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A high resolution lutetian-Bartonian planktonic foraminiferal zonation in the Crimean-Caucasus region of the northeastern Peri-Tethys
Abstract
The traditional Middle Eocene zonation in the Crimean-Caucasus region contains 4 zones. The infrazonal scale contains 7 subdivisions ranked as subzones. The lower boundaries of the zones are defined on first or last appearances of stratigraphically important species. Six stages can be recognized in the evolutionary and ecological progression of the planktonic foraminifers. The similarity and unidirectional morphologic and taxic evolution in the rapidly evolving group of planktonic foraminifera in the Crimean-Caucasus Region and Tethys provide a firm basis for correlation of Lutetian-Bartonian zonations and regional and international (standard) Tethyan stages.
... The Kuma Formation is widely spred in the tonic foraminifer assemblages are observed, along with the extinction of benthic forms: over 40 genera of benthic foraminifers disappeared there (Bugrova, 2000). According to Beniamovski et al. (2003) and Benyamovskiy (2012), the deep-water Kuma Basin spread over the Northern Greater Black Sea region, Crimea, the Northern Caucasia, the Southern Emba and the western part of Central Asia (Fig. 1). ...
... Based on foraminifer studies, the Kuma Formation belongs to the Subbotina turcmenica Zone (Bugrova, 1988;Akhmetiev and Beniamovski, 2003;Zernetsky et al., 2003;Akhmets'ev and Beniamovski, 2006;Akhmetiev et al., 2015;Zernyetskiy et al., 2015), which is divided into two subzones, i.e., Globigerina azerbaidjanica and Globigerina instabilis subzones (Korovina, 1970;Zernetsky et al., 2003;Akhmetiev and Beniamovski, 2004). The foraminiferal zonal divisions of Crimean are consistent with the international foraminifer zonation (Benyamovskiy, 2012;Zernyetskiy et al., 2015;Ryabokon, 2016). The bottom of the Kuma Formation lies either within the Bartonian (Zernetsky et al., 2003;Akhmetiev and Beniamovski, 2004), or within the lowermost Bartonian (Bugrova et al., 2008;Akhmetiev et al., 2015;Zernyetskiy et al., 2015), or within the Lutetian (Akhmetiev and Beniamovski, 2003). ...
... The Kuma Formation most probably correlated with the Tishkino Forma- Beniamovski et al., 2003). 1 -Cretaceous deposits; 2 -Paleogene deposits; 3 -Neogene deposits; 4 -studied sections: I -Bakhchisaray quarry, II -Ravninnaya R-43 well, III -Keresta-1 well, IV -Belaya river section; 5 -foothill Mesozoic suture under Cretaceous-Paleogene deposits; 6 -distribution area of the Kuma Formation. tion from the North Ukrainian province, the Solonka Formation from the Lower Volga Region (Benyamovskiy, 2012), the Keresta and the Solonka formations from the south of the Russian Plate (Musatov and Bogachkin, 2019a;Musatov and Muzylev, 2021). ...
The stratigraphic correlation of the Kuma Formation from the south of the Russian Platform and the Crimea-Caucasian region has been a matter of debate for decades. A bed-by-beds study of dinocysts and nannoplankton from the the Kuma Formation made it possible to recognize a sequence of biotic events, important for defining and correlating the biozones. At the Bakhchisarai limestone quarry, six dinoflagellate zones and six nannoplankton zonal units were recognized, assignable to the Middle Eocene Lutetian and Bartonian stages. Our paleoecological analyses of the organic-walled microphytoplankton assemblages and of the palynofacies indicate that the the Kuma Formation deposited in the inner shelf zone, probably of anoxic and eutrophic settings within the Pontic-Transcaucasian magmatic belt. Assemblages of organic-walled microphytoplankton comprise potentially toxic dinoflagellate species of Alexandrium. The Middle Eocene Climatic Optimum event is recorded in the upper part of the the Kuma Formation, presumably indicated by the Dracodinium rhomboideum dinoflagellate zone, which is characterized by an acme of Dracodinium laszczynskii Gedl and the lowest occurrence of nannofossils Reticulofenestra bisecta (Hay, Mohler and Wade) Roth. Two new species are described: Pentadinium rugosum Vasilyeva, n. sp. (dinocyst) and Corannulus tauricum Musatov, n. sp. (nannofossil). The bioevents and biozones established herein are significant for correlations of the Middle Eocene of the Crimean Peninsula and the south of the Russian Platform.
... The Northern Tethyan basins partly reveal conditions like the epeiric sea of the Peri-Tethys. Such resemblance with Caucasian, Crymean and Black sea coast sections is documented by Paleocene hyperthermals (Dinarès-Turell et al., 2010, 2012, deoxygenation and stress biotic conditions during the PETM (Gavrilov et al., 2003;Dickson et al., 2014;Shcherbinina et al., 2016;Aleksandrova and Shcherbinina, 2011), a high planktic productivity and diversity during the Early and Middle Eocene greenhouse (Oberhänsli and Beniamovski, 2000;Beniamovski et al., 2003;Deprez et al., 2015;Popov et al., 2019), etc. ...
... This zonation has been completed by other species, which were used as supplementary zonal markers in parastratigraphic schemes (e.g. Molina et al., 1999Molina et al., , 2011Schmitz et al., 2011;Payros et al., 2007;Beniamovski, 2012;Luciani and Giusberti, 2014). Abbrevations: SE -Selandian, TH -Thanetian, BAR -Bartonian, HOZ -Highest-occurrence Zone; TRZ -Taxon range Zone; LOZ -Lowest-occurrence Zone; CRZ -Concurrent-range Zone, AZ -Acme Zone. ...
... Our study area was located along the Belaya River in the North Caucasus region of Russia (44.3665°N, 40.1970°E; paleolatitude ∼42°N at 40 Ma according to Paleolatitude.org; van Hinsbergen et al., 2015), ∼25 km south of the town of Maikop (Fig. 1). The studied section contains a succession of middle-late Eocene sediments divided into the Cherkessk, Keresta, Kuma, and Belaya Glina Formations (Zakrevskaya et al., 2011;Beniamovski, 2012), which were deposited in a continental shelf setting (van der Boon et al., 2019). Here, we defined the base of the section (0 m) as the sharp transition from the green clays of the Cherkessk Formation to the white marls of the Keresta Formation (Fig. 2). ...
