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Orbital calibration of the Early Kimmeridgian (southeastern France): Implications for geochronology and sequence stratigraphy
Abstract
Classic stratigraphic methods rarely provide high-resolution correlations between intrabasinal sedimentary sequences, which are important to understand the origin of sedimentation process and its environmental change. In this study, we investigate high-resolution cyclostratigraphic correlation from magnetic susceptibility in two Early Kimmeridgian pelagic marl-limestone successions, at La Méouge and Châteauneuf-d'Oze, southeastern France. Spectral analysis reveals the complete suite of orbital frequencies (precession, obliquity, and eccentricity) with the marl-limestone couplets being primarily precession-driven. Frequencies detected by the spectral analysis are similar between the sections, but their relative amplitudes are somewhat different, linked to the palaeoenvironmental position and the completeness of the sections. High-resolution correlation reveals two significant hiatuses at Châteauneuf-d’Oze. Early Kimmeridgian Platynota, Hypselocyclum, and Divisum ammonite zones were orbitally calibrated for an ultra-high resolution assessment of geological time. Finally, strong 405-kyr eccentricity cycles are recorded as third-order depositional sequences.
... In addition, the climatic oscillations had also a marked influence on sea-level changes, especially those of longer duration related to 100kyr and 405-kyr eccentricity cycles. Such a study to attempt to recognize the climatic cycles was presented on the basis of detailed geochemical analysis of the Lower Kimmeridgian pelagic deposits of the south-eastern France having a good ammonite stratigraphy (Atrops, 1982;Boulila et al., 2008). It resulted in recognition of three main eccentricity cycles within deposits strictly coeval to those studied herein and showing similar assemblage of ammonites: beginning with the important transgressive level corresponding to minimum of 405-kyr MS cycle developed at the base of the whole succession (Min. ...
... It resulted in recognition of three main eccentricity cycles within deposits strictly coeval to those studied herein and showing similar assemblage of ammonites: beginning with the important transgressive level corresponding to minimum of 405-kyr MS cycle developed at the base of the whole succession (Min. 4 in Fig. 2 of Boulila et al., 2008), and the following two minima of 100-kyr cycles. The duration of the whole stratigraphical interval corresponding to the broadly treated Divisum Zone can be estimated as 260 to 300 kyr (Boulila et al., 2008). ...
... 4 in Fig. 2 of Boulila et al., 2008), and the following two minima of 100-kyr cycles. The duration of the whole stratigraphical interval corresponding to the broadly treated Divisum Zone can be estimated as 260 to 300 kyr (Boulila et al., 2008). ...
The transgressive succession of deposits of the upper Lower Kimmeridgian at Małogoszcz in the south-western margin of the Holy Cross Mts. in central Poland yielded diversified faunas of ammonites. The commonly represented Submediterranean ataxioceratid ammonites include the last members of Ataxioceras in the Hypselocyclum Zone and the assemblage of various Crussoliceras , Garnierisphinctes and Progeronia , mostly developed in the Divisum Zone, and associated upwards (Uhlandi Subzone) with aspidoceratids ( Pseudhimalayites ) . A few typical Mediterranean ammonites ( Nebrodites , Presimoceras , Idoceras , Taramelliceras ) are indicative of the Herbichi Zone. The Subboreal ammonites include mostly Eurasenia and Involuticeras in addition to some Rasenia and Rasenioides of the uppermost Cymodoce Zone, corresponding to the Askepta Subzone. The changes in composition of ammonite faunas and comparison with the coeval faunas of other areas of Europe give indications on the evolutionary development of some Ataxioceratidae and Aulacostephanidae at the end of Early Kimmeridgian. The development of the Crussoliceras , Garnierisphinctes and Progeronia , having possibly their roots in the Mediterranean areas, was strictly correlated with the overall transgression and oscillations of sea-level controlled possibly by climatic eccentricity cycles of the northern Tethyan shelf. This resulted also in the decline of older Ataxioceras and its nearby allies. The indigenous lineage of Aulacostephanidae includes the transition from Eurasenia to “ Pararasenia”. The development from Rasenioides to Aulacostephanoides occurred mostly in the Subboreal areas – although some late representatives of Rasenioides like R. moeschi reached the area of study. The existence of an independent lineage leading from Rasenia involuta to heavily-ribbed Aulacostephanoides/Aulacostephanus is also suggested.
... In addition, the climatic oscillations had also a marked in uence on sea-level changes, especially those of longer duration related to 100-kyr and 405-kyr eccentricity cycles. Such a study to attempt to recognize the climatic cycles was presented on the basis of detailed geochemical analysis of the Early Kimmeridgian pelagic deposits of the south-eastern France having a good ammonite stratigraphy (Boulila et al., 2008; see also Atrops, 1982). (Atrops, 1982). ...
... All these data strongly suggests a transgressive character of unit C. It should be remembered that the deposits of the Uhlandi Subzone are treated as transgressive in character in many areas of Europe (e.g., Marques & Olóriz, 1992). This high sea-level can be correlated possibly with the minimum of 100-kyr eccentricity cycle (see Boulila et al., 2008Boulila et al., , 2010. ...
... It seems highly probable that the concentration of all these shells at the top of unit E resulted from a very high sea-level. This may correspond to the minimum of the next 100-kyr eccentricity cycle well documented in the late Divisum Subchron (see Boulila et al., 2008Boulila et al., , 2010. This level corresponds possibly also to the balderum horizon (or subzone) as marked by common occurrence of the Tethyan form Idoceras balderum (Oppel) well documented at the top of the Uhlandi Subzone of the Divisum Zone in the Submediterranean areas of southern Germany to south-eastern France (see e.g., Hantzpergue et al., 1997). ...
The transgressive succession of deposits of the late Early Kimmeridgian at Małogoszcz in the south-western margin of the Holy Cross Mts. in central Poland yielded diversified faunas of ammonites. The commonly represented Submediterranean ataxioceratid ammonites include the last members of Ataxioceras in the Hypselocyclum Zone and the assemblage of various Crussoliceras , Garnierisphinctes and Progeronia , mostly developed in the Divisum Zone, and associated upwards (Uhlandi Subzone) with aspidoceratids ( Pseudhimalayites ). A few typical Mediterranean ammonites ( Nebrodites , Presimoceras , Idoceras , Taramelliceras ) are indicative of the Herbichi Zone. The Subboreal ammonites include mostly Eurasenia , Involuticeras in addition to some Rasenia and Rasenioides of the uppermost Cymodoce Zone, corresponding to the Askepta Subzone. The changes in composition of ammonite faunas and comparison with the coeval faunas of other areas of Europe give indications on the evolutionary development of some Ataxiocertidae and Aulacostephanidae at the end of Early Kimmeridgian. The development of the Crussoliceras , Garnierisphinctes and Progeronia , having possibly their roots in the Mediterranean areas, was strictly correlated with the overall transgression and oscillations of sea-level controlled possibly by climatic eccentricity cycles in northern Tethyan shelf. This resulted also in decline of older Ataxioceras and its nearby allies. The indigenous lineage of Aulacostephanidae includes the transition from Eurasenia to Pararasenia. The development from Rasenioides to Aulacostephanoides occurred mostly in the Subboreal areas – although some late representatives of Rasenioides like R. moeschi reached the area of study. The existence of an independent lineage leading from Rasenia involuta to heavily-ribbed Aulacostephanoides/Aulacostephanus is also suggested.
... Additionally, the continuously gradual variations of carbonate content, which closely track the highest frequency cyclicity corresponding to the basic marl-limestone couplets, are typical of a periodic process that controls their deposition. Lower-frequency cyclicity (i.e., supercouplets) modulates the couplets in an orbital precession/eccentricity fashion 10,13 . In particular, in time-equivalent sections, we have shown the potential use of MS in the detection/preservation of the primary Milankovitch climate cycles, also expressed in marl-limestone facies 12,13 (see also for e.g., Fig. 1 of Boulila et al. ...
... Lower-frequency cyclicity (i.e., supercouplets) modulates the couplets in an orbital precession/eccentricity fashion 10,13 . In particular, in time-equivalent sections, we have shown the potential use of MS in the detection/preservation of the primary Milankovitch climate cycles, also expressed in marl-limestone facies 12,13 (see also for e.g., Fig. 1 of Boulila et al. 21 ). ...
... 21 ). There are numerous studies showing the powerful use of MS as a proxy for Mesozoic cyclostratigraphy 12,13,27,28 . Therefore, our results exclude a severe diagenetic overprint that could obliterate the primary signal, although a very early diagenesis is likely, which could mimic or amplify the primary (climate) marl-limestone lithological signal, expressed in the MS data. ...
Earth’s past climate exhibits short-term (1500-year) pronounced fluctuations during the last glacial period, called Dansgaard–Oeschger (DO) glacial events, which have never been detected in pre-Quaternary times. The record of DO equivalent climate variability in Mesozoic strata can provide constraints on understanding these events. Here we highlight a prominent 1500-year cyclicity in a Jurassic (~ 155 Ma) ice-free sedimentary record from the Tethyan Basin. This Jurassic 1500-year cyclicity is encoded in high-resolution magnetic susceptibility (MS) proxy data reflecting detrital variations, and expressed as marl-limestone couplets. Additionally, MS data detect the modulation of these DO-scale couplets by supercouplet sets, reflecting the precession and its harmonics. We suggest that this Jurassic DO-like cyclicity may originate from paleo-monsoon-like system, analogous to the record of DO events in the Pleistocene East Asian monsoon archives. Paleogeographic reconstructions and atmosphere–ocean simulations further support the potential existence of strong, ancient monsoon circulations in the Tethyan Basin during the Jurassic.
... The stratigraphical position of sequences of strata can be based on fossils important for age-correlation, especially ammonites (which occur, however, only at some levels), but it can be also based on orbitally-controlled sedimentary cyclicity ( Fig. 6). Such as an attempt to recognize climatic cycles of longer duration (of 100-kyr and 405-kyr) can be proposed when comparing the lithological character of the deposits studied and their chronobiostratigraphically established position with the detailed cyclostratigraphic correlation chart based on detailed geochemical analysis of the Ear ly Kim mer idgian pelagic deposits of south-eastern France, having a good ammonite stratigraphy (Boulila et al., 2008(Boulila et al., , 2010cf. Atrops, 1982). ...
... The youngest deposits studied correspond possibly to the uppermost part of the minutum=schroederi ammonite horizon at the top of the Planula Zone (treated as the base of the Galar Subzone of the Platynota Zone, see Wierzbowski, 2017a), whereas the same level as documented by ammonites in the pelagic succession of SE France corresponds to the minimum (Min.1) of the 405-kyr eccentricity cycle (and nearly coeval minimum of the 100-kyr eccentri city cycle). This level marks the minimum of the magnetic susceptibility (MS), and corresponds to enhanced carbonate production, showing the maximum insolation, which appears to have induced a very high sea-level according to the model proposed by Boulila et al. (2008Boulila et al. ( , 2010. This interpretation seems to be in full accordance with the end of the influx of detrital material in relation to a higher sea-level, which flooded the carbonate platform of the Holy Cross Mts. ...
... Stratigraphical condensation at this level marked by the common occurrence of ammonites is commonly recognized to the west in the neighboring areas of the northern part of the Polish Jura 2) of the 405-kyr eccentricity cycle (and nearly coeval minimum of the 100-kyr eccentricity cycle). This level marks the minimum of the magnetic susceptibility (MS) and very high sea-level, according to the model proposed by Boulila et al. (2008Boulila et al. ( , 2010, which is in accordance with the suggestions given above (see also Wierzbowski, 2017a, fig. 12). ...
... andraeai FIGURE 26.9 Interregional correlation of latest Jurassic through earliest Cretaceous ammonite zones and regional stages. Magnetostratigraphic correlations to the marine magnetic anomaly M-sequence and cycle stratigraphy provide the reference numerical scale and absolute durations for Tethyan ammonite zones (e.g., Ogg et al., 2010a;Boulila et al., 2008bBoulila et al., , 2010aPruner et al., 2010). Sub-Boreal ammonite calibrations to Tethyan zone and/or M-sequence incorporates biostratigraphic unit. ...
