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Supplementary modification and introduction of code numbers to the low-latitude coccolith biostratigraphic zonation (BUKRY, 1973; 1975)
... The age of the respective core intervals was determined according to nannoplankton species, with a focus on index species of main biozones and subzones [16][17][18]. The intervals of the identified сalcareous nannofossils were correlated with ample biostratigraphic evidence from oceanic sediments [16][17][18][19][20][21][22][23][24]. ...
... Nannofossils were found and identified in Fe-Mn crust (Unit III, points 1 and 2) and in tuff section at points 3, 4, and 5. Colored zones show age ranges for different samples based on extant periods for identified nannoplankton species. Cenozoic time scale is based on Neogene (NN), Martini [16], (CN), Okada, Bukry [22], and Palaeogene (NP), Martini [16], and (CP) Okada, Bukry [22] zonal scales correlated to ages by Shumenko [24]. Numbers 1 to 21 refer to zone numbers. ...
... Nannofossils were found and identified in Fe-Mn crust (Unit III, points 1 and 2) and in tuff section at points 3, 4, and 5. Colored zones show age ranges for different samples based on extant periods for identified nannoplankton species. Cenozoic time scale is based on Neogene (NN), Martini [16], (CN), Okada, Bukry [22], and Palaeogene (NP), Martini [16], and (CP) Okada, Bukry [22] zonal scales correlated to ages by Shumenko [24]. Numbers 1 to 21 refer to zone numbers. ...
New data obtained from core samples of two boreholes in Alba Guyot in the Magellan Seamount Trail (MST), Western Pacific, including 40Ar/39Ar age of basanite, mineralogy of basanite, tuff, tuffite, mantle-derived inclusions in basanite and tuff (lherzolite xenolith and Ol, Cpx, Opx xenocrysts), and calcareous nannofossils biostratigraphy, have implications for the guyot history. Volcanics in the upper part of the Alba Guyot main edifice and its Oma Vlinder satellite, at sea depths between 3600 and 2200 m, were deposited during the Cretaceous 112 to 86 Ma interval. In the following ~60 myr, the Alba Guyot became partly submerged, and denuded with the formation of a flat summit platform while the respective fragment of the Pacific Plate was moving to the Northern Hemisphere. Volcanic activity in the northeastern part of the guyot summit platform rejuvenated in the Miocene (24–15 Ma) and produced onshore basanitic volcanoes and layers of tuff in subaerial and tuffite in shallow-water near-shore conditions. In Middle-Late Miocene (10–6 Мa), after the guyot had submerged, carbonates containing calcareous nannofossils were deposited on the porous surfaces of tuff and tuffite. Precipitation of the Fe-Mn crust (Unit III) recommenced during the Pliocene-Pleistocene (< 1.8 Mа) when the guyot summit reached favorable sea depths. The location of the MST guyots in the northwestern segment of the Pacific Plate near the Mariana Trench, along with the Miocene age and alkali-basaltic signatures of basanite, provide evidence for petit-spot volcanism on the Alba Guyot. This inference agrees with the geochemistry of Cenozoic petit-spot basaltic rocks from the Pacific and Miocene basanite on the Alba Guyot. The numerous volcanic cones reaching up to 750 m high and 5.1 km in base diameter, which were discovered on the Alba summit platform, provide the first evidence of voluminous Miocene petit-spot basanitic volcanism upon the Cretaceous guyots and seamounts of the Pacific.
... The age of the respective core intervals was determined according to nannoplankton species, with a focus on index species of main biozones and subzones [16][17][18]. The intervals of the identified calcareous nannofossils were correlated with ample biostratigraphic evidence from oceanic sediments [16][17][18][19][20][21][22][23][24]. ...
... The age of the respective core intervals was determined according to nannoplankton species, with a focus on index species of main biozones and subzones [16][17][18]. The intervals of the identified сalcareous nannofossils were correlated with ample biostratigraphic evidence from oceanic sediments [16][17][18][19][20][21][22][23][24]. ...
... Nannofossils were found and identified in the Fe-Mn crust (Unit III, points 1 and 2) and in the tuff section at points 3, 4, and 5. Colored zones show age ranges for different samples based on extant periods for identified nannoplankton species. The Cenozoic time scale is based on Neogene (NN), Martini [16], (CN), Okada and Bukry [22], and Palaeogene (NP), Martini [16], Figure 2. Calcareous nannofossil biostratigraphy, core sample 15B13. Nannofossils were found and identified in the Fe-Mn crust (Unit III, points 1 and 2) and in the tuff section at points 3, 4, and 5. Colored zones show age ranges for different samples based on extant periods for identified nannoplankton species. ...
New data obtained from core samples of two boreholes and dredged samples from the Alba Guyot in the Magellan Seamount Trail (MST), Western Pacific, including the 40Ar/39Ar age determinations of basanite, and the mineralogy of basanite, tuff, tuffite, mantle-derived inclusions in basanite and tuff (lherzolite xenolith and Ol, Cpx, and Opx xenocrysts), and calcareous nannofossil biostratigraphy, have implications for the guyot′s development and history. Volcanic units in the upper part of the Alba Guyot main edifice and its Oma Vlinder satellite, at sea depths between 3600 and 2200 m, were deposited during the Cretaceous 112 to 86 Ma interval. In the following ~60 myr, the Alba Guyot became partly submerged and denuded with the formation of a flat summit platform while the respective fragment of the Pacific Plate was moving to the Northern Hemisphere. Volcanic activity in the northeastern part of the guyot summit platform was rejuve-nated in the Miocene (24–15 Ma) and produced onshore basanitic volcanoes and layers of tuff in subaerial and tuffite in shallow-water near-shore conditions. In the Middle‒Late Miocene (10–6 Мa), after the guyot had submerged, carbonates containing calcareous nannofossils were deposited on the porous surfaces of tuff and tuffite. Precipitation of the Fe-Mn crust (Unit III) recommenced during the Pliocene‒Pleistocene (< 1.8 Mа) when the guyot summit reached favorable sea depths. The location of the MST guyots in the northwestern segment of the Pacific Plate near the Mariana Trench, along with the Miocene age and alkali-basaltic signatures of basanite, provide first evi-dence for petit-spot volcanism on the Alba Guyot. This inference agrees with the geochemistry of Cenozoic petit-spot basaltic rocks from the Pacific and Miocene basanite on the Alba Guyot. Pet-it-spot volcanics presumably originated from alkali-basaltic melts produced by decompression partial melting of carbonatized peridotite in the metasomatized oceanic lithosphere at the Litho-sphere–Asthenosphere Boundary level. The numerous volcanic cones with elevations of up to 750 m high and 5.1 km in basal diameter, discovered on the Alba summit platform, provide the first evidence of voluminous Miocene petit-spot basanitic volcanism upon the Cretaceous guyots and seamounts of the Pacific.
... According to the marker species, three nanno-biozones were determined that are: Sphenolithus predistentus, Sphenolithus distentus Zone and Sphenolithus ciperoensis zones (Fig. 4). The three identified biozones comprise the CP (Coccolith Paleogene) biozones of Okada and Bukry (1980) zonation and the CNO (Calcareous Nannofossils Oligocene) biozones of Agnini et al. (2014) zonation. These biozones are as follow: Sphenolithus predistentus Zone (NP23 zone): This zone was proposed by Bramlette and Wilcoxon (1967) then Martini (1970). ...
... The mentioned zone is the oldest identified zone from the studied sections attaining about 90 meters in thickness. The NP23 zone is equivalent to CP17 and CP18 zones of the Okada and Bukry (1980) and the CNO3-CNO4 zones of Agnini et al. (2014). Due to the lithological aspect of the lower boundary of the section (samples No.1 to No.13, 50 m-thick) and because the absence of index nannofossil species, it was not possible to determine the age of the lower boundary of the section. ...
... Its thickness is about 154 meters. The NP24 zone is equivalent to the CP19a zone of Okada and Bukry (1980) and the upper part of CNO4lower part of CNO5 zones of Agnini et al. (2014). ...
