Search

Erosional scars, slumps, slides and debrites (mass-transport deposits) on submarine slopes form relief that influences turbidity current behaviour. However, the interaction of mass-transport deposit emplacement kinematics (i.e. rapid emplacement versus creep), the morphology of the evolving seafloor topography and subsequent flow types is complicated. This study describes two outcrop examples of deep-water, predominantly turbiditic, deposits overlying mass-transport deposits, from the Eocene slope succession of the Aínsa Basin (Spanish Pyrenees). In both examples, the mass-transport deposit substrate continued to creep contemporaneously with turbidity current deposition and bypass. In the first case study, structures in the mass-transport deposits are extensional and oriented parallel to flow. In the second, structures are compressional and oriented perpendicular to flow. Mudstones dominate the slope succession, but deposits overlying mass-transport deposits form sandstone-prone accumulations. Lateral confinement by flow-parallel extensional faults enhanced channel-formation. Channel incision occurred close to the exhumed fault plane on the hangingwall. Incision ceased as the fault gradually locked-up, and channels avulsed to the hangingwall of a newly active normal fault, while the abandoned channel was filled by a thinning and fining-upward succession. Barriers formed where the long axes of compressional anticlines developed in mass-transport deposits formed perpendicular to flow. Here, turbidites filled the bathymetric lows in the axes of synclines. Continued tightening of synclinal depocentres led to repeated stoss side trapping and upslope accretion of coarse-grained sediment accumulation. This generated thickening and coarsening-up, followed by thinning and fining-upward successions, tracking the decreasing, then increasing flow bypass associated with topographic expression on the mass-transport deposit. This study shows how post-emplacement creep, and orientation of topographic features on mass-transport deposits, influence the routing and deposition of contemporaneous turbidity currents, and illustrates examples of facies successions that could be misinterpreted as the product of other autogenic submarine slope processes, such as lateral migration of sinuous channels, or compensational lobe stacking.

We describe the first definite fossil of the water scavenger beetle subfamily Enochrinae (Coleoptera: Hydrophilidae): Cymbiodyta samueli sp. n. from the Eocene Baltic amber from the Lithuanian coast. The new species is extremely similar and likely closely related to the only European species, C. marginella and confirms the European occurrence of the genus since the Eocene. A reanalysis of the historical biogeography of the genus, including the fossil taxon, revealed a wide Euro-American distribution of the ancestor of all modern species of the genus, corresponding to the position of landmasses and existing land connections between North America and Europe in the Late Cretaceous. The biogeographic reconstructions and the fossil both suggest that European Cymbiodyta is an ancient relict lineage which used to be more diverse in the past but survived until today in a single species C. marginella.

Les Amynodontidae Scott& Osborn, 1883 sont une famille éteinte de Rhinocerotoidea Owen, 1845 connue depuis l’Éocène moyen jusqu’à la fin de l’Oligocène en Asie, en Amérique du Nord et en Europe. Nous présentons ici deux spécimens inédits d’Amynodontidae, un crâne et une mandibule, de Zaisanamynodon borisovi Belyaeva, 1971, datés de la fin de l’Éocène du bassin de Zaïssan (Kazakhstan) et un crâne de Metamynodon planifrons Scott& Osborn, 1887, daté du début de l’Oligocène des Big Badlands (États-Unis). Ce nouveau matériel a été inclus dans une matrice de caractères morpho-­anatomiques. Elle a été complétée par le codage de l’espèce récemment décrite Amynodontopsis jiyuanensis Wang X.-Y., Wang Y.-Q., Zhang R., Zhang Z.-H., Liu & Ren, 2020 et les codages révisés de Cadurcotherium cayluxi Gervais, 1873 et Cadurcotherium minum Filhol, 1880. Nous avons réalisé une analyse cladistique basée sur cette matrice, incluant 31 taxons terminaux de Rhinocerotoidea. La nouvelle hypothèse phylogénétique proposée permet de discuter des positions phylogénétiques des spécimens étudiés au sein des Amynodontidae et de la position des Amynodontidae au sein des Rhinocerotoidea. Notre analyse cladistique clarifie la composition générique et spécifique des tribus Metamynodontini Kretzoi, 1942 et Cadurcodontini Wall, 1982 et soutient la monophylie de Zaisanamynodon Belyaeva, 1971. La dichotomie des deux tribus s’exprime notamment par la présence de plusieurs caractéristiques crâniennes telles que “l’allongement de l’incisure nasale” ou “la fosse préorbitaire bien développée” chez les Cadurcodontini. Ces spécialisations témoignent d’une adaptation de la région péri-nasale à la présence d’un proboscis. Notre étude ouvre également une discussion sur la biogéographie des Amynodontidae, leur émergence et dispersion en Asie à l’Éocène moyen puis leur colonisation de l’Amérique du Nord et de l’Europe de l’Est. Leur présence en Europe occidentale est, quant à elle, restreinte à l’Oligocène et liée à l’événement de la Grande Coupure.

The present research was carried out to investigate the behavior of radon (222Rn) concentrations over the carbonate and evaporite sequences and to assess the related health hazards. A total of 50 points from three different stratigraphic units, namely, the Bahadurkhel Salt, Jatta Gypsum, and the Kohat Formation of the Eocene age, were analyzed for radon concentrations in the district of Karak, Khyber Pakhtunkhwa, Pakistan. Measurements for radon levels were made by using RAD7 of Durridge, United States. The highest average 222Rn concentration (16.5 Bq/L) was found in the limestone unit of the Kohat Formation of the Eocene age. However, the lowest radon levels were observed in the salt-bearing strata of the Bahadurkhel Salt of the Eocene age. The study revealed that the average radon concentration in all the lithologies varied in the order of RnLimestone > RnSalt > RnGypsum. The findings of the current research suggest that the study area is safe from radon-related health hazards.

