Paleocene-Eocene Thermal Maximum Event Research Articles

Elevated physical weathering exceeds chemical weathering of clays during the Paleocene-Eocene Thermal Maximum in the continental Bighorn Basin (Wyoming, USA)

The Paleocene-Eocene Thermal Maximum (PETM) global warming event at ∼56 million years before present changed catchment weathering and erosion. Increased chemical weathering of silicate minerals is thought to be an important process removing CO2 from the atmosphere. However, changes in clay mineralogy can often be explained by enhanced erosion of catchment laterites during the event. Here, we investigate chemical and physical weathering and erosive flux changes through the PETM interval in the Bighorn Basin, Wyoming, a Laramide foreland basin, in a proximal continental-interior alluvial setting. These show an increase of detrital smectite with a lag time of 20-kyr after the main onset the PETM. The smectite increase continued for at least 50-kyr after the event. In-situ, post-depositional pedogenic clay mineral formation is similar between pre-PETM and PETM soil profiles, despite large macroscopic differences between soils that formed before and during the event. Drier, hotter summers during the PETM probably caused decreased vegetation cover that, in concert with more frequent and heavier rainstorms, intensified the erosion of smectite-rich Cretaceous bentonites on the margins of the catchment, which exceeded changes in chemical weathering within the catchment. The lagged response in reaching full PETM clay mineral values can be explained by the time required for upstream sediment to reach the catchment basin floodplain. The prolonged nature of smectite enhancement after the PETM event may again relate to signal propagation times that are now even longer due to lower fluvial recycling rates. Our results indicate that chemical weathering changes were probably superceded by enhanced physical weathering and clay-mineral transport from basin margins at this continental-interior study site.

Enhanced storm-induced turbiditic events during early Paleogene hyperthermals (Arabian continental margin, SW Iran)

Early Paleogene hyperthermal episodes including the Paleocene-Eocene Thermal Maximum (PETM) have long been viewed as analogues of the Anthropocene global warming. Few studies, however, have analyzed the environmental consequences of such climatic anomalies in deep-water turbidite-rich successions. This integrated sedimentological, biostratigraphic, and stable-isotope study of the Paleogene Pabdeh Formation, deposited along the Arabian continental margin of southwestern Iran, allowed us to document the geological response of hyperthermal events in deep Neo-Tethyan Ocean. The late Thanetian event (Pre-Onset Excursion or long-term late Paleocene climatic perturbation), the Early Eocene Climate Optimum, and the Middle Eocene Thermal Maximum were successfully identified within the Pabdeh Formation. The PETM event could not be documented because the Paleocene/Eocene boundary corresponds to a prolonged non-depositional hiatus marked by a glauco-phosphorite interval. Based on high-resolution microfacies analysis, three different processes in a carbonate slope to basin-margin environment were distinguished including pelagic settling, upwelling-condensation-reworking, and storm-induced turbiditic deposition. Detailed sedimentological analysis revealed an anomalous abundance of storm-induced proximal to distal turbidites represented by packstones with deep-water and reworked shallow-water bioclasts occurring during the hyperthermal intervals. A close causal link between climate warming and tropical storms during the early Paleogene hyperthermal events is thus envisaged. As a principal mechanism, we propose that rapid warming in response to massive carbon release triggered pronounced sedimentological changes along low-latitude tropical margins, leading to generation of storm-induced calciturbidite and re-deposition in the deep sea during hothouse stages.

Paleocene-Eocene Thermal Maximum lacustrine sediments in deep drill core SKD1 in the Jianghan Basin: A record of enhanced precipitation in central China