... Cycle stratigraphy at La Méouge (France) yielded durations for the Lower Kimmeridgian ammonite zones (Boulila et al., 2008b(Boulila et al., , 2010b that are quite similar to magnetostratigraphyderived estimates. The Kimmeridge Clay Formation of Dorset (southern England), which spans the Kimmeridgian and Lower Tithonian, has been subject of several cyclostratigraphic studies (e.g., Waterhouse, 1995;Huang et al., 2010b). ...
... The implied durations of zones are generally consistent with the cycle-derived durations from cycle stratigraphy (e.g., Boulila et al., 2008bBoulila et al., , 2010bStrasser, 2007), although the span of a couple of the ammonite zones implied "missing cycle beats" at sequence boundaries. For example, the Idoceras planula Zone of basal Kimmeridgian was estimated as B0.35 Myr by Strasser (2007), but the magnetostratigraphy implies a duration of 0.75 Myr, implying that a full 400-kyr long eccentricity cycle is probably missing at the regional Oxf-8 sequence boundary below its transgressive base. ...
Ammonites underwent an evolutionary diversification after the mass extinction of the end Triassic induced by the formation of a Large Igneous province (LIP), and this group provides the most useful marine biostratigraphy. Only two levels within the Jurassic are relatively well determined using U–Pb dating from single zircons in ash beds, at the base Hettangian and the Pliensbachian–Toarcian boundary. Otherwise the Lower Jurassic is scaled using astrochronology and the Middle and Upper Jurassic scaled from Pacific seafloor spreading rates correlated to magnetic reversals. LIP activity during the Early Jurassic (Triassic–Jurassic boundary and Toarcian) perturbed global environments to extents not evidenced since the end Permian, and age relationships allow for a strong causal connection between these LIP eruptions and mass extinctions caused by major paleoenvironmental change, including ocean anoxia. Breakup of the supercontinent Pangea dominated paleogeography and paleoceanography and created shallow seaways that form sources and traps for hydrocarbons. Calcareous planktonic algae diversified and migrated from shallow seaways to open oceans to set the stage for the beginning of modern oceanic biogeochemical cycling; calcareous nannofossils provide additional widely used correlation tools.
... We compared the interpreted 405-kyr cycles at Tojeira to those interpreted by Boulila et al. (2008) at La Méouge, southeastern France in Fig. 3. A 25.7-kyr/cycle bandpass shows precession periodicity at La Méouge modulated by long-term eccentricity (Boulila et al. 2008). ...
... We compared the interpreted 405-kyr cycles at Tojeira to those interpreted by Boulila et al. (2008) at La Méouge, southeastern France in Fig. 3. A 25.7-kyr/cycle bandpass shows precession periodicity at La Méouge modulated by long-term eccentricity (Boulila et al. 2008). We identified two maxima in long-term wavelength cyclicity at the Tojeira-1 section and, assuming a steady sedimentation rate, correlated the cycles to Max2-3 of Boulila et al. (2008) using the ammonite zonal boundaries of the Tojeira Formation proposed by Atrops and Marques (1986). ...
... A 25.7-kyr/cycle bandpass shows precession periodicity at La Méouge modulated by long-term eccentricity (Boulila et al. 2008). We identified two maxima in long-term wavelength cyclicity at the Tojeira-1 section and, assuming a steady sedimentation rate, correlated the cycles to Max2-3 of Boulila et al. (2008) using the ammonite zonal boundaries of the Tojeira Formation proposed by Atrops and Marques (1986). Thus, the A. hypselocyclum Zone falls approximately at Max2, and the I. planula-S. ...
Precise biostratigraphic dating of the Tojeira Formation (Late Jurassic, Early Kimmeridgian) of the Montejunto section of west-central Portugal, which has yielded important planktonic foraminiferal assemblages, is hindered by poor preservation in the upper part of the section as the lithology shifts from shale to coarser clastics. Assignment was previously made to the Idoceras planula and Sutneria platynota zones based on ammonites. Coccolith and dinoflagellate assemblages described here concur with the Early Kimmeridgian, yet, a finer age constraint is proposed by cyclo- and chemostratigraphical correlation. Peaks in δ¹³Corg and TOC, if equivalent to maxima in the envelope of clay/carbonate cycles in SE France, imply that the c. 50 m-thick section spans a 0.8-myr interval of the S. platynota through upper Ataxioceras hypselocyclum ammonite zones, with the approximate base of the A. hypselocyclum Zone at c. 15.4 m (level 13). Such stratigraphy provides new insights into the upper part of the formation by interbasinal correlation with other Tethyan records. An extended first occurrence of the dinoflagellate species Dichadogonyaulax? pannea in the S. platynota Zone is also proposed.
... The discovery of a possible link between orbital variations and sea-level depositional sequences may improve the de¢nition of orders of depositional sequences. For example , the stable 405 kyr orbital eccentricity cycle (Laskar etal., 2004 ) has been demonstrated to control the third-order depositional sequences in Jurassic and Cretaceous sedimentary records (Strasser et al., 2000; Gale et al., 2002; Boulila et al., 2008a), indicating that orbital forcing plays a major role in sedimentation processes via sea-level change. In other respects, sub-Milankovitch (millennial) scale cyclicity has also been highlighted in Quaternary and pre-Quaternary sediments (e.g. Park et al., 1993; McIntyre & Mol¢no, 1996; Ortiz et al., 1999; Reuning et al., 2006). ...
... Shackleton et al., 1995; Weedon et al., 1999; Huret, 2006; Boulila et al., 2008b) and for the correlation of the pelagic and hemipelagic sedimentary record (e.g. Ellwood et al., 2000; Boulila et al., 2008a). Sampling was performed at high resolution on these marls, whereas tempestite, bentonite and nodule levels were not sampled since these event beds could introduce spurious MS peaks. ...
... In the Callovian^Oxfordian iron ooid condensed sections of the Paris Basin, Courville & Collin (2002) demonstrated that a condensed interval may include several sea-level variations. A similar problem of missing sequences in the Jacquin et al. 's (1998) sins was encountered in the Early Kimmeridgian of the Vocontian Basin in which an additional sequence was discovered between the sequence boundaries Kim1and Kim3 of the chart (Boulila et al., 2008a). The northern Iberian Basin provides an additional example , in which the Oxfordian is condensed (only 10^20- m-thick sections, Ramajo, 2006,Fig. ...
High-resolution analysis (2277 samples) of magnetic susceptibility (MS) was performed on ∼700-m-thick Early–Middle Oxfordian marine marls of the Terres Noires Formation, SE France. MS variations within these sediments record sub-Milankovitch to Milankovitch frequencies with long-term eccentricity (405 kyr and ∼2 Myr) being the most prominent. The 405 kyr cycle was used as a high-resolution geochronometer for astronomical calibration of this poorly constrained interval of Late Jurassic time. The estimated duration of this Early–Middle Oxfordian interval concurs with the current International Geologic Time Scale GTS2004 (∼4 Myr), but the estimated durations of the corresponding ammonite zones are notably different. The calibration improves the resolution and accuracy of the M-sequence magnetic anomaly block model that was previously used to establish the Oxfordian time scale. Additionally, the 405 kyr cyclicity is linked to third-order sea-level depositional sequences observed for Early–Middle Oxfordian time. Strong ∼2 Myr cycles are consistent with long-term eccentricity modulation predicted for the Late Jurassic. These cycles do not match second-order sequences that have been documented for European basins; this raises questions about the definition and hierarchy of depositional sequences in the Mesozoic eustatic chart. Our results require substantial revisions to the chart, which is frequently used as a reference for the correlation of widely separated palaeogeographic domains. Finally, a long-term trend in the MS data reflects a progressive carbonate enrichment of the marls expressing an Early Oxfordian global cooling followed gradually by a warming in the Middle Oxfordian. This trend also records a major transgressive interval likely peaking at the Transversarium ammonite zone of the Middle Oxfordian.
... In this study, we demonstrate that chemical and physical proxies preserve primary environmental cyclicities reecting Earth's orbital parameters. The Lower Kimmeridgian marl–limestone alternations at Châteauneuf-d'Oze in the Vocontian Basin of southeastern France (Fig. 1) are correlatable over many kilometers in the basin (Pederneiras, 1995; Moussine-Pouchkine et al., 1998), and were demonstrated, using magnetic susceptibility (MS) variations, as orbitally controlled (Boulila et al., 2008c ). In this study, we analyse manganese (Mn) at highresolution and we measure stable isotope composition (δ 13 C and δ 18 O) of a ∼8.5-m long interval (Fig. 2) covering two complete short (∼100 kyr) eccentricity cycles. ...
... In this study, we analyse manganese (Mn) at highresolution and we measure stable isotope composition (δ 13 C and δ 18 O) of a ∼8.5-m long interval (Fig. 2) covering two complete short (∼100 kyr) eccentricity cycles. Specically, this study aims to: @BULLET decipher orbital-scale oceanic and climatic changes preserved in multiple proxies in these Jurassic sediments; @BULLET look for possible differential (nonlinear) responses of the oceanic– climatic system to orbital forcing via the studied proxies (e.g., Fischer, 1986; Rey et al., 2003); @BULLET delineate a depositional model that links oceanic and climatic variations to sea-level changes during the Jurassic greenhouse period; and @BULLET resolve the debated sequence stratigraphy interpretations of Kimmeridgian pelagic sequences (e.g., Colombié and Strasser, 2003; Pross et al., 2006; Boulila et al., 2008c). ...
... 1. Paleogeographic framework of the Vocontian Basin of southeastern France (indicated with the star) during the Early Kimmeridgian (modied from Thierry, 2000). susceptibility (MS) (Boulila et al., 2008c). Compared to previous studies (Jan du Chêne et al., 2000; de Rafélis et al., 2001) and the reference eustatic chart of Hardenbol et al. (1998), we argued that third-order depositional sequences are controlled by Earth's orbital 405-kyr eccentricity. ...
High-resolution analysis of multiple climatic proxies was carried out on a ∼ 8.5-m Lower Kimmeridgian interval of a pelagic marl–limestone succession at Châteauneuf-d'Oze (Vocontian Basin, southeastern France). The aim of the study was to characterize the orbitally controlled sedimentary cyclicity and to decipher paleoclimatic and paleoceanographic changes. All analysed proxies (magnetic susceptibility, carbonate content, manganese content, and bulk carbon and oxygen stable isotopes (δ13C and δ18O) respond in synchrony to orbitally forced climate change. Precession index cycles modulated by short (∼ 100 kyr) eccentricity cycles are strongly expressed in magnetic susceptibility, carbonate and Mn contents but less so in δ18O. Obliquity cycles are expressed in manganese and particularly in δ13C. The orbital forcing was conferred to these rhythmic pelagic sediments via paleoclimatic and paleoceanographic changes as follows. Detrital input and marine carbonate production are recorded by the magnetic susceptibility and carbonate signals with strong precession cyclicity. Calcareous nannofossil analysis shows the omnipresence of coccoliths and debris of coccoliths in the marls and limestones, suggesting that the carbonate production was in largest part in situ. Precession index may exert oscillations in the antagonist marine surface productivity and detrital flux processes via solar radiation change. Oxygenation of the seafloor leading to redox cycles is detected in the manganese signal and supported by the δ13C record, with a strong expression of the obliquity. Finally, paleotemperature variations were deduced from the δ18O record, although this latter has been in part perturbed by diagenesis.
... A 'floating' timescale was then constructed for the KCF using the interpreted obliquity cycles (38 kyr) as a basis for tuning. These authors reported only weak evidence for short eccentricity cycles (∼100 kyr) and no evidence for the long eccentricity cycle (405 kyr), contrasting with the prominent expression of eccentricity-scale cyclicity in other timeequivalent Jurassic successions (e.g., Strasser, 2007; Boulila et al., 2008). Sequence stratigraphy has been described in detail for the KCF, but inconsistently. ...
... km/Myr, virtually the same as the 30 km/Myr assumed in GTS2004. For M24 and M25, cyclostratigraphic data from Boulila et al. (2008) indicate a spreading rate of 32.46 km/Myr (see text for details). actually been designated as sequence boundaries (e.g., Km1-5 in Taylor and Sellwood, 2002, theirFig. ...