With the northward subduction and final closure of the Neo-Tethyan oceanic crust, the Indian and Eurasian plates finally collided together and underwent a strong collision orogenic event, resulting in large-scale crust–mantle magmatic interactions. In order to clarify the controversies about tectono-magmatic activities after the Indian–Eurasian continental collision, we report the newly dated Eocene Qiongduojiang gabbro explored in the Tethyan–Himalaya belt, southern Tibet. LA-ICP-MS zircon U-Pb dating shows that the crystallization age of the Qiongduojiang gabbro is 46.1 ± 1.7 Ma. The whole-rock major and trace elements, as well as Rb-Sr, Sm-Nd, and Pb isotopic data results, show that the Qiongduojiang gabbro is apparently depleted in Nd isotopes, is enriched in Pb isotopes, and has maintained a consistent 87Sr/86Sr(t) value. This paper argues that the E-MORB-like Qiongduojiang gabbro originated from asthenosphere upwelling caused by slab breakoff of the Neo-Tethyan oceanic plate. This event caused large-scale magmatic activities, a magmatic mixing process between ancient crust and deep mantle, and wild distribution of Eocene Gangdese plutons along the Yarlung–Tsangpo Suture Zone, and it rendered the subduction-modified Tibetan lithosphere fertile from the Gangdese porphyry Cu deposits.

Istrian Flysch was deposited during the Eocene in the Dinaric foredeep and is composed of hemipelagic marls and various gravity flow deposits. The latter are predominantly 5-40 cm thick turbidites, developed mostly as laminated and cross-rippled sandstone beds (Tb-e, Tc-e and Td-e Bouma sequences). In addition to the turbidites, there are deposits characterized by a significant thickness, occasionally more than 10 m, described as complex (bipartite) megabeds. The megabeds are composed of debrites in the lower part (Division I), and high-density turbidites in the upper part (Division II). The distinct clast composition of each megabed indicates that the lithoclasts were derived from tectonically active slopes and fault scarps along which collapses of the different parts of the Cretaceous to Palaeogene neritic carbonate succession, that underlie the Flysch, occurred. The Division II deposits are well cemented, normally graded calcirudite/calcarenites composed mostly of orthophragminids, nummulitids, and red algae, originating from outer ramp environments. Redeposited marl, observed in the matrix of the debrites and as intraclasts in some megabeds, implies that the collapses along the synsedimentary fault scarps and steep slopes also occurred within the foredeep itself, during the rapid tectono-sedimentary evolution of the Dinaric foreland basin.

A detailed systematic study of calcareous nannofossils was carried out for the Jaddala Formation in (Aj-10) well, Central Iraq. Seventy one species belong to twenty four genera of calcareous nannofossils were identified including sixty two of them were previously named and nine species were identified for the first time and they would not be given names until more information is obtained in the future to support this identification. It is a recorded of five biostratigraphic zone, which suggested the age of the Jaddala Formation to be of early to late Eocene. The recorded biozone includes the following: Reticulofenestra dictyoda (Deflandre in Deflandre & Fert, 1954) Stradner & Edwards, 1968 Partial Range Biozone (CNE 5); Discoaster sublodoensis Bramlette and Sullivan, 1961 Interval biozone (CNE 6-7); Nannotetrina cristata (Martini, 1958) Perch-Nielsen, 1971 Interval biozone (CNE 8); Nannotetrina alata (Martini in Martini & Stradner, 1960) Haq and Lohmann, 1976 Interval biozone (CNE 9); Chiasmolithus gigas Bramlette & Sullivan, 1961Range Biozone (CNE 10-11).

The mangrove communities of the Caribbean region are considered descendants of former pantropical Late-Cretaceous mangroves that underwent regional differentiation after the tectonic closure of the Tethys Sea. The southern Caribbean area has been considered the cradle of Neotropical mangroves. These inferences were based mainly on qualitative evidence, such as the presence/absence of fossils showing botanical affinities with present-day mangrove taxa. However, as demonstrated in Quaternary paleoecology, the most suitable approach for reconstructing past plant communities is the assemblage approach, which is based on quantitative palynology. Therefore, the problem of the origin of Caribbean mangroves, as ecological communities, is addressed here by reviewing in detail the Late Cretaceous to Eocene quantitative palynological studies available for the region to properly reconstruct past mangrove assemblages. No evidence has been found for the occurrence of mangrove ecosystems during the Late Cretaceous and the Paleocene, only records of the fossil representatives of some individual taxa (Nypa, Acrostichum), which are not mangrove-forming elements and, hence, are not reliable indicators of mangrove communities. The first robust evidence of true mangrove communities was found in the Middle Eocene (Lutetian). These mangrove communities were dominated by the fossil representative of Pelliciera, a mangrove-forming tree with a Neotropical distribution by that time. Back-mangrove communities were dominated by the palm Nypa (which was pantropical by that time but is now restricted to the Indo-Malayan region), the fern Acrostichum and palms, notably Mauritia, along a sea-land saline to freshwater community gradient. Pelliciera originated in the southern Caribbean during the Early Eocene and became dominant in the Middle Eocene, when it dispersed across the Caribbean area, probably favored by the migration of the Caribbean plate. Therefore, the first Caribbean mangroves were ecological and evolutionary innovations that emerged de novo during the Eocene, rather than a consequence of the regional evolutionary differentiation from hypothetical Late Cretaceous Tethyan mangroves, whose existence is not supported by quantitative palynological records. It is proposed to develop this type of study for other tropical/subtropical mangrove communities, for a sounder view of mangrove origin and evolution, at a global scale., 1. Introduction 2. Modern Caribbean mangroves 3. Quantitative fossil pollen records 3.1. Late Cretaceous 3.2. Paleocene 3.3. Eocene 4. The oldest Caribbean mangroves 5. Conclusions and final remarks Declaration of Competing Interest Acknowledgments References