Global warming has a significant effect on global and regional hydrological cycles and is expected to exacerbate the uneven distribution of rainfall in various regions, thereby influencing water-related human activities (e.g., agriculture) and the development of human society, especially in densely populated East Asia. As an analog to predict the future impact of global warming on hydrological regimes, the Paleocene-Eocene Thermal Maximum (PETM) at ~56 Ma is the most prominent and extensively studied Paleogene hyperthermal event, and it featured rapid and extreme global warming that caused intense environmental effects. However, the contradictory effects/mode of precipitation during the PETM has constrained our understanding of the hydrological response to global warming. Moreover, compared with marine records, continental sedimentary records of the PETM are very limited, and most are typically limited to weathered, often discontinuous, outcrop exposures, and relevant records of environmental perturbations in Asia are lacking. This study presents the first detailed record of the PETM in the Jianghan Basin, central China, and identifies the environmental and hydrological changes across the PETM. Based on high-resolution carbon and oxygen isotopes in the lacustrine carbonates (mainly calcite and dolomite) in the deep drill core SKD1, we identified the PETM event at the boundary of the Shashi and Xingouzui Formations. The carbon isotopic values of carbonate ( δ 13 C carb ) and calcite ( δ 13 C calcite ) show large negative excursions (~10.7‰ and 8.7‰, respectively) during the PETM. The oxygen isotopic values of carbonate ( δ 18 O carb ) and calcite ( δ 18 O calcite ) also show large negative excursions (7.9‰ and 6.1‰, respectively), indicating increased precipitation and a wetter climate across the PETM, as evidenced by the disappearance of evaporites and the dominance of calcite in the carbonates. Increased precipitation with elevated pCO 2 concentration might have caused the anomalous large negative excursion of the δ 13 C carb values in the SKD1 core and provided favorable living conditions for the oldest known primate, whose fossil was found in the Jianghan Basin. The δ 18 O carb and δ 18 O calcite values increase and show high-frequency and large-amplitude fluctuations above the PETM interval, indicating rapid shifts between wet and dry climatic conditions in an overall arid climate after the PETM. • The first detailed PETM record in the Jianghan Basin was found in deep drill core SKD1. • The carbonate carbon isotopes show large negative excursions (CIE, ~ − 10.7‰) during the PETM. • Precipitation in the Jianghan basin increased across the PETM. • Increased precipitation might have caused the anomalous large negative CIE in the carbonate.

Sedimentology and sediment geochemistry of the pelagic Paryab section (Zagros Mountains, Iran): implications for sea level fluctuations and paleoenvironments in the late Paleocene to middle Eocene

Sedimentological and geochemical records are presented for an upper Paleocene to middle Eocene deep-water pelagic succession of the Pabdeh Formation in the Paryab section, Zagros Mountains, NW, Iran. In this study, grain-size statistical parameters, cumulative curves, and bivariate analysis on twenty-five sediment samples were used to decipher depositional processes and paleoenvironments. XRD analysis of the fine-grained silt to clay sediments indicates that quartz, calcite, ankerite/dolomite, and clay minerals such as illite, chlorite, and kaolinite constitute the main minerals within these sediments. Elemental and isotopic chemostratigraphies are used to infer depositional conditions and sea level trends through time. TOC-CaCO3 trends of the samples are used to interpret the type of deposition and sediment accumulation rates, rhythmic bedding, and identification of regressional and transgressional phases. In the studied section, the manganese contents exhibit a declining trend along the lowstand systems tract that terminates in a sea level lowstand and the subsequent start of a transgressive trend. Some geochemical parameters such as Mn values and δ13C contents of sediments along a sequence can be used as potential sea level proxies that are tested in this study. The Paleocene-Eocene Thermal Maximum (PETM) interval of the Pabdeh Formation coincides with increasing Mn contents and Mn/Al ratios. Ti/Al and Si/Al ratios show contrasting trends to Mn values and Mn/Al ratios. Generally, elemental and isotopic results of the Pabdeh Formation confirm the presence of a long-term three-stage sea level cycle in the studied interval that is related to the PETM event. Based on elemental analyses such as Co, Mo, Ni, V, and Cr contents, the Pabdeh Formation sediments were deposited in suboxic to slightly anoxic conditions.

Larger benthic foraminiferal response to the PETM in the Potwar Basin (Eastern Neotethys, Pakistan)

