Middle-late Eocene dinoflagellate cysts from NE Ukraine (Borehole No. 230, Dnepr-Donets Depression): stratigraphic and palaeoenvironmental approach

Analysis of the stratigraphic and quantitative distribution of dinoflagellate cysts and other palynomorphs from a shallow marine Eocene section drilled from borehole No. 230 (NE Ukraine) resulted in an updated age-assessment of regional formations and a reconstruction of the major transgressive-regressive trends in the North Ukrainian palaeosedimentological province. Based on dinocyst age-diagnostic events, the Buchak Formation is attributed to the mid-upper Lutetian; the Kiev Formation is assigned to the Bartonian-?lowermost Priabonian; finally, the Obukhov Formation is dated Priabonian. The Buchak Formation accumulation reflects the first major transgressive episode in the North Ukrainian Province; the accumulation of the lower Kiev Formation corresponds to the maximum of regional marine transgression, while the palynological assemblages from the upper Kiev Formation indicate a protracted regression. The beginning of the Obukhov Formation accumulation corresponds to the last marine transgressive cycle

New insights on the Late Paleocene − Early Eocene dinoflagellate cyst zonation for the Paris and Dieppe basins

The Anglo-Belgo-Paris Basin, historical cradle of the Paleogene stratigraphy since the 19th century, is known by the presence of very specific so-called “Sparnacian” deposits (very diverse and laterally highly variable, predominantly lagoonal to terrestrial facies), which encompass the short stratigraphic interval of the Paleocene-Eocene Thermal Maximum (PETM). Due to the insufficient nature of the paleontological record, the “Sparnacian” succession of the Paris and Dieppe-Hampshire basins still needs to be robustly chronostratigraphically correlated with other Paleogene records worldwide. In order to refine the stratigraphy of the Thanetian-Lower Ypresian succession in northern France a number of cores and outcrop sections have been investigated palynologically. As a result, an updated version of the dinoflagellate cyst zonation for the Paris and Dieppe basins is proposed and contains six new or revised biozones for this stratigraphical interval: Alisocysta margarita, Apectodinium hyperacanthum, Apectodinium-acme, Biconidinium longissimum-acme, Dracodinium astra, and Axiodinium lunare/Stenodinium meckelfeldense. Based on combined bio-, litho- and chemostratigraphic data, it appears that the dinocyst assemblages, corresponding to the PETM event interval (“Sparnacian” deposits, Soissonnais and upper Mortemer formations), are characterized by an acme of Apectodinium spp. (70–98%) in both basins, sometimes alternating with an acme of a few gonyaulacoid groups in the Dieppe Basin. Dinocyst assemblages from the PETM interval contain a significant number of atypical, longer specimens of Apectodinium parvum, which could represent an ecological onshore substitute for Axiodinium augustum in the Paris and Dieppe-Hampshire basins. The establishment of a new Biconidinium longissimum-acme Zone suggests that the stratigraphic hiatus previously inferred within this sequence in the Paris Basin does not exist

Paleocene-Eocene warming and biotic response in the epicontinental West Siberian Sea

We present a Paleocene-Eocene (ca. 60-52 Ma) sea-surface temperature record from sediments deposited in the epicontinental West Siberian Sea. TEX86 paleothermometry indicates long-term late Paleocene (~17 °C ca. 59 Ma) to early Eocene (26 °C at 52 Ma) sea-surface warming, consistent with trends previously observed for the Southern Ocean and deep oceans. Photic zone and seafloor anoxia developed as temperatures rose by 7 °C to ~27 °C during the Paleocene-Eocene Thermal Maximum (PETM). Based on paired palynological and TEX86 data, we suggest that the minimum temperature for the proliferation of Paleocene and early Eocene members of the dinoflagellate family Wetzelielloideae, which includes the PETM marker taxon Apectodinium, was ~20 °C

Paleocene-Eocene Thermal Maximum impacts on terrestrial environments. Insights from the organic matter evolution in the Vasterival section (Dieppe-Hampshire Basin, France)