... Further upward, the succession continues into the Maikop Series. The Kuma Formation at the Belaya River has been dated as Bartonian in age based on biostratigraphy of planktonic foraminifera (regional Crimea-Caucasus zones PF13-PF14; Beniamovski, 2012) and calcareous nannofossils (zones NP16-NP17/CP14; Martini, 1971;Okada and Bukry, 1980;van der Boon et al., 2019;Popov et al., 2019b), in line with the age range inferred for the Kuma Formation within the broader region (ca. 44-36.5 Ma;Beniamovski et al., 2003). ...
The middle Eocene climatic optimum (ca. 40 Ma) stands out as a transient global warming phase of ∼400 k.y. duration that interrupted long-term Eocene cooling; it has been associated with a rise in atmospheric CO2 concentrations that has been linked to a flare-up in Arabia-Eurasia continental arc volcanism. Increased organic carbon burial in the Tethys Ocean has been proposed as a carbon sequestration mechanism to bring the middle Eocene climatic optimum to an end. To further test these hypotheses, we assessed the sedimentary and geochemical expression of the middle Eocene climatic optimum in the northern Peri-Tethys, specifically, the organic-rich Kuma Formation of the Belaya River section, located on the edge of the Scythian Platform in the North Caucasus, Russia. We constructed an age-depth model using nannofossil chronobiostratigraphy. Throughout the studied middle Eocene interval (41.2−39.9 Ma), we documented sea-surface temperatures of 32−36 °C based on the tetraether index of tetraethers consisting of 86 carbons (TEX86), depending on proxy calibration, and during the early middle Eocene climatic optimum, we observed sea-surface warming of 2−3 °C. Despite the proximity of the section to the Arabia-Eurasia volcanic arc, the hypothesized source of volcanic CO2, we found no evidence for enhanced regional volcanism in sedimentary mercury concentrations. Sedimentary trace-element concentrations and iron speciation indicate reducing bottom waters throughout the middle Eocene, but the most reducing, even euxinic, conditions were reached during late middle Eocene climatic optimum cooling. This apparent regional decoupling between ocean warming and deoxygenation hints at a role for regional tectonics in causing basin restriction and anoxia. Associated excess organic carbon burial, extrapolated to the entire regional Kuma Formation, may have been ∼8.1 Tg C yr−1, comprising ∼450 Pg C over this ∼55 k.y. interval. Combined with evidence for enhanced organic carbon drawdown in the western Peri-Tethys, this supports a quantitatively significant role for the basin in the termination of the middle Eocene climatic optimum by acting as a large organic carbon sink, and these results collectively illustrate that the closing Tethys Ocean might have affected global Paleogene climate. Moreover, this study highlights the importance of the interplay between global climate and regional oceanic gateway evolution in determining local climate and oceanographic change.
... The Northern Tethyan basins partly reveal conditions like the epeiric sea of the Peri-Tethys. Such resemblance with Caucasian, Crymean and Black sea coast sections is documented by Paleocene hyperthermals (Dinarès-Turell et al., 2010, 2012, deoxygenation and stress biotic conditions during the PETM (Gavrilov et al., 2003;Dickson et al., 2014;Shcherbinina et al., 2016;Aleksandrova and Shcherbinina, 2011), a high planktic productivity and diversity during the Early and Middle Eocene greenhouse (Oberhänsli and Beniamovski, 2000;Beniamovski et al., 2003;Deprez et al., 2015;Popov et al., 2019), etc. ...
... This zonation has been completed by other species, which were used as supplementary zonal markers in parastratigraphic schemes (e.g. Molina et al., 1999Molina et al., , 2011Schmitz et al., 2011;Payros et al., 2007;Beniamovski, 2012;Luciani and Giusberti, 2014). Abbrevations: SE -Selandian, TH -Thanetian, BAR -Bartonian, HOZ -Highest-occurrence Zone; TRZ -Taxon range Zone; LOZ -Lowest-occurrence Zone; CRZ -Concurrent-range Zone, AZ -Acme Zone. ...
Early Paleogene events of the Alpine Tethys were considerably upgraded for the Western Carpathians. The Kršteňany KRS-3 core section provides high-resolution data from the Cretaceous-Paleogene (K/Pg) transition to Lutetian/Bartonian boundary. The Upper Cretaceous sequence started from terrestrial red-beds superposed by transgressive sediments with Abathomphalus mayaroensis. The K/Pg transition is inferred in a horizon with reworked Maastrichtian microfossils and earliest Danian species of Globigerinidae. Multiple redeposition with eugubina-rich clasts implies a storm erosion and resuspension of the post K/Pg sequence during P0 - Pα Zones (approx. 300 kyr). The early Danian microfauna was initially impoverished, later enriched by first praemuricids, and after the Latest Danian Event (LDE) diversified to angulate morozovellids, igorinids and fasciculiths. Paleocene bioevents and polarity chrons imply a radiation of planktic foraminifera during transgressive cycles in the late Danian (P1, C28n), Middle Selandian (P3b, C26r/n) and late Thanetian (P4c/P5, C25n/C24r), and vacant P/C zones either in regressive cycles or during unconformities in the early Danian (P1a/C28r), Danian/Selandian transition (P2/P3a, C27r/n) and middle Thanetian (P4b/C25r). The late Thanetian transgression (Th-2) led to replacement of Assilina-rich beds (SBZ 4) by Nummulites-bearing marls (SBZ 5) at the base of Illerdian (= LFT). The Paleocene – Eocene transition is marked by Acarinina-rich marlstones with densely muricate species (Ac. acarinata) and excursion taxa (Ac. sibaiyaensis, D. araneus), which correspond to the Paleocene-Eocene Thermal Maximum (PETM). This horizon implies a warm-water productivity, eutrophication, humidity and upwelling activity (pteropods, diatoms). The hyperthermal conditions culminated at the beginning of the Early Eocene Climatic Optimum (EECO) with demise of morozovellids, intensification of hydrological cycles and enhanced continental input of siliciclastics, which progressed by accumulation of Ypresian nummulite banks and terminated by pelagic deposition with recovery of hispid morozovellids (E5 – E7 Zones, chron C23n - C22r). The lower Lutetian sequence reveals a post-EECO cooling by predominance of deep-dwelling habitats (subbotinids, turborotaliids, catapsydracids) and appearance of subtile morozovellids (M. gorrondatxensis), earliest globigerinathekids and another marker species of the E7 – E8 Zones (chron 22n - C21r). Late Lutetian warming (LLTM) is indicated by increased plankton productivity of mixed-layer habitats like strongly muricate species of anguloconical acarininids (Ac. topilensis, Ac. medizzai) and gracile species of morozovelloids (M. coronatus). The youngest part of the Kršteňany section belongs to the E11 Zone, indicating prior conditions of Middle Eocene Climatic Optimum (MECO) warming.