... InFig. S8 in the Appendix, we display the extent of the problem in the lowermost 80 m of the KCF, where recognizable signal is lost from 540 m to 580 m. Boulila et al. (2008) used cyclostratigraphy to estimate a total duration of 1.35 Myr for the combined platynota + hypselocyclum + divisum (Tethyan) ammonite zones at La Méouge (SE France). According to GTS2004, these three zones correspond approximately to the upper half of the cymodoce zone and lower half of the mutabilis zone (seeTable 1); the KCF-estimated duration for this interval is 0.58 Myr, i.e., less than half of the Tethyan estimate. ...
The Late Jurassic Kimmeridge Clay Formation (KCF) is an economically important, organic-rich source rock of Kimmeridgian–Early Tithonian age. The main rock types of the KCF in Dorset, UK, include grey to black laminated shale, marl, coccolithic limestone, and dolostone, which occur with an obvious cyclicity at astronomical timescales. In this study, we examine two high-resolution borehole records (Swanworth Quarry 1 and Metherhills 1) obtained as part of a Rapid Global Geological Events (RGGE) sediment drilling project. Datasets examined were total organic carbon (TOC), and borehole wall microconductivity by Formation Microscanner (FMS). Our intent is to assess the rhythmicity of the KCF with respect to the astronomical timescale, and to discuss the results with respect to other key Late Jurassic geological processes. Power spectra of the untuned data reveal a hierarchy of cycles throughout the KCF with ∼ 167 m, ∼ 40 m, 9.1 m, 3.8 m and 1.6 m wavelengths. Tuning the ∼ 40 m cycles to the 405-kyr eccentricity cycle shows the presence of all the astronomical parameters: eccentricity, obliquity, and precession index. In particular, ∼ 100-kyr and 405-kyr eccentricity cycles are strongly expressed in both records. The 405-kyr eccentricity cycle corresponds to relative sea-level changes inferred from sequence stratigraphy. Intervals with elevated TOC are associated with strong obliquity forcing. The 405-kyr-tuned duration of the lower KCF (Kimmeridgian Stage) is 3.47 Myr, and the upper KCF (early part of the Tithonian Stage, elegans to fittoni ammonite zones) is 3.32 Myr. Two other chronologies test the consistency of this age model by tuning ∼ 8–10 m cycles to 100-kyr (short eccentricity), and ∼ 3–5 m cycles to 36-kyr (Jurassic obliquity). The ‘obliquity-tuned’ chronology resolves an accumulation history for the KCF with a variation that strongly resembles that of Earth's orbital eccentricity predicted for 147.2 Ma to 153.8 Ma. There is evidence for significant non-deposition (up to 1 million years) in the lowermost KCF (baylei–mutabilis zones), which would indicate a Kimmeridgian/Oxfordian boundary age of 154.8 Ma. This absolute calibration allows assignment of precise numerical ages to zonal boundaries, sequence surfaces, and polarity chrons of the lower M-sequence.
... Among all, one of the widest currently used pro y is magnetic susceptibility (MS) due to its rapid, low-cost, and nondestructive data acquisition (e.g., Kodama and Hinnov, 2014;Li et al., 2019a). Since its precursor studies, MS was proven to be an effective and reliable pro y for cyclostratigraphy, particularly when applied to marllimestone successions (Boulila et al., 2008a(Boulila et al., , 2008b(Boulila et al., , 2008c. ...
... Low-field mass normalized magnetic susceptibility (χ, hereafter MS) is e tensively used as a paleoclimate pro y for cyclostratigraphic analyses since it is a rapid, non-destructive, and low-cost method (Kodama and Hinnov, 2014). Besides, it is considered as a reliable pro y for resolving astroclimatic cycles in mi ed carbonate-clay successions; increased susceptibility implies a relative increase of ferrimagnetic and or paramagnetic minerals associated to terrigenous detrital input (e.g., Boulila et al., 2008aBoulila et al., , 2008bBoulila et al., , 2008cKodama and Hinnov, 2014;Li et al., 2019a). The MCA interval that e tends from 58 to 72 msl has MS data available with ~5 cm resolution (Savian et al., 2014). ...
During the middle Eocene to early Oligocene Earth transitioned from a greenhouse to an icehouse climate state. The interval comprises the Middle Eocene Climatic Optimum (MECO; ~40 Ma) and a subsequent long-term cooling trend that culminated in the Eocene-Oligocene transition (EOT; ~34 Ma) with the Oi-1 glaciation. Here, we present a refined calcareous nannofossil biostratigraphy and an orbitally tuned age model for the Monte Cagnero (MCA) section spanning the middle Eocene to the early Oligocene (~41 to ~33 Ma). Spectral analysis of magnetic susceptibility (MS) data displays strong cyclicities in the orbital frequency band allowing us to tune the identified 405 kyr eccentricity minima in the MS record to their equivalents in the astronomical solution. Our orbitally tuned age model allows us to estimate the position and duration of polarity chrons (C18 to C13) and compare them with other standard and orbitally tuned ages. We were also able to constrain the timing and duration of the MECO event, which coincides with a minimum in the 2.4 Myr and 405 kyr eccentricity cycles. Our study corroborates the previous estimated age for the base of the Rupelian stage (33.9 Ma) and estimates the base of the Priabonian stage in the MCA section to be at 37.4 Ma. Finally, calcareous nannofossils with known paleoenvironmental preferences suggest a gradual shift from oligotrophic to meso-eutrophic conditions with an abrupt change at ~36.8 Ma. Besides, nannofossil assemblages suggest that enhanced nutrient availability preceded water cooling at the late Eocene. Altogether, this evidence points to a poorly developed water column stratification prior to the cooling trend.
... The Kimmeridge Clay succession of southern England and northern France is one such succession in which orbital forcing has been considered to have been a major driver of the deposition sequences present. Huang et al. (2010) noted that the c. 405-kyr eccentricity cycle plays a major role in controlling the transgressive/regressive cyclicity observed in the Kimmeridge Clay (see also Boulila et al., 2008aBoulila et al., ,b,c, 2010Simmons, 2012). ...
... For example, PlioceneÀPleistocene eustasy was considered from sections in the equatorial Atlantic, the Pacific, and the Mediterranean (Lourens and Hilgen, 1997). In addition, Jurassic sections were evaluated from outcrops in France (Boulila, 2008;Boulila et al., 2008aBoulila et al., ,b,c, 2010. The Early Jurassic was separately reviewed by Boulila et al. (2014) and Boulila and Hinnov (2017). ...
Isolation of the eustatic signal from the sedimentary record remains challenging, yet much progress is being made toward understanding the timing, magnitude, and rate of eustasy on both long-term and short-term scales throughout the Phanerozoic. Long-term eustasy is primarily driven by a number of factors relating to plate tectonics. The magnitude and rate of short-term eustatic change strongly suggests glacio-eustasy as the key driving mechanism, even in episodes of the Earth’s history often typified as having “greenhouse” climates. This notion is, in turn, supported by a growing body of both direct and proxy evidence for relatively substantial polar glaciation in many periods of the Earth’s history (with the possible exception of the Triassic). An understanding of eustasy is important for the development of the geologic time scale because it contributes to the sequence stratigraphic organization of sedimentary successions (including chronostratigraphic reference sections) and helps to understand the often incomplete nature of the geologic record. The integration of eustasy with our evolving knowledge of Earth systems science (e.g., paleoclimate evolution, orbital forcing of sedimentary systems, geochemical evolution of the oceans, and biological evolutions and extinctions) will help to provide the tools to develop a context for the subdivisions of the geologic
time scale.
... A transgression occurs between the maximum regression surface at the top of the quartz-bearing sequence and the maximum flooding surface with the bituminous limestones. Boulila et al. (2008Boulila et al. ( , 2010 have also discussed the reduction of clay content and increase in carbonate content in Kimmeridgian pelagic successions as being indicative of transgression. Having established the position of the MRS and the MFS in the succession, it is possible to then count the number of orbital forcing cycles that occur between them, in order to calculate the duration of the transgression. ...
... The coincidence of climatic change and eustasy is further amplified by the apparent concurrence of eustatic events and orbital forcing cycles (for example Immenhauser and Mathews, 2004;Immenhauser, 2005;Gale et al., 2002;Boulila et al., 2008Boulila et al., , 2010. ...
: The history of stratigraphic correlation and the subdivision of geological time have long been associated with understanding changes in sea level. Sequence stratigraphy can be summarized as an attempt to subdivide sedimentary successions (either at the local basinal scale or at the global scale) into packages relating to changes in relative sea level. Such sequences, being rooted in time-stratigraphy, can, for example, be the basis for correlation and mapping of facies. There is a growing set of observations that demonstrate the synchronicity of some sea-level changes globally, leading to the establishment of global eustatic models. These, in turn, require an explanation for the driving mechanisms of eustatic change. Growing direct and proxy evidence suggests a link between climatic change and eustasy and hence the presence of glacio-eustasy, even in “greenhouse” times. There are strong links between sequence stratigraphy and the geological time scale. Sequence stratigraphic surfaces, especially correlative conformities, may form “natural boundaries” to stages and are associated with biostratigraphic events. Such an approach would mark a return to the criteria upon which stages were originally defined.
... (A) Raw MS variations, the numbers show precession index cycles expressed in both lithology and MS. In addition, MS detects very well lower frequency (405 kyr eccentricity) cycles, which are strongly expressed in MS maxima of the marls, so in clay content (see also Boulila et al., 2008a their Figs. 2 and 5B). Each 405 kyr eccentricity cycle contains almost 20 marl–limestone couplets (see Boulila et al., 2008a,b for time-series analysis). ...
... In addition, MS detects very well lower frequency (405 kyr eccentricity) cycles, which are strongly expressed in MS maxima of the marls, so in clay content (see also Boulila et al., 2008a their Figs. 2 and 5B). Each 405 kyr eccentricity cycle contains almost 20 marl–limestone couplets (see Boulila et al., 2008a,b for time-series analysis). (B) MS filtered to precession 'P1' band and the extracted envelopes by Hilbert transform. ...
In their comment on our paper (Boulila S. et al. 2010 — Orbitally forced climate and sea-level changes in the Paleoceanic Tethyan domain, marl–limestone alternations, Lower Kimmeridgian, SE France, Palaeogeog. Palaeoclim. Palaeoecol., 292, 57–70), Mattioli and co-authors (E. Mattioli et al., Comment on "Orbitally forced climate and sea-level changes in the Paleoceanic Tethyan domain (marl–limestone alternations, Lower Kimmeridgian, SE France) " by S. Boulila, M. de Rafélis, L. A. Hinnov, S. Gardin, B. Galbrun, P.-Y. Collin [Palaeogeography Palaeoclimatology Palaeoecology 292 (2010) 57–70], Palaeogeography Palaeoclimatology Palaeoecology, this issue) criticize our depositional model of Lower Kimmeridgian marl-limestone alternations in the Vocontian Basin (SE France) and contest the nannofossil contribution to the build-up of micritic limestones. The model that we proposed links maxima of orbitally forced insolation with high sea-level, weaker continental erosion, and reduced detrital input, and insolation minima to low sea-level, increasing erosion of detrital materials and their transport to the basin. This involves a competition between multiple variable fluxes, and is supported by a multi-proxy study (magnetic susceptibility, weight percent carbonate, manganese content coupled with cathodoluminescence analysis, oxygen and carbon stable isotopes, and calcareous nannofossil analysis) on a 8.5-m thick interval from a ~ 40 m-thick section at Châteauneuf-d'Oze (SE France). This differs substantially from previous models suggesting that detrital input to this part of the Vocontian Basin constitutes ‘background noise’, and that the main mechanism inducing the marl–limestone rhythms was orbitally forced carbonate mud export from the Jura Platform.
... Several studies have proposed that MS is a correlation tool and generally records paleoclimatic variations (influencing or not eustacy) in sedimentary rocks (Boulila et al., 2010(Boulila et al., , 2008Da Silva et al., 2015;Ellwood et al., 2000;Font et al., 2011;Mead et al., 1986;Nowaczyk et al., 2002;Pas et al., 2019;Stage, 2001;Vanderaveroet et al., 1999;Whalen and Day, 2010;Wouters et al., 2019). This inference comes from the relationship between MS trends and oxygen isotopes in Pleistocene sections (Robinson, 1986) and astronomicallydriven Milankovitch cycles in Devonian and Jurassic sequences (Boulila et al., 2010;Da Silva et al., 2020Ellwood et al., 2015). ...