The Paleocene-Eocene Thermal Maximum (PETM) was the most pronounced global and transient warming event of the Cenozoic and was associated with marked changes in the biosphere, atmosphere and hydrosphere. On the basis of the large benthic foraminiferal (LBF) biostratigraphy coupled with δ13C record, the PETM event and the Paleocene-Eocene boundary are constrained in the Duleram section (Potwar Basin, Pakistan). This shallow-marine carbonate deposit offers a unique opportunity to study in detail the stratigraphic record of the PETM and its effect on LBF assemblages in the eastern Neotethyan Ocean. The ~5‰ negative carbon isotope excursion (CIE) is here used to pinpoint the Paleocene-Eocene boundary corresponding to the base of SBZ 5. The CIE is not directly associated with evident compositional changes in the LBF assemblages that are instead identified during the CIE recovery phase. The prominent LBF assemblages' changes are marked by the disappearance of Miscellanea juliettae, Miscellanea dukhani, Ranikothalia nuttalli, Ranikothalia sindensis, Daviesina tenuis, Daviesina langhami and Orbitosiphon punjabensis and by the appearance of Alveolina ellipsoidalis, Alveolina globula, Alveolina moussoulensis, Alveolina minervensis, Alveolina avellana aurignacensis, Orbitolites biplanus, Nummulites fraasi, Nummulites minervensis and miliolids that correspond to the boundary between SBZ 5 and SBZ 6. The change in the LBF assemblages during the CIE-recovery phase of PETM is attributed to enhanced continental weathering and increased temperature and organic content flux that altered the habitat from oligotrophic to eutrophic conditions. This study provides the first evidence of the PETM at shallow marine deposits in the Potwar Basin and shows that change in the LBF assemblages in response of the PETM warming event affected shallow seas bordering the eastern Neotethyan Ocean.

Stable isotope and chemical stratigraphy of the Eocene Tambaba Formation: correlations with the Paleocene–Eocene Thermal Maximum event

Abstract The Paraíba Basin has a well-defined carbonate depositional sequence from the Upper Cretaceous (Campanian) to the Eocene. The carbonate sequence consists of the Itamaracá, Gramame, Maria Farinha and Tambaba formations, which mainly contain calcareous sandstones and carbonates with siliciclastics, limestone–marl alternations, limestones and marls, and limestones, respectively. The Tambaba Formation is composed of reef limestones, ranging from fossil- and ichnofossil-rich calcilutite to calcarenite. We investigated rocks of this unit located in a representative geological section at the Tambaba Beach, northeastern Brazil, in order to elucidate the environmental responses recorded in geochemical proxies (C and O isotopic composition, and distribution of major and trace elements). The δ 13 C and δ 18 O values ranged from 1.0 to 2.7‰ VPDB and from −1.3 to 1.1‰ VPDB, respectively. The interpretation of this response suggests environmental changes, such as an increase or decrease in bioproductivity of the organisms that make up these reef limestones. These changes are also recorded in the behaviour of the major and trace elements – for example, the relationship between SiO 2 , Al 2 O 3 , MgO and CaO, characterizing two different cycles during the deposition of these limestones: the first one characterized by a predominantly carbonate deposition, and the second one presenting a pulse of siliciclastic content. In addition, palaeotemperature values (9–15°C, from δ 18 O data) obtained, together with chemostratigraphic profiles of previous studies (e.g. δ 13 C, CaO, MgO, SiO 2 , Al 2 O 3 ), indicate that the reef limestones of the Tambaba Formation were probably deposited about 5 myr after the Paleocene–Eocene Thermal Maximum event.

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, andAxiodinium 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 ofApectodiniumspp. (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 ofApectodinium parvum, which could represent an ecological onshore substitute forAxiodinium augustumin the Paris and Dieppe-Hampshire basins. The establishment of a newBiconidinium longissimum-acme Zone suggests that the stratigraphic hiatus previously inferred within this sequence in the Paris Basin does not exist.

Two types of hyperthermal events in the Mesozoic-Cenozoic: Environmental impacts, biotic effects, and driving mechanisms

A deeper understanding of hyperthermal events in the Earth’s history can provide an important scientific basis for understanding and coping with global warming in the Anthropocene. Two types of hyperthermal events are classified based on the characteristics of the carbon isotope excursion (CIE) of the five representative hyperthermal events in the Mesozoic and Cenozoic. The first type is overall characterized by negative CIEs (NCHE) and represented by the Permian-Triassic boundary event (PTB, ~252 Ma), the early Toarcian oceanic anoxic event (TOAE, ~183 Ma), and the Paleocene-Eocene Thermal Maximum event (PETM, ~56 Ma). The second type is overall characterized by positive CIEs (PCHE) and represented by the early Aptian oceanic anoxic event (OAE1a, ~120 Ma) and the latest Cenomanian oceanic anoxic event (OAE2, ~94 Ma). Hyperthermal events of negative CIEs (NCHE), lead to dramatic changes in temperature, sedimentation, and biodiversity. These events caused frequent occurrence of terrestrial wildfires, extreme droughts, acid rain, destruction of ozone layer, metal poisoning (such as mercury), changes in terrestrial water system, and carbonate platform demise, ocean acidification, ocean anoxia in marine settings, and various degree extinction of terrestrial and marine life, especially in shallow marine. In contrast, hyperthermal events of positive CIEs (PCHE), result in rapid warming of seawater and widespread oceanic anoxia, large-scale burial of organic matter and associated black shale deposition, which exerted more significant impacts on deep-water marine life, but little impacts on shallow sea and terrestrial life. While PCHEs were triggered by volcanism associated with LIPs in deep-sea environment, the released heat and nutrient were buffered by seawater due to their eruption in the deep sea, thus exerted more significant impacts on deep-marine biota than on shallow marine and terrestrial biota. This work enriches the study of hyperthermal events in geological history, not only for the understanding of hyperthermal events themselves, large igneous provinces, marine and terrestrial environment changes, mass extinctions, but also for providing a new method to identify the types of hyperthermal events and the inference of their driving mechanism based on the characteristics of carbon isotopic excursions and geological records.