... Although significant progress has been made during the last decades (e.g. Popov et al., 2004aPopov et al., ,b, 2018Benyamovskiy, 2012), a unified chronostratigraphy of the Eocene-Oligocene strata of the Peri-Tethys/Paratethys region is poorly constrained. We perform integrated stratigraphy using calcareous nannofossil biostratigraphy, magnetostratigraphy and Ar-Ar dating to better constrain the ages of the Kuma Formation and the lower boundary of the Maikop Group. ...
... These green mudstones are overlain by the Keresta Formation, consisting of white clayey marlstones (e.g. Benyamovskiy, 2012) that gradually transition to laminated, coffeecoloured marlstones of the Kuma Formation. The Kuma Formation contains sparse small pyrite nodules at the base, and abundant large ones (up to tens of centimetres Ø) at the top, near the transition to the Belaya Glina Formation. ...
The sedimentary succession along the Belaya River (North Caucasus) provides a record of middle Eocene to Miocene sediments. This time interval is well known for its important climatic transitions (e.g., Middle Eocene Climate Optimum (MECO) and Eocene-Oligocene Transition (EOT)), and changes in basin configuration from Peri-Tethys to Paratethys. The Belaya section contains two intervals marked by oxygen-depleted sediments; the Eocene Kuma Formation of the Peri-Tethys and the Oligocene Maikop Group of the Paratethys. Both are considered important source rocks for hydrocarbon exploration in the Black Sea and Caspian Sea. We present integrated stratigraphic results of the Belaya River section using calcareous nannoplankton biostratigraphy, magnetostratigraphy and 40Ar/39Ar dating. Furthermore, we investigate the geochemical character of the sediments using X-ray fluorescence (XRF) and stable carbon and oxygen isotopes. A middle Eocene age for the lower part of the succession is established from nannoplankton biostratigraphy. The Kuma Formation is dated between 42.1 and 38.4 Ma based on the assumption of constant sediment accumulation rates. A negative oxygen isotope excursion in the middle part of the Kuma Formation could be related to the MECO (~40 Ma). The onset of the Maikop Group is dated around the base of chron C13n at an age of ~33.7 Ma, close to the Eocene-Oligocene boundary. Based on geochemical results, we show that the Kuma Formation and Maikop Group correspond to two different episodes of intensified oceanic oxygen depletion in the succession. We hypothesise that oxygen-depletion as recorded in the Kuma Formation is linked to an increased nutrient input in the open marine Peri-Tethys due to widespread volcanism in the Neotethys subduction zone, while oxygen-depletion as recorded in the Maikop Group is linked to basin restriction caused by the eustatic sea-level fall straddling the Eocene – Oligocene boundary triggering stratified conditions in the semi-isolated Paratethys Sea.
... Although significant progress has been made during the last decades (e.g. Popov et al., 2004aPopov et al., ,b, 2018Benyamovskiy, 2012), a unified chronostratigraphy of the Eocene-Oligocene strata of the Peri-Tethys/Paratethys region is poorly constrained. We perform integrated stratigraphy using calcareous nannofossil biostratigraphy, magnetostratigraphy and Ar-Ar dating to better constrain the ages of the Kuma Formation and the lower boundary of the Maikop Group. ...
... These green mudstones are overlain by the Keresta Formation, consisting of white clayey marlstones (e.g. Benyamovskiy, 2012) that gradually transition to laminated, coffeecoloured marlstones of the Kuma Formation. The Kuma Formation contains sparse small pyrite nodules at the base, and abundant large ones (up to tens of centimetres Ø) at the top, near the transition to the Belaya Glina Formation. ...
The sedimentary succession along the Belaya River (North Caucasus) provides a record of middle Eocene to Miocene sediments. This time interval is well known for its important climatic transitions (e.g., Middle Eocene Climate Optimum (MECO) and Eocene-Oligocene Transition (EOT)), and changes in basin configuration from Peri-Tethys to Paratethys. The Belaya section contains two intervals marked by oxygen-depleted sediments; the Eocene Kuma Formation of the Peri-Tethys and the Oligocene Maikop Group of the Paratethys. Both are considered important source rocks for hydrocarbon exploration in the Black Sea and Caspian Sea. We present integrated stratigraphic results of the Belaya River section using calcareous nannoplankton biostratigraphy, magnetostratigraphy and 40Ar/39Ar dating. Furthermore, we investigate the geochemical character of the sediments using X-ray fluorescence (XRF) and stable carbon and oxygen isotopes. A middle Eocene age for the lower part of the succession is established from nannoplankton biostratigraphy. The Kuma Formation is dated between 42.1 and 38.4 Ma based on the assumption of constant sediment accumulation rates. A negative oxygen isotope excursion in the middle part of the Kuma Formation could be related to the MECO (~40 Ma). The onset of the Maikop Group is dated around the base of chron C13n at an age of ~33.7 Ma, close to the Eocene-Oligocene boundary. Based on geochemical results, we show that the Kuma Formation and Maikop Group correspond to two different episodes of intensified oceanic oxygen depletion in the succession. We hypothesise that oxygen-depletion as recorded in the Kuma Formation is linked to an increased nutrient input in the open marine Peri-Tethys due to widespread volcanism in the Neotethys subduction zone, while oxygen-depletion as recorded in the Maikop Group is linked to basin restriction caused by the eustatic sea-level fall straddling the Eocene – Oligocene boundary triggering stratified conditions in the semi-isolated Paratethys Sea.
... Our interpretation thus assumes an essential role played by the Ukrainian Shield and sea level changes for the circulation pattern of water masses between the recent Black Sea and North Sea basins during Eocene. It has been known for decades that Palaeogene foraminifera assemblages (e.g., [5]) from territories in between these two basins (e.g., northern Poland) were characterized by temporal incomes of high-or low-latitude «migrants». Their appearances were interpreted as results of new sea-ways openings and/or as reflections of climatic changes. ...