Despite belonging to an important time slice in the geological history, the Eocene shallow-marine beds of the Alborz region in Iran have received little attention from researchers. We selected two stratigraphic sections (Mojen and Kalateh) ascribed to the Ziarat Formation as suitable representatives for the current analysis, emphasising on their constituent microfacies and paleoenvironmental implications. The biotic communities are characterised by larger benthic foraminifera (LBF), coralline algae, corals, and bivalves as the major carbonate facies components. The microfacies gradients and paleoenvironmental analysis suggest deposition in a shallow-marine oligotrophic ramp environment within two platform stages. Both these stages indicate an increase in water depth from the inner to the middle ramp settings with spatial distribution of the LBF and other benthic components. Our data support the previous view that the early Eocene witnessed an increase in LBF taxa with near obliteration of the coral reefs in the sedimentary platforms across the Tethys. The corals reinitiated building reefal structures in the Middle Eocene, marking an important phase in the Tethyan paleoenvironmental evolution.

The importance of topography generated by Eocene Eurekan deformation as a sediment source for sandstones deposited on the western Barents Shelf margin is evaluated through a sediment provenance study conducted on wellbore materials retrieved from Spitsbergen and from the Vestbakken Volcanic Province and the Sørvestsnaget Basin in the southwest Barents Sea. A variety of complementary techniques record a provenance change across the Paleocene-Eocene boundary in wellbore BH 10-2008, which samples Paleogene strata of the Central Tertiary Basin in Spitsbergen. Sandstones containing K-feldspar with radiogenic Pb isotopic compositions, chrome spinel in the heavy mineral assemblage, and detrital zircons and rutiles with prominent Palaeoproterozoic and Late Palaeozoic—Early Mesozoic U-Pb age populations are up-section replaced by sandstone containing albitic plagioclase feldspar, metasedimentary schist rock fragments, a heavy mineral assemblage with abundant chloritoid, metamorphic apatite with low REE contents, metapelitic rutile with Silurian U-Pb ages and zircons with predominantly Archaean and Palaeoproterozoic U-Pb age populations. Our results clearly demonstrate the well-known regional change in source area from an exposed Barents Shelf terrain east of the Central Tertiary Basin during the Paleocene to the emerging Eurekan mountains west and north of the Central Tertiary Basin during the Eocene. Eocene sandstones deposited in the marginal basins of the southwestern Barents Shelf, which were sampled in wellbores 7316/5-1 and 7216/11-1S, contain elements of both the Eurekan and the eastern Barents Shelf provenance signatures. The mixing of the two sand types and delivery to the southwest margin of the Barents Shelf is consistent with a fill and spill model for the Central Teritary Basin, with transport of Eurekan-derived sediment east then south hundreds of kilometres across the Shelf.

The large and distinctive chalcidoid wasp Leptoomus janzeni Gibson, 2008, originally described from late Eocene Baltic amber, is newly recorded from coeval Rovno amber (Ukraine) based on a single well-preserved female specimen. Only 66 species of Rovno hymenopterans (49%) are also known from Baltic amber. High resolution photomicrographs and measurements of the specimen are given. Some character states of the new specimen, such as a green metallic coloration, a bare and flat prepectus, location and number of multiporous plate sensillae on the flagellum, sclerotized spur vein of the hind wing, and two metatibial spur are reported in this species for the first time.

The evolution of the brain at the origin of Carnivora remains poorly understood, largely owing to the limited number of cranial endocasts known from Carnivoramorpha and basal crown Carnivora. Here, we use x-ray computed tomography to create digital endocasts of two early carnivores, Quercygale angustidens and Gustafsonia cognita. Quercygale angustidens is generally regarded as the sister taxon to Carnivora and Nimravidae and is thus of great interest to further our understanding of the evolutionary changes that occurred at the origin of Carnivora. Gustafsonia cognita provides a comparison to a contemporary crown carnivoran. We describe the endocasts of these two taxa, placing them in the context of carnivoramorphan phylogeny. Both endocasts preserve the cerebellum in great detail, resulting in a better understanding of the morphology of this part of the brain in early carnivores. Gustafsonia cognita, despite its small size, geological age and basal position, displays a sulcal pattern typical of Amphicyonidae, reaffirming its position within the family. Nimravids; and early carnivorans, such as Gustafsonia cognita, Proailurus lemanensis and Hesperocyon gregarius, have more expanded neocortices than Quercygale angustidens. Current evidence suggests that the increase in gyrification in basal Carnivoramorpha occurred mainly through elongation of existing sulci and entered a new phase at the origin of crown Carnivora. Additional sulci appeared in early members of the order, resulting in distinctive sulcal patterns in the different carnivoran families. Nevertheless, more endocasts of basal carnivorans and carnivoramorphans are needed to better understand the processes driving the evolution of the brain in this group.

