies. The obtained data point to normal marine conditions during the deposition of the older part of the quarry section in an offshore setting and a gradual transition into lagoonal environment characterized by high-amplitude variations in seawater salinity and oxygenation level of bottom waters, both of which resulted in considerable changes in benthic fauna assemblages or in the total lack of the fauna at some intervals. Above-mentioned conditions during the deposition of the middle part of the quarry section have probably allowed the preservation of diversified fauna with soft tissues. The microfacies and chemical data indicate that dysoxic/anoxic episodes may have occurred not only during the deposition of known fauna-rich beds but also during the deposition of poorly studied, so far, younger part of the section. The uppermost part of the carbonates exposed in the Owadów-Brzezinki quarry originated during the re-appearance of normal marine chemistry mostly in the intertidal-subtidal settings. The depositional conditions of the Owadów-Brzezinki site are non- typical, among famous conservation Lagerstätten, owing to the rapid fluctuations in the oxygenation and salinity of bottom waters.
A well preserved Upper Tithonian–Lower Berriasian Strapkova sequence of hemipelagic limestones improves our understanding of environmental changes occurring at the Jurassic/Cretaceous boundary in the Western Carpathians. Three dinoflagellate and four calpionellid zones have been recognized in the section. The onset of the Alpina Subzone of the standard Calpionella Zone, used as a marker of the Jurassic/Cretaceous boundary is defined by morphological change of Calpionella alpina tests. Calpionellids and calcified radiolarians numerically dominate in microplankton assemblages. The first occurrence of Nannoconus wintereri indicates the beginning of the nannofossil zone NJT 17b Subzone. The FO of Nannoconus steinmannii minor was documented in the lowermost part of the Alpina Subzone. This co-occurrence of calpionellid and nannoplankton events along the J/K boundary transition is typical of other Tethyan sections. Correlation of calcareous microplankton, of stable isotopes (C, O), and TOC/CaCO3 data distribution was used in the characterization of the J/K boundary interval. δ13C values (from +1.09 to 1.44 ‰ VPDB) do not show any temporal trends and thus show a relatively balanced carbon-cycle regime in sea water across the Jurassic/Cretaceous boundary. The presence of radiolarian laminites, interpreted as contourites, and relatively high levels of bioturbation in the Berriasian prove oxygenation events of bottom waters. The lower part of the Crassicolaria Zone (up to the middle part of the Intermedia Subzone) correlates with the M19r magnetozone. The M19n magnetozone includes not only the upper part of the Crassicollaria Zone and lower part of the Alpina Subzone but also the FO of Nannoconus wintereri and Nannoconus steinmannii minor. The reverse Brodno magnetosubzone (M19n1r) was identified in the uppermost part of M19n. The top of M18r and M18n magnetozones are located in the upper part of the Alpina Subzone and in the middle part of the Ferasini Subzone, respectively. The Ferasini/Elliptica subzonal boundary is located in the lowermost part of the M17r magnetozone. A little bit higher in the M17r magnetozone the FO of Nannoconus steinmannii steinmannii was identified.
We obtained material from the Puerto Escano section (southern Spain) to study the Jurassic/Cretaceous (J/K) boundary interval. The same samples had already been processed for magnetostratigraphic studies and biostratigraphic zonation based on calpionellids and ammonites (Pruner et al. 2010), but not for calcareous nannofossils. The aim of this study was to process the samples using micropalaeontological analysis and to compare and calibrate results for calcareous nannofossils with existing magnetostratigraphic and other biostratigraphic data. The calcareous nannofossil assemblage was dominated by the genera Watznaueria, Cyclagelosphaera, Nannoconus, Conusphaera and Polycostella. Several nannofossil bioevents were recorded on the basis of the distribution of stratigraphically important taxa, including zonal and subzonal markers. Based on the lowest occurrences (LO) of M. chiastius, N. globulus minor, N. wintereri, N steinmanii minor, N. steinmannii steinmannii, N. kamptneri minor and N. kampteri kamptneri, two nannofossil subzones (NJT 15b, NJT 17a) and two nannofossil zones (NJT 16, NK-1) were recognized. The paper introduces new palaeoecological data based on geochemical analysis and macrofauna occurrences.
Oued Bahloul is a reference section for the Cenomanian–Turonian that was located on the North African palaeomargin, where Oceanic Anoxic Event 2 (OAE2) is represented by black limestones and grey marls. Biostratigraphic study allowed the identification of calcareous nannofossil UC3 to UC6 zones. Quantitative analyses of calcareous nannofossil assemblages indicate that high-fertility surface-water conditions predominated throughout most of the OAE2 interval. The most eutrophic conditions probably developed during deposition of the lowermost part of the Whiteinella archaeocretacea Zone (UC3 to UC4 zones), where nannofossil-derived fertility indices reach high values and the small Zeugrhabdotus gr. predominates over Biscutum spp. The temperature index based on calcareous nannofossil assemblages indicates a warming at the beginning of the OAE2, followed by progressive cooling (the same trend indicated by δ¹⁸Obulk values). The significant proportion of holococcoliths suggests high-stress conditions in surface waters during most of the OAE2 interval. The enrichment in redox-sensitive elements, together with the abundance of low-oxygen tolerant benthic foraminifera, indicates dysoxic conditions both in the deep-water column and sea-bottom at the beginning of the OAE2 (W. archaeocretacea Zone). Geochemical detrital proxies indicate an enhanced rate of terrigenous supply during the OAE2 interval resulting from increased riverine influx related to a more humid climate. Enhanced fluvial run-off increased nutrient input to marine surface waters contributing to eutrophication (recorded by calcareous nannoplankton and planktic foraminifera). Plankton consumption of surface water nutrients increased organic matter production, whose decay contributed to the decrease in dissolved oxygen, generating increasingly dysoxic/anoxic conditions and favoring preservation of organic matter. Although low-latitude nannofossil assemblages such as those of Oued Bahloul reflect an increase in nutrient availability during the OAE2 interval, assemblages from mid-latitude areas record a decreased nutrient content.