International audienceThe Paleocene-Eocene Thermal Maximum (PETM, 55.8 Ma [1]) is regarded as one of the most rapid global warming of the Cenozoic era, with temperature increase of 4-8°C in about 10-20 ka [2]. Thus, it is often proposed as a potential analogue of future climatic conditions expected in the IPCC screenplays. The PETM is recorded in both marine and continental deposits by an abrupt negative Carbon Isotope Excursion (CIE) associated with other sedimentary and biological anomalies. The consequences of the PETM on terrestrial environments are less documented than in marine ones. This limits our regional- and global-scale understanding of the impact of such a climate change on continents and the associated response of ecosystems. This study focuses on the Vasterival section (Seine- Maritime, Upper Normandy) located in the southern part of the Dieppe-Hampshire Basin, in which the PETM is attested by a negative 13Corg shift in the organic matter (OM), and confirmed by the stratigraphic record in this locality belonging to the Cap dAilly composite section [3]. The 2 m thick section, which presents a notably well preserved OM, is mainly constituted by terrestrial sediments from lacustrine to coastal swamp environments, and in which OM-poor clays are followed by OM-rich clays, centimetric lignite beds and clays with roots evidences. The uppermost part of the section is constituted by 50 cm thick lagoonal clay with shell debris that records the Apectodinium acme. Global organic geochemical, palynofacies and isotopic analyses were performed on thirty samples. The total organic carbon of this section is ranging from 0.5 % for OM-poor-clays to 45 % for lignite levels. Hydrogen Index (from 6 to 210 mg HC/g TOC), Oxygen Index (from 80 to 630 mgCO2/g TOC) and Tmax values (from 410 to 430°C) show that the OM is of Type III (terrestrial higher plants), and immature. These results are reinforced by palynofacies observations that show a large amount of ligno- cellulosic phytoclasts in most of the samples. In the uppermost shale the presence of many Apectodinium species would suggest the continuity of the PETM in marine deposits. Thus, the continental deposits would represent a time interval that includes the uppermost Paleocene and the basal part of the PETM. Lipid biomarkers extracted from twenty five samples were quantified and their hydrogen and carbon isotopic composition were determined by GC-irMS. Important changes in palynofacies, biomarker assemblages and compound-specific isotopic data are coincident with the CIE onset interval. This is consistent with an important environmental modification in the Vasterival area during the Early Eocene that could be linked to the PETM climatic change. References [1] Aubry, M. P., Ouda, K., Dupuis, C ., Berggren, W. A., Van Couvering, J A., and the Members of the Working Group on the Paleocene/Eocene Boundary, 2007. The Global Standard Stratotype-section and Point (GSSP) for the base of the Eocene Series in the Dababiya section (Egypt). Episodes 30 (4): 271-286. [2] Zachos, J. C., Pagany, N., Sloan, L., Thomas, E., Billups, K., 2001. Trends, rythms, and aberrations in global climate 65 Ma to Present. Science 292: 686 693. [3] Dupuis, C., Steurbaut, E., De Coninck, J. and Riveline, J., 1998. The Western Argiles à Lignites facies. In: M. Thiry and C. Dupuis (Eds.), The Paleocene/Eocene boundary in Paris basin: the Sparnacian deposits. Field trip guide. ENSMP Mém. Sc. De la Terre, 34, 60-71

Unravelling the PETM record in the “Sparnacian” of NW Europe: new data from Sinceny, Paris Basin, France