Calcareous nannofossils are one group of microfossils that use in biostratigraphy studies since the 1950 ′ s and 1960 ′ s. Recently, because of the potential of nannofossil species for age determination, several authors use this fossil-group in the study of Cenozoic sediments and rocks. Here, we present a nannofossil biozonation based on biostratigraphic information from the Sabzevaran section (Central Iran). The Sabzevaran section mainly consists of marl, limestone, and shaly limestone. Based on index nannofossil species, three nanno-bizones (NP23-NP25) were recognized in this section. According to the identified biozones, the age of the studied deposits in the Sabzevaran section is middle to late Oligocene (Rupelian to Chattian stages). In this section, calcareous nannofossils abundance and diversity are medium to low with a sharp decrease slightly near the conglomerate and sandstone layers and are absence in conglomerate and sandstone beds. Paleoecological data indicate the shallow marine, low latitude and low productivity for the marine deposits of Sabzevaran section.
... Marine Micropaleontology 191 (2024) 102395 adopted the terms Base absence (Ba) and Top absence (Ta) (Backman et al., 2012) to define intervals in which a taxon temporary shows abundances ranging from very rare to zero and then increases in abundance again, with values comparable to the pre paracme interval. The biostratigraphic schemes applied are those of Martini (1971), Okada and Bukry (1980), and Backman et al. (2012). Taxonomic concepts from several authors and sources are used to determine calcareous nannofossils (Farinacci andHowe, 1969-2022;Perch-Nielsen, 1985;Rio et al., 1990;Raffi and Flores, 1995; and the online atlas Nannotax). ...
... Marine Micropaleontology 191 (2024) 102395 Table 1 Biohorizons used to biostratigraphically classify the studied section. From left to right: type of event (T, top; Ta, Top Absence; B, base; Ba, Base Absence; Bc, Base Common), species and the base of the biozone they define (Martini, 1971;Okada and Bukry, 1980;Backman et al., 2012), samples and their depths, and the age associated to each biohorizon (GTS2020; Raffi et al., 2020). M.E. ...
... At Site U1488, we recorded the disappearance (Top) of R. pseudoumbilicus between samples U1488C-11H-3 W, 62-64 cm and U1488B-11H-6 W, 82-84 cm, at 105.46 (± 1.08) m, where the abundance of R. pseudoumbilicus decreases from 100 to 130 to 0 specimens per mm 2 . This event marks the base of Zone NN16 (Martini, 1971), of Subzone CN12a (Okada and Bukry, 1980), and of Zone CNPL4 (Backman et al., 2012). ...
The Late Miocene-Early Pliocene Biogenic Bloom (9.0–3.5 Ma) is a widespread paleoceanographic phenomenon marked by increased marine biological productivity and by high accumulations of biological components documented at multiple open ocean sites in the Indian, Pacific, and Atlantic oceans. We investigate the expression of the Biogenic Bloom at International Ocean Discovery Program (IODP) Site U1488 in the western equatorial Pacific Ocean. We generated an improved age model based on calcareous nannofossil biostratigraphy and a quantitative benthic foraminiferal record across the Late Miocene to the Early Pliocene. Increased carbonate mass accumulation rates suggest the Biogenic Bloom occurs between 8.1 and 4.0 Ma at Site U1488. We described four intervals with paleoenvironmental significance: Interval 1 (8.1–6.2 Ma), Interval 2 (6.2–5.5 Ma), Interval 3 (5.5–4.5 Ma), and Interval 4 (4.5–3.1 Ma), the Biogenic Bloom spans across Interval 1 and 3. Intervals 1, 3, and 4 are marked by high abundance of phytodetritus exploiting taxa, related to phases of El Niño-like conditions. The highest abundance of these species during Interval 1 has been related to a phase of higher seasonality. In contrast, intervals 3 and 4 show reduced seasonality and a steadier input of food to the seafloor, associated with increased dust supply through wind transport and/or increased continental weathering during the Pliocene. Interval 2 stands out as the sole interval encompassing La Niña-like conditions, marked by a shift in the nutrient composition reaching the seafloor, from labile phytodetritus to refractory organic matter, and possibly a decrease in seasonality.
... For datum levels, we used FO (first occurrence), LO (last occurrence), PB (paracme beginning), PE (paracme end) and LCO (last common occurrence). The zonal schemes that were employed in nannofossil biostratigraphic investigations are Okada and Bukry (1980), Martini (1971), Di Stefano et al. (2008) for the subdivision of the Zone NN4, Bergen et al. (2019) and Backman et al. (2012).The qualitative and quantitative nannofossil taxa are counted from 100 to 600 individuals except for a few samples that show low abundance and scarcity. The species were grouped into clusters and diversity parameters such as dominance index, Shannon-Weiner diversity index and species richness were described using PAST4 software (Hammer et al., 2001;Hammer and Harper, 2006). ...
... It is identified from the LO of Triquetrohabdulus carinatus to the LO of Sphenolithus belemnos. It is correlated with the CN2 S. belemnos Zone of Okada and Bukry (1980) and is compatible with the CNM5 Zone ( Figure 5) of Backman et al. (2012). It spans 30 m at Wadi Baba (samples 71-95) and 7.5 m at Wadi Gharandel (samples G1 to G9) and is representative of important species. ...
... Helicosphaera ampliaperta shows very low and scattered abundance during the end of its stratigraphic range and may show an expanded range by reworking . The LO of H. ampliaperta was used by Martini (1971) to define NN4/NN5 and by Okada and Bukry (1980) to define the CN3/CN4 zonal boundary. Di Stefano et al. (2008) segmented the NN4 Zone of Martini (1971) into three subzones (MNN4a, MNN4b, and MNN4c). ...
The Burdigalian/Langhian (B/L) boundary has not yet been designated as a Global Stratotype Section and Point (GSSP), despite various proposed zonal schemes. In the Gulf of Suez region of Egypt, the Burdigalian-Langhian successions are notable for hosting significant hydrocarbon reservoirs within a tectonic rift setting. Therefore, biostatigraphy plays a crucial role in exploration endeavors in this area. The nannofossil biostratigraphy is investigated in two sections, Wadi Baba and Wadi Gharandel, of the lower-middle Miocene from west-central Sinai. Three biozones, NN3 (Sphenolithus belemnos) Zone, NN4 (Helicosphaera ampliaperta) Zone, and NN5 (Sphenolithus heteromorphus) Zone, are identified from the studied interval. The NN4 Zone could be divided into MNN4a/b and MNN4c. Important biovents are discussed, such as the S. heteromorphus paracme interval and the first occurrence and evolution of the Discoaster exilis and Discoaster variabilis groups. Based on the cluster analysis, the recorded taxa can be subdivided into four groups that reflect their palaeoclimatic preferences. The paleoecological interpretation of the studied Rudies Formation indicates prevailing cool and eutrophic nutrient conditions based on the dominance of taxa such as Coccolithus pelagicus, Reticulofenestra minuta, and Cyclicargolithus floridanus. The nannofossil taxa responses to sea level curve are interpreted. Fluctuations in taxa abundance and diversity indicate a slight rise in the sea level at the base of the Burdigalian followed by sudden drop in the sea level at the middle Burdigalian. High sea-level conditions prevailed again until the B/L boundary. During the Langhian period, many small-scale fluctuations in sea-level curve are detected.
... По нанопланктону и фораминиферам уточнен возраст отложений, а на основании изменений изотопов кислорода и углерода было доказано, что верхняя часть мергелей, содержащая прослои сапропелитов, является результатом седиментации в тепловодном морском бассейне и соответствует эпизоду раннеэоценового климатического оптимума [18,21]. Таким образом, исходя из зонирования по нанопланктону по шкале E.Martini [24] и шкале Okada & Bukry [25], разрез Актулагая является возрастным аналогом черкесской свиты, представленной в разрезе по р. Хеу (Северный Кавказ) [6,7,8,27,28]. ...