The first late-Cambrian aged palynomorph assemblage of Bolivia is presented. The sampled material comes from the Cambro-Ordovician Iscayachi Formation cropping out in the Antenna of the Sierra de Sama, Tarija department, southern Bolivia. The palynomorph assemblage occurs in levels correlated to the Parabolina (Neoparabolina) frequens argentina trilobite biozone. It is comprised of Acanthodiacrodium spp., Cristallinium cambriense, Cymatiogalea cf. C. aspergillum, C. velifera, C. virgulta, Dasydiacrodium spp., Eliasum llaniscum, Impluviculus multiangularis, Ladogella rommelaerei, Ladogella sp., Leiofusa sp., Leiosphaeridia sp., Lophosphaeridium sp., Lusatia? sp., Micrhystridium sp., Poikilofusa squama, Poikilofusa sp., Polygonium dentatum, Retisphaeridium brayense, Saharidia fragilis, Solisphaeridium akrochordum, S. lucidum, Timofeevia phosphoritica, Timofeevia microretis, Vulcanisphaera africana and V. turbata. The assemblage provides elements of comparison with previously reported palynofloras in northern Argentina, eastern Newfoundland, southwestern Sardinia, Algeria, northern Spain, Baltica and Avalonia (Arctic Russia, East-European Platform). All microphytoplancton are indicative of cold water affinities as expected from the western margin of Gondwana, showing some Baltic affinities as well.

Explaining where plants originated and how plants migrated between eastern Asia and other Northern Hemisphere regions is still challenging. The genus Arisaema is considered a good example to illuminate this process, due to its wide distribution in both the tropical and temperate zones. Based on comprehensive taxon sampling, the historical biogeography of Arisaema was conducted using the molecular data from four chloroplast DNA regions. The phylogeny of Arisaema was studied by using ML and BI methods. Divergence times of Arisaema species were estimated by the uncorrelated lognormal Bayesian method. The ancestral area reconstruction of Arisaema was performed with BioGeoBEARS and Bayes-DIVA. Our results indicated that the crown group of Arisaema originated in Southeast Asia ca. 31.28 Ma. After the initial origin, Arisaema was inferred to have become widespread in Southeast Asia. Members in Himalayas, Africa and North China, Japan, the Korean Peninsula region (NJK region) were derived from migrants originating in Southeast Asia. American members were derived from migrants originating in the NJK region. Arisaema originated in Southeast Asia during the Oligocene with the development of tropical rainforest and a warm, moist climate. During the Oligocene to Miocene, Southeast Asia was the original center for the diversification of Arisaema in the NJK region.

Шелиховский бассейн в северо-восточном секторе Охотского моря остается слабоизученным редкой сетью 2D сейсмических профилей, поисково-разведочное бурение в пределах бассейна не проводилось. На текущей региональной стадии изученности бассейна внимание привлекают достаточно крупные поисковые структуры, однако основные проблемы здесь связаны с большими геологическими рисками и неопределенностями. Обобщение результатов исследований разных лет, с учетом открытий в аналогичном бассейне, позволяет выявить ряд закономерностей и дополнительных аргументов в пользу перспективности рассматриваемой территории., The Shelikhovsky basin in the northeast of the sea of Okhotsk remains poorly covered by rare 2D seismic profiles, the basin has not been studied by the exploration drilling. At the current regional stage of the basin knowledge, attention is attracted by rather large promising areas, but the main challenges here are associated with high geological risks and uncertainties. Summarizing the results of the studies of different years, taking into account discoveries in a similar basin, allows to identify a number of patterns and additional arguments in favor of the prospects within the area of interest.

The bituminous black pelite of the Messel UNESCO world heritage site is an exceptional palaeobiological archive from the Middle Eocene greenhouse climate. The pronounced homogeneity of the annually laminated pelite through a time interval of 640 kyr complicates the relative stratigraphic classification of fossil remains and is, thus, largely dependent on particular marker horizons within the uniform sedimentary column. We analyzed the most prominent marker horizon M using petrographic microscopy, X-ray powder diffraction, and electron probe microanalyses to identify and characterize its structure and phosphate-dominated mineralogy. Based on our analytical data, we suggest that this phosphatic marker horizon resulted from the exceptional combination of external tephra enclosed in bacteria and algae-rich layers, producing a coupled phosphorus and cation diffusion during diagenesis. Mantienneite (KMg2Al2Ti(PO4)4(OH)3 • 15H2O) is documented for the first time in the Messel fossil deposit. The diagenetic succession of messelite, montgomeryite, and mantienneite precipitation reflects the internal heterogeneities in primary mineral composition of an ash layer. Kerogen maturation and hydrocarbon migration produced acidic, reducing pore fluids with high P concentration, which enhanced the mobility of Al and Ti. The mantienneite-forming reaction marks the change from a regime of reducing to oxidizing conditions. With the deposition and diagenesis of the marker horizon M, a singular event is preserved in a sedimentary sequence otherwise regarded as largely uniform over a time span of about 640 kyr.