In order to decipher the PETM (Paleocene-Eocene Thermal Maximum) impact on the “Sparnacian” diversified and interconnected paleoenvironments of the Paris Basin, and to ensure correlation of the events and processes identified, a high resolution temporal framework is essential. Historically, the Paris and adjacent basins are the cradle of stratigraphy, where the notion of "Sparnacian" took shape (Dollfus 1880), pointing terrestrial to lagoonal deposits with particular facies and faunas, interstratified between two easily distinguishable Thanetian and Ypresian sandy marine formations. Since that time stratigraphy has evolved, and we refer now to the lithostratigraphy of Aubry et al. (2005). A 31.5 m deep drilling has been augered at Sinceny, a key locality for the “Sparnacian” of the Paris Basin. Various analyses have been performed on the samples collected: granulometry, XRD mineralogy, carbonate and organic carbon contents, biostratigraphy, palynofacies, rock-eval pyrolysis and chemostratigraphy (δ13C of the dispersed organic matter). Seven lithological units are defined among which five may be attributed to the “Sparnacian” intercalated between fine glauconiferous sands of Late Thanetian and Early Ypresian, with in ascending order: 1) a carbonated silty medium-sized sand, 2) a sandy marl with carbonated concretions and limestone beds, 3) a plastic clay, oxidized at the bottom, but with increasing pyrite upwards, 4) lignite and clay beds, all pyritic but more shelly upwards, 5) a shelly crag with small flint pebbles (“Falun et Sable à Galets Avellanaires de Sinceny”: FSGA). The CIE (Carbon Isotopic Excursion), proxy of the PETM, extents over nearly 20 m of the section. In this interval, isotopic values fluctuate around – 26 to – 28 ‰. They are more negative in the lower part and show short term fluctuations in the upper part, which may reflect changes in depositional environment. The Apectodinium acme, another proxy of the PETM, is recorded in the lagoonal facies. Clay minerals do not show any kaolinite influx in relation with the CIE, and interstratified kaolinite/smectite is characteristic of the third unit. The palynofacies and pollen and spore assemblages are fairly similar to those from other “Sparnacian” NW European units, with some charcoal beds and Plicapollis pseudoexcelsus, Juglandaceae and other taxa acmes. The FSGA is chemostratigraphically (averaging -24 ‰) and biostratigraphically different (Apectodinium less abundant, other taxa present or abundant). Correlation with published sections in the Paris Basin is possible using litho- and bio-stratigraphy, but not chemostratigraphy (Thiry et al, 2006). Indeed such a long, regular and unequivocal CIE had never been recorded in the Paris Basin, neither in Limay, nor in the Mont Bernon and Provins reference sections, all situated on the Paris Basin edges where the deposits are more prone to sedimentary hiatuses. The FSGA unit postdates the PETM episode and evidences the Ypresian s.s. transgression in the “Sparnacian” lagoonal setting. Correlation with the P/E successions of the Belgian, London and Dieppe-Hampshire Basins is also possible, although further high resolution data are necessary in the Paris Basin

Paleocene-Eocene Thermal Maximum consequences on terrestrial environments. Insights from the evolution of organic matter in the Vasterival section (Dieppe-Hampshire Basin, France)

The Paleocene-Eocene Thermal Maximum (PETM, 55.8 Ma, Aubry et al, 2007) is regarded as one of the most rapid global warming of the Cenozoic era, with temperature increase of 4-8°C in about 10-20 ka. Thus, it is often proposed as a potential analogue of future climatic conditions expected in the screenplays provided by the International Panel on Climate Change (IPCC). The PETM is recorded in both marine and continental deposits by an abrupt negative Carbon Isotope Excursion (CIE) associated with other sedimentary and biological anomalies. The consequences of the PETM in terrestrial environments are less documented than in marine ones. This limits our regional- and global-scale understanding of the impact of such a climate change on continents and the ecosystems response. This study focuses on the Vasterival section (Seine-Maritime, Upper Normandy) located in the southern part of the Dieppe-Hampshire Basin, in which the PETM is recorded in the organic matter (OM) by the negative shift in δ13Corg of the CIE, and confirmed by the stratigraphic record in this locality belonging to the Cap d'Ailly composite section (Dupuis et al., 1998). The 2 m thick section, which presents a notably well preserved OM, is mainly constituted by terrestrial sediments from lacustrine to coastal swamp environments and in which OM-poor clays are followed by OM-rich clays, centimetric lignite beds and clays with roots evidences. The uppermost part of the section is constituted by 50 cm thick lagoonal clay with shell debris that records the Apectodinium acme. Global organic geochemical, palynofacies and isotopic analyses were performed on thirty samples. The total organic carbon of this section is ranging from 0.5 % for OM-poor-clays to 45 % for lignite levels. Lipid biomarkers extracted from twenty five samples were quantified and their hydrogen and carbon isotopic composition were determined by GC-irMS. Important changes in palynofacies, biomarker assemblages and compound-specific isotopic data are coincident with the CIE onset interval. This is consistent with an important environmental modification in the Vasterival area during the Early Eocene that could be linked to the PETM climatic change