... However, Paleogene foraminiferal assemblages of shallow water sections of the Kopet-Dagh Basin are not suitable for the application of these global zonal schemes and this basin should be studied on regional schemes and regional biozonation, although this basin still lacks a regional biozonation scheme. There was an obvious difference in the composition of Paleogene foraminiferal fauna in our studied region (Fig. 1) such as some parts of CAR and former Soviet Union with those in the rest of the world (Beniamovsky, 2012;King et al., 2013). Generally, current understanding of Paleogene palaeogeography and palaeobiogeography of the middle latitudes of CAR was based on studies of A.L. Yanshin performed in the second quarter of the twentieth century. ...
... This also helps to reconcile a rapid cooling and drawdown of CO 2 after the MECO with the absence of any carbonate overshoot due to silicate weathering, such as is seen at the PETM . We note that enhanced burial of organic carbon, such as is observed in the Peri-Tethys of Italy (Spofforth et al., 2010) and the Crimea-Caucasus (Benyamovskiy, 2012), and consistent with globally increased δ 13 C in carbonates following the MECO (Bohaty et al., 2009), may have also played an important role in carbon drawdown. ...
The Middle Eocene Climatic Optimum (MECO) was a gradual warming event and carbon cycle perturbation that occurred between 40.5 and 40.1 Ma. A number of characteristics, including greater‐than‐expected deep‐sea carbonate dissolution, a lack of globally coherent negative δ¹³C excursion in marine carbonates, a duration longer than the characteristic timescale of carbon cycle recovery, and the absence of a clear trigger mechanism, challenge our current understanding of the Earth system and its regulatory feedbacks. This makes the MECO one of the most enigmatic events in the Cenozoic, dubbed a middle Eocene “carbon cycle conundrum.” Here we use boron isotopes in planktic foraminifera to better constrain pCO2 changes over the event. Over the MECO itself, we find that pCO2 rose by only 0.55–0.75 doublings, thus requiring a much more modest carbon injection than previously indicated by the alkenone δ¹³C‐pCO2 proxy. In addition, this rise in pCO2 was focused around the peak of the 400 kyr warming trend. Before this, considerable global carbonate δ¹⁸O change was asynchronous with any coherent ocean pH (and hence pCO2) excursion. This finding suggests that middle Eocene climate (and perhaps a nascent cryosphere) was highly sensitive to small changes in radiative forcing.
... The revision of species of the genus Hantkenina shows that the form identified by Subbotina (1953) During the evolution of the genus Globigerinatheka, the species G. index follows G. subconglobata (Schutz.)-an ancestral form of many Middle Eocene Globigerinatheka species (Pearson et al., 2006), including G. index (Benyamovskiy, 2012). (Fig. 2). ...
The early Cenozoic marine sedimentary record is punctuated by several brief episodes (<200 kyr) of abrupt global warming, called hyperthermals, that have disturbed ocean life and water physicochemistry. Moreover, recent studies of fluvial–deltaic systems, for instance at the Palaeocene–Eocene Thermal Maximum, revealed that these hyperthermals also impacted the hydrologic cycle, triggering an increase in erosion and sediment transport at the Earth's surface. Contrary to the early Cenozoic hyperthermals, the Middle Eocene Climatic Optimum (MECO), lasting from 40.5 to 40.0 Ma, constitutes an event of gradual warming that left a highly variable carbon isotope signature and for which little data exist about its impact on Earth surface systems. In the South Pyrenean foreland basin (SPFB), an episode of prominent deltaic progradation (Belsué–Atarés and Escanilla formations) in the middle Bartonian has been usually associated with increased Pyrenean tectonic activity, but recent magnetostratigraphic data suggest a possible coincidence between the progradation and the MECO warming period. To test this hypothesis, we measured the stable-isotope composition of carbonates (δ13Ccarb
and δ18Ocarb) and organic matter (δ13Corg) of 257 samples in two sections of SPFB fluvial–deltaic successions covering the different phases of the MECO and already dated with magnetostratigraphy. We find a negative shift in δ18Ocarb and an unclear signal in
δ13Ccarb around the transition from magnetic chron C18r to chron C17r (middle Bartonian). These results allow, by correlation with reference sections in the Atlantic and Tethys, the MECO to be identified and its coincident relationship with the Belsué–Atarès fluvial–deltaic progradation to be documented. Despite its long duration and a more gradual temperature rise, the MECO in the South Pyrenean foreland basin may have led, like lower Cenozoic hyperthermals, to an increase in erosion and sediment transport that is manifested in the sedimentary record. The new data support the hypothesis of a more important hydrological response to the MECO than previously thought in mid-latitude environments, including those around the Tethys.