An integrated biostratigraphic investigation has been performed of section Z of the Río Argos successions. Section Z is situated along the Barranco de Tollo, a left tributary of the Río Argos three kilometres west of the city of Caravaca, Province of Murcia, SE Spain. The sediments of section Z form part of the External Subbetic Zone of the Betic Cordillera. Section Z comprises the Jacobi Zone and the Subalpina Subzone, which is the lower part of the Occitanica Zone. The base of the Jacobi Zone, i.e. the base of bed Z1, conformably overlies beds in ammonitico rosso facies yielding ammonites of the Durangites vulgaris Zone. Sequence boundary Be1 is situated on top of bed Z4. The top of the Jacobi Zone (major sequence boundary Be3) is situated in a continuously deposited succession. The Jacobi zone can be divided into two parts, which are separated by sequence boundary Be2. Berriasella (Hegaratella) jacobi can still function as the index species for the lower part (equivalent to depositional sequence Be1). Instead of the appearance of Pseudosubplanites grandis in bed Z139, a more obvious and natural boundary between the ammonite faunas of the lower and upper part of the Jacobi Zone is formed by sequence boundary Be2. However for this upper part (equivalent to depositional sequence Be2) no index species could be indicated yet. However, Subthurmannia floquinensis is provisionally used as index species for the upper part of the Jacobi Zone. Hitherto the base of the Cretaceous System was defined by ammonites. The base of the Jacobi ammonite Zone is the base of the Berriasian Stage, which is the lowest stage of the Cretaceous. Bed Z1 yielded the first Berriasella (Hegaratella) jacobi (Wiedmann in Allemann et al., 1975). In the sections of Puerto Escaño (S. Spain) and Le Chouet SE France) the base of the Jacobi Zone is virtually situated at the same level as the base of polarity chron M19n, but it is not known how large the lacuna is at the major sequence boundary Be1. The belemnites from section Z are not well-preserved, and difficult to identify. The belemnite fauna mainly consists of species that have traditionally been recognized as indicative for the Late Jurassic (Tithonian Belemnite Association IV) and that were previously unknown from the earliest Cretaceous. The first "typical" Cretaceous belemnite, which is related to the Duvalia lata group, appears in bed Z131. The ranges of the species encountered in section Z should be considered with a certain reservation. As to the calpionellid zones, section Z covers the upper part of the Crassicolaria Zone, viz. the upper part of the Intermedia Subzone and the Colomi Subzone, and the lower part of the Calpionella Zone, viz. the Alpina (with the bloom of Calpionella alpina at its base), Ferasini, and Elliptica subzones. For specialists in calpionellids the bloom of Calpionella alpina at the base of the Calpionella Zone, which is also the base of the Alpina Zone, is considered the base of the Cretaceous. This base was demonstrated at the base of bed Z40. Calcareous nannofossil biostratigraphy was achieved on a total of 56 samples from section Z. Several primary and secondary biohorizons were detected, allowing us to recognize three zones and two subzones in section Z, viz. the upper part of NJT-17a Subzone, the NJT-17b Subzone, the NKT and NK-1 zones, and a part of NK-2 Zone. Three (on a total of four) bio-horizons selected by the Berriasian Working Group as useful in locating the Jurassic/Cretaceous boundary were recognized. The first appearances of important nannoplankton species are marked in the lithological column. It appeared that, because of a nearby volcanic heat source, all non-calcareous dinoflagellate cysts of section Z are carbonized and that the rocks were totally remagnetized during the Miocene, so that magnetostratigraphy was not possible (Hoedemaker et al., 1998). However, sequence stratigraphy was quite clear and three sequences could be distinguished bounded by three sequence boundaries: Be1, Be2, and Be3.
The Late Jurassic to Early Cretaceous interval represents a time of environmental upheaval and cataclysmic events,combined with disruptions to terrestrial and marine ecosystems. Historically, the Jurassic/Cretaceous (J/K) boundary was classified as one of eight mass extinctions. However, more recent research has largely overturned this view, revealing a much more complex pattern of biotic and abiotic dynamics than has previously been appreciated. Here, we present a synthesis of our current knowledge of Late Jurassic – Early Cretaceous events, focusing particularly on events closest to the J/K boundary. We find evidence for a combination of short-term catastrophic events, large-scale tectonic processesand environmental perturbations, and major clade interactions that led to a seemingly dramatic faunal and ecologicalturnover in both the marine and terrestrial realms. This is coupled with a great reduction in global biodiversity whichmight in part be explained by poor sampling. Very few groups appear to have been entirely resilient to this J/K boundary‘event’, which hints at a ‘cascade model’ of ecosystem changes driving faunal dynamics. Within terrestrial ecosystems,larger, more-specialised organisms, such as saurischian dinosaurs, appear to have suffered the most. Medium-sized tetanuran theropods declined, and were replaced by larger-bodied groups, and basal eusauropods were replaced by neosauropod faunas. The ascent of paravian theropods is emphasised by escalated competition with contemporary pterosaur groups, culminating in the explosive radiation of birds, although the timing of this is obfuscated by biases in sampling. Smaller, more ecologically diverse terrestrial non-archosaurs, such as lissamphibians and mammaliaforms,were comparatively resilient to extinctions, instead documenting the origination of many extant groups around theJ/K boundary. In the marine realm, extinctions were focused on low-latitude, shallow marine shelf-dwelling faunas,corresponding to a significant eustatic sea-level fall in the latest Jurassic. More mobile and ecologically plastic marinegroups, such as ichthyosaurs, survived the boundary relatively unscathed. High rates of extinction and turnover in other macropredaceous marine groups, including plesiosaurs, are accompanied by the origin of most major lineages ofextant sharks. Groups which occupied both marine and terrestrial ecosystems, including crocodylomorphs, document a selective extinction in shallow marine forms, whereas turtles appear to have diversified. These patterns suggest thatdifferent extinction selectivity and ecological processes were operating between marine and terrestrial ecosystems, which were ultimately important in determining the fates of many key groups, as well as the origins of many major extantlineages. We identify a series of potential abiotic candidates for driving these patterns, including multiple bolide impacts,several episodes of flood basalt eruptions, dramatic climate change, and major disruptions to oceanic systems. The J/K transition therefore, although not a mass extinction, represents an important transitional period in the co-evolutionary history of life on Earth.
We present coupled ocean–sea-ice simulations of the Middle Jurassic (∼165 Ma) when Laurasia and Gondwana began drifting apart and gave rise to the formation of the Atlantic Ocean. Since the opening of the Proto-Caribbean is not well constrained by geological records, both the configurations with and without an open connection between the Proto-Caribbean and Panthalassa have been examined. We use a sea-floor bathymetry obtained by a recently developed three-dimensional (3D) elevation model which compiles geological, palaeogeographical and geophysical data. Our original approach consists in coupling this elevation model, which is based on detailed reconstructions of oceanic realms, with a dynamical ocean circulation model. We find that the Middle Jurassic bathymetry of the Central Atlantic and Proto-Caribbean seaway only allows for a weak current of the order of 2 Sv in the upper 1000 m even if the system is open to the west. The effect of closing the western boundary of the Proto-Caribbean is to increase the transport related to barotropic gyres in the southern hemisphere and to change water properties, such as salinity, in the Neo-Tethys. Weak upwelling rates are found in the nascent Atlantic Ocean in the presence of this superficial current and we discuss their compatibility with deep-sea sedimentological records in this region.