Magnetic susceptibility (MS) variations are commonly attributed to eustatic and/or climatic changes that impact the delivery of fine-grained detrital magnetic minerals. However, the mechanism responsible for sourcing magnetic minerals from land to the ocean is not fully understood. Bulk mineralogy, Rietveld refinements of powder XRD patterns, and whole-rock geochemistry, combined with a MS investigation across a ∼290 m-thick Upper Cretaceous/Paleogene sedimentary sequence at Erguita, Morocco, imply that iron is exclusively detrital in origin. Moreover, MS fluctuations occurred independently from depositional setting and sea-level variations. Rock magnetism investigations further show that a complex assemblage of ferromagnetic sensu lato minerals is recorded in the Erguita sedimentary section, and a proportion of more or less oxidized magnetite supplied to the depositional setting controls the MS variations. This study chronicles that the weathering of the Anti-Atlas crystalline basement led to the supply of detrital Fe-bearing phyllosilicates and ferromagnetic (sensu lato) Fe-oxides to the eastern passive margin of the Atlantic Ocean from the Late Cretaceous to the mid-Paleogene. Higher weathering intensity drove up the detrital magnetic material in all lithologies, which, in turn, increased the MS signal. Importantly, this model nicely coincides with the climatic upheavals of the Paleogene. We propose that this unrecognized link between MS and climate-driven weathering intensity is paramount to unraveling the origin of the low MS interval below the Cretaceous-Paleogene boundary. Climate cooling resulting in reduced weathering rather than a global acidification triggered by Phase 2 of Deccan volcanism could help explain the MS trend at that time.
... Numerous quantitative studies of time series of basinal Kimmeridgian deposits have demonstrated astronomical forcing (House 1985;Waterhouse 1995;Weedon et al. _####_ Page 2 of 18 2004; Boulila et al. 2008). Because basinal facies commonly are deposited relatively continuously, they are excellent repositories of global climate signals. ...
We document for the first time that downhole gamma ray logs and carbonate cycles in the upper Jurassic (Kimmeridgian) Jubaila and superjacent lower Arab platform carbonates (up to 240 m thick) in Saudi Arabia exhibit Milankovitch forcing. The succession consists of a lower carbonate mud-prone succession (deeper shelf) with storm beds and hardgrounds arranged in upward-deepening units. The overlying ramp slope interval has intraclastic–oncoidal rudstone and lime mudstone/wackestone, while the upper grain-dominated middle and inner ramp facies are upward-shallowing parasequences of stromatoporoid carbonates, peloid grainstone–packstone, and beneath anhydrite strata, ooid grainstone, and microbial dololaminite. Gamma ray signal in the Jubaila–lower Arab interval is related to a fine siliclastic component in the carbonates and is the highest near parasequence tops or associated floodbacks. The accumulation rates were determined by assessing the correlation for various sedimentation rates against an astronomical model and tested against a null hypothesis of no astronomical forcing. Detrended gamma ray logs were tuned using either the 405 or 100 kyr cycle, and the resultant spectral peaks are compatible with the astronomical solution for the Upper Jurassic. The ~70 m (~1 Myr) long-obliquity modulation cycle formed the third-order sequences. Long eccentricity (405 kyr) and short eccentricity (~100 kyr) formed the fourth-order sequences/parasequence sets, while obliquity and precession formed parasequences. Milankovitch forcing was responsible for ~50% of the gamma ray signal, the remainder being non-Milankovitch noise. This study shows that downhole gamma ray logs in platform carbonates are a potentially important record of global climate changes.
... Factors affecting sedimentation and creating depositional sequences have been traditionally divided into allocyclic and autocyclic factors (Aigner, 1985a, b;Strasser, 1991;Hilgen et al., 2000Hilgen et al., , 2003Van Couvering et al., 2000;Lourens et al., 2004;Hilgen et al., 2006;Hüsing et al., 2007;Boulila et al., 2008aBoulila et al., , 2008b2008c, 2010a2010b;Huret et al., 2011). Indeed, the mineralogy of evaporite minerals depends on the composition of the initial solution, commonly known as a brine. ...
... Several studies have successfully identified the imprint of astronomical climate forcing in Paleozoic records and calibrated portions of the geologic timescale (for a review on this topic, see Hinnov 2013). Magnetic susceptibility data are commonly used for this type of analysis in Cenozoic and Mesozoic rocks (Shackelton et al. 1995;Weedon et al. 1999;Boulila et al. 2008aBoulila et al. , 2008bHinnov 2013) and, more recently, have been applied to sequences of Paleozoic age (De Vleeschouwer et al. 2012a, 2012b, 2014aDa Silva et al. 2013;Wu et al. 2013). ...
... Changes in mineralogical and faunal changes (ratio of pelagic organisms) between limestone beds and marlstone interbeds (DARMEDRU et al., 1982) indicated environmental changes possibly under astronomical control due to frequencies close to those of the terrestrial orbit (RIO et al., 1989), following the MILANLOVITCH theory of climate changes in the Quaternary. Later, the development of FOURRIER transform analysis on such limestone-marl successions led to the emergence of a way to calibrate geological time (BOULILA et al., 2008(BOULILA et al., , 2010CHARBONNIER et al., 2013;MARTINEZ et al., 2013). In this respect, the VT is a good candidate, given that most of its Jurassic to Lower Cretaceous stratigraphic column pre-sents this primary alternating pattern. ...
... Factors affecting sedimentation and creating depositional sequences have been traditionally divided into allocyclic and autocyclic factors (Aigner, 1985a, b;Strasser, 1991;Hilgen et al., 2000Hilgen et al., , 2003Van Couvering et al., 2000;Lourens et al., 2004;Hilgen et al., 2006;Hüsing et al., 2007;Boulila et al., 2008aBoulila et al., , 2008b2008c, 2010a2010b;Huret et al., 2011). Indeed, the mineralogy of evaporite minerals depends on the composition of the initial solution, commonly known as a brine. ...
Integrated sedimentological studies, diagenesis, sequential analysis and clay mineralogy on the Upper Paleocene rocks in Tamerza area provide important information on the reconstruction of the depositional basin, cyclicity, and paleoclimatic contexts. Facies analysis and petrographic studies have led to the recognition of nine facies that were deposited in three facies belts: Sebkha, inner ramp and outer ramp summarized in a carbonate ramp model: Homoclinal ramp under an arid climate.The upward and lateral changes in thickness and composition show a general regressive trend that records a transition from an outer ramp to Sebkha, creating different types of confinement. The facies stacking patterns constitute several kinds of meter-scale, shallowing-upward cycles. Nine different types of depositional cycles and several models of Sebkha sequences were defined. These different types of facies, characterized within the Thelja Formation, compose seven depositional sequences, mainly made of carbonates, marls and evaporates. Detailed multi approach analysis provides important information on evaporitic sequence stratigraphy.In carbonates beds, the diagenetic analysis provides an overview and chronology of diagenetic processes. A particular attention was paid to early stage cementation which enables us to characterize better the depositional environments. In addition to cementation, other features define the diagenetic history.X-ray diffraction reveals the presence of smectite suggesting an arid climate. Moreover, the clinoptilolite and the frequency of primary dolomite indicate different degrees of confinement.The seven depositional sequences showing a hierarchical organization of many cycles, as described above, suggested that eustatic sea level oscillations caused by cyclic perturbations of the Earth's orbit play a fundamental role in determining the formation of hierarchical cyclic rhythmicity.
... Certains privilégient les effets diagénétiques (Ricken 1986), d'autres l'export à partir des plates-formes carbonatées (Colombié et Strasser 2003, Reboulet et al. 2003, d'autres enfin les variations de la productivité planctonique primaire (Cotillon et al. 1980;Darmedru et al., 1982;Boulila et al. , 2011. Le développement des théories astro-climatiques (cycles de Milankovitch) fait que ces séries sont maintenant utilisées pour réaliser un calibrage temporel indépendant des méthodes classiques (Boulila et al. 2008, Charbonnier et al. 2013. A, alternance équilibrée (Hauterivien), alternance à dominante calcaire, banc épais/interbanc mince (Barrémien supérieur) ; C, passage d'une alternance équilibrée à une alternance à dominante marneuse où les bancs sont seulement marqués par des différences légères de teneur en carbonate et de couleur au sein des marnes (Clansayésien) ; D, alternance à dominante marneuse dans les Marnes Bleues albiennes où l'alternance est à peine soulignée par un rubannement de couleur ténu. ...
... Interestingly, highresolution cyclostratigraphic correlation (Section 2.3.2) allowed the detection and quantification of the hiatuses, that occur mainly within the questionable interval. Potential hiatuses have also been detected in the Lower Kimmeridgian, using a cyclostratigraphic correlation, while no sedimentary indicators are seen in the field because of the relatively homogeneous facies (Boulila et al., 2008a). Another evidence for precession forcing from the Orpierre section, which again disagrees with the hypothesis of obliquity driven couplets , is the documentation of the short eccentricity modulations. ...
The Valanginian sediments outcropping in the Vocontian Basin (SE France) exhibit striking marl-limestone alternations, which were formed under the influence of orbital forcing and which have served for geochronological and paleoenvironmental studies. Previous studies have suggested an obliquity forcing during the Late Valanginian interval, reflecting specific environmental conditions such as polar ice. Using a cyclostratigraphic correlation of previously studied sections and performing time-series analysis on the most complete Late Valanginian interval we argue that the climatic precession cycle is the primary driver of these marl-limestone alternations. In addition, we highlight the modulation of the precession by the ~ 100 and 405 kyr eccentricity cycles. We suggest that the cyclostratigraphic misinterpretation (i.e., obliquity-forcing hypothesis) results mainly from poorly preserved 405 kyr eccentricity cycles, due to local hiatuses and/or “missed beats”. This study shows the potential of cyclostratigraphic correlations for the detection and quantification of differential hiatuses and/or “missed beats” within intrabasinal sequences, hence providing constraints on cyclostratigraphic interpretations. The recorded 405 kyr eccentricity cycle is of prominent amplitude, and controlled the fourth-order sea-level sequences. These latter are faithfully detected through cyclostratigraphically inferred sedimentation rate. Finally, we show that the well-known, pronounced lithostratigraphic markers/intervals in the basin were orbitally paced by the 405 kyr eccentricity extrema. This is a good argument for the strong impact of this cyclicity on the sedimentary processes, especially during greenhouse periods.
... Certains privilégient les effets diagénétiques (Ricken 1986), d'autres l'export à partir des plates-formes carbonatées (Colombié et Strasser 2003, Reboulet et al. 2003, d'autres enfin les variations de la productivité planctonique primaire (Cotillon et al. 1980;Darmedru et al., 1982;Boulila et al. , 2011. Le développement des théories astro-climatiques (cycles de Milankovitch) fait que ces séries sont maintenant utilisées pour réaliser un calibrage temporel indépendant des méthodes classiques (Boulila et al. 2008, Charbonnier et al. 2013. A, alternance équilibrée (Hauterivien), alternance à dominante calcaire, banc épais/interbanc mince (Barrémien supérieur) ; C, passage d'une alternance équilibrée à une alternance à dominante marneuse où les bancs sont seulement marqués par des différences légères de teneur en carbonate et de couleur au sein des marnes (Clansayésien) ; D, alternance à dominante marneuse dans les Marnes Bleues albiennes où l'alternance est à peine soulignée par un rubannement de couleur ténu. ...
... The 100-kyr cycles are visually less well expressed than in the platform sections. However, Boulila et al. (2008) performed a cyclostratigraphic analysis including the Châteauneuf-d'Oze section and confirmed the presence of the 100-kyr as well as the 400-kyr eccentricity cycles. ...