The PETM record revealed by a new integrated high-resolution dinoflagellate cyst and geochemical data from the "Sparnacian" sediments in the Paris and adjacent basins

International audienceThe Paris Basin represents an historical cradle of the Paleogene stratigraphy, where the Paleocene Epoch and the "Sparnacian Stage" have been erected (Schimper, 1874; Dollfus, 1880). As highlighted by Aubry et al. (2005), whereas the chronostratigraphic connotation of the Sparnacian Stage occurred to be controversial since its definition, modern studies of the Late Paleocene - Early Eocene interval have revealed that the so-called "Sparnacian" deposits encompass a remarkable and short (~170 kyr) episode in the Cenozoic history, the Paleocene-Eocene Thermal Maximum (PETM, ~55.8-55.6 Ma). However, due to a large development of diverse and laterally variable, predominantly lagoonal and non-marine facies, the Paris Basin Upper Paleocene-Lower Eocene succession is still poorly documented and needs an updated chronostratigraphic correlation with other Paleogene records in adjacent basins and worldwide. Since almost 45 years the dinoflagellate cyst stratigraphy has significantly contributed to correlations of the Thanetian-Ypresian deposits in the Paris and adjacent basins (Châteauneuf & Gruas-Cavagnetto, 1968, 1978; Gruas-Cavagnetto, 1974; Costa and Downie, 1976). Nevertheless, data published on dinoflagellate cysts distribution in the Paleogene sediments of those basins remain too scattered (see Aubry et al., 2005) and need to be calibrated to the most recent biozonations. With the aim at reconstructing the "Sparnacian" palaeoenvironments as well as ensuring correlation with the PETM (and its Carbon Isotopic Excursion, CIE) events and related processes, new or already well known "Sparnacian" Dieppe-Hampshire and Paris Basins key localities (Cap d'Ailly and Sotteville-sur-Mer sections, Therdonne and Sinceny cores) have been investigated in details palynologically and chemostratigraphically. According to our new high-resolution data, the CIE begins within the Mortemer Fm in terrestrial or coastal environments and continues until the top of the Soissonnais Fm (Quesnel et al, this meeting). Within the CIE, δ13Corg values fluctuate between -25 and -30 ‰, while above and below they fluctuate between -22 and -26 ‰. The CIE interval contained in the lagoonal and shallow marine units reveals an extremely pronounced (compared with other PETM records worldwide) Apectodinium-acme (70-98% of dinocyst assemblage), sometimes accompanied by Pediastrum-blooms (fresh water algae). As mentioned by Gruas-Cavagnetto (1974), dinoflagellate assemblages from the Dieppe-Hampshire and Paris Basins "Sparnacian" do not contain the key species Apectodinium augustum (nominate species of the A. augustum zone corresponding the PETM-interval worldwide, Crouch et al., 2001), whereas it is present in the northern Belgian Basin Tienen Fm (De Coninck, 1975, 1999) and is coeval there with the CIE and Apectodinium-acme interval (Steurbaut et al., 2000, 2003). However, our calibration of the Apectodinium-acme to the CIE in the Dieppe-Hampshire and Paris Basins suggests its attribution to the A. augustum zone. As it was previously noted from southern England (Powell et al., 1996), the absence of species A. augustum in the Anglo-Paris Basin may be explained by its restriction to more offshore conditions. In localities studied here dinocyst assemblages dominated by Apectodinium spp. are characterized by a significant number of longer (compared to the holotype) specimens of A. parvum, which could represent an ecological onshore substitute of species A. augustum during the PETM