The Huizhou Movement refers to the Middle Eocene tectonic transition from the early to the late Wenchang Rifting stage (about 43 Ma ago) in the Pearl River Mouth Basin. Based on seismic reflection, drilling, logging and geological data, fault characteristic analysis, denudation thickness recovery, magmatism statistics, regional tectonic dynamics comparison and other methods are used to reveal the characteristics, properties and dynamic mechanism of the Huizhou Movement. The Huizhou Movement mainly shows the North-South transition of rifting and the migration along the faults, basement uplift, magmatic diapir and stratigraphic denudation. It is believed that the Huizhou Movement is a comprehensive reflection of plate interaction and lithospheric thinning process in the Pearl River Mouth Basin, which is closely related to the transition of lithosphere from initial rifting to rapid thinning, the India-Eurasia hard collision and the change of subduction direction of the Pacific plate. The Huizhou Movement has significant influence and control on the Paleogene hydrocarbon-generating sags and the development of hydrocarbon source rocks, sedimentary system and deep high-quality reservoir, hydrocarbon migration and accumulation in the Pearl River Mouth Basin.

The taxonomical consideration, probable phylogeny and stratigraphic significance of twenty-eight middle Eocene (Bartonian) planktic foraminiferal species from the eastern limb of Jabal Hafit, Al Ain area, United Arab Emirates (UAE), Northern Oman Mountains (NOM) are presented, and twenty one of them are illustrated. Identification of these twenty-eight species belonging to ten genera Globoturborotalia, Subbotina, Globigerinatheka, Inordinatosphaera, Orbulinoides, Hantkenina, Acarinina, Morozovelloides, Pseudohastigerina and Turborotalia has led to the recognition of three biostratigraphic zones, in ascending order: Morozovelloides lehneri PRZ (E11), Orbulinoides beckmanni TRZ (E12) and Morozovelloides crassata HOZ (E13). Eight out of the identified species are recorded, in this study, for the first time from Jabal Hafit: Globoturborotalia martini, Subbotina gortanii, S. jacksonensis, S. senni, Globigerinatheca barri, Acarinina praetopilensis, A. punctocarinata and Morozovelloides bandyi. The second or third record of three species from J. Hafit outside its original records are recently documented by the present author: Inordinatosphaera indica, Hantkenina australis and H. compressa. The paleontology, paleoclimatology and paleogeographic distribution of the identified taxa at Jabal Hafit and other Paleogene outcrops in the UAE and Tethys are presented and discussed. The identified fauna emphasis the wide geographic areas in the Tethys, from Atlantic to Indian-Pacific Oceans via Mediterranean.

At the end of the Cretaceous Period, an asteroid collided with the Earth and formed the Chicxulub impact structure on the Yucatan Platform. International Ocean Discovery Program (IODP) Expedition 364 drilled into the peak ring of the Chicxulub impact crater. The post-impact section of the core was sampled for terrestrial palynological analysis, yielding a high-resolution record ranging from the early Paleocene to the earliest Eocene (Ypresian), including a black shale deposited during the Paleocene–Eocene Thermal Maximum (PETM). The IODP 364 core provides the first record of floral recovery following the K–Pg mass extinction from inside the Chicxulub impact crater. The systematic taxonomy of the angiosperm pollen provided here follows a separate publication describing the systematic paleontology of the plant spores and gymnosperm pollen from the IODP 364 core (Smith et al. 2019). The Paleocene section of the core is nearly barren, but with unusually high relative abundances of the angiosperm pollen Chenopodipollis sp. A (comparable to the Amaranthaceae), possibly indicating an estuarine pollen source. Pollen recovery is higher in the PETM section, and variable but generally increasing in the later Ypresian section, with excellent preservation in several samples. Estimated absolute ages of several potentially useful regional biostratigraphic events are provided. One new genus (Scabrastephanoporites) and five new species (Brosipollis reticulatus, Echimonocolpites chicxulubensis, Psilastephanocolporites hammenii, Scabrastephanoporites variabilis, and Striatopollisgrahamii) are formally described.

Subsurface information on source rock potential of the Eocene shale unit of the Abakaliki Fold Belt is limited and has not been widely discussed. The total organic carbon (TOC) content and results of rock-eval pyrolysis for nine shale samples, as well as the one-dimensional (1D) geochemical model, from an exploration well in the Abakaliki Fold Belt were used to evaluate the source rock potentials and timing of hydrocarbon generation of Lower Eocene source rocks. The TOC content values of all the samples exceeded the minimum threshold value of 0.5 wt.% required for potential source rocks. A pseudo-Van Krevelen plot for the shale samples indicated Type II–III organic matter capable of generating gaseous hydrocarbon at thermally mature subsurface levels. The 1D burial model suggests that the Eocene source rock is capable of generating oil and gas at the present time. The modelled transformation ratio trend indicates that a fair amount of hydrocarbon has been expelled from the source rocks. The results of this study indicate that the Eocene source units may have charged the overlying thin Eocene sand bodies of the Abakaliki Fold Belt.

Isolated cheek teeth of the Asian dipodidHeosminthus primiverisfrom four early Oligocene localities in the Koritnica-Babušnica basin, south-east Serbia, are described. The record of the Paleogene Dipodidae of Central Asia and Europe is briefly discussed. The current view of the migration pattern of the Paleogene Dipodidae between central Asia and Europe is revised: the migration ofPlesiosminthusinto Europe during the late Oligocene was preceded by the immigration ofHeosminthusinto the Serbo-Macedonian high (S. E. Europe) during the early Oligocene.