Magneto-Susceptibility Event and Cyclostratigraphy (MSEC) is used here as a means of establishing sensitive chronostratigraphic markers and chronohorizons useful for high-resolution correlation. MSEC is a composite of the magnetic susceptibility (MS) record of marine strata and the coeval biostratigraphic record and, similar to chronozones, zones based on MSEC data have boundaries that are isochronous. MS, a measure of the concentration of magnetic grains in sediments, proxies for the ratio of lithogenic to biogenic components. Controls on the detrital input of lithogenic material include eustasy and climate, however induced, and sea floor/basin subsidence. The development of an initial MSEC composite reference curve for the Middle-Upper Devonian of the Anti-Atlas region of southern Morocco is presented and discussed in the context of global sea level transgressive and regressive cycles. MSEC trends, composed of increasing MS magnitudes, correlate well with episodes of regression, whereas trends of decreasing MS magnitudes correlate with episodes of transgression.
A detailed geochemical analysis has been conducted in the Fuente de la Vidriera section of the External Subbetic (Betic Cordillera, southern Spain) in order to interpret the incidence of the Toarcian Oceanic Anoxic Event (T-OAE) in the westernmost end of the Tethys. The obtained values of detrital, redox and palaeoproductivity proxies throughout the succession show minor fluctuations, but only punctual significant changes. Detrital input is nearly constant during the studied interval, except in the upper part, characterized by an increase in both fluvial and eolian detrital transport. Associated to this local higher fluvial and eolian activity, a comparatively higher concentration in organic matter is punctually registered, as revealed by the comparatively highest total organic carbon (TOC) value. The rest of the section shows TOC values in the lower range of those registered in the Tethyan Toarcian sections. Obtained ratios of redox-sensitive trace metals lead to the interpretation of oxic to dysoxic bottom-waters, with a singular sharp decrease in oxygenation corresponding to a short interval within the serpentinum Zone (sample FV-18) correlated to the T-OAE. The minor incidence of the T-OAE registered in this westernmost end of the Tethys —in which punctual dysoxic conditions are restricted only to a decimetric interval— reveals the importance of regional context and particular oceanic-atmosphere dynamics on the local record of this phenomenon.
Middle–Upper Jurassic pelagic carbonates and radiolarites were studied in the Krížna Nappe of the Tatra Mountains (Central Western Carpathians, southern Poland and northern Slovakia). A carbon isotope stratigraphy of these deposits was combined with biostratigraphy, based on radiolarians, calcareous dinoflagellates and calpionellids. In the High Tatra and Belianske Tatra Mountains, the Bajocian and part of the Bathonian are
represented by a thick succession of spot ted lime stones and grey nodular limestones, while in the Western Tatra Mountains by relatively thin Bositra-crinoidal limestones. These deposits are referable to a deeper basin and a pelagic carbonate platform, respectively. The various carbonate facies are followed by deep-water biosiliceous facies, namely radiolarites and radiolarian-bearing limestones of Late Bathonian–early Late Kimmeridgian age. These fa cies pass into Upper Kimmeridgian–Lower Tithonian pelagic carbonates with abundant Saccocoma sp. The bulk-carbonate isotope composition of the carbonate-siliceous deposits shows positive and negative δ13C
excursions and shifts in the Early Bajocian, Late Bajocian, Early Bathonian, Late Bathonian, Late Callovian, Middle Oxfordian and Late Kimmeridgian. Additionally, the δ13C curves studied show a pronounced increasing trend in the Callovian and a steadily decreasing trend in the Oxfordian–Early Tithonian. These correlate with the trends known from the Tethyan region. The onset of Late Bathonian radiolarite sedimentation is marked by a decreasing trend in δ13 C. In creased δ13C values in the Late Callovian, Middle Oxfordian and Late Kimmeridgian (Moluccana Zone) correspond with enhanced radiolarian production. A significant increase in CaCO3 content is re corded just above the Late Callovian δ13C excursion, which coincides with a transition from green to variegated radiolarites.
This report describes a macrofloral fossil assemblage discovered in travertine deposits of the Tithonian-Berriasian Aguilar Formation (provinces of Palencia and Burgos, N Spain). The assemblage includes megaremains of a single species of Filicales (Cladophlebis denticulata) and of eleven taxa tentatively identified as Bennettitales (Otozamites mundae, Otozamites sp., Ptilophyllum pecten, Ptilophyllum pectiniformis, Ptilophyllum sp. cf. pectiniformis, Ptilophyllum acutifolium, Ptilophyllum sp., Pterophyllum cycadites, Pterophyllum sp. cf. thomasii, Zamites pumilio, and cf. Pseudocycas sp.). Specimens were preserved as impressions coated with a microbial film up to 5 mm thick made up of: bacteria and cyanobacteria. Based on the available sedimentological and palaeobotani-cal data, a dry-savannah vegetation and an arid climate were deduced. Late Jurassic macrofloras are globally scarce and have not previously been reported in Spain. Hence, the Aguilar Formation macroflora provides valuable information on the coeval phytogeography and palaeoclimate of southwestern Europe. Furthermore, the lack of floras observed so far in palaeotravertine deposits older than Pliocene in age makes this macroflora exceptional.
Eustatic sea-level changes of the Cretaceous are reevaluated based on a synthesis of global stratigraphic data. A new terminology for local/regional or relative sea-level changes (eurybatic shifts) is proposed to distinguish them from global (eustatic) sea-level changes, with the observation that all measures of sea-level change in any given location are eurybatic, even when they include a strong global signal. Solid-earth factors that influence inherited regional topography and thus modify physical measures of amplitude of the sea-level rises and falls locally are reviewed. One of these factors, dynamic topography (surface expression of mass flow in the upper mantle on land- and seascapes), is considered most pertinent in altering local measures of amplitude of sea-level events on third-order time scales (0.5-3.0 Myr). Insights gained from these models have led to the reconciliation of variance between amplitude estimates of eurybatic shifts in any given region and global measures of eustatic changes. Global estimates of third-order events can only be guesstimated at best by averaging the eurybatic data from widely distributed time-synchronous events. Revised curves for both long-term and short-term sea-level variations are presented for the Cretaceous Period. The curve representing the long-term envelope shows that average sea levels throughout the Cretaceous remained higher than the present day mean sea level (75–250 m above PDMSL). Sea level reached a trough in mid Valanginian (~ 75 m above PDMSL), followed by two high points, the first in early Barremian (~ 160-170 m above PDMSL) and the second, the highest peak of the Cretaceous, in earliest Turonian (~ 240-250 m above PDMSL). The curve also displays two ~ 20 Myr-long periods of relatively high and stable sea levels (Aptian through early Albian and Coniacian through Campanian). The short-term curve identifies 57 third-order eustatic events in the Cretaceous, most have been documented in several basins, while a smaller number are included provisionally as eustatic, awaiting confirmation. The amplitude of sea-level falls varies from a minimum of ~ 20 m to a maximum of just over 100 m and the duration varies between 0.5 and 3 Myr. The causes for these relatively rapid, and at times large amplitude, sea-level falls in the Cretaceous remain unresolved, although based mainly on oxygen-isotopic data, the presence of transient ice cover on Antarctica as the driver remains in vogue as an explanation. This idea has, however, suffered a recent setback following the discovery of pristine foraminiferal tests in the Turonian of Tanzania whose oxygen- isotopic values show little variation, implying absence of glacioeustasy at least in the Turonian. The prevalence of 4th-order (~ 400 Kyr) cyclicity through most of the Cretaceous (and elsewhere in the Paleozoic and Cenozoic) strongly implies that the periodicity on this time scale, presumably driven by long-term orbital eccentricity, may be a fundamental feature of depositional sequences throughout the Phanerozoic.