Benthic foraminiferal turnover across the Paleocene–Eocene Thermal Maximum (PETM) event in Eastern Desert, Egypt

Benthic foraminiferal fauna are analyzed quantitatively and qualitatively at three stratigraphic sections in Eastern Desert of Egypt (Serai, Duwi, and Um El Huetat). These sections embrace the Paleocene–Eocene Thermal Maximum (PETM) interval which is represented by the occurrence of five distinctive beds. These beds constitute the Dababiya Quarry Member at the lower part of Esna Formation. The occurrence of them indicates an expanded and relatively continuous record across the P/E boundary. The organic-rich clay layer (bed no. 1 of the Dababiya Quarry Member) marks the start of the PETM event. This bed is characterized by the extinction of all benthic foraminiferal fauna except for the occurrence of rare agglutinated foraminiferal species. The presence of these species indicates an oceanic anoxic event at the sea floor. High concentration of phosphatic contents including fish remains occurred in the middle part of the PETM (bed nos. 2 and 3 of the Dababiya Quarry Member) with the continuous absence of benthic foraminiferal fauna except for few specimens at the top of bed 3. Bed nos. 4 and 5 of the Dababiya Quarry Member represent the upper part of the PETM and the initial stage of sea floor recovery. Low diversity and abundance of benthic foraminiferal taxa occurred within these beds, represented by Valvulineria scrobiculata, Lenticulina midwayensis, Loxostomoides appliane, and Siphogenerinoides eleganta. This phenomenon continues upward during the post-PETM event. The Paleocene velasco-type benthic foraminifera Angulogavelinella avnimelechi and Coryphostoma midwayensis species are extinct within the advent of the PETM event. The benthic foraminiferal assemblages at the studied sections are dominated by midway-type fauna with little representative of velasco-type fauna. The velasco-type species are represented with high abundance at Serai section and with low densities at Um El Huetat section, while at Duwi section, they rarely occurred. This suggests outer neritic-upper bathyal (150–400 m) setting at Serai section and mostly middle-outer neritic (50–150 m) setting at Um El Huetat and Duwi sections.

Environmental changes during the Cretaceous-Paleogene mass extinction and Paleocene-Eocene Thermal Maximum: Implications for the Anthropocene

The Cretaceous-Paleogene boundary (KPB) mass extinction (~66.02Ma) and the Paleocene-Eocene Thermal Maximum (PETM) (~55.8Ma) are two remarkable climatic and faunal events in Earth's history that have implications for the current Anthropocene global warming and rapid diversity loss. Here we evaluate these two events at the stratotype localities in Tunisia and Egypt based on climate warming and environmental responses recorded in faunal and geochemical proxies. The KPB mass extinction is commonly attributed to the Chicxulub impact, but Deccan volcanism appears as a major culprit. New mercury analysis reveals that major Deccan eruptions accelerated during the last 10ky and reached the tipping point leading up to the mass extinction. During the PETM, climate warmed rapidly by ~5°C, which is mainly attributed to methane degassing from seafloor sediments during global warming linked to the North Atlantic Igneous Province (NAIP). Biological effects were transient, marked by temporary absence of most planktic foraminifera due to ocean acidification followed by the return of the pre-PETM fauna and diversification. In contrast, the current rapid rise in atmospheric CO2 and climate warming are magnitudes faster than at the KPB or PETM events leading to predictions of a PETM-like response as best case scenario and rapidly approaching sixth mass extinction as worst-case scenario.