... Rel.4.8.2 (06-2010). Весьма богатые в видовом отношении комплексы нанопланктона обнаружены практически во всех образцах, что позволило уверенно выделить зональные подразделения по зональным шкалам Martini [24], Okada & Bukry [25] и Agnini et al. [13]. ...
... Слой 5 (образцы [24][25][26][27][28][29][30][31][32]. Ритмичное переслаивание темно-коричневых, насыщенных органикой глин «сапропелевых» прослоев (0,1-0,5 м) и желтовато-светло-серых мергелей (0,2-2,1 м), в верхней части разреза мергели становятся почти белыми. ...
Abstract: the results of a detailed study of nanoplankton and paleomagnetic characteristics of the Ypresian stage section on the Aktolagai plateau (variant name-Aktulagai) are presented. The zonal division of nanoplankton has been clarified. Stratigraphically important levels and changes in nanofossil assemblages have been identified, allowing assessment of paleoecological changes during the Early Eocene Climatic Optimum (EECO). For the first time, based on the development of the species Discoaster lodoensis, a range of maximum temperatures and, probably, maximum depths that contributed to the accumulation of layers of organically saturated non-carbonate clays (sapropels) has been identified. A correlation was carried out with the reference section of the Ypresian stage along the river. Heu (North Caucasus).
... The biozonation of calcareous nannofossils during the Paleogene has been proposed by some authors. For this study area, we used calcareous nannofossils zonation as proposed by Martini (1971), and Okada and Bukry (1980). The Tonasa Formation consists of interbedded limestone and Globigerina marl (Sukamto and Supriatna 1982). ...
... Observation under a polarized microscope with 1000× magnification was carried out to recognize the species present in the assemblage (Bown 1999; Farida at al. 2019). The age was determined based on the First Occurrence (FO) and the Last Occurrence (LO) of marker species, following the standard zonation by Martini (1971), Okada and Bukry (1980), and also datum by Perch-Nielsen (1985). The paleotemperature could be analyzed based on the presence of species known to flourish under a specific climate. ...
... Biozonation schemes were used to determine biostratigraphy of the Tonasa Formation in the Karama A section on the basis of calcareous nannofossils from the NP zonation of Martini (1971), the CP Zonation of Okada-Bukry (1980), and the age correlation of Perch-Nielsen (1985) to examine the age of calcareous nannofossils (datums). The results of the biostratigraphy of the study area are (Fig. 6) as follows: ...
The biostratigraphy of the Tonasa Formation in the Jeneponto Regency of South Sulawesi, Indonesia, is still poorly known, and there are barren ages, such as much of the Oligocene to Early Miocene. The Tonasa Formation is well exposed along the coast of the Jeneponto Regency, in which the Karama area consists of the most important outcrops of this formation which in this area consists of interbedded marl and limestone. Our study focuses on the biostratigraphy of the Karama area section A based on nannofossil. Samples were collected by measured stratigraphy methods and then subjected to investigation using smear slides. The assemblages of species were determined by semiquantitative analysis. Data analysis obtained three nannofossil datums (boundaries): The First Occurrence (FO) of Sphenolithus pseudoradians NP19/NP20), the First Occurrence of Sphenolithus distentus (CP.16/CP.17), and the Last Occurrence (LO) Sphenolithus predistentus (NP.23/NP.24. The zonal boundary was determined based on calcareous nannoplankton; the Late Eocene to Middle Oligocene boundary of the Tonasa Formation was found in this section. Interestingly, throughout this period, the marker species in this section is Sphenolithus . In addition, the presence of Sphenolithus , Discoaster , and Zygrhablithus bijugatus indicated that the basin was in warm water condition.
... The procedure included indexing of chert sections recognized via searching the open-access database for the EP ODP and DSDP wells. Each of these chert (and/or porcellanite) sections was assigned a numerical age span utilizing biozonations of Okada and Bukry (1980), Berggren et al. (1995), and Kamikuri et al. (2012a, b) (Table 1; Fig. 2A). The chert intervals overlapping in age were then added-up together. ...
... Negative longitudes and latitudes indicate °W and °S, positive longitudes and latitudes being °E and°N. Standard calcareous nannofossil biozonations (Nannoplankton Neogene (NN) Zones, Nannoplankton Paleogene (NP) Zones, Coccolithus Neogene (CN) Zones, and Coccolithus Paleogene (CP) Zones) were adapted from Martini (1971) and Okada and Bukry (1980), foraminiferal zones (Neogene (N) and Paleogene (P)) from Berggren et al. (1995), and radiolaria biozones (Radiolarian Neogene (RN) and Radiolarian Paleogene (RP)) from Sanfilippo and Nigrini (1998) and Kamikuri et al. (2012b). The younger (Min = minimum) and older (Max = maximum) limit ages, the mean age, and the duration of chert intervals were derived based on these assigned biozones. ...
... Following interrogation of DSDP and ODP databanks for the selected EP sites, 58 chert and porcellanite age intervals were archived, with a numerical age domain, defined based on biozonal indicators of Okada and Bukry (1980), Berggren et al. (1995), Sanfilippo and Nigrini (1998), and Kamikuri et al. (2012a, b) allocated to each interval (Table 1; Fig. 2A). A summing up proceeding was pursued for intervals overlapping in age, and extension of this scheme to all 58 catalogued chert age segments generated a total of 91 time slices dispensed from 0.8 to 68 Ma. ...
Biosiliceous cherts hosting the transformation of biogenic silica to paracrystalline opal-CT, deposited in the low-latitude realms of Jurassic to Neogene, were recently interpreted as developing during episodes of elevated primary productivity along upwelling areas in equatorial and sub-equatorial paleo-latitudes. Geographically widespread distribution of chert and other rock types of biosiliceous origin, including porcellanite and siliceous claystones throughout the Eocene however indicates these diagenetic deposits are not in any case the dependable markers of latitude-driven upwelling regimes. This study aims to explore the dominance of early Eocene chert occurrences in the Equatorial Pacific (EP) sediments, and their contribution to the Cenozoic global climate change. Our new assessment of the age-abundance dispersal of EP Cenozoic chert sections accommodated by Deep Sea Drilling Project (DSDP)- and Ocean Drilling Program (ODP)-cored deposits realized that the cherts transformed from deposited opal-A sediments most commonly in the early Eocene, with a peak in abundance at ∼50 Ma. This age interval of significant chert occurrences coincided with the period of seawater-temperature maxima of the early Eocene climatic optimum (EECO), during which the world ocean was supposedly marked by highly reduced upwelling intensity and siliceous bioproduction. The spatio-temporal distribution model of the EP Cenozoic cherts with the peak occurrences during the EECO presented in this study bears close similarities to the global distribution patterns of chert during the Cenozoic, which strongly correspond to a global paleoclimatic driver rather than upwelling regimes. Following our survey, cherts occurred less frequently in the post-early Eocene, which is characterized by cooling bottom waters and amplified upwelling and bioproductivity. This model suggests the paleo-seawater rich in dissolved silicon (DSi) would have been imperative for peak incidences of early Eocene chert production, despite extreme surface warmth and greenhouse conditions of the EECO, making DSi available to opal-secreting phytoplankton via deep-water ventilation. These imply that the paleo-climate was more impactful to diagenetic chert production than latitudinally mediated ocean upwelling. The chert distribution events during the early Eocene reduced siliceous bioproductivity appear to have been insufficient to compensate for the significant silica input to the basin mainly from climate-controlled continental weathering. The DSi uptake by precipitation of authigenic clays which accompanies opal-A diagenesis in many depositional systems has been operative, with higher rates in carbonate- than clay-dominated sediments, so as to sustain balance between DSi released to the ocean from terrestrial sources and the silica expelled in sediments during the EECO weakened upwelling.
... The age range for the Tunga Formation is modified from the diatom age range (pale blue) to include an additional 100 000 years before and after (dark blue extensions) to accommodate basal and uppermost diatom-free sandstones. Calcareous nannofossil, planktic foraminifer, and diatom biozonations from Martini (1971), Okada and Bukry (1980), Barron (2006) and Wade et al. (2011). in planktic zones M1-M13 and thus suggests an age range of 21.12 through 6.14 Ma. ...