This paper discusses the results of a study of the Le Chouet section, its lithologies, facies, magnetic properties and fossil record (ammonites, calcareous nannofossils, calpionellids and calcareous dinoflagellates). Data obtained have been applied to give a precise biostratigraphy for this carbonate sequence as well as a paleoenvironmental recon- struction. Its relationship to magnetostratigraphy, based on a modern study of a French site, is important. Investigation of the micro- and macrofossils shows that the site comprises a sedimentary sequence in the Microcanthum to Jacobi ammonite Zones, and the Chitinoidella, Crassicollaria and Calpionella Zones. Several calpionellid and nannofossil bioevents have been recorded on the basis of the distribution of stratigraphically important planktonic organisms. The site allows us to calibrate the levels of various biomarkers and biozonal boundaries, and correlate them with the magnetozones M20n, M19r and M19n.
Radiolarites, commonly comprising chert-shale couplets, feature prominently in the Mesozoic stratigraphy of the Neotethyan realm. The origin and significance of these deposits, especially with regard to understanding palaeoproductivity in that region, remains controversial. This study examines transport processes and accumulation rates of radiolarians/radiolarites, as well as the chronology of radiolarite sedimentation based on revised data from the Southern Alps and new data from the Balagne Nappes, Alpine Corsica. Results suggest that the spatio-temporal distribution of carbonate and silica on Tethyan margins was governed by extensive lateral transport of radiolarian tests from topographic highs to basins. Palaeoclimatic, rather than palaeotectonic, changes seem to have triggered changes in surface fertility which, in turn, brought about major facies changes observed in Tethyan marginal basins: Regional platform demise – possibly due to eutrophication and onset of radiolarite deposition in the Early Bajocian – can be correlated with a positive shift in the carbon isotope curve, whereas platform recovery and the end of radiolarite accumulation correlates with a gradual decline in δ13C-values. The existence of a vigorous trans-Pangaean, equatorial current system that could have produced regional upwelling is questioned because of evidence for Middle Jurassic to Early Cretaceous oligotrophic conditions in the Proto-Caribbean and the Central Atlantic. The ‘Caribbean River Plume Model’ is proposed as a possible alternative to upwelling in the Jurassic Western Tethys. Dissolved nutrients may have been dispersed in low salinity lids that originated from river plumes of rivers from tropical Africa and warm-temperate Eurasia. Vast areas of the pre-Late Cretaceous world ocean must have accumulated radiolarites at low rates (<4 g cm−2 10−3years) represented by the condensed, long-lived (>50 Myr) radiolarite sections observed in many Circumpacific terranes. Radiolarian chert and claystone could be the normal pelagic sediment during Ordovician to Early Cretaceous time in far-offshore, open oceanic settings, where dilution by terrigenous material and periplatform shallow-water carbonates was absent.
Valanginian sedimentary archives display a positive anomaly in the carbon‐isotope record which is associated with a crisis in neritic and pelagic carbonate production. This study aims to reconstruct the evolution of palaeoenvironments in the Jura area and the Vocontian Basin during late Berriasian and early Valanginian times, in order to better understand the controlling factors leading to the Valanginian episode of major environmental change. Three sections along a transect through the Jura platform (Switzerland and France) and the Vocontian Basin (France) have been studied. Stratigraphic correlations have been established by combining biostratigraphy (benthic foraminifera, ammonites and calpionellids), with geochemistry (δ13C trends) and sequence stratigraphy. A change from a rimmed ramp to a swell‐dominated ramp morphology is observed through the Berriasian–Valanginian boundary. The disappearance of the barrier appears to have been controlled by large sea‐level variations in combination with the arrival of significantly more humid climate conditions. This barrier played a major role in the distribution of geochemical, mineralogical and palynological fluxes towards the basin: during the Berriasian, continental fluxes (detrital particles, nutrients, pollen and spores) were buffered by the platform morphology, whereas in the early Valanginian they were more readily transported towards the basin. The initiation of a major transgression onto lateritic soils, leading to their intense reworking, instigated a fertilization of ocean waters during the earliest Valanginian and with that a change towards heterozoan carbonate production, and subsequently to the demise of the already weakened carbonate platform.
This research focuses on the cephalopod fauna and biostratigraphy of the
latest Jurassic succession of the Lókút Hill (Bakony Mts,
Transdanubia, Hungary). Fossils were collected bed-by-bed from
Ammonitico Rosso facies and from the subsequent Biancone type rock. The
poorly preserved cephalopods from the lowermost part of the profile,
immediately above the radiolarite, may represent a part of the Oxfordian
stage. The rich Kimmeridgian ammonite fauna is published for the first
time while the formerly illustrated Tithonian fauna is revised. All the
successive Kimmeridgian and Early Tithonian Mediterranean ammonite zones
can be traced. The highest documented ammonite zone is the Late
Tithonian Microcanthum Zone. The beds above yielded no cephalopods.
Particular attention was paid to the belemnite fauna of over 120
specimens collected under strict ammonite control. Among the belemnite
faunas an Early Tithonian, an early middle Tithonian, a late middle
Tithonian, and a latest Tithonian assemblage can be distinguished.
Thereby, an association is distinguished in the middle Late Kimmeridgian
and one that characterizes the Oxfordian-Kimmeridgian boundary beds. The
main difference from previously published belemnite data appears to be
that the Hungarian assemblages are impoverished with respect to
contemporary faunas from Italy and Spain (Mediterranean Province). An
isotopic analysis of the belemnites show that the carbon-isotope data
are consistent with carbon-isotope stratigraphies of the Western Tethys
and show a decrease in values towards the Jurassic-Cretaceous boundary.