The Jurassic – Tertiary unconformity: A new exploration target for supergene-enriched iron oxide copper-gold –style mineralization in the Humboldt mafic complex, Nevada, USA

A Late Cretaceous to Early Oligocene episode of paleoweathering and supergene activity has been identified within the Jurassic-age (170Ma) Humboldt mafic complex (HMC) and associated Boyer Ranch Formation of west-central Nevada, USA. This episode is responsible for significant subaerial weathering, erosion, oxidation and most importantly local supergene metal enrichment which could potentially have a major economic impact upon iron oxide copper-gold (IOCG)-style mineralization within the complex and in the Boyer Ranch Formation. Paleoweathering profiles that developed on the exposed Jurassic surface during this time now mark an angular unconformity (J-T unconformity) with a stratigraphically overlying, Tertiary (Oligocene) rhyolitic volcanic-volcaniclastic sequence.Differential uplift of the Jurassic surface is a direct result of the Middle and/or Late Jurassic Luning-Fencemaker compressional overthrust faulting event during which the entire complex was tectonically transported to its present location. The uplifted Jurassic paleosurface experienced one or more cycles of weathering, erosion, depression of the water table and uninterrupted supergene activity beginning at the end of the Cretaceous and possibly accelerating during the Paleocene-Eocene Thermal Maximum Event (∼56Ma). Geochemically mature supergene Cu-oxide profiles developed over exhumed mineralized sections in terrains with favorable fault block movements. These paloweathering systems evolved from moderately acidic pH to near-neutral or slightly alkaline pH environments over time. High protolith reactivity and low hypogene pyrite concentrations modified acidity of supergene fluids thus limiting Cu mobility.Profiles that survived erosion were later buried and preserved by the Oligocene-age rhyolitic volcanic-volcaniclastic sequence before the onset of mid-Tertiary Basin and Range normal faulting. Subsequent partial unroofing of overlying Tertiary volcanic cover resulted in further erosion of some profiles. Erosional remnants mapped in the field include all or some components of the original supergene Cu-oxide profiles. Drilling results suggest profiles that remain buried are generally intact.Although this field-oriented study is considered preliminary, it concludes that known Jurassic-age IOCG-style mineral occurrences in the central HMC have been subjected to prolonged subaerial paleoweathering and supergene activity that has not been previously recognized. Where complete or nearly complete profiles are preserved, efficient cumulative Cu-enrichment to potentially ore grades has been documented in well defined oxide zones. These findings can be extrapolated to the entire J-T unconformity along which concealed and enriched deposits may exist. As such, the unconformity is considered a prime exploration target that is highly prospective for new discoveries of economically viable, supergene-enriched IOCG resources.

Experimentos de disolución de CaCO<sub>3</sub> en foraminíferos bentónicos aglutinados del Paleoceno-Eoceno en Zumaya (Cuenca Vasco-Cantábrica, España)

The largest extinction of deep-sea benthic foraminifera in the Cenozoic occurred during the Paleocene-Eocene Thermal Maximum event (PETM, ~55.8 Ma). Much has been speculated about the causes of such extinction, and proposed mechanisms include changes in productivity and/or oxygenation of bottom waters, metabolic changes and in the composition of the food supply to the seafloor, or the ocean acidification related to the massive input of isotopically light carbon into the ocean-atmosphere system, among others. Here we analyse ocean acidification as a potential triggering mechanism of the extinctions. The early Eocene at the Zumaya section (Basque-Cantabrian Basin) is marked by a 4 m-thick interval with a very low CaCO 3 content. In order to analyse whether CaCO 3 dissolution had a direct effect on the extinctions across the PETM, we car-ried out dissolution experiments on various species of agglutinated benthic foraminifera from Zumaya. In general, agglutinated species that do not disappear in the interval of most intense dissolution at Zumaya were not -or only slightly- affected by our dissolution experiments, since they do not have calcareous particles or cement. However, some species that went extinct or locally disappeared during the early Eocene, such as Dorothia cylindracea, Spiroplectammina spectabilis and Haplophragmoides cf. walteri , are resistant to dissolution. These results sug-gest that, in addition to ocean acidification, other factors must have contributed to the destabilization of benthic foraminiferal assemblages.