The aim of the present contribution is to describe a new genus and species of Pipoidea from the Huitrera Formation (Eocene) from Patagonia, Argentina. The new genus shows a unique combination of characters indicating that it is a valid taxon different from other pipimorphs, including the coeval Llankibatrachus truebae. The phylogenetic analysis resulted in the nesting of the new taxon within a previously unrecognized endemic clade of South American aglossans. This new clade turns out to be the sister-group of crown-group Pipidae. This phylogenetic proposal reinforces the hypothesis sustaining the dispersal of pipids between Africa and South America through an island chain or a continental bridge across the Atlantic Ocean by Early Tertiary times. Le but de cet article est de décrire de nouveaux genre et espèce de Pipioidea de la formation Huitrera (Éocène) de Patagonie, Argentine. Le nouveau genre montre une combinaison unique de caractères indiquant que c’est un taxon valide, différent des autres pipimorphes incluant Llankibatrachus truebae, contemporain. L’analyse phylogénétique résulte en la nidification du nouveau taxon au sein d’un clade endémique, auparavant non reconnu, d’aglosses d’Amérique du Sud. Il en résulte que le nouveau clade est le groupe frère du groupe couronne des Pipidae. Cette proposition phylogénétique renforce l’hypothèse en faveur d’une dispersion des pipidés entre l’Afrique et l’Amérique du Sud au moyen d’une chaîne insulaire ou d’un pont continental à travers l’Océan atlantique au Tertiaire inférieur. Fil: Aranciaga Rolando, Alexis Mauro. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales "Bernardino Rivadavia"; Argentina Fil: Agnolin, Federico. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales "Bernardino Rivadavia"; Argentina. Fundación de Historia Natural Félix de Azara; Argentina Fil: Corsolini, Julián. Museo de Geología y Paleontología del Lago Gutierrez “Dr. Rosendo Pascual”; Argentina

A new species, Janzenella theia Bremer & Talamas, sp. nov., is described from Baltic amber, which is the second known species of the family Janzenellidae (Platygastroidea). Synchrotron scanning was performed to observe internal structures and external morphology that was occluded by turbidity in the amber matrix surrounding the specimen.

Lower to Middle Eocene organic-rich deep-water limestones of the ∼335-m-thick (1100 ft) Radwany (Thebes-equivalent) Formation represent a source rock and a potential reservoir unit at the October Oil Field in the Gulf of Suez. However, in spite of recent exploration advances, the pore system and diagenetic history of the formation are still poorly understood. This study aims to discriminate porosity types and their vertical distribution, assess the diagenetic processes controlling porosity evolution, and evaluate the unit's overall reservoir potential. To achieve these goals, we utilized an integrated petrographic, mineralogical, geochemical and petrophysical dataset from four offshore wells. At October Oil Field, the Radwany Formation is informally divided into three intervals (from the base up: C, B and A) which are composed of planktonic foraminiferal wackestone, wackestone-packstone and packstone microfacies. Pores include both fabric selective (interparticle, intraparticle and moldic) and non-fabric selective (fracture) types. Visible porosity reaches up to 11.6%, and the highest porosity values are associated with interparticle pores in foraminiferal packstone in interval C. The two overlying intervals have lower porosities but have TOC values of up to 6 wt %. The Nuclear Magnetic Resonance (NMR) analysis yields low amplitudes of short T2 components (max. 52 ms), which suggests the presence of small pores (intraparticle, moldic, fracture, and fissure). Based on the electrical quality index (EQI) rock classification, nine groups were identified, suggesting a high heterogeneity of the formation. The highest EQI values positively correlate with high porosity (visible and estimated) in the lower part of Interval C which is dominated by interparticle/intraparticle porosity, thus reflecting the low tortuosity values of this microfacies. Dominantly low EQI values in Intervals A and B indicate low porosity efficiency and higher tortuosity. Carbonate sediments of the Radwany Formation are interpreted to have undergone a complex series of diagenetic processes. These processes modified the primary pore system either by enhancing the reservoir properties (dissolution and fracturing), or by reducing or destroying porosity (cementation, mechanical and chemical compaction, and minor pyritization, chertification, and asphaltene precipitation). The study highlights the unconventional reservoir potential of the middle and upper parts of the Radwany Formation (intervals B and A) at October Oil Field, and the conventional reservoir potential of interval C. It emphasizes the complexity of diagenetic controls on the porosity evolution in deep-water limestones of the Gulf of Suez, and may provide valuable insight into similar deep-water carbonate systems in rift basin reservoirs elsewhere.

Ceratophyllum L. is a cosmopolitan genus of perennial aquatic herbs that occur in quiet freshwaters. Fossils of this genus have been widely reported from the Northern Hemisphere, most of them occurring in the temperate zone. Here, we describe two species of fossil fruits discovered from subtropical areas of China. The fossil fruit discovered from the upper Eocene Huangniuling Formation of the Maoming Basin is designated as C. cf. muricatum Chamisso, and fruits discovered from the Miocene Erzitang Formation of the Guiping Basin are assigned to the extant species C. demersum L. The discovery of these two fossil species indicates that Ceratophyllum had spread to South China by the late Eocene and their distribution expanded in subtropical China during the Miocene.

The Paleoproterozoic (1.7 Ga [billion years ago]) metasedimentary rocks of the Mount Barren Group in southwestern Australia contain burrows indistinguishable from ichnogenera Thalassinoides, Ophiomorpha, Teichichnus, and Taenidium, known from firmgrounds and softgrounds. The metamorphic fabric in the host rock is largely retained, and because the most resilient rocks in the sequence, the metaquartzites, are too hard for animal burrowing, the trace fossils have been interpreted as predating the last metamorphic event in the region. Since this event is dated at 1.2 Ga, this would bestow advanced animals an anomalously early age. We have studied the field relationships, petrographic fabric, and geochronology of the rocks and demonstrate that the burrowing took place during an Eocene transgression over a weathered regolith. At this time, the metaquartzites of the inundated surface had been weathered to friable sandstones or loose sands (arenized), allowing for animal burrowing. Subsequent to this event, there was a resilicification of the quartzites, filling the pore space with syntaxial quartz cement forming silcretes. Where the sand grains had not been dislocated during weathering, the metamorphic fabric was seemingly restored, and the rocks again assumed the appearance of hard metaquartzites impenetrable to animal burrowing.