... The age range for the Tunga Formation is modified from the diatom age range (pale blue) to include an additional 100 000 years before and after (dark blue extensions) to accommodate basal and uppermost diatom-free sandstones. Calcareous nannofossil, planktic foraminifer, and diatom biozonations from Martini (1971), Okada and Bukry (1980), Barron (2006) and Wade et al. (2011). ...
The East Pisco Basin, occupying the coastal plain of Peru between 13°S and 16°S, is widely known for its extensive Eocene to Quaternary biosiliceous deposits and excellent preservation of fossil marine vertebrates. Biochronologic studies published over the past 35 years record a hiatus of about 13 million years (*32–19 Ma) separating the youngest Paleogene deposits (Otuma Formation) from the oldest Neogene deposits (Chilcatay Formation). We describe a newly identified Lower Miocene depositional sequence that lies below documented Chilcatay strata, rich in diatoms and benthic foraminifers, which we name the Tunga Formation. A low-latitude diatom assemblage from the Tunga Formation indicates an age of 21.6 to 20.5 Ma age, whereas an ash within basal Tunga strata yields an 206Pb/238U weighted mean age of 20.58 ± 0.13 Ma. Benthic foraminifer paleodepth analysis and the diatom assemblage of the Tunga Formation indicate deposition took place along the continental margin at upper bathyal depths under hypoxic conditions beneath highly productive waters, a scenario also supported by the presence of abundant clupeoid fish scales and dolomitized horizons. The Tunga Formation is characterized by a profound scarcity of cetacean fossils, unlike the cetacean-rich neritic sediments of the overlying Chilcatay Formation.
... The age range for the Tunga Formation is modified from the diatom age range (pale blue) to include an additional 100 000 years before and after (dark blue extensions) to accommodate basal and uppermost diatom-free sandstones. Calcareous nannofossil, planktic foraminifer, and diatom biozonations from Martini (1971), Okada and Bukry (1980), Barron (2006) and Wade et al. (2011). in planktic zones M1-M13 and thus suggests an age range of 21.12 through 6.14 Ma. ...
... The age range for the Tunga Formation is modified from the diatom age range (pale blue) to include an additional 100 000 years before and after (dark blue extensions) to accommodate basal and uppermost diatom-free sandstones. Calcareous nannofossil, planktic foraminifer, and diatom biozonations from Martini (1971), Okada and Bukry (1980), Barron (2006) and Wade et al. (2011). ...
The East Pisco Basin, occupying the coastal plain of Peru between 13°S and 16°S, is widely known for its extensive Eocene to Quaternary biosiliceous deposits and excellent preservation of fossil marine vertebrates. Biochronologic studies published over the past 35 years record a hiatus of about 13 million years (*32-19 Ma) separating the youngest Paleogene deposits (Otuma Formation) from the oldest Neogene deposits (Chilcatay Formation). We describe a newly identified Lower Miocene depositional sequence that lies below documented Chilcatay strata, rich in diatoms and benthic foraminifers, which we name the Tunga Formation. A low-latitude diatom assemblage from the Tunga Formation indicates an age of 21.6 to 20.5 Ma age, whereas an ash within basal Tunga strata yields an 206 Pb/ 238 U weighted mean age of 20.58 ± 0.13 Ma. Benthic foraminifer paleodepth analysis and the diatom assemblage of the Tunga Formation indicate deposition took place along the continental margin at upper bathyal depths under hypoxic conditions beneath highly productive waters, a scenario also supported by the presence of abundant clupeoid fish scales and dolomitized horizons. The Tunga Formation is characterized by a profound scarcity of cetacean fossils, unlike the cetacean-rich neritic sediments of the overlying Chilcatay Formation.
... The sample was prepared as a smear slide following the standard preparation technique of Monechi and Thierstein (1985) and analysed using a polarizing microscope at 1250× magnification. The biostratigraphic investigation was conducted following the zonations of Backman et al. (2012), Okada and Bukry (1980) and Martini (1971). ...
... Moderately preserved specimens, despite the evidence of etching and/or overgrowth in the primary morphological characters, do not prevent identification at the species level. The assemblage consists of abundant small Gephyrocapsa spp., common Coccolithus pelagicus, occasional Pontosphaera spp., Reticulofenestra minutula (5-6 μm) and rare Discoaster in the form of D. asymmetricus, D. Okada and Bukry (1980) and NN16 of Martini (1971), spanning from the late Zanclean to Piacenzian. The assemblage is also characterized by Paleogene and Cretaceous reworked taxa in the form of occasional Sphenolithus spp. ...
... According to the systematic categorization of these fossils, there are 18 species of calcareous nannofossils based on numerous paleontological sources [13,14] (Figure 3). [15] which determinates at the late Early Miocene, and correlated Triquetrorhabdulus carinatus NN1, Discoaster druggii NN2 biozones which thoughtful by [16], which aged Early Miocene in age; and correlated with Sphenolithus conicus biozone ; Sphenolithus disbelemnos / Triquetrorhabdulus carinatus biozone ; Helicosphaera euphratis biozone; Helicosphaera carteri biozone CNM1-4 biozones which thoughtful by the [17], which determinates at the Early Miocene, and correlated (Triquetrorhabdulus carinatus biozone) which thoughtful by [18,19,20], which aged Early Miocene in age, and correlated (Discoaster deflandrei and Discoaster druggii biozones) which thoughtful by [21], which aged Early Miocene in age therefore we determinates the age of biozone as Early Miocene [22], ( Figure 4,5). ...
... Thickness: 25 meters Correlation and Discussion: This biozone is correlated with CN1 (Sphenolithus belemnos biozone) which thoughtful by the [15]which determinates at the late Early Miocene, and correlated Sphenolithus belemnos NN3 biozones, which is studied by [16], which determinates at Early Miocene in age; and correlated with Sphenolithus belemnos CNM5 biozones which thoughtful by the [17], which determinates at the Early Miocene, and correlated (Sphenolithus belemnos biozone) which thoughtful by [20,21], which aged Early Miocene, and correlated (Discoaster deflandrei biozone) which thoughtful by [18,19], which aged Early Miocene, therefore, it was determinated the age of biozone as the Early Miocene [22], (Figure 4 ...
Investigations of calcareous nannofossils were done on the Serikagni Formation in the southern limb of the Sinjar anticline northwest of Iraq, specifics of the identification process's investigation (18 species of calcareous nannofossils belonging to 10 genera). Two biozones were proposed in this study based on their stratigraphic distribution, and they are as follows: Triquetrorhabdulus carinatus partial range Biozone CN1 and Sphenolithus belemnos Interval Biozone CN2. Correlation with other calcareous nannofossil biozones from regional schemes led to the conclusion that the Serikagni Formation's age is Early Miocene (Aquitanian)in the studied sections. It can conclude from higher speciation for calcareous nannofossils that the bloom at the Miocene because of increased temperature impacts climate change on the warm ocean's ecosystem.
... Marls of the Keresta Formation in the Volgograd-Volga region yielded rich nannofossil assemblages (Musatov and Musylev 2021), belonging to subzones CP13c-CP14a of Okada and Bukry (1980). The depositional environments of the Keresta Formation differ substantially from the depositional environments of both the underlying Kuberla Formation and the overlying Solonka Formation. ...
... are described formally from the Middle Eocene Keresta Formation, in the Volgograd-Volga region of the south-west part of Russia. The new species were found in the Enneadocysta arcuata dinoflagellate cyst Zone and the CP13c Nannofossil Subzone sensu Okada and Bukry (1980), which constrain their stratigraphical ranges to Lutetian (Middle Eocene). ...