The continuous and well exposed sections of the Upper Ordovician on the Upper Yangtze Platform were surveyed and sampled for δ¹³C and δ¹⁸O isotope and conodont fossils. The geochem-stratigraphic work in the Pagoda Formation has resulted in the recognition of a positive δ¹³C excursion, the Pagoda Positive δ¹³C Excursion (PPCE). The PPCE is a distinctive positive excursion occurring in the Middle-Late Katian, consists of three minor excursions ranging from 1.5‰ to 3‰, which has been identified in all the study sections on the Upper Yangtze Platform. The PPCE interval ranges through the conodont Hamarodus brevirameus and Protopandeordus inscrulptus conodont zones in ascending order, which indicates that the PPCE develops in the Middle-Late Katian of the Late Ordovician, while the Guttenberg δ¹³C Excursion (GICE) in the Baltoscandia and America extended from the Late Sandbian to the Early Katian. Spectral analysis of high-resolution magnetic susceptibility (MS) logs for the four study sections shows consistent wavelengths of ca. 2.0, 0.5, 0.18 and 0.15 m. The outcrop depth-series were tuned using 405-kyr long-eccentricity cycles and the astronomical tuning yields the duration of 3.7 to 4.4 myr for the PPCE event in different sections. This is the first documentation of the PPCE event on the Upper Yangtze Platform according to the geochemo-bio-cyclostratigraphy evidences, being identified within all portions of this platform in South China. It revised the previous description of the positive δ¹³C excursion of the Pagoda Formation on the Upper Yangtze Platform. The trigger of the PPCE was also briefly discussed in this paper.
Several research works have demonstrated that climate variations are consistent with quasi-periodic orbital parameters, particularly ∼1.2-Myr obliquity amplitude modulation cycle has been demonstrated as a controlling factor of glacio-eustasy sequence formation in icehouse periods. In the current research, we have studied the glacio-eustasy third-order sequences of Late Miocene to Pliocene age in Qiongdongnan Basin (QDNB), South China Sea and identified a prominent ∼1.2-Myr periodicity in a 41kyr-tuned gamma ray series of Well LS33-1-1. In the current research, we developed an astronomical time scale (ATS) for Late Miocene to Pliocene in QDNB and conducted cyclostratigraphic analyses on Huangliu and Yinggehai Formations in Well LS33-1-1 using high-resolution natural gamma-ray (GR) data. Time-series analyses on GR data revealed rich Milankovitch frequency band series and ∼5.6, 3.8 and 6.0 m cycles were respectively filtered for three segments in depth domain which presented direct correlation with 41-kyr obliquity cycles in La2004 solution. In this work, foraminiferal and calcareous nannofossil biozones in South China Sea were selected as age markers for tuning. Correlation coefficient analysis was applied to quantitatively measure the fitting of witnessed sedimentary cycles to astronomical periods and provide a possible range for sedimentation rate. Also, we developed a sedimentary noise model to detect high-resolution sea-level variations under the control of orbital forcing which were supported by previous third-order eustasy variations. In addition, six third-order sequences were identified in the range of Late Miocene to Pliocene representing astronomical forcing through both ∼1.2-Myr filtering of DYNOT model and ∼1.2-Myr modulation of obliquity amplitude based on sedimentary noise modeling. Finally, it was concluded that the ∼1.2-Myr cycle was the most important driving force for sequence development and third-order sea-level changes.
The Eocene–Oligocene Transition (EOT) marks the onset of the Antarctic glaciation and the switch from greenhouse to icehouse climates. However, the driving mechanisms and the precise timing of the EOT remain controversial mostly due to the lack of well-dated stratigraphic records, especially in continental environments. Here we present a cyclo-magnetostratigraphic and sedimentological study of a ∼ 7.6 Myr long lacustrine record spanning the late Eocene to the earliest Oligocene, from a drill core in the Rennes Basin (France). Cyclostratigraphic analysis of natural gamma radiation (NGR) log data yields duration estimates of Chrons C12r through C16n.1n, providing additional constraints on the Eocene timescale. Correlations between the orbital eccentricity curve and the 405 kyr tuned NGR time series indicate that 33.71 and 34.10 Ma are the most likely proposed ages of the EO boundary. Additionally, the 405 kyr tuning calibrates the most pronounced NGR cyclicity to a period of ∼1 Myr, matching the g1–g5 eccentricity term, supporting its significant expression in continental depositional environments, and hypothesizing that the paleolake level may have behaved as a low-pass filter for orbital forcing. Two prominent changes in the sedimentary facies were detected across the EOT, which are temporally equivalent to the two main climatic steps, EOT-1 and Oi-1. We suggest that these two facies changes reflect the two major Antarctic cooling/glacial phases via the hydrological cycle, as significant shifts to drier and cooler climate conditions. Finally, the interval spanning the EOT precursor glacial event through EOT-1 is remarkably dominated by obliquity. This suggests preconditioning of the major Antarctic glaciation, either from obliquity directly affecting the formation/(in)stability of the incipient Antarctic Ice Sheet (AIS), or through obliquity modulation of the North Atlantic Deep Water production.
The long-term variations of the orbital and rotational parameters of the Earth are the key ingredients for the insolation forcing in the Milankovitch theory. This chapter describes the main aspects of these variations, concentrating on the aspects that are currently recovered in the stratigraphic record. A special emphasis is given to the very long periodic terms (>1 Myr period) that modulate the astronomical solutions and that are essential for understanding the chaotic behavior of the solar system.
Detailed analysis of the Chouabine Formation exposed in the western part of the Gafsa basin, southern Tunisia shows the presence of six principal facies. Vertical and lateral evolution of facies showed a gradual transition from intertidal to circatidal environments summarized in a carbonate ramp model: homoclinal ramp under the control of synsedimentary faults and, episodically, swept by upwelling currents. Phosphogenesis indicates that early diagenetic organic matter degradation can be a source of authigenic phosphate during the first stage of transgression. The concentration of phosphate was under the control of hydrodynamic processes as testified by angular unconformities, erosive surfaces, current structures and reworked clasts. Phosphate genesis seems under the control of sea level changes. It begins with the upper LST where diagenetic processes allow the dissolution of fauna remains (bones and fish teeth) and a prelude precipitation of authigenic phosphates. During the TST stage, transgression was associated with upwelling currents, which enable faunal blooming. Phosphatization, which requires suboxic conditions, occurs in shells or in troughs, preferentially in infratidal to circatidal environments. During the HST, the shift of the sea level leads to a sea level fall and, thus, to a basinward migration of depositional environments. Accordingly, infratidal environment becomes intertidal. A detailed analysis of facies in the field shows the fossilization of current structures (cross-bedding structures capped by planar laminations and sheet deposits). Tidal currents sweep the deposits and allow phosphate concentration and deposition in troughs. The model proposed does not necessitate major rises and falls of the relative sea level to produce economic phosphorite, but emphasizes the interplay of both autocyclic and allocyclic controls to form phosphate strata during the highstand system tract.
: Ammonites exploded in diversity after the end-Triassic near-extinction of their precursor taxa and have been the main tool for global correlation for nearly two centuries. The Pangea super-continent split during mid-Jurassic into Laurasia and Gondwana separated by a Tethys-Atlantic seaway. Late Jurassic organic-rich shales would later provide nearly half of our oil-gas source rocks. Dinosaurs dominated the land surface, and their cousins took to the air.
: The Milankovitch theory that quasi-periodic oscillations in the Earth-Sun position have induced significant 10 4 -10 6 year variations in the Earth’s stratigraphic record of climate is widely acknowledged. This chapter summarizes the Earth’s astronomical parameters, the nature of astronomically forced solar radiation, fossil astronomical signals in the stratigraphic record, and the use of these signals in calibrating geologic time.
The patterns of marine magnetic anomalies for the Late Cretaceous through Neogene (C-sequence) and Late Jurassic through Early Cretaceous (M-sequence) have been calibrated by magnetostratigraphic studies to biostratigraphy, cyclostratigraphy, and a few radiometrically dated levels. The geomagnetic polarity time scale for the past 160 myr has been constructed by fitting these constraints and a selected model for spreading rates. The status of the geomagnetic polarity time scale for each geological period is summarized in Chapters 11–22 as appropriate. PRINCIPLES Magnetic field reversals and magnetostratigraphy The principal goal of magnetostratigraphy is to document and calibrate the global geomagnetic polarity sequence in stratified rocks and to apply this geomagnetic polarity time scale for high-resolution correlation of marine magnetic anomalies and of polarity zones in other sections. The basis of magnetostratigraphy is the retention by rocks of a magnetic imprint acquired in the geomagnetic field that existed when the sedimentary rock was deposited or the igneous rock underwent cooling. The imprint most useful for paleomagnetic directions and magnetostratigraphy is recorded by particles of iron oxide minerals. Most of the material in this chapter is updated from summaries in Harland et al. (1990) and Ogg (1995). Excellent reviews are given in Opdyke and Channell (1996) for magnetostratigraphy and McElhinny and McFadden (2000) for general paleomagnetism.
The recurrence of the same types of sequence stratigraphic surface through geologic time defines cycles of change in accommodation or sediment supply, which correspond to sequences in the rock record. These cycles may be symmetrical or asymmetrical, and may or may not include all types
of systems tracts that may be expected within a fully developed sequence. Depending on the scale of observation, sequences and their bounding surfaces may be ascribed to different hierarchical orders. Stratal stacking patterns combine to define trends in geometric character that include
upstepping, forestepping, backstepping and downstepping, expressing three types of shoreline shift: forced regression (forestepping and downstepping at the shoreline), normal regression (forestepping and upstepping at the shoreline) and transgression (backstepping at the shoreline). Stacking
patterns that are independent of shoreline trajectories may also be defined on the basis of changes in depositional style that can be correlated regionally. All stratal stacking patterns reflect the interplay of the same two fundamental variables, namely accommodation (the space available
for potential sediment accumulation) and sediment supply. Deposits defined by specific stratal stacking patterns form the basic constituents of any sequence stratigraphic unit, from sequence to systems tract and parasequence. Changes in stratal stacking patterns define the position and timing
of key sequence stratigraphic surfaces. Precisely which surfaces are selected as sequence boundaries varies as a function of which surfaces are best expressed within the context of the depositional setting and the preservation of facies relationships and stratal stacking patterns in that
succession. The high degree of variability in the expression of sequence stratigraphic units and bounding surfaces in the rock record means ideally that the methodology used to analyze their depositional setting should be flexible from one sequence stratigraphic approach to another. Construction
of this framework ensures the success of the method in terms of its objectives to provide a process-based understanding of the stratigraphic architecture. The purpose of this paper is to emphasize a standard but flexible methodology that remains objective.
The sensitivity of the amplitudes and frequencies in the development of the Earth's orbital elements involved in the astronomical theory of palaeoclimates (obliquity and climatic precession) to the Earth-Moon distance and consequently to the length of the day and to the dynamical ellipticity of the Earth is investigated for the last few billions of years. The influence of the stability of the fundamental frequencies of planetary motion is also discussed. -from Authors
DURING periods of time when the Earth supports ice caps, sea level
fluctuates periodically at intervals of 104-105
yr, with amplitudes of tens to more than 100 metres. These fluctuations
result from expansions and contractions of continental ice sheets that
occur in phase with the Milankovitch periodicities of the Earth's
orbit1,2. Smaller-amplitude sea-level fluctuations associated
with Milankovitch periodicities are also evident during warm periods,
such as the Late Triassic3-5, which lack strong evidence for
continental glaciation6. We argue here that, in times of
limited ice volume, periodic climate-induced changes in lake and
groundwater storage have the potential to produce small fluctuations in
sea level. This mechanism could contribute a small component of the
sea-level change observed in the Quaternary period, and may dominate the
Milankovitch eustatic sea-level signal during earlier periods with
limited ice volume6. We present evidence of contemporaneous
Milankovitch periodicities in Late Triassic lake sediments7
and sea-level fluctuation3-5 which support the causal link
between lake water storage and eustasy.
This book views the Earth's climate as a global system, by describing the evolution of climate throughout the past 600 million years, from the Cambrian to the Quaternary. Palaeoclimates are examined in terms of Cold and Warm modes--phases during which the Earth's climates were either relatively cool with ice forming in high latitudes or when high levels of CO2 led to "greenhouse" warmings and temperate floras and faunas inhabited polar regions. Evidence for climate changes, such as biological indicators, geochemical parameters, and the presence of ice, are compared between these modes. These studies have highlighted the crucial role of tectonics and continental distribution in governing ocean circulation, the distribution of sea ice, sea level changes and global temperature distribution. Orbital forcing and the carbon cycle are also shown as important influences, particularly on short term climatic variations.