Biostratigraphy and Geochemistry of Upper Paleocene - lower Eocene Oceanic Red Beds from the Zagros Mountains, SW Iran

Oceanic Red Beds studied are well known in the upper Cretaceous (CORBs, i.e. Cretaceous Oceanic Red Beds), but their presence and genesis have hitherto not been intensively discussed for equivalent Paleogene deposits. We describe a red to purple shale interval from the Pabdeh Formation, Zagros basin, Iran, which can be assigned to Late Paleocene to Early Eocene age, nannofossil zones NP9-NP12. Parts of the purple marl interval within NP9/NP10 coincide with the PETM (Paleocene-Eocene Thermal Maximum) interval. Coccolithus pelagicus, Sphenolithus moriformis, Sphenolithus orphanknollensis, and Toweius ssp. are dominant in nannofossil assemblages in this interval, and PETM event taxa such as Discoaster araneus appear. Based on whole rock geochemistry and microfossil assemblages, the red to purple marls were deposited in an oligotrophic environment with low nutrient (Ba) values, and were accompanied by a shift to more oxic conditions and low amount of TOC in an oceanic basin. Low amount of major elements like Si, Al and Fe indicates low terrestrial input and relatively high amount of CaO (biogenic element) emphasizes the open sea and pelagic deposition of the shale. Warm deep water can be inferred by the presence of the dinoflagellate taxa Impagidinium and nannoplankton taxa, Discoaster. As a result, the purple shale can be considered as typical Paleogene ORBs in the Zagros basin deposited under very similar conditions as well studied Tethyan Cretaceous oceanic red beds.

Toward a better understanding of Paleocene-Eocene Thermal Maximum: A multidisciplinary record from Dababiya GSSP, Luxor, Egypt

The Paleocene-Eocene thermal maximum (PETM) shows an extraordinary drop in both δ 13 Ccarb and δ 13 Corg values, suggesting that a massive amount of 12 C-rich carbon dioxide was released into the atmosphere in a very short time (on the order of few hundred ky). The Dababiya GSSP (Luxor, Egypt) is thought to be the most complete known PETM section. The expanded sedimentary record of the Dababiya GSSP improves our understanding of the processes leading to the PETM events. Our multiproxy dataset, which includes geochemistry, mineralogy, micropaleontology and sedimentology, provided the following crucial clues for the PETM interval at Dababiya GSSP (Fig. 1). The Dababiya GSSP is deposited in the deepest part of an asymmetric submarine channel as indicated by the paleotopography, and absence of uppermost Paleocene and lowermost Eocene sediments from the Eastern section located 25m away from the main GSSP outcrop (Fig.1). At 50 m to the NW, the sediment beds thin out and finally disappear at about 150 m from the main GSSP outcrop. Thus, the Dababiya GSSP represents a localized expanded PETM sequence with a maximum extent of about 200m. At the GSSP, the PaleoceneEocene boundary (PEB) coincides therefore with a sequence Toward a better understanding of Paleocene-Eocene Thermal Maximum: A multidisciplinary record from Dababiya GSSP, Luxor, Egypt

Geology and geochemistry of Kurkur bentonites, southern Egypt: provenance, depositional environment, and compositional implication of Paleocene–Eocene thermal maximum

A large lower Eocene bentonite deposit at the top of Sinn El-Kaddab plateau, southern Egypt, is investigated. It forms isolated anticlinal hills as mesa and cuesta geomorphic units. The Sinn El-Kaddab plateau (497 m above sea level) with Gebel Abyad in northern Sudan represent the most southern margin of Tethys realm in East Africa. Clay and silt fractions constitute up to 95 % of the bentonite and calcium montmorillonite is the predominant phase (70–87 %). These sediments were deposited during the Paleocene–Eocene Thermal Maximum (PETM) event. Grain-size distribution in conjunction with their geologic setting argues in favor of a low energy deep hemipelagic, restricted basin within the outer shelf zone. They suggest sporadic deposition in a basin characterized by relief oscillation, in response to continuous tectonic uplifting. The sediments of the peripheral parts of the basin are more calcareous and were deposited in an arid climatic condition. Calcium montmorillonite was deposited in subtropical warm climate, with alternating wet and dry seasons. Compositionally, the bentonite shales are basic to intermediate and exhibit a rather limited range of K2O/Na2O and SiO2/Al2O3 ratios. They suggest mature polycyclic siliciclastics as the main provenance and within-plate alkali basalts as a main igneous precursor. They are the product of intensive physical weathering process in response to combined effects of both tectonic disturbance and prevailed climatic conditions during the PETM event. Geochemically, they are interpreted in terms of mixing of two end-members: pure clastic terrigenous component (inherited from the source area) and carbonate-rich matrix.