Calcareous nannofossil biostratigraphy was investigated in uppermost Callovian-lower Berriasian sections from Southern Alps, previously detected through magnetostratigraphy, in order to achieve an integrated stratigraphie framework valid at low latitudes. Nannofossil investigations were carried out on smear slides and ultra-thin sections, revealing generally scarce to common abundances and poor-moderate preservation of nannofloras. An exhaustive taxonomie revision was performed to unambiguously separate forms which are transitional between two species and better delineate rapidly evolving groups. Four new species have been described: Zeugrhabdotus fluxus, Nannoconus puer, Nannoconus erbae, Hexahthus geometricus. Particular attention was paid to taxonomical aspects of primitive nannoconids, appearing and evolving across the early-late Tithonian transition and the Tithonian/Berriasian boundary intervals; the revision was also verified at DSDP Site 534A from Atlantic Ocean. Fourty-eight nannofossil bioevents were detected and the results help to increase potential stratigraphie resolution in this interval. Thirty-seven nannofossil bioevents in the upper Kimmeridgian-lower Berriasian interval have been directly correlated to magnetostratigraphy (CM22-CM17) revealing a systematically older stratigraphie occurrence of these taxa than previously reported. A revised and partly new Tethyan calcareous nannofossil zonation scheme is here proposed for the uppermost Callovian-lower Berriasian interval. It consists of seven bio-zones and eight subzones based on thirty-one bioevents, thirteen of them related to dissolution resistant taxa assuring highest reproducibility even in sections with high diagenetic overprint. The proposed biostratigraphic scheme gives higher resolution than previous zonations, especially for the Callovian-Kimmeridgian interval, where no biozonation was available for the Tethyan Realm.
Compared to coeval successions from the Carpathians, the continuous
Jurassic-Cretaceous (J/K) pelagic limestone succession of the Brodno
section offers the best possibility to document the J/K passage in a
wide area. This section comprises a complete calpionellid, and
nannofossil stratigraphic record, that supports the older paleomagnetic
data. Moreover, the sequence stratigraphy and stable isotope
(δ18O, δ13C) data gave important
results, too, enabling comparison with known key sections from the
Mediterranean Tethys area.
The pre-conference field trip will present the main structural phases
of the Mesozoic deformation of the northern Transdanubian Range
(TR) (Fig. 1, 2), starting from the Early Jurassic rifting through different
Cretaceous deformation phases. The Mesozoic evolution of the
TR was equally linked to the opening and closure of the Meliata-Vardar
branch of the Neotethys ocean, but also to the events in Alpine
Tethys (Ligurian-Piemont ocean) (Fig. 4). Excursion will present outcrops
showing the structures and sediments connected to minor extension,
which is related to the Early Jurassic rifting and Late Jurassic
bending of the lithosphere, respectively. During the early Cretaceous,
the northern part of the TR was the location of a flexural basin with
clastic infill, which is in contrast with the carbonate sedimentation of
the remaining part of the TR. New sedimentological and structural
observations reposition the present-day outcrops within the basin. Finally,
the excursion visit sites where the mid-Cretaceous deformation
is well pronounced in the structure of the Range.
The present study analyses the stratal architecture of the Late Jurassic (Kimmeridgian) to Early Cretaceous (Berriasian) sedimentary succession of Mount Salève (E France), and four Berriasian stratigraphic intervals containing four sequence-boundary zones reflecting lowering trends of the relative sea-level evolution. Massive Kimmeridgian limestones characterized by the presence of colonial corals appear to be stacked in an aggrading pattern. These non-bedded thick deposits, which are interpreted to have formed in balance between relative sea-level rise and carbonate accumulation, suggest a keep-up transgressive system. Above, well-bedded Tithonian-to-Berriasian peritidal carbonates reflect a general loss of accommodation. These strata are interpreted as a highstand normal-regressive unit. During the early phase of this major normal regression, the vertical repetition of upper intertidal/lower supratidal lithofacies indicates an aggrading depositional system. This is in agreement with an early stage of a highstand phase of relative sea level. The Berriasian sequence-boundary zones investigated (up to 4 m thick) developed under different climatic conditions and correspond to higher-frequency, forced- and normal-regressive stages of relative sea-level changes. According to the classical sequence-stratigraphic principles, these sequence-boundary zones comprise more than one candidate surface for a sequence boundary. Three sequence-boundary zones studied in Early Berriasian rocks lack coarse siliciclastic grains, contain a calcrete crust, as well as marly levels with higher abundances of illite with respect to kaolinite, and exhibit fossilized algal-microbial laminites with desiccation polygons. These sedimentary features are consistent with more arid conditions. A sequence-boundary zone interpreted for the Late Berriasian corresponds to a coal horizon. The strata above and below this coal contain abundant quartz and marly intervals with a higher kaolinite content when compared to the illite content. Accordingly, this Late Berriasian sequence-boundary zone was formed under a more humid climate. The major transgressive–regressive cycle of relative sea level identified and the climate change from more arid to more humid conditions recognized during the Late Berriasian have been reported also from other European basins. Therefore, the Kimmeridgian to Berriasian carbonate succession of Mount Salève reflects major oceanographic and climatic changes affecting the northern margin of the Alpine Tethys ocean and thus constitutes a reliable comparative example for the analysis of other coeval sedimentary records. In addition, the stratigraphic intervals including sequence-boundary zones characterized in this study constitute potential outcrop analogues for sequence-boundary reflectors mapped on seismic profiles of subsurface peritidal carbonate successions. The detailed sedimentological analyses provided here highlight that on occasions the classical principles of sequence stratigraphy developed on seismic data are difficult to apply in outcrop. A sequence-boundary reflector when seen in outcrop may present successive subaerial exposure surfaces, which formed due to high-frequency sea-level changes that were superimposed on the longer-term trend of relative sea-level fall.
Hungary lies in the central part of the Pannonian Basin, surrounded by the ranges of the Alps, Carpathians, and Dinarides. The geology of the country can be summarized as a process whereby complicated plate collision-type orogeny was followed by the formation of a young basin in which a relatively complete sequence of basin infill has been preserved. The handbook “Geology of Hungary” presents an outline of the main features of the geology and geohistory of the region in a single volume, illustrated by a great number of color figures and photos for the benefit of foreign geoscientists interested in this area. The volume follows the evolutionary history of the major structural units prior to their juxtaposition in the Tertiary and discusses the subsequent evolution of the Pannonian Basin. Due to the geohistorical approach to this study it was necessary to extend the scope of the discussion beyond the present-day political boundaries of Hungary, to cover most of the Pannonian region.