Environmental and biotic responses to early Eocene hyperthermal events in the southwest Pacific are critical for global paleoclimate reconstructions during Cenozoic greenhouse intervals, but detailed multidisciplinary studies are generally missing from this time and location. Eocene carbonate sediments were recovered during International Ocean Discovery Program Expedition 371 at Site U1510 on southern Lord Howe Rise in the Tasman Sea. Part of the Early Eocene Climatic Optimum (EECO; 53.26–49.14 Ma) and superimposed hyperthermal events have been identified based on refined calcareous nannofossil biostratigraphic data and carbon stable isotope records on bulk sediment and benthic foraminifera. Four negative carbon isotope excursions (CIEs) associated with negative oxygen isotope excursions are recognized within the EECO. Comparison with a global compilation of sites indicates these CIEs correlate to the K event (Eocene Thermal Maximum 3), and tentatively to the S, T, and U events. Sediments with a high carbonate content throughout the EECO provide an excellent opportunity to examine these CIEs, as carbonate dissolution often impacts correlative records elsewhere. Benthic foraminifera and calcareous nannoplankton taxa indicative of warm waters are most abundant during the K event, the most prominent hyperthermal of the EECO. Eutrophication of surface waters during the K event did not lead to increased trophic conditions at the seafloor, whereas a coupled response is observed during smaller hyperthermals. The biotic turnover sheds new light on the paleoenvironmental consequences of hyperthermal events.

[ES]Los cocodrilos del Eoceno y Oligoceno de la Cuenca del Duero están representados, según se desprende del estudio de los dientes aislados, por tres géneros Asiatosochus Mook (exclusivo del Nivel "Salzones", Iberosuchus Antones (no presente en el Nivel "Molino de Pico")y Diplocynodom Pomel. Los osterodermos de tres tipos muy distintos, al presentar una distribución similiar, permiten una correlación anatómica con los tres géneros. Se ha realizado un estudio estadístico de los dientes y cráneos, elaborándose diagramas triangulares, Rectas BC-RC y diagramas alveolares. En cuanto a la determinación, se prefiere Iberosuchus frente a Pristichompsum y se descarta Allognathosuchus., [EN] According to the study of isolated teeth, the crocodiles found in the Eocene and oligocene sediments of the Duero basin (Spain) belong to the three diferent Asiatosuchus Mook specifics of the sanzoles horizon, iberosuchus Antunes, not present in the "Molino del Pico" horizon, and Diplocynodon Pomel. Three diferent types of the osteoderms presenting a similar chronostratigraphical distribution to that of the teeth, allow to establish a morphological correlation between the osteoderms and the three above mentioned genera. Another crocodilia genus ocurring in the "Molino del Pico" horizon has not been yet classified.

International audience; The theoretical prediction of Earth-Moon dynamics in deep geologic time is hampered by limited knowledge of Earth's past tidal dissipation and dynamical ellipticity. Cyclostratigraphy can, however, provide valuable information on the geologic evolution of the Earth-Moon dynamical parameters. Here we investigate Eocene cyclostratigraphy to estimate Earth's precession rate (p), Earth-Moon distance (EMD) and length-of-day (LOD). Two highly-resolved deep sea records are selected from the Atlantic Ocean, with ages centered on 42.5 Ma (40.9–44.3 Ma; IODP Site U1410) and 54.95 Ma (54.1–55.8 Ma; ODP Site 1262). The sedimentary sequences at these sites recorded Milankovitch forcing signals with prominent precession index (Site 1262) and obliquity (Site U1410) frequencies and their amplitude modulations. At Site U1410, amplitude modulation of the main obliquity cycle was tuned to the Earth's 173-kyr orbital inclination (s3-s6) metronome, and at Site 1262, the dominant precession index amplitude modulation to the 405-kyr orbital eccentricity (g2-g5) metronome. This enabled estimation of Earth's precession rate p of 51.486 ± 0.064 arcsec/yr and 51.546 ± 0.168 arcsec/yr for 42.5 Ma and 54.95 Ma, respectively. These p estimates indicate EMD values of 383.710 ± 0.090 × 103 km and 382.625 ± 0.265 × 103 km, and LOD values of 23.679 ± 0.0115 h and 23.667 ± 0.039 h for 42.5 Ma and 54.95 Ma, respectively. These estimates deviate from theoretical predictions based on back calculation assuming present-day tidal dissipation. In particular, a significant discrepancy between the model and observations (cyclostratigraphy) occurs at 54.95 Ma (Site 1262) suggesting contributions from other effects on Earth's rotation, including changes in tidal dissipation and/or Earth's dynamical ellipticity related to mantle convection and the early Eocene global warming.