Calcareous nannofossil stratigraphy has been investigated in six European land sections and at two Deep Sea Drilling Project Sites (391C and 534A) ranging from the Upper Kimmeridgian to the Lower Valanginian. Most of the sections contain a continuous record of the Jurassic-Cretaceous boundary interval, a time of rapid increase in nannofossil abundance and diversity and allow development of a revised nannofossil zonation scheme for this period. Numerous nannofossil lineages have been studied in detail and the results help to increase potential stratigraphic resolution in this interval. The proposed scheme consists of six zones which are units recognizable in all sections regardless of nannofossil preservation and eleven subzones determinable in all but the most poorly preserved material. Thirty-eight additional biohorizons are proposed based on the stratigraphy of the two DSDP sites. These can be accurately established only in moderately well-preserved material but spotty occurrences of these taxa in other sections may be stratigraphically useful.Most of the sections studied have been investigated magnetostratigraphically and the results of this study allow correlation between nannofossil zonation and the geomagnetic polarity time scale. Magnetostratigraphy indicates that many nannofossil events can be quite precisely determined and are not significantly time-transgressive. Finally, the magnetostratigraphic definitions of two stage boundaries are refined. The Kimmeridgian-Tithonian and Berriasian-Valanginian boundaries are placed within Chrons CM22n and CM15n respectively. Two new genera,Faviconus andUmbria, and seven new species are described:Umbria granulosa, Rhagodiscus nebulosus, Cretarhabdus octofenestratus, Faviconus multicolumnatus, Nannoconus infans, Nannoconus compressus andNannoconus wintereri. Eight subspecies and three taxonomic emendations are also described.
The origin of third-order depositional sequences remains debatable, and in many cases it is not clear whether they were controlled by tectonic activity and/or by eustatic sea-level changes. In Oxfordian and Berriasian-Valanginian carbonate-dominated sections of Switzerland, France, Germany and Spain, high-resolution sequence-stratigraphic and cyclostratigraphic analyses show that the sedimentary record reflects Milankovitch cyclicity. Orbitally induced insolation changes translated into sea-level fluctuations, which in turn controlled accommodation changes. Beds and bedsets formed in rhythm with the precession and 100-kyr eccentricity cycles, whereas the 400-kyr eccentricity cycle contributed to the creation of major depositional sequences. Biostratigraphical data allow the correlation of many of the 400-kyr sequence boundaries with third-order sequence boundaries recognized in European basins. This implies that climatically controlled sea-level changes contributed to the formation of third-order sequences. Furthermore, this cyclostratigraphical approach improves the relative dating of stratigraphic intervals.
À l'heure actuelle, peu de travaux concernent les épaisses séries calcaires soi-disant homogènes du Kimméridgien du Jura central. Ainsi, la stratigraphie comme les facteurs (tectonique, eustatisme, climat, production et accumulation de carbonates) qui déterminent la dynamique de la plate-forme sont respectivement mal définis voire inconnus. L'analyse sédimentologique détaillée, l’interprétation séquentielle et cyclostratigraphique du Kimméridgien du Jura central et des corrélations avec le Kimméridgien du Bassin vocontien aboutissent à un cadre stratigraphique précis et de haute-résolution, à la définition des principaux facteurs qui déterminent le développement de la plate-forme peu profonde du Jura au cours du Kimméridgien, et à l’établissement d’un modèle de formation des séquences de dépôt du Kimméridgien inférieur du Bassin vocontien. L’étude détaillée des faciès sédimentaires de trois coupes – Gorges du Pichoux, Gorges de Court, et Péry-Reuchenette – situées au Nord-Est de Bienne en Suisse permet d’établir un modèle de faciès et une interprétation séquentielle et cyclostratigraphique précise du Kimméridgien du Jura central. Les faciès sédimentaires sont relativement diversifiés, et correspondent principalement à des milieux de dépôt de plate-forme interne, très peu profonds, calmes et à salinité variable. Basés sur l’évolution au cours du temps des environnements de dépôt, de l’épaisseur des bancs et des discontinuités, quatre ordres de séquences de dépôt sont définis: les séquences élémentaires, de court terme, de moyen terme et de long terme. Les différents types de séquences de dépôt sont hiérarchiquement empilés, et leurs rapports suggèrent que la dynamique de la plate-forme peu profonde du Jura était au Kimméridgien en partie contrôlée par les variations des paramètres orbitaux de la Terre. En l’absence de marqueurs biostratigraphiques précis, qui sont indispensables pour dater les intervalles stratigraphiques et confirmer l’hypothèse d’un contrôle orbital sur la sédimentation, les coupes du Jura central sont corrélées avec trois coupes du Bassin vocontien parfaitement datées par ammonites. L’interprétation sédimentologique, séquentielle et cyclostratigraphique de trois coupes – Montagne de Crussol, Châteauneuf d’Oze, et Gorges de la Méouge – situées dans le Bassin vocontien en France, aboutit à la définition de plusieurs ordres de séquences de dépôt, qui correspondent aux différents types de séquences observés dans le Kimméridgien du Jura central. Les similitudes qui existent entre l’interprétation séquentielle et cyclostratigraphique des coupes du Jura et du Bassin vocontien permettent à partir d’un niveau repère de corréler les coupes de la plate-forme et du bassin. À partir de ces corrélations de haute résolution, le cadre chronostratigraphique défini pour le Kimméridgien du Jura central et du Bassin vocontien est comparé à celui qui est proposé par HARDENBOL et al. (1998) pour le Kimméridgien du domaine téthysien. Cinq limites de séquences de troisième ordre sont définies qui correspondent à cinq limites de séquences de moyen terme définies dans le Jura et dans le Bassin vocontien. La durée des séquences de troisième ordre qui est donnée par HARDENBOL et al. (1998) est divisée par le nombre de séquences élémentaires qui est compté pour le même intervalle de temps dans la coupe des Gorges de la Méouge, qui est la plus éloignée de la plate-forme du Jura. D’après ces calculs, la durée d’une séquence élémentaire est approximativement égale à la période du cycle de la précession (i.e. 20 ka). De plus, les séquences de court terme sont généralement composées de 5 séquences élémentaires, et les séquences de moyen terme contiennent 4 séquences de court terme. En supposant qu’une séquence élémentaire dure 20 ka, la durée des séquences de court terme et de moyen terme correspond respectivement à la période du premier et du deuxième cycle de l’excentricité (i.e. 100 et 400 ka). De même, la durée des séquences de long terme varie entre 800 ka et 1,2 Ma, et correspond au troisième ordre de VAIL et al. (1991). Enfin, l’intervalle étudié comprend 32 séquences de court terme, qui représentent une durée totale de 3,2 Ma. La durée du Kimméridgien obtenue à partir des données radiométriques est égale à 3,12 Ma (GRADSTEIN et al., 1994; 1995; HARDENBOL et al., 1998). Par conséquent, la durée calculée à partir de l’interprétation cyclostratigraphique des coupes du Jura et du Bassin vocontien correspond aux résultats obtenus par ailleurs, et confirme la validité de la méthode employée dans ce travail. L’analyse des isotopes stables de l’oxygène et du carbone et des éléments traces (Sr, Mg, Na, Fe et Mn) a été réalisée sur la coupe des Gorges du Pichoux pour confirmer les corrélations entre la plate-forme et le bassin. La relation entre les résultats obtenus dans ce travail et ceux qui sont publiés pour les coupes de Châteauneuf d’Oze et de la Méouge (DE RAFÉLIS, 2000) n’est à priori pas évidente. Néanmoins, les variations du ∂13C et des concentrations en éléments traces sont cohérentes avec l’évolution de la plateforme du Jura au cours du Kimméridgien, et offrent de très intéressantes perspectives de recherche. Les corrélations des coupes du Jura central mettent en évidence deux parties principales. La partie inférieure s’étend de la zone d’ammonites à Platynota à la zone à Acanthicum. Elle est essentiellement composée de bancs calcaires fins à moyennement épais, et présente une quantité relativement importante de terrigènes (argiles, quartz et charbon) et de nombreux indices d’émersion. La partie supérieure comprend les zones d’ammonites à Eudoxus et à Beckeri. Elle se distingue par une grande proportion de bancs calcaires épais, par la quasi-disparition des terrigènes et des indices d’émersion, et par le développement des algues vertes. La limite entre ces deux parties correspond à la plus importante augmentation d’espace d’accommodation enregistrée au cours du Kimméridgien dans le Jura central. Par ailleurs, la partie inférieure se compose de deux parties distinctes qui sont interprétées comme des séquences de dépôt de long terme. La première séquence est comprise entre les zones d’ammonites à Platynota et à Divisum, et enregistre une diminution de l’espace d’accommodation et de la production de carbonates, alors que la deuxième séquence coïncide avec la zone à Acanthicum, et enregistre une importante augmentation de l’espace disponible et de la production de carbonates. Les deux séquences qui composent la partie inférieure de l’intervalle étudié correspondent respectivement à la fin du dépôt de haut-niveau (lHD) et au dépôt de bas niveau et transgressif (LD et TD) d’une séquence de dépôt de plus basse fréquence, alors que la partie supérieure est interprétée comme le début du dépôt de haut niveau (eHD). Enfin, les variations latérales de l’épaisseur des séquences de dépôt et l’évolution dans le temps des faciès sédimentaires mettent en évidence des événements tectoniques d’extension croissante de la partie inférieure à la partie supérieure du Kimméridgien du Jura central. Sur la base de l’ensemble des résultats obtenus dans ce travail, la diminution de l’espace disponible et de la production de carbonates entre les zones d’ammonites à Platynota et à Divisum résulte probablement des effets combinés d’un climat semiaride avec une saison humide relativement importante et d’une diminution du niveau marin eustatique de long terme. De plus, l’augmentation de l’espace disponible et de la production de carbonates dans la zone à Acanthicum est vraisemblablement la conséquence d’une augmentation de l’aridité, de la vitesse de subsidence du bassin et/ou du niveau marin eustatique. Enfin, les mêmes facteurs sont probablement la cause de l’importante augmentation de l’espace disponible et de la production de carbonates qui caractérise le Kimméridgien supérieur du Jura central. Conformément au Kimméridgien du Sud de l’Angleterre (TAYLOR et al., 2001), l’approfondissement majeur enregistré dans le Jura central est situé dans la zone d’ammonites à Eudoxus, et résulte de changements environnementaux majeurs liés au renforcement de l’activité tectonique globale. Les corrélations de haute résolution entre le Jura et le Bassin vocontien révèlent que les périodes de diminution ou d’augmentation de la production de carbonates mises en évidence sur la plate-forme coïncident respectivement avec des périodes de diminution ou d’augmentation de l’accumulation de carbonates dans le bassin. Par conséquent, le mécanisme déterminant dans la formation des séquences de dépôt au Kimméridgien dans le Bassin vocontien est probablement l’exportation de carbonates de la plate-forme vers le bassin. Différents modèles basés sur la combinaison des variations du potentiel de production des environnements marins peu profonds et du potentiel d’exportation, qui sont probablement influencées par plusieurs ordres superposés de variations du niveau marin relatif, sont proposés pour expliquer la formation des séquences de plus basse fréquence d’une part et des séquences de long, de moyen et de court terme d’autre part. A detailed sedimentological, sequential and cyclostratigraphic interpretation of the Kimmeridgian in the Swiss Jura defines the principal factors which control the different stages in the development of a shallow-water carbonate platform. A comparative study in the Vocontian Basin reveals their impact on hemipelagic and pelagic sedimentation. The sedimentary facies of three platform sections – Gorges de Court, Gorges du Pichoux, and Péry- Reuchenette – located to the North of Biel in the central Jura have been studied in great detail. Facies are representative of restricted to open-marine depositional environments. Low-energy lagoonal deposits such as mudstones and bioclast-peloid wackestones to packstones are dominant. Higher-energy grainstones composed of bioclasts, peloids, and ooids occur in lesser proportion. The analysis of the evolution through time of sedimentary facies, bed thicknesses, and sedimentological features of bedding surfaces results in a precise sequential and cyclostratigraphic interpretation of the Kimmeridgian in the central Jura. Different orders of depositional sequences are defined: elementary, small-scale, medium-scale and large-scale sequences, which are hierarchically stacked and suggest an orbital control on sedimentation. In order to confirm the cyclostratigraphic interpretation of the Kimmeridgian in the central Jura, where a precise biostratigraphic and chronostratigraphic framework is lacking, the platform sections are correlated with welldated sections in the Vocontian Basin. The sedimentological, sequential and cyclostatigraphic interpretation of three basinal sections – Montagne de Crussol, Châteauneuf d’Oze, and Gorges de la Méouge – leads to the definition of different orders of depositional sequences, which are comparable to the ones defined on the platform. The Vocontian Basin sections are correlated with the Jura sections according to the similarity that exists between the sequential and cyclostratigraphic framework defined in both realms. Thanks to the high-resolution platform-to-basin correlations, the Kimmeridgian chronostratigraphy