High-resolution carbon isotope record for the Paleocene-Eocene thermal maximum from the Nanyang Basin, Central China

The Paleocene-Eocene thermal maximum (PETM) was a transient episode of global warming, associated with massive atmospheric greenhouse gas input that occurred at the Paleocene/Eocene boundary. Biostratigraphic and isotope stratigraphic studies indicate that the PETM event is well documented in the marl deposits of the Yuhuangding section in the Nanyang Basin, Central China, with a carbon isotope negative excursion of ~6.1‰ within 19-m-thick marl deposits. This is the highest resolution record of the PETM so far found in the world. The PETM event was triggered within 2-cm-thick marl sediments, with a decrease of δ 13 C (stable carbon isotope ratio) from –3.2‰ to –5.2‰, suggesting a massive methane hydrate release for a transient period that was possibly caused by a catastrophic event. A comparison between marine and terrestrial records indicates a “Three-Phase Model” for the PETM event. Initially there is a rapid negative excursion in the δ 13 C record, followed by a slowly decreasing trend, and then a gradual positive recovery, corresponding respectively to a rapid dissociation of oceanic methane hydrate, followed by a slow release of methane and then the consumption of the released methane.

Black carbon in Paleocene–Eocene boundary sediments: A test of biomass combustion as the PETM trigger

Several explanations have been proposed to account for the dramatic perturbation to Earth's carbon cycle that led to extreme warming, ocean acidification, mass extinction, and a major negative carbon isotope excursion (CIE) at the Paleocene–Eocene (P/E) boundary. One reason that the ultimate cause for this event remains ambiguous is the difficulty in directly testing these multiple hypotheses. We conducted a test of one proposed mechanism, the “wildfire hypothesis,” that suggests that combustion of a significant fraction of abundant Paleocene peat deposits within several thousand years could release enough CO 2 to Earth's atmosphere to account for all of these observations. Soot and graphitic black carbon (hereafter collectively referred to as GBC), both combustion byproducts, are widely distributed (through smoke) by subaerial combustion, and are remarkably resistant to diagenetic degradation. Using samples provided by the Ocean Drilling Program, we measured GBC concentrations across the P/E boundary in two important Paleocene–Eocene Thermal Maximum (PETM) sections to test a prediction of the wildfire hypothesis, namely that the combustion of Paleocene organic matter at the onset of the PETM would produce a peak in sedimentary GBC. In the Bass River section (New Jersey margin), GBC concentrations are uniformly high (121–358 ppm), consistent with the core's continental margin setting, but there is no evidence of increased GBC flux at the PETM. Furthermore, carbon isotopic ratios of GBC display the negative CIE seen in PETM organic matter, indicating that this material was sourced from contemporaneous (P/E boundary) biomass, not geologically old carbon. At site 1210 (Shatsky Rise), GBC concentrations were uniformly below our method's detection limit (0.5 ppm), whereas the wildfire hypothesis would predict high GBC concentrations (∼ 3000) ppm accompanying the event. Together, these data appear to refute but cannot conclusively rule out biomass burning as the cause for the PETM event.

The Paleocene–Eocene Thermal Maximum as recorded by Tethyan planktonic foraminifera in the Forada section (northern Italy)