Data on the Global Stratotypes Sections and Points of the Paleogene Stages of the modern International Stratigraphic Scale, as well as the criteria for determining the boundaries of the Paleogene Stages in North-Western Europe are presented. The characteristics of the position of the stage boundaries in the sedimentary section of the platform Ukraine are given. In the Paleogene section of Southern Ukraine, the lower boundaries of the Ypresian and Priabonian were recognized by global correlation markers. According to the modern International Stratigraphic Scale, the position of the Lutetian / Bartonian and Rupelian / Chattian boundaries in the sedimentary sections of Southern and Northern Ukraine has been clarified in comparison with previous views. The position of most stage boundaries in the biostratigraphic (zonal) scheme of the Paleogene of Ukraine is more accurately determined. The criteria for identification for some of them in the section of the south and north of Ukraine are proposed. Most of the stage boundaries are represented by hiatus in the sedimentary cover of the platform Ukraine. Part of the boundaries of the Paleogene stages coincides with the boundaries of the regional stratigraphic units of Southern and Northern Ukraine, namely: – the Cretaceous / Paleogene boundary is at the base of the Belokamenskia and Pselian regional stages; – the Paleocene/Eocene boundary coincides with the boundary of the Merlian/Kanevian regional stages; – the Ypresian/Lutetian boundary coincides with the Kanevian/Buchakian regional stages; – the lower boundary of Priabonian is at the base of the Almian and Obukhovian regional stages; – the Eocene/Oligocene boundary passes on the limit of Almian/Planorbellian and Obukhovian/Mezhygorian regional stages; – the Rupelian/Chattian boundary is at the limit of the lower and upper regional substages of Kerleutian regional stage and at the limit of the lower and upper regional substages of the Berekian regional stage. The following stage boundaries are not coinciding with regional stage boundaries: – the Danian/Selandian boundary is within upper part of the Belokamenskian and Pselian regional stages; – the Selandian/Thanetian boundary is trassing in the lower part of the Kachian and Merlian regional stages; – the lower boundary of Ypresian is in the uppermost part of the Kachian regional stage; – the Ypresian/Lutetian boundary is within the Simferopolian regional stage; – the Lutetian/Bartonian boundary is in the lowest part of the Kumian regional stage and within the Kievian regional stage. Key words: International Stratigraphic Chart, Paleogene, stage, boundary, regional stage, Ukraine
A complex interplay of palaeoclimatic, eustatic and tectonic processes led to fragmentation and dissipation of the vast Tethys Ocean in Eocene-Oligocene times. The resulting Paratethys Sea occupied the northern Tethys region on Eurasia, grouping water masses of various subbasins, separated from each other and from the open ocean through narrow and shallow gateways and land bridges. Changes in marine gateway configuration and intra-basinal connectivity affected the regional hydrology, shifting most Paratethyan basins to extreme carbon-sink anoxic environments, anomalohaline evaporitic or brackish conditions or even endorheic lakes. Paratethys gateway restriction triggered the onset of a long-lasting (∼20 Myr) giant anoxic sea, characterised by stratified water masses and anoxic bottom water conditions, resulting in thick hydrocarbon source rocks. Here, we review the geological evolution of the “dire straits” of Paratethys that played a crucial role in the Eocene-Oligocene connectivity history of the Central Eurasian seas and we show that the main anoxic phases (Kuma and Maikop) correspond to restricted connectivity with the global ocean and a period of CO2 depletion in the atmosphere. Paratethys represents one of the largest carbon sinks of Earth's history and may thus have played a prominent role in global climate change.
Cenozoic sediments are spread across southeast and eastern Anatolia, including the Adıyaman–Malatya regions of southeast Turkey. This study presents the first detailed petrographic, micropaleontologic, and strontium isotope analyses of the Eocene marl, clayey limestone, and limestone units that outcrop unconformably above the Mesozoic Meydan and İspendere ophiolitic rocks in the Adıyaman and Malatya regions, respectively. These carbonate rocks contain abundant planktonic foraminifera, including Turborotalia frontosa, Subbotina senni, Subbotina eocaena, Acarinina bullbrooki, Guembelitrioides nuttalli, Globigerinatheka subconglobata, and G. curryi, and benthic taxa (Nummulites, Discocyclina, and Chapmanina).Two planktonic foraminiferal zones were defined: the Turborotalia frontosa zone representing the Early–Middle Eocene (Ypresian–Lutetian/Bartonian), and the Turborotalia possagnoensis zone representing the Middle Eocene (Lutetian–Bartonian). Strontium isotope ratios (87Sr/86Sr) calculated for four samples ranged between 0.707663 and 0.707784, indicating an age of 45.1–51.9 million years (Ypresian–Lutetian/Bartonian). The presence of echinoid thorns in the units indicates a shallow marine environment where carbonates developed on the seaward side of a reef. For the first time in the study region and southeast Anatolia, this study has revealed the stratigraphic position of the Nummulitic limestone of the Kırkgeçit Formation unconformably overlying the ophiolites. Therefore, based on strontium isotope analyses and planktonic foraminiferal micropaleontology, the Kırkgeçit Formation is estimated as Early–Middle Eocene (Ypresian–Lutetian/Bartonian) in age.
Cenozoic sediments are spread across southeast and eastern Anatolia, including the Adıyaman–Malatya regions of southeast Turkey. This study presents the first detailed petrographic, micropaleontologic, and strontium isotope analyses of the Eocene marl, clayey limestone, and limestone units that outcrop unconformably above the Mesozoic Meydan and İspendere ophiolitic rocks in the Adıyaman and Malatya regions, respectively. These carbonate rocks contain abundant planktonic foraminifera, including Turborotalia frontosa, Subbotina senni, Subbotina eocaena, Acarinina bullbrooki, Guembelitrioides nuttalli, Globigerinatheka subconglobata, and G. curryi, and benthic taxa (Nummulites, Discocyclina, and Chapmanina).Two planktonic foraminiferal zones were defined: the Turborotalia frontosa zone representing the Early–Middle Eocene (Ypresian–Lutetian/Bartonian), and the Turborotalia possagnoensis zone representing the Middle Eocene (Lutetian–Bartonian). Strontium isotope ratios (⁸⁷Sr/⁸⁶Sr) calculated for four samples ranged between 0.707663 and 0.707784, indicating an age of 45.1–51.9 million years (Ypresian–Lutetian/Bartonian). The presence of echinoid thorns in the units indicates a shallow marine environment where carbonates developed on the seaward side of a reef. For the first time in the study region and southeast Anatolia, this study has revealed the stratigraphic position of the Nummulitic limestone of the Kırkgeçit Formation unconformably overlying the ophiolites. Therefore, based on strontium isotope analyses and planktonic foraminiferal micropaleontology, the Kırkgeçit Formation is estimated as Early–Middle Eocene (Ypresian–Lutetian/Bartonian) in age.
A detailed zonal stratigraphy by nanofossils of the Middle Eocene deposits in the sections of the Kheu and Belaya rivers (Ciscaucasia) is considered and the age of the distinguished chrones of the Lutetian-Barton interval of the studied sections is specified. The age of the so-called Middle Eocene climatic optimum (MECO), which corresponds to the level of occurrence of Dictyococcites bisectus and the beginning of the CNE15 zone (according to the scale of Agnini et all, 2014), is specified. In the Lutetian-Barton interval, a number of transgressive-regressive cycles were identified that correspond to the maxima and minima of warming and cooling. It is proposed that the level of the lower boundary of the Bartonian stage be taken to be ~43.3 Ma, which corresponds to the bottom of the Kuma Formation in southern Russia. According to nannoplankton it corresponds to the level of the appearance of numerous Discoaster bifax in the complex. On the graph of oxygen isotopes (Zachos et al., 2001, 2008), this boundary corresponds to the beginning of significant warming and the large transgressive stage of the epicontinental sea basins.