A summary of calcareous nannofossil biostratigraphy performed for Late Jurassic (Kimmeridgian) to Early Cretaceous (Hauterivian) cores of Site 765 (Cores 123-765C-58R to -55R) and Site 261 (Core 27-261-33 to -27), Argo Abyssal Plain, off northwestern Australia is presented. Precise age determinations were limited by variable preservation and the exclusion of a number of marker species due to provincialism. However, the presence of certain species results in a reasonably good degree of biostratigraphic control. Biogeographic interpretation of the nannofossil data suggests that the Argo Basin occupied a position transitional between the Tethyan and Austral nannofloral realms. A cooler water regime is suggested by the absence of thermophyllic Tethyan forms, and the presence of taxa that display bipolar distribution. Two new species and one new combination are described. -from Authors
A continuous Late Berriasian sedimentary and stratigraphic record is here presented from a hemipelagic succession from theWestern Balkan (Barlya section, Bulgaria). The section, 39-m-thick,was stratigraphically calibrated using a variety of methods: biostratigraphy (calpionellids, calcareous nannofossils and calcareous dinocysts), magnetostratigraphy and carbon isotope stratigraphy. Additionally, hemostratigraphy and rock magnetic stratigraphy were applied in order to identify major paleoenvironmental changes: lithogenic input and paleoredox variations. Polarity zones from M17r to M14r were identified from the uppermost Lower Berriasian up to the Berriasian/Valanginian boundary (Elliptica to Darderi calpionellid subzones and NK-1 to NK-3 nannofossil zones). Late Berriasian calcareous dinocyst zones of Stomiosphaerina proxima, Stomiosphaera wanneri and Colomisphaera confertawere correlatedwith magnetostratigraphy for the first time. A carbon isotope profile correlates very well with the δ13C records from SE France and the Western Atlantic, documenting some well-resolved minima and maxima in a generally decreasing trend. Magnetic susceptibility (MS) reveals a very good positive correlation with lithogenic elements (e.g., Al, Ti, Zr, Th and others) and is regarded as a reliable proxy
of detrital input. Influx of fine grained terrigenous material increases in the Upper Berriasian up to the
Berriasian/Valanginian boundary. A prominent MS increase takes place in the lowermost part of polarity zone M16n (close to the Simplex/Oblonga subzonal boundary). The MS event can be traced in the Central Carpathian, Apennine and SE France sections, exactly in the same stratigraphic position. It is coevalwith an important climatic turnover in Western Tethys; however, it might have been strengthened by a general regression and regional tectonic events in the Carpatho–Balkan area. Two oxygen deficient intervals were documented: the first in the Lower Berriasian (M17r to M16r); the second one in the uppermost Upper Berriasian up to the boundary with Valanginian (M15r to M14r). Both intervals correlate with an elevated sea-level in the Western Tethys.
Sedimentology and sequence stratigraphy of Upper Tithonian and Berriasian carbonate beds and carbonate-marlstone alternation have been studied at three different localities in the realm of the Vocontian Trough (SE France). The carbonate rocks yield an unequivocal hemipelagic to pelagic fossil assemblage. They can be subdivided into three facies types: facies type I: fossil wackestones (periplatform ooze); facies type IIm/IId: intraclastic-fossil wackestones/floatstones ; facies type III: intraclast-fossil grainstones/rudstones (grain flows). Facies type I represents autochthonous deep-marine deposits, whereas the monomictic mass-flow breccias (facies types II and III) record the collapse of the carbonate slope during relative sealevel lowstands. The sedimentological and sequential development of the studied formations is mainly controlled by third-order sea-level variations and, in some cases, also by synsedimentary tectonics. from Authors
The most striking feature occurring in the Berrias section is the fact that kaolinite disappears in the grandis and at the base of the subalpina Ammonite subzones. This reflects arid climatic conditions probably related to a second-order lowstand of sea-level. The control of third-order eustatic fluctuations on the clay mineral sedimentation is overprinted by this climatic factor. In the Berriasian of Angles, the influence of burial diagenesis on clay assemblages is expressed by the replacement of smectite by chlorite in limestone beds. -from Author
The following Late Jurassic depositional systems have been recognized in the W Ukrainian and SE Polish margin of the East European Platform: shelf slope/basin, open shelf, carbonate ramp, siliciclastic shelf, fluvial/playa, deltaic/swamp, restricted marine/evaporate lagoon. Three depositional megasequences have been identified. Their upper boundaries have been dated by means of targeted stratigraphic studies, compilation of existing data and reinterpretation of stratigraphic correlation concepts respectively as: lower Kimmeridgian divisum/hypselocyclum zones boundary, uppermost upper Kimmeridgian and lower Berriasian. Analysis of thickness and depositional system architecture within the megasequences in six regional cross-sections indicates that depocentre was located in the SW margin of the Mid-Polish Trough during Oxfordian and early Kimmeridgian times and propagated in Tithonian time to the Lviv region. This can be explained by changes in the palaeostress field. Approximately N-S oriented extension during Oxfordian and earliest Kimmeridgian times was replaced by approximately NE-SW oriented extension in Tithonian time. The thickness pattern of the megasequences as well as proximity trends of the system tracts within the sequences clearly coincide with the depocentre propagation.
How are mountains formed? Why are there old and young mountains? Why do the shapes of South America and Africa fit so well together? Why is the Pacific surrounded by a ring of volcanoes and earthquake-prone areas while the edges of the Atlantic are relatively peaceful? Frisch and Meschede and Blakey answer all these questions and more through the presentation and explanation of the geodynamic processes upon which the theory of continental drift is based and which have led to the concept of plate tectonics.
The pelagic Jurassic successions of the Trapani region of western Sicily are dominated by the characteristic Tethyan Rosso Ammonitico lithofacies. In order to revise the stratigraphy (sedimentology, microbiofacies, ammonite and calpionellid biostratigraphy, isotope stratigraphy) and to define a reference section, a well exposed succession of Rosso Ammonitico, spanning the Callovian - Upper Berriasian interval, has been selected in the eastern sector of Monte Inici. Trapani province. A sedimentological study has enabled us to distinguish three subfacies within the Rosso Ammonitico: nodular, pseudo-nodular, and intraclastic nodular subfacies. The two latter subfacies are characterized by the presence of intraclasts produced largely by mechanical abrasion, that suggest a formation by hydrodynamic processes. Increasing hydrodynamic energy is inferred from Lower Kimmeridgian to Upper Berriasian deposits. The vertical evolution of the microfacies shows the greatest skeletal diversity in the Middle Oxfordian, coinciding with a peak of δ13C. Ammonites are abundant in the Middle Oxfordian - Lower Kimmeridgian, where several ammonite zones have been recognized. With the aid of calpionellids we have been able to identify the Jurassic - Cretaceous boundary and to recognized high frequency biostratigraphic intervals in the Berriasian, that can be correlated throughout palaoetethys. The δ13C curve shows a marked positive peak at the base of the section (Lower to Middle Callovian) and a second, composite, positive excursion in the Middle-Upper Oxfordian. From the base of the Kimmeridgian, δ13C values slowly decrease, remaining low in the Berriasian. Oxygen isotope values exclude late burial diagenetic overprinting and the carbon peaks are interpreted as reflecting carbon cycle perturbations due to high biological productivity that may mirror global palaeoenvironmental variations. The Middle Oxfordian peak coincides with the highest skeletal diversity, with the first occurrence of the nodular facies, and with the onset of cherty limestones (lateral equivalents of radiolarites) in the southern sector of Monte Inici, and in localities to the west and north. The heteropy between Rosso Ammonitico and radiolarites s.l. suggests that sedimentation was controlled by local palaeotopography.