The Keresta Formation, located in the Volgograd-Volga region (the Volga-Caspian subregion of southwest Russia) has been dated as Middle Eocene, Lutetian, based on dinoflagellate cysts of the Enneadocysta arcuata Zone and nannofossils from the Lutetian subzones CP13c-CP14a. Within this interval , four new species of dinoflagellate cysts are described: Spiniferella grigorovichiae sp. nov., Impagidinium tuberculatum sp. nov., Hystrichostrogylon crassitunicatum sp. nov. and Hystrichosphaeropsis tenerum sp. nov. The new species present a high correlation potential for Middle Eocene stratigraphy over the southern part of the Russian Platform. Also, the assemblage of organic-walled microphytoplank-ton from the Keresta Formation indicates warm-water marine environments within the marginal part of the Paratethys Basin.
... The taxonomy follows that presented by Aubry (1984Aubry ( , 1988Aubry ( , 1989, Perch-Nielsen (1985), Bown (2005), Bown and Dunkley Jones (2012), and Newsam et al. (2017), except for Dictyococcites and Reticulofenestra for which we use the taxonomy expressed by Agnini et al. (2014). Key calcareous nannofossil datums can be placed into the biostratigraphic frame using three different Cenozoic zonation schemes, NP (Martini, 1971), CP (Okada & Bukry, 1980), and CN of Agnini et al. (2014). The taxonomy of reticulofenestrids is not well constrained due to the heterogeneity of this group (Young, 1990). ...
... To the right, percentage of reworking and number of reworked specimens (n) in 1 mm 2 . To the left, depth (CSF-A, m), recovery(Sutherland et al., 2019), magnetostratigraphy, calcareous nannofossil biozonations (CP Zone:Okada & Bukry, 1980; NP Zone: Martini, 1971; CN Zone:Agnini et al., 2014), planktonic foraminifera biostratigraphy (E Zone:Wade et al., 2011) and chronostratigraphy. Other nannofossil genera (%) discussed in the main text are provided in ...
The Eocene‐Oligocene transition (EOT; ∼34 Ma) was one of the most prominent global cooling events of the Cenozoic, coincident with the emergence of continental‐scale ice‐sheets on Antarctica. Calcareous nannoplankton experienced significant assemblage turnover at a time of long‐term surface ocean cooling and trophic conditions, suggesting cause‐effect relationships between Antarctic glaciation, broader climate changes, and the response of phytoplankton communities. To better evaluate the timing and nature of these relationships, we generated calcareous nannofossil and geochemical data sets (δ¹⁸O, δ¹³C and %CaCO3) over a ∼5 Myr stratigraphic interval recovered across the EOT from IODP Site U1509 in the Tasman Sea, South Pacific Ocean. Based on trends observed in the calcareous nannofossil assemblages, there was an overall decline of warm‐oligotrophic communities, with a shift toward taxa better adapted to cooler more eutrophic conditions. Assemblage changes indicate four distinct phases caused by temperature decrease and variations in paleocurrents: late Eocene warm‐oligotrophic phase, precursor diversity‐decrease phase, early Oligocene cold‐eutrophic phase, and a steady‐state cosmopolitan phase. The most prominent shift in the assemblages occurred during the ∼550 kyr‐long precursor diversity‐decrease phase, which has relatively high bulk δ¹⁸O and %CaCO3 values, and predates the phase of maximum glacial expansion (Earliest Oligocene Glacial Maximum–EOGM).
... The Bipalla oamaruensis zone is established in the Tishki and Kasyanovka formations in most of the studied sections and corresponds to the sequence of the Bartonian-lower Priabonian Cyrtophormis alta-Etmosphaera polysiphonia-Theocyrtis andriashevi radiolarian zones. An exception is the Sergeevka section, where a diatom association with Bipalla oamaruensis was found in carbonate sediments of the Sergeevka Formation (Khokhlova et (Okada and Bukry, 1980). In the Kantemirovka section (Musatov, 2021), the age of the Sergeevka Formation is also dated as the end of the Lutetian (nannoplankton zones CNE12-CNE13 on the scale (Agnini et al., 2014)). ...
... samples 14, 17 and 19a, considered by him as characteristic of the NP24 to CP 19b Zones of Martini ( 1971) and Okada and Bukry ( 1980 Colorado section nor in Arroyo San Hilario. In addition, he noted that the beds that past workers called diatomites are actually white tuffs (Beal, 1948;Ojeda-Rivera, 1979;Alatorre-Campos in López-Ramos, 1982). ...
The foraminifera and associated microfossils from the type section of the Cerro Tierra Blanca Member (El Cien Formation), supposedly of late Oligocene age, indicate these strata to be of latest Oligocene to late Miocene age. The analysis done from the sequence demonstrates severa! stratigraphic discontinuities that, associated with the scarce geological information from the area, are indicative of structural complexities not detected during the establishment of the type section. lt was impossible to determine the stratigraphical relation between the strata studied and the supposed two other members of the formation for the same reasons -at El Cien- as well as with other sequences that crop out at El Cien-San Hilario, La Purísima or San Juan de la Costa. The micropaleontological assemblage suggests initial subsidence and deposition of early Miocene volcanics and shelf marine clastics, followed by deposition of upper-bathyal diatomaceous sediments during earliest late Miocene. The observed microfossils are a mixture of low- and high-latitude species, such as the ones found at present, near the distal end of the California current off Baja California Sur, and indicate periods of low and high fertility. Based on the present results, it is not possible to determine if the El Cien Formation is a valid name for the beds surrounding El Cien, nor for those to the east.
... The original age model for the late Eocene of ODP Site 1053 is based on the shipboard data which indicates that the study interval is located in the upper Eocene calcareous nannofossil Subzone CP15b (base Isthmolithus recurvus; Okada and Bukry, 1980). Since then, significant advances have been made in Paleogene nannofossil biozonation, including the replacement of unreliable marker taxa (e.g. ...
The Gulf Stream, a western boundary current transporting warm water into the North Atlantic, plays a key role in climate regulation and oceanographic stability at a regional and global scale as part of the Atlantic Meridional Overturning Circulation (AMOC). Evidence suggests that an ancestral Gulf Stream has existed since the Mesozoic, and it has altered its course repeatedly over Cenozoic times. In this study, we focus on the upper Eocene (Priabonian, ca. 36 Ma) from Ocean Drilling Program Site 1053 on Blake Nose (subtropical North Atlantic). Bulk carbon and oxygen stable isotopes, as well as benthic foraminiferal and calcareous nannofossil assemblages, provide an integrated assessment of the palaeoceanographic changes impacting the area through the water column to the seafloor. Micropaleontological assemblages suggest changes in surface ocean stratification and nutrient supply to the seafloor coeval with a paired negative carbon and oxygen isotope excursion and the return to background conditions higher up in the study section. These transitory changes are compatible with the longitudinal displacement of the proto-Gulf Stream and its related eddies. Our results build on previous work and support the hypothesis that links palaeoceanographic changes in the Blake Nose area with shifts in the proto-Gulf Stream during the middle and late Eocene.
... The presence of Emiliania huxleyi in Samples 398-U1590A-1H-1, 5-7 cm, to 11H-1, 0-5 cm (0.12-90.86 mbsf ), and Sample 398-U1590B-2R-CC, 17-20 cm, indicates a Holocene age (≤0.05 Ma) in Zones MNN21b (CNPL11, Backman et al., 2012;NN21, Martini, 1971; CN15, Okada and Bukry, 1980) of Rio et al. (1990) and Di Stefano and Sturiale (2010) (Figure F13). The sequence of Hole U1590A and Sample 398-U1590B-2R-CC, 17-20 cm, is interpreted to be above the acme base of E. huxleyi, which correlated the MNN21a/b boundary and Marine Isotope Stage 4-5a (0.05 Ma) by Rio et al. (1990), Castradori (1993), and Lourens et al. (2004 in the eastern Mediterranean. ...
... mbsf ), indicates a Middle Pleistocene to Holocene age (≤0.265 Ma) within Zones MNN21a and MNN21b (CNPL11: Backman et al., 2012;NN21: Martini, 1971; CN15: Okada and Bukry, 1980) of Rio et al. (1990) and Di Stefano and Sturiale (2010) (Figure F13). The last appearance datum of Pseudoemiliania lacunosa defines the Zone NN19/20 boundary. ...