The Eocene interval of the section in the Belaya River valley is continuously exposed and is represented (from the bottom up) by green clays of the Cherkessk Formation, the marl–clayey member of the Keresta Formation, bituminous marls of the Kuma Formation, and light intensely bioturbated marls of the Belaya Glina Formation. There are gradual transitions between formations without signs of hiatuses. Eocene deposits are characterized by rich assemblages of nannoplankton, planktonic and benthic foraminifers (PF, BF), and organic-walled phytoplankton. The shallower water facies are recorded in the composition of benthos and mollusks at the boundaries of formations. The data on these groups of fossils make it possible to trace an almost complete zonal characterization of nannoplankton, dinocysts and PF and to compare these subdivisions of the middle–upper Eocene and early Oligocene both with other reference sections of the Eastern Peri-Tethys and standard zones and stages of the international stratigraphic scale. The following zones are distinguished: the upper part of the Cherkessk Formation—nannoplankton (NP15) and Acarinina bullbrooki PF zones; the Keresta Formation—nannoplankton (NP15+NP16) and Hantkenina “alabamensis” PF zones; the Kuma Formation—the nannoplankton (NP16+NP17) zones, Hantkenina “alabamensis” (at the lower boundary of the formation) and Subbotina turсmenica PF zones (above basal part), and Areosphaeridium diktyoplokum–Rhombodinium porosum dinocyst zone; the Belaya Glina Formation—nannoplankton (NP18, NP19+NP20, NP21) zones, Turborotalia centralis–Globigerinatheka tropicalis PF zone, and Charlesdowniea clathrata angulosa dinocyst zone; the lower part of the Pshekha Formation—nannoplankton (NP21) zone, Globigerina officinalis PF zone, and Phtanoperidinium amoenum dinocyst zone. These data make it possible to clearly correlate the Belaya River section with the sections studied in detail in Ciscaucasia (Kheu, Kuban, and Gubs rivers) and to reconstruct the conditions of sedimentation.
The Paratethys area extends from Central Europe to the borders of the Caspian Sea in Central Asia and hosts a significant number of petroleum provinces, many of which have been charged by Eocene to Miocene source rocks of supra‐regional significance. These include highly oil‐prone Middle Eocene marls and limestones in the Eastern Paratethys (Kuma Formation and equivalents) which are several tens of metres thick. Estimates of the source potential index (SPI) indicate that the Kuma Formation in the northern Caucasus and the Rioni Basin (Georgia) may generate 1 to 2 tons of hydrocarbons per square metre (tHC/m²). This implies that the Kuma Formation may also be an important and additional source rock in the eastern Black Sea.
Oligocene and Lower Miocene pelitic rocks (Maikop Group and equivalents) are considered to be the most important source rocks in the Paratethys. Vertical variations in source potential record different stages of basin isolation that reached a maximum during the Early Oligocene (NP23) Solenovian Event. However major variations exist between different sub‐basins in the Central and the Eastern Paratethys. In the Central Paratethys, the highest quality source rocks occur in the Carpathian Basin where the Menilite Formation, several hundreds of metres thick, can generate up to 10 tHC/m². Locally the Menilite Formation is about 1500 m thick and continues into the Lower Miocene. In these settings, the Menilite Formation can generate approximately 70 tHC/m². In the Alpine Foreland Basin (Schöneck and Eggerding Formations) and the Pannonian Basin (Tard Clay Formation), oil‐prone source rocks are restricted to the Lower Oligocene. In the Eastern Paratethys, the best source rock intervals of the Maikop Group are typically associated with the Early Oligocene Solenovian Event. By contrast, with the exception of the Kura Basin in Azerbaijan, the potential of Upper Oligocene and Lower Miocene rocks is often limited. In total, the Maikop Group may generate up to 2 tHC/m² in the North Caucasus area and 4 tHC/m² in the Rioni Basin.
A particular source rock facies is found in the Western Black Sea where diatomaceous rocks with good oil potential accumulated in the Kaliakra Canyon during Early Miocene time. This facies may generate up to 8 tHC/m², but is probably limited to shelf‐break canyons.
Middle and Upper Miocene rocks are the main source for oil and thermogenic gas in the Pannonian Basin System, and also contributed to thermogenic hydrocarbons in the Moesian Platform and the South Caspian Basin. In addition, Upper Oligocene and Miocene rocks are the source for microbial gas in several basins including the Alpine and Carpathian foredeeps.
A zonal scheme for the Lower Paleogene of the northern Pacific Ocean is proposed on the basis of
the stratigraphic distribution of benthic foraminifers in the lower bathyal–abyssal beds studied in boreholes
in the North and South Pacific regions. This scheme includes eight subdivisions (six zones and two subzones).
The boundaries of the benthic zonal subdivisions are defined by bioevents (appearance or disappearance of
stratigraphically important taxa) and are linked to the zonal scales based on planktonic foraminifers and cal�
careous nannoplankton. It is established that most of these bioevents are recognized subglobally. Apart from
the evolutionary events, changes in the deep�water benthic foraminiferal assemblages were caused by changes
in the paleooceanological environment. This allowed detailed characterization of a global mass extinction of
assemblages of deep�water benthic foraminifers in the region studied. It is also established that changes in the
assemblages of deep�water benthic foraminifers, observed in either change in their taxonomic composition
or changes in abundance and diversity, resulted from the presence of different deep�water masses in the
region.
The newly discovered planktonic foraminifer Hantkenina gohrbandti nov. spec. forms the evolutionary link between the genera Clavigerinella and Hantkenina. This ancestor of the genus Hantkenina is characterized by pointed chamber ends with a nub (prototubulospines) and in some cases by the first tubulospines appearing in a juvenile growth stage. The transition from Clavigerinella caucasica to Hantkenina mexicana is observed in a 2 m thick part of the Middle Eocene Holzhäusl section (Mattsee, Austria) within planktonic foraminifera Zone E8 and calcareous nannoplankton Sub-Zone NP15b. The section was deposited in bathyal waterdepths in the northwestern Tethyan realm and is now part of the Ultrahelvetic thrust unit.