defined in the Jura and in the Vocontian Basin is compared with the one proposed by HARDENBOL et al. (1998). The thirdorder sequence boundaries defined by HARDENBOL et al. (1998) in the Kimmeridgian of the Tethyan realm correspond to five medium-scale sequence boundaries revealed in the Jura and the Vocontian Basin. The third-order sequence duration given by HARDENBOL et al. (1998) is divided by the number of elementary sequences counted in the same time interval in the Gorges de la Méouge section, which is the section remotest from the Jura platform. According to these calculations, the duration of an elementary sequence is approximately equivalent to the 20 ky orbital precession cycle. Furthermore, small-scale sequences are generally composed of five elementary sequences, and medium-scale sequences contain four small-scale sequences. Assuming that an elementary sequence is equal to 20 ky, small-scale and medium-scale sequences coincide with the first and second eccentricity cycles respectively (i.e. 100 and 400 ky). The duration of the large-scale sequences is comprised between 800 ky and 1.2 My, which corresponds to the third order of VAIL et al. (1991). The studied interval is composed of 32 small-scale sequences or 8 medium-scale sequences, implying a duration of 3.2 My for the Kimmeridgian. This cyclostratigraphic interpretation is consistent with the radiometrically deduced duration of 3.12 My (GRADSTEIN et al. 1994, 1995; HARDENBOL et al., 1998). Consequently, the dynamics of the Jura platform and the Vocontian Basin were partly controlled by cyclic environmental changes induced by insolation variations in the Milankovitch frequency band. The combination of detailed sedimentology, sequence stratigraphy, cyclostratigraphy, and high-resolution platform-to-basin correlation represents an excellent alternative to biostratigraphy for the dating of the Upper Jurassic shallow-water carbonate deposits, which are devoid of precise biostratigraphic markers. Analysis of stable isotopes and trace elements (Sr, Mg, Na, Fe, and Mn) has been performed in the Gorges du Pichoux section in order to confirm the high-resolution platform-to-basin correlation. The correlation between the variations of ∂13C and trace elements defined on the platform and the ones available in the basin (DE RAFÉLIS, 2000) seems a priori difficult. However, the variations of ∂13C and trace elements are consistent with the platform evolution during the Kimmeridgian, and their contribution to a better understanding of the global system is important. The correlation of the platform sections reveals two parts with different characteristics, corresponding approximately to the Lower and Upper Kimmeridgian. The first part exhibits thinly bedded limestones with siliciclastics and desiccation features. The second part is characterised by thickly bedded limestones, the quasidisappearance of siliciclastics and desiccation features, and the development of green algae. The transition between the Lower and the Upper Kimmeridgian corresponds to the strongest increase of accommodation recorded in the central Jura during the Kimmeridgian. Furthermore, the Lower Kimmeridgian comprises two different intervals, which correspond to largescale sequences. The first one is comprised between the Platynota and Divisum ammonite zones and records a decrease of accommodation and carbonate production, while the second interval coincides with the Acanthicum zone and implies an important increase of accommodation and carbonate production. The two lower intervals correspond respectively to the late highstand deposit (lHD) and to the lowstand and transgressive deposits (LD and TD) of a lowerfrequency depositional sequence, while the upper part coincides with the early highstand deposit (eHD). Finally, lateral variations of sequence thicknesses and the evolution through time of sedimentary facies reveal local to regional tectonic events, which occur in pulses during the Lower and Upper Kimmeridgian. According to the results obtained in this work, the decrease of accommodation and carbonate production between the Platynota and Divisum ammonite zones is probably due to the combination of a semi-arid climate with a prominent humid season and a eustatic sea-level drop. The increase of accommodation and carbonate production in the Acanthicum zone results from a more arid climate, an increased subsidence rate and/or a rise of eustatic sea-level. The same factors are probably responsible for the strong increase of accommodation and carbonate production that characterise the Upper Kimmeridgian. In conformity with southern England (TAYLOR et al., 2001), the most important gain in accommodation recorded in the central Jura coincides with the second-order Upper Jurassic transgression, which reached its maximum in the Eudoxus ammonite zone. This evolution is probably linked to major environmental changes due to global tectonics. The sedimentological features of the Kimmeridgian hemipelagic and pelagic facies in the Vocontian Basin, the variations of carbonate production in the Jura and carbonate accumulation in the basin reveal that carbonate export from the platform to the basin is probably the controlling process for cycle formation in the Vocontian Basin. Different models combining carbonate productivity in shallow-water marine environments and carbonate export from the platform to the basin (influenced by several superimposed orders of sea-level fluctuations) are proposed for the generation of lower-frequency, largescale, medium-scale, and small-scale sequences.
In the choice of an estimator for the spectrum of a stationary time series from a finite sample of the process, the problems of bias control and consistency, or "smoothing," are dominant. In this paper we present a new method based on a "local" eigenexpansion to estimate the spectrum in terms of the solution of an integral equation. Computationally this method is equivalent to using the weishted average of a series of direct-spectrum estimates based on orthogonal data windows (discrete prolate spheroidal sequences) to treat both the bias and smoothing problems. Some of the attractive features of this estimate are: there are no arbitrary windows; it is a small sample theory; it is consistent; it provides an analysis-of-variance test for line components; and it has high resolution. We also show relations of this estimate to maximum-likelihood estimates, show that the estimation capacity of the estimate is high, and show applications to coherence and polyspectrum estimates.
The analysis of univariate or multivariate time series provides crucial information to describe, understand, and predict climatic variability. The discovery and implementation of a number of novel methods for extracting useful information from time series has recently revitalized this classical field of study. Considerable progress has also been made in interpreting the information so obtained in terms of dynamical systems theory. In this review we describe the connections between time series analysis and nonlinear dynamics, discuss signal- to-noise enhancement, and present some of the novel methods for spectral analysis. The various steps, as well as the advantages and disadvantages of these methods, are illustrated by their application to an important climatic time series, the Southern Oscillation Index. This index captures major features of interannual climate variability and is used extensively in its prediction. Regional and global sea surface temperature data sets are used to illustrate multivariate spectral methods. Open questions and further prospects conclude the review.
The results presented in this paper have to be considered as a contribution to an important project whose aim is the geological study and global sequence stratigraphie correlation (multidisciplinary approach) of the Middle Oxfordian to Tithonian of different French areas, from the Sub-Boreal sections of Boulonnais, Normandy, Charente, Quercy, to the Tethyan sections of the Vocontian Trough. The review includes shallow water as well as deep water sections. The concept of this project is similar to the SE France Berriasian study published by the same working group (JAN DU CHÊNE et al., 1993). A dinocyst stratigraphie distribution chart zone is proposed between the Middle Oxfordian Transversarium Zone and the basal Upper Kimmeridgian Acanthicum of the Mesogean deep water reference sections of Vergons and Châteauneuf-d'Oze (Vocontian Trough; SE France). The two sections studied are rich in ammonites and are there-fore easily correctable with other Vocontian Trough sections to propose a sequence stratigraphic break-up primarily based on bed geometry, lithofacies and stratonomic observation, complemented by palynological and geochemical data, such as Mn content. The 3rd order sequences are stratigraphically calibrated using biostratigraphic information based on ammonites and dinocysts. From Sequence Ox 5 to Kim 3, most of the 3rd order sequences proposed by HARDENBOL et al. (1998) are stratigraphically recognised correctly with the exception of Kim 2. Data given by different geological tools as well as from other areas (particularly from the north of the Aquitaine Basin) suggest a double sequence Kim 2. To avoid any confusion with the HARDENBOL et al. cycle chart, the sequences proposed in this paper are called Kim 2' and Kim 2" respectively at the base and at the top of the interval. Correlation with the Boreal and Sub-Boreal realms are also proposed. The correlation takes into account recent papers on ammonite distribution at the Oxfordian-Kimmeridgian boundary. The joint occurrence of both Amoeboceras bauhini(a boreal species common in the base of the Baylei Zone) and Taramelliceras hauffianum (a Mesogean species) in outcrops of South Germany strongly suggests that the base of the Baylei Zone (and consequently the Oxfordian-Kimmeridgian boundary) corresponds to the base occurrence of T. hauffianum in the uppermost part of the Hauffianum subzone in the Tethyan realm. Most of the important dinocyst species have been observed in fairly comparable stratigraphic position to those known in the Boreal and Sub-Boreal realms. Additional information will be given in the near future by integrated studies presently in progress along the Upper Jurassic margins of the Aquitaine Basin (Quercy and Charente) and in Normandy.
The mid-Cretaceous (Albian) deep-water sediments (coccolith–globigerinacean marls) of the Umbria–Marche Apennines show complex rhythmic bedding. We integrated earlier work with a time-series study of a digitized and image-processed photographic log of the Piobbico core. A drab facies is viewed as recording normal stratified conditions, and a red facies as the product of downwelling warm saline (halothermal) waters. Both are pervaded by orbital (Milankovitch) rhythms. These reflect fluctuations in the composition and abundance of the calcareous plankton in the upper waters. The drab facies is overprinted by redox oscillations on the bottom, including episodic precessional anaerobic pulses (PAPs). Contrasts between the individual beds representing the alternate phases of the precessional rhythm rose and fell with orbital eccentricity, in the classical pattern of Berger’s climatic precession or precession index curve, varyingly complicated by the obliquity rhythm. We conclude that greenhouse oceans in general, and perhaps this area in particular, were very sensitive to orbital forcing. Our count of 29 406-ky eccentricity cycles yields an Albian duration of 11.8 ± 0.4 My.
A successor to A Geologic Time Scale 1989 (Cambridge, 1990), this volume introduces the theory and methodology behind the construction of the new time scale, before presenting the scale itself in extensive detail. An international team of over forty stratigraphic experts develops the most up-to-date international stratigraphic framework for the Precambrian and Phanerozoic eras. A large wallchart (not available for eBook) summarizing the time scale at the back of the book completes this invaluable reference for researchers and students.
The manganese contents of the Oxfordian-Kimmeridgian pelagic carbonates in the section at Châteauneuf d'Oze (Vocontian Basin, Hautes Alpes, France) are used to define 11 geochemical units. These units are interpreted in terms of sequence stratigraphy and grouped into 6 third-order sequences, which then are compared with those of the sequence-chronostratigraphic chart of Hardenbol et al. (1998). Using this approach, two modifications to the chart are proposed: (i) the Oxfordian-Kimmeridgian boundary in the Tethyan realm should be set in the upper part of the Hauffianum subzone, as clearly proposed by biostratigraphic studies from Wierzbowski (1991), Atrops et al. (1993), and Schweigert and Callomon (1997). (ii) a new sequence (Kim2′) should be introduced in the Hypselocyclum zone, and the sequence Kim2″ (Hypselocyclum - Divisum zones) becomes the equivalent of the cycle chart Kim2 sequence.
Detailed sedimentological analyses and sequential and cyclostratigraphic interpretations in the Kimmeridgian of the Swiss Jura and the Vocontian Basin lead to a high-resolution correlation from the platform to the basin where the biostratigraphy is well established. Several orders of depositional sequences are defined. Their duration is estimated from the time frame given in the sequence-chronostratigraphic chart of Hardenbol et al. (1998). It is suggested that an elementary sequence formed in tune with the 20 ky precession cycle. Small-scale and medium-scale sequences correspond to the 100 and 400 ky eccentricity cycles, respectively. The platform-to-basin correlation shows that the composition of the hemipelagic and pelagic deposits depends to a large part on cyclical variations of carbonate production in shallow-marine environments and subsequent export to the basin. The distribution of thick versus thin marl-limestone alternations and carbonate-dominated versus marl-dominated intervals observed in the basinal sections is explained by the superposition of high- and low-frequency sea-level changes that controlled the carbonate productivity on the platform and the export potential of carbonate mud to the basin.