... The sandstones and siltstones in the Ardath Shale in this area at beach level have been noted by May (1982) as typical overbank (interchanneling) depositon from diluted density currents and to be the proximal part of a submarine-fan complex (see above, May 1985;Stright et al. 2014). The Ardath Shale has been been assigned to the early Lutetian (early middle Eocene) calcareous nannofossil Subzone CP12b (Bukry and Kennedy 1969;Kennedy and Moore 1971;Okada and Bukry 1980). The Ardath Shale has yielded well documented assemblages of marine microfossils (Bukry and Kennedy 1969;Gibson 1971;Steineck et al. 1972) and macroinvertebrates (Hanna 1927;Givens and Kennedy 1979;Teichert and Stanley 1975;Squires 1998;Schweitzer et al. 2002). ...
Large and diverse Eocene otolith assemblages have been described from the US Gulf and Atlantic coastal plains, various basins in Europe, and New Zealand. Here we described a highly diverse otolith association from the middle Eocene (Lutetian and Bartonian) strata of southern California, San Diego County, which was retrieved
from the heritage of John E. Fitch (1918-1982) in the archives of the Ichthyology Department of the Natural History Museum of Los Angeles County, Los Angeles, Califronia. The collection represents the first Eocene otolith assemblage described from the Northeastern Pacific and stems from two localities: the Ardath Shale at Black’s Beach in the Torrey Pines Park just south of Black’s Canyon Road and north of the Salk Fault on the Pacific shore face, and the MissionValley Formation from the west-facing graded hill just east of the Miramar Water Treatment Plant
near the southern shore of Miramar Reservoir. The Ardath Shale was deposited on the deep shelf and continental slope while the Mission Valley Formation represent an inland, nearshore environment during times of the maximum transgression.
A total of more than15,000 otoliths were found representing 96 species of which 53 are described as new and 12 remain in open nomenclature. The fauna of the Ardath Shale is distinctly richer containing 88 species while the one from the Miramar Reservoir site yielded 38 species. The low diversity at the Miramar Reservoir site is thought to be related to the shallow-water environment in which it was deposited whereas the high diversity at Black’s Beach reflects a mixture of shelf and bathyal fishes. In addition, 24 new otolith-based genera are established, four of which are in the category “incertae sedis”. Furthermore, five new species are described from a comparative otolith collection from the US Gulf Coast Eocene and one new species from a comparative collection from the Lutetian of Balegem in Belgium.
The Eocene otolith-based fish fauna from California is assessed for its paleoecological, paleobiogeographic and evolutionary significance. Particular emphasis is directed towards the elucidation of the evolution of the early
Ophidiiformes, which during the early Paleogene were predominantly adapted to warm, clastic shallow-water environments and there were competing in abundance and diversity with other percomorphs (e.g., perciforms s.l.). A warm Eocene paleobioprovince is proposed for the Californian fish fauna which is not related to today’s endemic Northwest Pacific fish fauna along the regime of the cold-water California Current.
... The biostratigraphic data for the BDF are in published works (Ferjani et al., 1990 (Okada and Bukry, 1980) zonation scheme that correlates to the NP10 to NP 13 241 interval in the (Martini, 1971) scheme. 247 This SAR closely aligns with the 2.55 cm/kyr SAR determined by ASM analysis. ...
The Early Eocene Bou Dabbous Formation (BDF) source rock is an economically important source rock in the SW Neo-Tethys covering most of the Ypresian outer ramp to basin deposits in Tunisia. The main rock types of the BDF in central Tunisia include globigerinids-rich grey to black laminated marl and limestone, which occur with an obvious cyclicity at astronomical timescales. In this study, we examine two high-resolution borehole records from northern and eastern Tunisia and an outcrop analog in central Tunisia. The datasets examined were total organic carbon (TOC), magnetic susceptibility, CaCO3, δ13C, δ18O, and Gamma-Ray (GR). Our aim is to investigate the relationship between the rhythmic patterns observed at the BDF outcrop and the Milankovitch cycles and to contextualize the findings within the Ypresian Astrochronological Time Scale (YATS). Additionally, we will discuss the impact of astronomical forcing on sea-level variations and the upwelling system during a greenhouse world. Field measurements and power spectra of the untuned data reveal a hierarchy of cycles throughout the BDF with ∼11.1 m, 4.1, 2.4 m, 1.1 m, and 0.6 m wavelengths. Tuning the 11.1 m cycles to the 405 kyr eccentricity cycle, the astronomical parameters—eccentricity, obliquity, and the precession index—become apparent. The 405 kyr eccentricity cycle is linked to relative sea-level changes inferred from sequence stratigraphy analysis and sedimentary noise modeling. Periods with increased TOC are associated with strong obliquity forcing inferred from the power decomposition analysis and the strong 173-kyr obliquity modulation cycles. The Ypresian record from Tunisia demonstrates the influence of orbital pacing on the strength of the upwelling system, by affecting both the sea level and the climatic belt (wind regime). From 53.89 Ma to 53.2 Ma (TOC > 2 wt %), our model demonstrates that obliquity-driven changes in water stratification led to episodes of varying oxygen levels at the bottom of the basin, affecting organic matter decay and preservation. During the Early Eocene Climatic Optimum, shifts in climatic belts and wind patterns, coupled with rising sea levels, resulted in a weakened upwelling system and reduced the preservation of organic matter (TOC < 0.5 wt%).
... Its depths range from 960 to 940 meters. This biozone shares similarities with the higher altitudes of Nannotetrina fulgens biozone that [18] examined and to the middle Eocene (Lutetian) biozone Coccolithus staurion biozone, which was examined by [24]. Additionally, this biozone matches with Nannotetrina spp. ...
From the Jaddala Formation in northern Iraq in the (K152) well, there are (12 species) of calcareous nannofossils described (belonging to 8 genera), (6 families) following a detailed analysis of calcareous nannofossils. The Jaddala Formation comprises one biostratigraphic zones that have been discovered, Coccolithus staurion Partial Taxon range biozone (CP13c) and its age has been assessed to be in the middle Eocene. Therefore, we proposed a middle Eocene (Lutetian to Bartonian) date for the Jaddala Formation.
... Diatoms, radiolarians, calcareous nannofossils, and planktonic foraminifera contained in the depositional sequences recovered at the analysed sites were the main set of biostratigraphic evidence used by the ODP and DSDP for age determination of the sediment column hosting the silica reaction boundary. Depending on aboundancy and the degree of preservation, the calcareous nannofossils were commonly used to develop the biostratigraphic framework for some sequences following the zonation scheme of Okada and Bukry (1980). Relating to contrast in the aboundancy of diatom tests above and below the silica transition zone, diatoms were employed to especially control the biostratigraphy at the sites sufficiently containing biosilica. ...
Based on an integration of borehole and reflection seismic data, the opal-A to opal-CT transformation front was identified at all the 68 Ocean Drilling Program and Deep Sea Drilling Project sites analyzed. The silica front is represented by a sub-bottom depth interval of various thicknesses where the physical properties of the hosting sediment unit, including bulk density, porosity, resistivity, and P-wave velocity, drastically change. The boundary of sharp physical-property changes is tied to the exhibition of a high-amplitude high-impedance reflection on seismic profiles that commonly cross-cuts the host lithology. The objective and downhole criteria for differentiating between the active and relict silica phase-change transitions were extended. The association with rootless polygonal faults and domal contractional folds, intersecting relationship with the encompassing stratigraphy, the development of irregular morphologies, and wide ranges of thickness, age, and temperature indicated that a greater number of the examined opal-A to opal-CT conversion boundaries (66 out of 68) are currently fossilized. The upward advancement and arrest of fossilized silica transitions is believed to be controlled by an episode of increased palao heat flow whose mechanism is presently unknown. The temperature is known to be the main control for silica-front thickness. The hosting lithology, age, pore geochemistry, and test surface area play a secondary role in thickness variations. The opal-A to opal-CT conversion time-temperature stability zone proposed by Hein et al. (1978) was modified based on the fossilization age and temperature of the reaction fronts. The older reaction boundaries (> 25 Ma in age) were developed as a response to the low-temperature (< 30 °C) active-diagenesis under shallow burial while the formation of younger transitions (< 25 Ma in age) at higher temperatures (< 30 °C), according to the opal-CT formation stability field defined by the present work. Revealed through the decreased trend of geothermal evolution in time, three time spans of different thermal histories were introduced for the silica transitions examined: high thermal-evolution records (> 15 °C/Ma) of the silica fronts migrated upwards since the Early Pliocene and arrested in the Late Pliocene, transitions of thermal-history values between 5 and 15 °C/Ma being active since the Late Oligocene and fossilized in the Late Miocene, and those with low thermal-history records (< 5 °C/Ma) advanced in the Early Paleocene and arrested from the Late Oligocene to Early Miocene.