The Forada section in the Venetian Pre-Alps of northern Italy represents an expanded record of the Paleocene–Eocene Thermal Maximum (PETM) at a depositional paleodepth of about 1 km ± 0.5 km. High-resolution planktonic foraminiferal analysis of this section, in a time interval of approximately 1.3 Myr across the Paleocene/Eocene boundary, reveals striking faunal changes that allow the identification of eight phases (a–h). The late Paleocene was represented by stable, warm and oligotrophic surface water conditions (phase a). Unstable environmental conditions start well before the onset of PETM (ca. 150 kyr, phase b) and involved a change towards eutrophy, as marked by the increase of Subbotina and the concomitant decrease of Morozovella. This step is also characterized by enhanced fragmentation and dissolution. The interval corresponding to the main body of the carbon isotope excursion (CIE) is characterized by a marked increase of Acarinina, though with some differences in the species composition and relative abundance, both in high-and low-latitudes, particularly in the Tethyan area. Forada is no exception to this pattern. However, at Forada, two prominent peaks in abundance of acarininids are recorded ca. 30 kyr prior to the onset of the CIE, thus suggesting an increase in temperature heralding the onset of the PETM (phase c). Interestingly, the lower peak in abundance of Acarinina just precedes the 1‰ carbon isotope negative shift occurring below the onset of the main CIE. The basalmost Eocene, corresponding to the lower part of CIE curve, is represented by intense planktonic foraminiferal dissolution, implying an extraordinary rise of the CCD. This interval has an estimated duration of about 16 kyr (phase d). The dominance of acarininids in the lower part of the CIE (phase e, f; ca. 14 and 22.5 kyr) is interpreted as a consequence of the extreme warmth coupled with eutrophic conditions characterizing the Forada depositional environment at that time. These acarininids include at Forada also the temporally constrained Acarinina sibaiyaensis and A. africana. The morphological similarity between these peculiar species with the radially elongated chambered forms characterizing the Cretaceous anoxic events, suggests the hypothesis that depletion of oxygen in the upper water column might have been one of the factors causing their conspicuous occurrence at the PETM. The recovery in abundance of the specialized morozovellids and of other planktonic foraminiferal groups (e.g., biserials, globanomalinids, igorinids, planorotalids and pseudohastigerinids), occurring in the middle part of the CIE (ca. 30 kyr after the onset of the PETM), indicates an initial environmental recovery (phase g). A new stable state is definitely reached in the upper part of the Forada section where the relative proportions of the main component of planktonic foraminiferal assemblages move towards values similar to those of the late Paleocene conditions (phase h). However, the perturbation during the PETM produced significant changes in the ocean geochemistry that endured after the PETM event, as testified by the prominent high carbonate dissolution characterizing the marly levels, and the large variability in relative abundance among different components of the planktonic foraminiferal assemblages. These striking oscillations were not present in the latest Paleocene.

長鎖ノルマルアルカンの炭素同位体比が示す暁新世／始新世境界の温暖化イベント(PETM)に伴う陸上植生撹乱の証拠

長鎖ノルマルアルカンの炭素同位体比が示す暁新世／始新世境界の温暖化イベント(PETM)に伴う陸上植生撹乱の証拠

Surface-water chemistry and fertility variations in the tropical Atlantic across the Paleocene/Eocene Thermal Maximum as evidenced by calcareous nannoplankton from ODP Leg 207, Hole 1259B

Calcareous nannoplankton assemblages at Ocean Drilling Program (ODP) Site 1259 on Demerara Rise (western equatorial Atlantic) underwent an abrupt and fundamental turnover across the Paleocene/Eocene Thermal Maximum (PETM) ~55.5 m.y. ago. The PETM is marked by a dissolution interval barren or nearly-barren of nannofossils due to the rapid acidification of the world oceans. Toweius, Fasciculithus, and Chiasmolithus sharply decrease at the onset, whereas Chiasmolithus, Markalius cf. M. apertus, and Neochiasmolithus thrive immediately after the event, which also signals the successive first appearances of Discoaster araneus, Rhomboaster, and Tribrachiatus. The environmental indications of these changes were further investigated by correspondence analysis on quantitative nannofossil counts. The PETM event has been attributed to CO 2-forced greenhouse effects. At Site 1259, the elevated pCO 2 and subsequent lowered surface-water pH values at the onset of the PETM caused intensive carbonate dissolution, producing the nannofossil-barren interval. The chemically stressed habitats may well have also induced the evolution of ephemeral nannofossil “excursion taxa”, such as Rhomboaster and malformed discoasters ( D. araneus and Discoaster anartios). Based on its sudden increase, Markalius cf. M. apertus is considered to have been a local opportunistic species that took advantage of the surface-water changes. At the same time, a presumably higher runoff from continental areas fertilized the western equatorial Atlantic as indicated by an increase in the abundance of r-mode specialists preferring high-nutrient conditions, such as Chiasmolithus, Coccolithus pelagicus, and Hornibrookina arca. Contrasts between the results of this study and previous work at ODP Site 690 in the Southern Ocean, the New Jersey continental margin, and the central paleoequatorial Pacific further demonstrate that the response to the PETM can be influenced by local differences in geologic setting and oceanographic conditions.