ABsTRAсT In thе lаtе middlе tо еarliеst latе Еoсеnе, a vast dysохiс to anoхiс bаsin еxtеndеd from thе Сrimеа in thе Wеst through thе northеrn Cauсasus to thе Aгal Sеа in thе Еast' and a hugе amount оf organiс сarbon was dеpositеd in thе оrganiс.riсh sedi-mеnts of thе Kuma Formation. Wе dосumеnt thе palеo-еnvirоnrnеntal соnditions in thе basin using bеnthiс foraminifеral аnd organiс сaгbon data. oхygеn lеvеls wеге lowest duгing thе dеpоsition of thе middle part оf thе Кuma Formatiоn, a timе of rеl. ativеly сool сlimatе. WЪ еstimatе thе timе of dерositiоn аnd its durаtion as гanging from planktoniс foraminifеral zonеs uppеr Pll through P14, аnd сalсarеous nаnno. fоssil zonеs CP13с to lоwеrmost сP15 (-44_36.5 Мa). Wе arguе that this laгgе-sсalе stoгagе of organiс сaгbon oуer 1 m.y. rеsultеd frоrn a соmplех intегaсtiоn of tесtoniс and сlirnatiс faсtors, and that it maу havе influenсеd thе global сarbоn budgеt in thе осеan-atmosphеrе systеm. lt pгobably was at lеast а сontгitluting faсtor to thе glоbаl сooling in thе middle Еoсеnе that led tо thе еstablishmеnt of iсе shееts on thе Antarс-tiс сontinеnt by thе еnd ofthе Еoсеnе.
This integrated study across the Ypresian/Lutetian boundary in the Fortuna Section (Spain) allowed us to recognize a bundle of events in the transitional interval between the Ypresian and Lutetian stages. Planktic foraminifera show an apparently continuous succession spanning the planktic foraminiferal zones P9, P10 and P11. Calcareous nannofossils allowed the recognition of the nannofossil subzones NP14b, NP15a, NP15b and of zone NP16. Small benthic foraminiferal assemblages may indicate a hyperthermal event as evidenced by a bloom of Aragonia aragonensis, which is coeval with a major change in clay mineralogy. This event coincides with the first occurrence of Hantkenina specimens at the base of planktonic foraminiferal zone P10 in the uppermost part of nannofossil subzone NP14b, which could be used to define the Ypresian/Lutetian boundary.
German
Im Profil von Fortuna (SE Spanien) weisen die planktonischen Foraminiferen im Übergangsbereich vom Yprésien zum Lutétien eine kontinuierliche Abfolge auf, welche die Planktonforaminiferen-Zonen P9, P10 und P11 umfasst, während die kalkigen Nannofossilien die Nannofossil-Subzonen NP14b, NP15a, NP15b und die Nannofossil-Zone NP16 anzeigen. Bei den benthonischen Kleinforaminiferen wurde möglicherweise eine von einem bedeutenden Wechsel im Spektrum der Tonmineralien begleitete Blüte von Aragonia aragonensis durch ein hyperthermales Ereignis verursacht. Dieses fällt mit dem ersten Vorkommen von Individuen der Gattung Hantkenina an der Basis der Planktonforaminiferen-Zone P10 und im obersten Teil der Nannofossil-Subzone NP14b zusammen und kann damit der Festlegung der Yprésien/Lutétien-Grenze dienen.
The planktic foraminiferal first and last appearances across the Lower - Middle Eocene transition in the Alamedilla and Agost sections (Betic Cordillera) allows us to establish a detailed new biozonation. This biozonation has been correlated with the Ypresian and Lutetian marine European standard stages and can be correlated with sections located in subtropical and temperate latitudes. The following biozones have been established: Morozovella subbotinae Biozone, with Morozovella formosa Subzone, Morozovella aragonensis Biozone, with Morozovella aragonensis Subzone and Morozovella caucasica Subzone, Acarinina pentacamerata Biozone, with Acarinina pentacamerata Subzone, Subbotina boweri Subzone and Truncorotaloides praetopilensis Subzone (Late Ypresian, Early Eocene), and Hantkenina nuttalli Biozone with Hantkenina nuttalli Subzone and Globigerapsis subconglobata Subzone (Early Lutetian, Middle Eocene).
The initial appearance of the planktonic foraminiferal genus Hantkenina has been used for about fifty years to recognize the base of the Lutetian and middle Eocene. However, probably as a result of incomplete stratigraphic records, discrepant ranges of Hantkenina have been reported by various investigators at many Eocene sections. Here we report the first complete evolutionary transition from Clavigerinella to Hantkenina, front the northwestern Tethyan deep-water section at Holzhausl (Salzburg, Austria). A newly discovered species, Hantkenina nov. sp., is the link between Clavigerinella caucasica and Hantkenina mexicana. This finding unequivocally heralds the initial entry of Hantkenina, which is correlated to the upper part of calcareous nannoplankton Subzone NP15b (Sullivania gigas Subzone), to be defined. This indicates a mismatch of similar to 4.5 m.y. between the base of the Lutetian at the type locality, which has been placed within Subzone NP14b, and the first appearance datum of Hantkenina. Consequently, the first occurrence of Hatakenina can no longer be used as a marker for the base of the middle Eocene.
Analysis of a quantitative and synoptic data base of Eocene Atlantic planktonic foraminifera has illuminated many facets of foraminiferal faunal structure and composition reflective of bioprovince and useful for empirical establishment of ecologic and paleohydrographic indices.Tropical indigenes, such as the morozovellids, turborotaliids, subquadrate acarininids, and some globigerinathekids dissolve most rapidly along with juveniles of most species. Tropical faunas are high in diversity and dominance, include oxygen minimum indices such as the biserial heterohelicids only in high productivity times such as the middle Eocene, are dominated by genera with high numbers of species and species consistently typical of warm water regions until the late Eocene when faunas include a higher number of middle than lower latitude types. Truly tropical genera are replaced by subtropical, eutrophic indicators, such as the globigerinathekids, and contract to the Florida Current region prior to their extinctions at the end of the middle Eocene. Atlantic late Paleogene tropical forms first appear in the Gulf of Mexico at the end of the middle Eocene.Middle latitude faunas include high numbers of chiloguembelinids, pseudohastigerinids, small and biconvex morozovellids, round and globigerinid-form acarininids, low-spired subbotinids in the late middle Eocene, high-spired subbotinids, large and typical globigerinids in the late Eocene. These forms have intermediate dissolution susceptibilities. Middle latitude faunas are often high in diversity in midddle latitude frontal regions. Dominance is low even in warm intervals when tropical indigenes increase in number in middle latitude faunas, especially in boundary currents. Low latitude species penetrate temperate areas also during cool, eutrophic periods of vigorous circulation such as the late middle Eocene. Typical of temperate slope faunas are high abundances of high-spired subbotinids and small-sized catapsydracids.High latitude faunas are usually low in diversity except in the middle to late Eocene when frontal regions were located in the southern Labrador Sea and over Rockall Bank. Typical forms are the low-spired subbotinids until the late middle Eocene, globorotaloids, catapsydracids, tenuitellids, and in the late Eocene, the biserial heterohelicids. Indigenous species are the most solution resistant and many are mesopelagic. During warmings rare low latitude indices penetrate high latitudes; subpolar faunas have greatest affinities with middle latitude faunas at these times.