... The Madeago interval studied here spans the planktic foraminiferal Zone E4 (Wade et al., 2011) and calcareous nannofossils Zones CP8 to CP10 of Okada and Bukry (1980) and Zones CN2 to CN3 pars of Agnini et al. (2014). The same calcareous plankton zones were detected at the Madeago section as previously identified for the Terche section (D'Onofrio et al., 2016). ...
Pronounced warming negatively impacts ecosystem resilience in modern oceans. To offer a long‐term geological perspective of the calcareous plankton response to global warming, we present an integrated record, from two Tethyan sections (northeastern Italy), of the planktic foraminiferal and calcareous nannofossil response to the Eocene Thermal Maximum 2 hyperthermal (ETM2, ∼54 Ma). Our study reveals pronounced changes in assemblage composition and a striking dwarfing of planktic foraminiferal tests of up to 40% during the event, impacting both surface and deeper dwellers. The increased abundance of small placoliths among calcareous nannofossils is interpreted as community size reduction. Literature and our foraminiferal size data from Sites 1263 and 1209 (Atlantic and Pacific Oceans) highlights that the pronounced dwarfism is restricted to the Tethyan area. The ETM2 is characterized by warm sea surface temperatures as indicated by our δ¹⁸O data, but this warming is of global extent and cannot explain the unique dwarfism. Excluding evolutionary modifications, other potential drivers of dwarfism (eutrophication, deoxygenation, metabolic adaptation) cannot explain the exceptional dwarfism by themselves. The smallest sizes are in close temporal association with peaks in volcanic derived Hg/Th‐Hg/Rb recorded just before and at the ETM2 which could not have been brought into our sections through weathering. In contrast, size reductions are absent below and above the ETM2 at Hg peaks where δ¹⁸O data do not show warm conditions. We speculate that the local input of toxic metals from submarine volcanic emissions could have acted synergistically to warming, causing the unique dwarfism.
... It unconformably covers the Yoshinotani Formation of the chi Group and is conformably overlain by the Sari Formation of the Kishima Group. Okada (1992) correlated the Kishima Formation with the calcareous nannofossil subzone CP16a of Okada & Bukry (1980). This subzone is the equivalent of the zones CNE21 and lower part of CNO1 of Agnini et al. (2014), which ranges from 33.88 to 33.2 Ma (latest Priabonian to earliest Rupelian). ...
A new ungulinid bivalve species, Transkeia sagaensis n. sp, is described from the uppermost Eocene-lowest Oligocene Kishima Formation in Kyūshū, southwestern Japan. The present new species is the oldest member in the genus Transkeia Huber, 2015. In the previous molluscan studies of the formation, no ungulinid species have been recognized. This is probably due to the misidentification to a venerid, Cyclinella? compressa (Nagao, 1928b).
... A possible explanation for this diachroneity is the latitudinal difference between sites with well-defined biostratigraphic tie points (Agnini et al., 2007(Agnini et al., , 2014 and Site U1553. Indeed, the traditionally used Paleogene calcareous nannofossil biozones are predominantly based on low-to mid-latitude assemblages (Agnini et al., 2014;Martini, 1971;Okada & Bukry, 1980) and therefore include many warm-water taxa (e.g., Discoaster spp.) that only have rare or spotty occurrences at high latitude sites such as U1553. Despite the apparent latitudinal diachroneity of nannofossil datums, it is striking that the sequence of biostratigraphic events at Site U1553 is identical to those at low-and mid-latitude sites. ...
The late Paleocene to early Eocene interval is characterized by a series of carbon perturbations that caused transient warming (hyperthermal) events, of which the Paleocene‐Eocene Thermal Maximum (PETM) was the largest. These hyperthermals can be recognized in the pelagic sedimentary record as paired negative δ¹³C and δ¹⁸O excursions, in addition to decreased calcium carbonate and increased iron content caused by carbonate dissolution. However, current data are predominantly sourced from the equatorial‐to subequatorial regions. Here we present a new high‐latitude late Paleocene—early Eocene record, recovered during International Ocean Discovery Program (IODP) Expedition 378 on the Campbell Plateau off New Zealand, in the southwest Pacific Ocean. To construct an age model, we correlated our chemostratigraphic and biostratigraphic data to existing astronomically‐tuned age models from Walvis Ridge (South Atlantic Ocean) and Demerara Rise (equatorial Atlantic Ocean). Our results indicate that the Site U1553 composite section spans ∼7 million years of the latest Paleocene to early Eocene (50.5–57.5 Ma), and preserves many of the early Eocene hyperthermals; including a PETM interval that is more expanded than elsewhere in this region. However, construction of the age model also revealed discrepancies between the chemostratigraphic and biostratigraphic tie points used for correlation. This is likely due to latitudinal diachroneity in the calcareous nannofossil biostratigraphic datums, which are primarily based on low‐to mid‐latitude assemblages. Therefore, our study highlights the need to establish a revised calcareous nannofossil biozonation that is more appropriate for high‐latitude age models.
The Early Eocene Bou Dabbous Formation (BDF) source rock is an economically important source rock in the SW Neo-Tethys covering most of the Ypresian outer ramp to basin deposits in Tunisia. The main rock types of the BDF in central Tunisia include globigerinids-rich grey to black laminated marl and limestone, which occur with an obvious cyclicity at astronomical timescales. This study examines two high-resolution borehole records from northern and eastern Tunisia and an outcrop analog in central Tunisia. The datasets examined were total organic carbon (TOC), magnetic susceptibility, CaCO3, δ13C, δ18O, and Gamma-Ray (GR). We aim to investigate the relationship between the rhythmic patterns observed at the BDF outcrop and the Milankovitch cycles and contextualize the findings within the Ypresian Astrochronological Time Scale (YATS). Additionally, we will discuss the impact of astronomical forcing on sea-level variations and the upwelling system during a greenhouse world. Field measurements and power spectra of the untuned data reveal a hierarchy of cycles throughout the BDF with ∼11.1 m, 4.1, 2.4 m, 1.1 m, and 0.6 m wavelengths. Tuning the 11.1 m cycles to the 405 kyr eccentricity cycle, the astronomical parameters—eccentricity, obliquity, and the precession index—become apparent. The 405 kyr eccentricity cycle is linked to relative sea-level changes inferred from sequence stratigraphy analysis and sedimentary noise modeling. Periods with increased TOC are associated with strong obliquity forcing inferred from the power decomposition analysis and the strong 173-kyr obliquity modulation cycles. The Ypresian record from Tunisia demonstrates the orbital pacing on the strength of the upwelling system, by affecting both the sea level and the climatic belt (wind regime). From 53.89 Ma to 53.2 Ma (TOC > 2 wt %), our model demonstrates that obliquity-driven changes in water stratification led to episodes of varying oxygen levels at the bottom of the basin, affecting organic matter decay and preservation. During the Early Eocene Climatic Optimum, changes in climatic belts and wind patterns, along with rising sea levels, led to a shift in the high organic matter accumulation zone. This resulted in a weakened upwelling system in central Tunisia and reduced organic matter accumulation (TOC < 0.5 wt%).