The Pieniny Klippen Belt represents the trace of a major axial suture in the Carpathian fold belt, about 600km long but only from a few 100m to about 20km wide. It is a heterogenous structure consisting of the Klippen successions proper and their sedimentary cover, moreover of Inner Carpathian (Manin etc) and Outer Carpathian (Magura) units incorporated in the Belt during its long deformational history. Nine distinctive stages of structural evolution of the Belt have been distinguished and are described.-after Author
Oxygen and carbon isotope values and elemental ratios of well-preserved belemnite rostra, brachiopod shells and bulk-carbonates from the Upper Callovian–Lower Kimmerdgian of the Polish Jura Chain, Kujawy (Poland) and Swabian Alb (Germany) are investigated to reconstruct environmental conditions and perturbations in the marine carbon cycle. Belemnite δ¹⁸O values show relatively constant temperatures (ca. 12°C) of bottom waters in the Polish Jura Chain basin during a major part of the Late Callovian–Middle Oxfordian, except for a short-term cooling (to ca. 9°C) at the Callovian–Oxfordian transition. Belemnite and brachiopod δ¹⁸O values show a gradual increase in temperature during the Submediterranean Late Oxfordian; the highest temperatures (ca. 16°C) are calculated for the Submediterranean Oxfordian–Kimmeridgian transition. Belemnite and brachiopod Mg/Ca and Sr/Ca ratios are disregarded as a palaeotemperature proxy because of their weak correlation with δ¹⁸O values.
The Transdanubian Central Range (TCR) is a flattened range of hills in northern Transdanubia (Hungary), formed mainly by Mesozoic carbonate rocks showing strong facies similarities with the Southern Alps and the Austroalpine domain. The Jurassic system is divided into several formations of predominantly pelagic limestones. Ammonoids are frequent and were collected bed-by-bed in numerous sections, providing an excellent biostratigraphic resolution. The thickness of the Jurassic system is usually small but changes along the strike of the TCR. It reaches a maximum thickness of 500 m in the western part; is very variable (10-400 m) in the central segment (Bakony Mts.) and rather low (less than 100 m) in the east (Gerecse). In the Bakony segment, the thickness variation reflects the strongly dissected topography of the Jurassic sea-floor. Synsedimentary tectonics is dominated by normal faults; tilted blocks and listric faults may be inferred only in the east. Five main steps were identified in the palaeogeographic evolution: 1) Late Hettangian: carbonate oolitic shoals prevail, except for a few sites where non-deposition or neritic sediments occur. 2) Sinemurian and Pliensbachian: tectonic disintegration resulted in an intricate pattern of submarine horsts and intervening basins, with condensed sedimentation or non-deposition on the horsts and thicker, continuous sedimentary sequences in the basins. The submarine topographic highs are surrounded by aprons of redeposited material (scarp breccias, brachiopod coquinas, crinoida calcarenites, spiculitic cherry limestones), while pure or argillaceous limestones (Rosso Ammonitico) prevail in the distal areas. 3) Early Toarcian: the Tethys-wide anoxic event is superimposed on the previous submarine bottom topography; the resulting black shales and sedimentary Mn-ores are concentrated on the western sides of some horsts. 4) Dogger to Early Maim: radiolarites with heterochronous lower and upper boundaries (Aalenian to Kimmeridgian) prevail, except for the top of some submarine topographic highs. The absence of uppermost Bathonian to Lower Oxfordian carbonates suggests that the whole TCR sunk below the CCD in those times. 5) Latest Jurassic: the uniform deposition of Rosso Ammonitico and Biancone in the Late Kimmeridgian and Tithonian is interrupted only in the Early Tithonian by local intercalations of scarp breccias and coarse biodetrital limestones. This is interpreted as the last manifestation of synsedimentary tectonic movements along the faults bordering the submarine horsts. Based on palaeogeographic similarities and analogies in Jurassic times, the TCR is visualized as the northern foreground of the Trento platform/plateau (lying north of the later Insubric lineament), where the block-tectonic disintegration and differential subsidence started earlier and resulted in a bottom morphology more dissected than in the South Alpine part of this west Tethyan passive margin.
A new high-resolution carbon-isotope stratigraphy of the Late Jurassic has been generated from Tethyan carbonate sections. Sections chosen for this study are from the Helvetic nappes of the Swiss Alps, from the Jura Mountains, from the Provence (France) and from the Southern Alps (N. Italy). The limestones and marls used for this isotope geochemical investigation were deposited along the northern (Helvetics, Jura, Provence) and the southern (S. Alps) margin of the Alpine Tethys. Isotope curves were first established in well-dated sections of the Jura Mountains, the Southern Alps and the Vocontian Basin. Isotope curves generated from the poorly dated Helvetic nappe sections could then be correlated with the bisotratigraphically dated sections. This comparison produces greatly improved age control for the Helvetic sections and a more detailed composite δ 13C curve for the Late Jurassic than has been published previously. The composite δ 13C curve features two short-lived negative excursions in the Oxfordian, a δ 13C maximum in the Late Kimmeridgian and steadily decreasing δ 13C values throughout the Tithonian. These δ 13C events are consistent with previous, lower resolution data sets and are valuable tie-points, which can be used for correlating upper Jurassic successions among different lithologies and across different depositional settings. The new carbon isotope record is not only useful as a stratigraphic tool but it records fluctuations in Late Jurassic global carbon cycling. The negative carbon isotope events lasting up to a few 10 5 years are interpreted as primary perturbation signals recording anomalies in the atmospheric and marine carbon reservoirs. The perturbations of the global C-cycle were triggered by a sudden and massive release of methane stored in deep-sea gas hydrates. Positive carbon isotope excursions lasting up to millions of years record changes in carbonate and organic carbon production and sedimentation.