There are a number of fundamental problems in assessing the astronomically forced cyclostratigraphy of the Jurassic Period. First, Jurassic geochronology is not well constrained, due to a general scarcity of radiometric dates, inferior precision of the existing ones, and large inaccuracies in stratigraphic constraints. These problems are particularly troublesome in the Early to Middle Jurassic cyclic carbonates of the Colle di Sogno section in the Lombardy Pre-Alps, Italy. Second, Jurassic sedimentary formations have undergone significant diagenesis, and again, the Colle di Sogno carbonates, with their location on the southern edge of the Alpine fold belt, are no exception. This prevents the recovery of the primary geochemical proxies needed to evaluate the relationship between cyclic sedimentation and orbital forcing. Finally, even when a strong case can be made for orbitally forced cycles, a direct calibration between the Jurassic and existing theoretical orbital solutions is not yet possible. However, at Colle di Sogno new nannofossil biostratigraphy provides the opportunity to make significant headway in recognizing Jurassic signals consistent with orbital theory, and to propose cyclochronological estimates for a portion of the Pliensbachian, and for the combined Toarcian-Aalenian Stages. We evaluate the presence of orbital signals in the sequence through the use of frequency modulation analysis of the cycles, as well as by spectral analysis of lithologic rank time-series reconstructions. The results show that the Pliensbachian Domaro Limestone contains a dual-component precession-like signal that undergoes frequency variation indicative of modulation by orbital eccentricity. The signal subsequently evolves into a single-component signal with frequency perturbations similar to those of the obliquity variation in the overlying Toarcian-Aalenian Sogno Formation. This switch in response to the fundamental orbital modes occurs during the deposition of the Lower Toarcian black shale, a time of significant global environmental change. The biostratigraphy at Colle di Sogno has well-defined Pliensbachian-Toarcian and Toarcian-Aalenian boundaries, allowing a cyclochronologic minimum estimate of 11.37 +/- 0.05 (1 sigma) Ma for the duration of the Toarcian-Aalenian interval (not accounting for stratigraphic and taxonomic noise). This compares well with the 13.1 +/- 2.8 (1 sigma) Ma estimated for this same stratigraphic interval using the current radiometric geochronology. The underlying precession-forced Pliensbachian Domaro Limestone limestone-shale couplets suggest a time of formation for the sequence of least 5 Ma, with an age of onset in the jamesoni or polymorphus subzone.
A magnetic reversal block model for the Early Cretaceous-Late Jurassic period was developed from four closely spaced profiles across the Hawaiian lineation pattern by Hilde (1973) and Hilde el al. (1974). Larson (1974) independently developed an improved model of this reversal period by reanalyzing the data presented by Larson and Chase (1972) plus a profile collected during Deep Sea Drilling Project (DSDP) leg 32. These two models are similar and contain nearly twice as many reversals as the original late Mesozoic reversal model proposed by Larson and Pitman (1972). These models are combined in this paper and are basis for a revised magnetic reversal stratigraphy for the Early Cretaceous-Late Jurasic. The model is placed in a framework of geologic time by analyzing magnetic data in the vicinity of DSDP drill holes that reached volcanic basement on various late Mesozoic lineation patterns. The magnetic ages of these sites are plotted as a function of paleontologic ages at the bottom of the holes to determine a revised time scale of magnetic reversals for the Early Cretaceous-Late Jurassic. Fundamental to this analysis are the assumptions that the Hawaiian lineation pattern was generated at a constant spreading rate and that the paleontologic ages in the DSDP holes closely approximate the basement ages. This analysis shows that the M reversal pattern spans the Aptian to Oxfordian stages and ranges in chronologic age from 107 to 153 m.y.
High-resolution magnetic susceptibility (MS) analysis was carried out on a Lower Kimmeridgian alternating marl–limestone succession of pelagic origin that crops out at La Méouge (Vocontian Basin, southeastern France). The aim of the study was to characterize the strong, dm-scale sedimentary cyclicity of the succession at a very high resolution, and to analyze the cycles for evidence of astronomical forcing. From marl to limestone, MS varies progressively and closely tracks the highest frequency cyclicity corresponding to the basic marl–limestone couplets. Long-term wavelength cycling modulates the high-frequency cyclicity (couplets), and appears to be controlled by clay content. Spectral analysis of the MS record reveals the presence of the complete suite of orbital frequencies in the precession, obliquity, and eccentricity (95–128 ka and 405 ka) bands with very high amplitude of the precession index cycles originating from dm-scale couplets. 405 ka-eccentricity cycles are very pronounced in the MS maxima of the marl members of the couplets, suggesting eccentricity-driven detrital input to the basin. 405 ka-orbital tuning of the MS maxima further sharpens all of the orbital frequencies present in the succession. These results are similar to those of previous studies at La Méouge that used carbonate content observed in field. Our results are also in accordance with cyclostratigraphic studies in Spain and Canada that report dominant precession index forcing. By contrast, in the Kimmeridge Clay (Dorset, UK), obliquity forcing dominates cyclic sedimentation, with weaker influence from the precession index. Ammonite zone duration estimates are made by counting the interpreted precession cycles, and provide an ultra-high resolution assessment of geologic time. In sum, this study demonstrates the power of the MS as a proxy in characterizing the high-resolution cyclostratigraphy of Mesozoic sections, particularly in alternating marl–limestone successions, and for high-resolution correlation and astronomical calibration of the geologic time scale.
Sedimentological evidence indicates metre-scale, cyclic changes in global sea-level during Mesozoic greenhouse climates; the cyclicity is thought to be due to Milankovitch forcing. The absence of continental ice-caps requires other mechanisms than glacier build-up to explain these variations. We propose that thermal expansion of the entire oceanic water column may partly explain the observed sea-level variations on Milankovitch timescales. Using existing climate model results, we show that an increase in deep water temperature of ∼ 2°C and a corresponding sea-level rise of 1.7 m by thermal expansion can be induced by Milankovitch forcing via increased formation of warm deep waters in low latitudes.
We present a new technique for isolating climate signals in time series with a characteristic red noise background which arises from temporal persistence. This background is estimated by a robust procedure that, unlike conventional techniques, is largely unbiased by the presence of signals immersed in the noise. Making use of multiple-taper spectral analysis methods, the technique further provides for a distinction between purely harmonic (periodic) signals, and broader-band (quasiperiodic) signals. The effectiveness of our signal detection procedure is demonstrated with synthetic examples that simulate a variety of possible periodic and quasiperiodic signals immersed in red noise. We apply our methodology to historical climate and paleoclimate time series examples. Analysis of a 3 million year sediment core reveals significant periodic components at known astronomical forcing periodicities and a significant quasiperiodic 100 year peak. Analysis of a roughly 1500 year tree-ring reconstruction of Scandinavian summer temperatures suggests significant quasiperiodic signals on a near-century timescale, an interdecadal 16–18 year timescale, within the interannual El Nio/Southern Oscillation (ENSO) band, and on a quasibiennial timescale. Analysis of the 144 year record of Great Salt Lake monthly volume change reveals a significant broad band of significant interdecadal variability, ENSO-timescale peaks, an annual cycle and its harmonics. Focusing in detail on the historical estimated global-average surface temperature record, we find a highly significant secular trend relative to the estimated red noise background, and weakly significant quasiperiodic signals within the ENSO band. Decadal and quasibiennial signals are marginally significant in this series.
Two coeval sections of red to white ammonite-rich pelagic limestones spanning the complete Kimmeridgian and most of the Tithonian were sampled in detail. All samples were treated by progressive thermal demagnetization to remove a present field overprint. Characteristic magnetization is carried primarily by magnetite. Polarity intervals are easily identified and correlate well between the two sections. The Tithonian polarity sequence can also be correlated to sections in northern Italy. The similarity between the polarity sequence and the M-sequence of marine magnetic anomalies, coupled with the precise biostratigraphic control, allows assignment of the following ages to the M-sequence: the Late/Early Tithonian boundary is correlated to the end of M-20, the Tithonian/Kimmeridgian boundary to the end of M-23, the Late/Early Kimmeridgian boundary to the latter part of M-24, and the Kimmeridgian/Oxfordian boundary within or slightly after M-25.The mean directions of characteristic magnetization have α95's less than 3° and demonstrate extensive differential block rotation within the Subbetic province. Paleolatitudes during the Kimmeridgian/Tithonian are in the range of 16–24°N.
Geomagnetic reversals and magnetic polarity chrons provide an important chronostratigraphic tool for global correlation. An integrated Tithonian-Berriasian biostratigraphic and magnetic polarity time scale for the Tethyan faunal realm for the Tithonian and Berriasian stages is compiled from 17 independent biomagnetostratigraphic sections. This time scale incorporates zones and first/last appearance datums from ammonites, calpionellids, calcareous nannofossils, and dinoflagellates. This database provides an estimate of the range of observed appearance datums or zonal boundaries relative to polarity chrons; such apparent “diachroneity” probably results from a combination of preservation of species and of paleontological methodology, rather than from migration. The lithologic transition from “Rosso Ammonitico” red marly limestone to “Maiolica” white limestone occurs at different times during the Tithonian among the various sections, ranging from polarity zone M22n (mid-Early Tithonian) in some Spanish “slope” and Italian basinal-facies sections to polarity zone M19n (mid-Late Tithonian) in the central Atlantic and some plateau-facies Italian sections. This widespread lithologic change is, therefore, probably a result of shifting local patterns of fertility overprinted on the main regional trend. Magnetostratigraphy from the Purbeck Limestone Formation in the English Boreal faunal realm was obtained from the “classic” section at Durlston Bay in Dorset. The Dorset section displays predominantly normal polarity with a minimum of three reversed-polarity zones, but distortion of the magnetic polarity pattern by variable rates of sedimentation in this marginal clastic environment coupled with lack of independent correlation methods currently precludes a unique correlation to the Tithonian-Berriasian magnetic polarity time scale. The Tithonian-Berriasian magnetic polarity time scale may eventually provide a global chronostratigraphic definition of the Jurassic-Cretaceous boundary.
The standard Tethyan Berriasian–Barremian successions of France and Spain are correlated with the Boreal successions of England, Germany and the Netherlands. Special emphasis is placed on the correlation and sequence stratigraphy of the main hydrocarbon-producing strata of the Berriasian–Barremian stages in the four main basins in the subsurface of the Netherlands and the Dutch part of the North Sea continental shelf. All available biostratigraphic, magnetostratigraphic, and sequence-stratigraphic correlation data-sets were used to draw this correlation chart. Many lacunae in shallow marine successions could be correlated with sediments in deeper marine successions. Some sequence boundaries are tectonically enhanced and were accompanied by extra large falls in sea level; they initiated important changes in the biota and sedimentary regimes of western Europe, viz, the boundaries of the so-called ‘transgressive regressive facies cycles’ of Jacquin & de Graciansky.
A detailed analysis of sedimentary organic matter (SOM) has been carried out in Upper Jurassic deep-water marls and carbonates of the Vocontian Basin (SE France). Its main purpose is to analyse the vertical and lateral trends of SOM distribution, in order to better understand processes and factors controlling the accumulation and preservation of organic constituents in basinal environments. The Vocontian Basin is characterized by widespread oxic depositional environments in the Upper Jurassic, as confirmed by the very low total organic carbon content (less than 0.25 wt.%). For such organic-poor deposits, palynofacies analysis represents the best tool to investigate SOM. Stratigraphic analysis of palynofacies trends has been performed within a pre-established sequence stratigraphic framework, defined by means of field sedimentology and, subsequently, complemented through lateral correlations, biostratigraphical constraints and geochemistry. This approach highlights the vertical signatures which are directly related to relative sea level changes. Furthermore, lateral correlations of palynofacies trends, at the scale of 3rd and 2nd order cyclicity, permit the signatures observable at basin scale to be distinguished from those detectable only at local scale. The former are controlled by factors affecting the whole basin, such as eustasy, regional tectonics and climate.
Data derived from tide-gauge stations throughout the world indicate that the mean sea level rose by about 12 centimeters in the past century. The sea level change has a high correlation with the trend of global surface air temperature. A large part of the sea level rise can be accounted for in terms of the thermal expansion of the upper layers of the ocean. The results also represent weak indirect evidence for a net melting of the continental ice sheets.
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