This study investigated the calcareous nannofossil assemblages in detail from the early Miocene aged Lice Formation outcropping in the Kahramanmaraş basin. The biostratigraphy of calcareous nannofossils was outlined and paleoenvironmental features determined. In 81 samples taken from three measured sections in the region, 17 calcareous nannofossil genus and 48 nannofossil species were identified. These calcareous nannofossil genus and species identified the Lice Formation as being in the CNM4 nannofossil biozone. The abundance and diversity of early Miocene calcareous nannofossil species varied in the measured sections, with the samples generally moderate‐poor, apart from a few samples. The relative abundance of individuals of Cyclicargolithus floridanus, Coccolithus pelagicus, Reticulofenestra hagii and Sphenolithus moriformis species, with paleoecological importance identified in the study region, indicate that in early Miocene times, the basin in which the Lice Formation deposited was meso‐eutrophic with excess nutrient input, temperate and generally stable shallow marine conditions.
The award-winning first volume in this 28-volume series. Complete coverage of the geology and geophysics of the western North Atlantic Ocean basin in 41 chapters, organized into 8 sections: Introduction; Present Accretion Axis; Regional Geology and Geophysics; Plate Tectonic Evolution; Surficial Sedimentation; Biofacies; Paleoceanography; and Resources and Law of the Sea. The editors received the 1986 Alan Berman Research Publication Award for this volume. Includes 11 plates, several in color.
Sedimentary rocks containing molluscan and cetacean fossils occur along the Narashi–Moto Coast in Iwado, Muroto City, Kochi Prefecture, southwestern part of Shikoku Island, Japan. Here we describe the Narashi Formation of the Tonohama Group and estimate its depositional age based on planktonic foraminifera and calcareous nannofossil assemblages. The depositional age indicated by planktonic foraminifera is 8.58–4.37 Ma, and the age inferred from the calcareous nannofossil assemblage is 5.53–3.82 Ma. Therefore, the Narashi Formation is estimated to have been deposited at 5.53–4.37 Ma. The formation contains a pectinid-dominated molluscan association (i.e., the Amussiopecten–Mimachlamys–Amusium association). Based on the extant species present in the association, we estimate that the formation was deposited at depths shallower than 20–30 m. This association includes several characteristic species of the Kakegawa fauna, a Pliocene to early Pleistocene molluscan fauna on the Pacific side of southwest Japan. In contrast, the assemblage does not contain characteristic species of the Zushi fauna, which is a warm-marine molluscan fauna of the late Miocene to early Pliocene. The results suggest the Kakegawa fauna became established in Shikoku before 4.37 Ma.
The suggested marine geochemical pattern implies the role of diatoms in absorption of atmospheric carbon-dioxide and oxygenation along with bioproductivity in the Cenozoic depocenters. The dissolution, burial, and recycling of diatom assemblages regulates the deep-water silicon, nitrogen, iron, calcium, and phosphorus nutritional elements in addition to biogenic fixation of aqueous silicon. This synoptic notion also involves constraints from non-nutritional trace elements and continental terrigenous inputs released into the ocean water from terrestrial weathering.
Background
Calcareous nannofossils are minute microfossils widely present in marine strata. Their identification holds significant value in studies related to stratigraphic dating, paleo-environmental evolution, and paleoclimate reconstruction. However, the process of identifying these fossils is time consuming, and the discrepancies between the results obtained from different manual identification methods are substantial, hindering quantification efforts. Therefore, it is necessary to explore automated assisted identification of fossil species. This study mainly focused on 18 key fossil species from the Miocene era. Five convolutional neural network (CNN) models and 10 data augmentation techniques were compared. These models and techniques were employed to analyze and collectively train two- and three-dimensional fossil morphologies and structures obtained from three different fossils observed under single-polarized light microscopy, orthogonal polarized light microscopy, and scanning electron microscopy. Finally, the model performance was evaluated based on the predictive outcomes on the test set, using metrics such as confusion matrix and top-k accuracy.
Result
The results indicate that, for the calcareous nannofossil images, the most effective data augmentation approach is a combination of four methods: random rotation, random mirroring, random brightness, and gamma correction. Among the CNN models, DenseNet121 exhibits the optimal performance, achieving an identification accuracy of 94.56%. Moreover, this model can distinguish other fossils beyond the 18 key fossil species and non-fossil debris. Based on the confusion matrix, the evaluation results reveal that the model has strong generalization capability and outputs highly credible identification results.
Conclusion
Drawing on the identification results from CNN, this study asserts a robust correlation among extinction photographs, planar images, and stereoscopic morphological images of fossil species. Collective training facilitates the joint extraction and analysis of fossil features under different imaging methods. CNN demonstrates many advantages in the identification of calcareous nannofossils, offering convenience to researchers in various fields, such as stratigraphy, paleo-ecology, paleoclimate, and paleo-environments of ancient oceans. It has great potential for advancing the development of marine surveys and stratigraphic recognition processes in the future.
The deposition of a substantial amount of clastic sediments in the Krishna Godavari Basin formed a thick layer of nannofossil-rich clay known as the Godavari Clay Formation. This clayey sequence is a treasure trove for unveiling paleoclimatic and paleoceanographic information. Numerous radiometric dates from the topmost portion of this clay (top 27 m) are available, covering the last 43 ka. However, the availability of data on age connotation with considerably high resolution for the deeper sediments is rare and is still awaited. In this study, we pursued nannoplankton and planktic foraminiferal investigations on the top 198 m (Hole 10D), 300 m (Hole 3B), and 198 m (Hole 5C) sediments of this basin to generate multiple age data with a relatively high resolution. First Occurrence (FO) and Last Occurrence (LO) of nannoplankton taxa Emiliania huxleyi, Helicosphaera inversa, Helicosphaera sellii, large Gephyrocapsa spp., Pseudoemiliania lacunosa, Reticulofenestra asanoi, and planktic foraminiferal taxa Globorotalia flexuosa and Globigerinella calida are considered as potential index taxa for establishing the bioevents as well as biostratigraphy. Based on these, we have identified nine events from Hole 10D, six events from Hole 3B, and seven events from Hole 5C, which are potential for assigning the relative ages. We also observed twofold variations in sedimentation rates in all the holes and one hiatus at 110.73 mbsf in Hole 5C, indicating a shift in climate and basinal settings. A high sedimentation rate of >20.59 cm/ka after~0.4 Ma at all the holes is probably linked to the intensification of the Indian summer monsoon across the mid-Brunhes Epoch. The significantly low sedimentation rates (<14.62 cm/ka) in older sediment sequences before 0.4 Ma is probably related to the relatively weak monsoonal activity. The generated age data, variations in sedimentation rates, and identified hiatus are considered to be potential for delineating paleoclimatic and paleoceanographic changes of this area since the Calabrian Stage.
Региональная зональная радиоляриевая шкала палеогена, разработанная для территории Европейской России, Западной Сибири и прилегающих регионов Казахстана (Северо-Восточный Прикаспий, Тургай) (бореальный стандарт) скорректирована и уточнена в соответствии с новыми данными, полученными при современном изучении биостратиграфии палеогена. Ведущее значение при этом имели новые данные по сопровождающим радиоляриевые комплексы диатомовым водорослям и цистам динофлагеллят. Важным аспектом актуализации явилось сопоставление его с современным глобальным низкоширотным радиоляриевым зональным стандартом. Коррекции и уточнению подверглись стратиграфическая позиция, возраст и фиксация границ биостратонов шкалы; в частности, выявлены три перерыва в последовательности зон бореального стандарта, ранее не отмеченные в нем.
THE stratigraphic value of a group of marine minute algae usually referred to as the calcareous nannoplankton, first shown by Bramlette and Riedel1, has already been discussed2. A standard zonation, based partly on the investigations of Hay et al.3 and Bramlette and Wilcoxon4, has been proposed, and the Neogene calcareous nannoplankton zones have been numbered NN 1 to NN 21.
Zonation of the Paleocene—Lower Eocene interval
- Mohler