Marker events to define the stratotype for the base of the Lutetian Stage are poorly defined. To elucidate such markers and characterize palaeoenvironmental turnovers, we conducted an integrated study of the Ypresian–Lutetian (Y–L; early-middle Eocene) transition at the continuous Agost section (southeastern Spain). This 115-m-thick section, which consists of hemipelagic marls intercalated with hemipelagic limestones and turbidity sandstones, spans from planktic foraminiferal Zones P9 to P12 (E7 to E10) and calcareous nannofossil Zones CP11 to CP14a (NP13 to NP16). We report quantitative analyses of planktic and benthic foraminifera and characterization of trace fossil assemblages that are integrated with mineralogical analyses.
In this paper, we present an integrated study of a 115-m-thick section that spans the Ypresian/Lutetian boundary at Agost (Betic Cordillera, SE Spain). Our study includes magnetostratigraphic results and biostratigraphic and palaeoenvironmental data derived from planktic foraminifera, small and larger benthic foraminifera, and calcareous nannofossils. Our results demonstrate that the Agost section is continuous and spans from Zones P9 to P12 (E7 to E10), Zones CP11 to CP14a (NP13 to NP16), Zones SBZ11 to SBZ15, and Chrons C22n to C19r. The first occurrence (FO) of H. nuttalli (base of P10) and the FO of G. nuttalli (base of E8) are found within Chron C20r, at a much younger age (3–5 Myr) than previously considered in standard calibration schemes. Similarly, the boundary between SBZ12 and SBZ13 is located within Chron C21n, also at a younger age than previously considered. On the contrary, the FO of B. inflatus (base of CP12b) is found within Chron C21r, which conforms to the magnetostratigraphically calibrated age of ca. 48 Ma (middle part of C21r) considered in standard calibration schemes. These results corroborate earlier studies and indicate that all the events that have been proposed to mark the Ypresian/Lutetian boundary appear at different stratigraphic intervals and have different ages. Based on our results from Agost and on data from other sections elsewhere, we suggest that the Ypresian/Lutetian boundary might be approximated by the FO of B. inflatus (base of CP12b). The Agost section might be considered as a potential candidate to locate the Global Stratotype Section and Point (GSSP) of the base of the Lutetian Stage, because it includes all the events that might be selected as marker events for the Ypresian/Lutetian boundary and it fulfils most of the geological, biostratigraphic and infrastructure requirements demanded for definition of a GSSP.
Biostratigraphic charts of marine Paleocene and Eocene in the European and West Siberian parts of Russia include the unified
zonations of nannoplankton, planktonic and benthic foraminifers, dinocysts, radiolarians, diatoms, and palynomorphs of higher
plants. These regional zonations summarize comprehensive data on the Lower Paleogene, which have been obtained by paleontologists
and biostratigraphers in the last century. In the content and resolution degree, they represent a solid basis for geological
and paleogeographic consideration and characterize the time succession of diverse biotic and abiotic events. On the other
hand, the depicted biotic events have been controlled by successive tectonic, paleogeographic, and paleoclimatic events, because
organisms determining contents of biostratigraphic zones changed not only in the course of evolution, but also in response
to transformation of surroundings. As elements of general communication systems, epicontinental seas of the Paleogene have
been interconnected via straits and seaways, which promoted interchange of water masses and biotas belonging to the Tethys,
Atlantic or Arctic oceans, and inner seas. Size and configuration of the seas and seaways changed under influence of tectonic
processes and eustatic events of epeirogenic or regional origin. Widening, narrowing, and cessation of communication ways
have been responsible for different-scale changes in sedimentation and biotic environments. New materials on the Paleogene
in a vast territory of Russian sector of West Eurasia offer an opportunity to revise somewhat the dynamics of climatic changes
in the Northern Hemisphere during the Early Cenozoic, which characterize the terminal phase of transition from the warm to
cold biosphere of the Earth.
The Gorrondatxe section, a prospective Lutetian Global Stratotype Section and Point (GSSP), has recently been used as the master reference section to reassess the correlation between Eocene magnetostratigraphic and calcareous planktonic biostratigraphic scales. However, the exact calibration of some events remained ill defined, as they were thought to be missing in Gorrondatxe due to a fault. The most important missing events were the first occurrence of the planktonic foraminifera Turborotalia frontosa and the C22n/C21r chron boundary. Either might be a reliable correlation criterion for the Ypresian/Lutetian boundary, as both approach the age of the original Lutetian Stratotype. New studies allowed the identification of the former event 9 m above the Gorrondatxe fault, within magnetic polarity Chron C21r and calcareous nannofossil Zone CP12a. Distinctive test features that characterize the most primitive morphotype of T. frontosa are described. Despite the high turbidite content, recurrent pelagic limestone–marl couplets and bundles occur, whose formation was driven by precession and eccentricity astronomical cycles. The first occurrence of T. frontosa was found 27 couplets and 5.5 bundles (60 m) below the first occurrence of the calcareous nannofossil Blackites inflatus, which is dated at 48 Ma. Hence, the age of the first occurrence of T. frontosa is estimated at 48.55 Ma, confirming that it is the most suitable planktonic foraminiferal correlation criterion for the Ypresian/Lutetian boundary. These results show that the stratigraphic interval missing due to the Gorrondatxe fault cannot be greater than a few metres and reinforce the value of this section as a prospective Lutetian GSSP. In press 2.2. Laboratorio di paleomagnetismo JCR Journal