Recently established separate dinoflagellate cyst zonation combined with the successive calpionellid events contribute to the HIRES of the Upper Jurassic and Lower Cretaceous Tethyan pelagic carbonate sequences. Compositional changes in dinoflagellate and calpionellid assemblages are correlated with eustatic sea-level fluctuations. Thus, parallel calpionellid and cyst zonations give us more precise tools for the subdivision of deposits investigated as well as for better understanding and reconstruction of the paleoceanographical and paleoecological conditions of the ancient marine environments. The calcareous resting cyst distribution is shown to be influenced by the whole complex of environmental factors such as sea-level transgressive/regressive pulses, hydrological regime, nutrient content etc.
Our tentative proposal is that several biological markers have potential to help define any putative boundary in the traditional basal Berriasian interval. That is, between the base of the Berriasella jacobi Subzone and the base of the Pseudosubplanites grandis Subzone, and therefore straddling the base of magnetozone M18r. Promising micropalaeontological markers are the FADs of Nannoconus steinmannii minor and Nannoconus kamptneri minor, plus the base of the Calpionella alpina Zone, and the bloom(s) of Calpionella alpina and Crassicollaria parvula. The testing and calibration of this constraining event-matrix in the most complete and fossiliferous sections is our task for the near future.
In this paper, we report on a new magnetic stratigraphy from the Jurassic Salto del Cieco section (Italy), which is barely known in the literature and has not been previously investigated for magnetostrati graphy. This approximately 130-m-thick section is the most temporally extended
section that has ever been studied for the Jurassic magnetostratigraphy in the Tethyan realm and is the third section spanning the Jurassic/Cretaceous boundary in the Apennines. Our main goals are to document magnetic polarities and to investigate the Jurassic/Cretaceous boundary. A total
of 435 cylindrical samples have been collected with a sampling resolution of 30 cm as low sedimentation rate and high frequency polarity reversals were expected. After thermal cleaning, 89% of the samples show a primary component of magnetization that is isolated in temperature ranges depending
upon lithologies. The succession of normal- and reverse-polarity magnetozones matches the Geomagnetic Polarity Time Scale in the M19–M25n, while it was inferred in the Toarcian-Aalenian intervals due to the presence of a slump. A total absence of correlation characterizes 17 Myr between
the Early Kimmeridgian and Early Bajocian. Instead, the Carixian interval only correlates with other condensed successions known from the literature. The Jurassic/Cretaceous boundary is constrained with the Calpionella alpina explosion and located at 60% of the M19n.2n. We found two
possible polarity subchrons that have not been previously referred in the literature: one in the middle of M20r and one at the top of M21n. Finally, the comparison with the GPTS yields to a detailed estimate of sedimentation rates and enables to evaluate the diachronicity of Maiolica onset
between different land sections.
This contribution presents the first detailed oxygen and carbon isotope record from the latest Jurassic-early Cretaceous interval of the Yatria River, subpolar Urals, Siberia. Isotopic compositions have been determined on well-preserved belemnite samples from the genera Lagonibelus, Cylindroteuthis and Acroteuthis. These new data indicate a shift to lower temperatures from the late Volgian into the late Valanginian, with some warmer phases recognized within the Ryazanian and earliest Valanginian. The lowest temperatures of the late Valanginian, consistent with subfreezing polar temperatures, are coincident with an inferred eustatic sea-level fall. A late Valanginian positive shift in carbon isotopes correlates with the carbon isotope excursion recorded from Tethyan successions. The most positive carbon isotope values correspond to the most positive oxygen isotope values (and hence lowest palaeotemperatures). In the absence of widespread Valanginian organic-rich black shale deposition, the carbon isotope excursion may point to increased storage of organic carbon in coastal areas and/or enhanced preservation within stratified waters in high-latitude basins. At these higher latitudes, where rates of weathering were presumably much lower because of the prevalent cold climate, the isotopic data may point to pulses of productivity being brought about by increased riverine nutrient transfer and also by nutrients being released by the melting of ice. The correlation between positive carbon isotopes and cool climates may indicate the effectiveness of these high-latitude carbon sinks and their ability to draw down atmospheric CO(2), resulting in an 'inverse greenhouse' effect.
The radiolaritic facies (red/green cherts with radiolarians) is a very characteristic feature of the Tethyan realm. For a long time, its presence has been interpreted as a consequence of depth of an oceanic environment. It is now preferable to consider it as high productivity sediment. We here underline the interpretation inferring the role of monsoons for such productivity according to the relative position of lands at that time.
Paleoenvironmental and paleoclimatic changes during the Valanginian carbon isotopic excursion (CIE) have been investigated in the western Tethys. For this purpose, bulk-rock and clay mineralogies, as well as phosphorus (P) contents were evaluated in a selection of five sections located in the Vocontian Basin (Angles, SE France; Alvier, E Switzerland; Malleval, E France), and the Lombardian Basin (Capriolo, N Italy; Breggia, S Switzerland).
Within the CIE interval, bulk-rock and clay mineralogies are inferred to reflect mostly climate change. The onset of the CIE (Busnardoites campylotoxus ammonite Zone) is characterized by higher detrital index (DI: sum of the detrital minerals divided by calcite contents) values and the presence of kaolinite in their clay-mineral assemblages. In the late Valanginian (from the Saynoceras verrucosum Zone up to the end of the Valanginian), the samples show relatively variable DI and lower values or the absence of kaolinite. The variation in the mineralogical composition is interpreted as reflecting a change from a climate characterized by optimal weathering conditions associated with an increase in terrigenous input on the southern European margin during the CIE towards an overall unstable climate associated with drier conditions in the late Valanginian. This is contrasted by a dissymmetry (proximal vs distal) along the studied transect, the northern Tethyan margin being more sensitive to changes in continental input compared to the distal environments.
P accumulation rates (PAR) present similar features. In the Vocontian basin, P content variations are associated with changes in terrigenous influx, whereas in the Lombardian basin (i.e. Capriolo and Breggia), PAR values are less well correlated. This is mainly because the deeper part of the Tethys was less sensitive to changes in continental inputs. The onset of the CIE (top of the B. campylotoxus Zone) records a general increase in PAR suggesting an increase in marine nutrient levels. This is linked to higher continental weathering rates and the enhanced influx of nutrients into the ocean. In the period corresponding to the shift itself, P contents show a dissymmetry between the Vocontian and Lombardian basins (proximal vs distal). For the sections of Malleval, Alvier and Angles, a decrease in P concentrations associated to a decrease in detrital input is observed. In Capriolo and Breggia, PAR show maximum values during the plateau, indicating a more complex interaction between different P sources. The time interval including the top of S. verrucosum Zone up to the end of the Valanginian is characterized by variable PAR values, suggesting variable nutrient influxes. These changes are in agreement with an evolution towards seasonally contrasted conditions in the late Valanginian.