The Eocene-Miocene successions recovered at DSDP sites on the Jan Mayen Ridge (NE Atlantic) and on the adjacent East Greenland margin provide a sedimentary record of the rifting and separation of the Jan Mayen Microcontinent from East Greenland. A combination of palynology, conventional heavy mineral analysis, single-grain major and trace element geochemistry and radiometric dating of amphibole and zircon has revealed a major change in sediment provenance took place at the Early/Late Oligocene boundary corresponding to a prominent seismic reflector termed JA. During the Eocene and Early Oligocene, lateral variations in provenance character indicate multiple, small-scale transport systems. Site 349 and Kap Brewster were predominantly supplied from magmatic sources (Kap Brewster having a stronger subalkaline signature compared with Site 349), whereas Site 346 received almost exclusively metasedimentary detritus. By contrast, Late Oligocene provenance characteristics are closely comparable at the two Jan Mayen sites, the most distinctive feature being the abundance of reworked Carboniferous, Jurassic, Cretaceous and Eocene palynomorphs. The Site 349 succession documents an evolution in the nature of the magmatic provenance component. Supply from evolved alkaline magmatic rocks, such as syenites, was important in the Middle Eocene and lower part of the Early Oligocene, but was superseded in the later Early Oligocene by mafic magmatic sources. In the latest Early Oligocene, the presence of evolved clinopyroxenes provides evidence for prolonged magmatic fractionation. Initial low degrees of partial melting led to generation of alkaline (syenitic) magmas. The extent of partial melting increased during the Early Oligocene, generating basaltic rocks with both subalkaline and alkaline compositions. Towards the end of the Early Oligocene, the amount of partial melting and magma supply rates decreased. In the Late Oligocene, there is no evidence for contemporaneous igneous activity, with scarce magmatic indicator minerals. The provenance change suggests that the hiatus at the Early/Late Oligocene boundary represents the initiation of the proto-Kolbeinsey Ridge and separation of the Jan Mayen Microcontinent from East Greenland.

Ethmoturbinates, nasoturbinates, and maxilloturbinates are well developed in the narial tract of land-dwelling artiodactyls ancestral to whales, but these are greatly reduced or lost entirely in modern whales. Aegyptocetus tarfa is a semiaquatic protocetid from the middle Eocene of Egypt. Computed axial tomography scans of the skull show that A. tarfa retained all three sets of turbinates like a land mammal. It is intermediate between terrestrial artiodactyls and aquatic whales in reduction of the turbinates. Ethmoturbinates in A. tarfa have 26% of the surface area expected for an artiodactyl. These have an olfactory function and indicate that early whales retained a sense of smell in the transition from land to sea. Maxilloturbinates in A. tarfa have 6% of the surface area expected for an artiodactyl. These have a respiratory function and their markedly reduced size suggests that rapid inhalation and exhalation was already more important than warming and humidifying air, in contrast to extant land mammals. Finally, the maxilloturbinates of A. tarfa, although greatly reduced, still show some degree of similarity to those of artiodactyls, supporting the phylogenetic affinity of cetaceans and artiodactyls based on morphological and molecular evidence.

The late early Eocene to middle Eocene ~51–45 Million years ago (Ma) time interval in the middle bathyal, pelagic/hemipelagic succession of the western Tethys Possagno section in the Carcoselle quarry (Southern Alps, northeastern Italy), contains several episodes of negative carbon isotope excursions (CIEs) and concomitant dissolution of carbonates. Comparison with previously published carbon isotope records from deep-sea successions allows the identification of long-term trends and short-term events in our record, which provides a sound chemostratigraphic basis for correlation against the robust bio- and magnetostratigraphic scheme available for the studied succession and additional evidence of the global significance of the long-term trend and superposed perturbations tracked changes in δ13C values. Spectral analysis indicates that CIEs and associated lithological cycles are paced by orbital forcing, similar to what previously observed on the same interval in other deep-sea successions. The identification of astronomically forced geochemical cycles allows us to develop an orbitally tuned age model allowing to test the astrochronology of the ~56.0 Ma to ~47.5 Ma time interval.

Classification of tribe Cardueae in natural subtribes has always been a challenge due to the lack of support of some critical branches in previous phylogenies based on traditional Sanger markers. With the aim to propose a new subtribal delimitation, we applied a Hyb-Seq approach to a set of 76 Cardueae species representing all subtribes and informal groups defined in the tribe, targeting 1061 nuclear conserved orthology loci (COS) designed for Compositae and obtaining chloroplast coding regions as by-product of off-target reads. For the extraction of the target nuclear data, we used two strategies, PHYLUCE and HybPiper, and 776 and 1055 COS loci were recovered with each of them, respectively. Additionally, 87 chloroplast genes were assembled and annotated. With three datasets, phylogenetic relationships were reconstructed using both concatenation and coalescent approaches. Phylogenetic analyses of the nuclear datasets fully resolved virtually all nodes with very high support. Nuclear and plastid tree topologies are mostly congruent with a very limited number of incongruent nodes. Based on the well-solved phylogenies obtained, we propose a new taxonomic scheme of 12 monophyletic and morphologically consistent subtribes: Carlininae, Cardopatiinae, Echinopsinae, Dipterocominae (new), Xerantheminae (new), Berardiinae (new), Staehelininae (new), Onopordinae (new), Carduinae (redelimited), Arctiinae (new), Saussureinae (new), and Centaureinae. In addition, we further updated the temporal framework for origin and diversification of these subtribes. Our results highlight the power of Hyb-Seq over Sanger sequencing of a few DNA markers in solving phylogenetic relationships of traditionally difficult groups., Financial support from the Ministerio de Ciencia e Innovación (Project CGL2015-66703-P and Ph.D. grant to Sonia Herrando-Moraira) and the Catalan government (“Ajuts a grups consolidats” 2017-SGR1116) is also gratefully acknowledged.

In the summer of 2016, the International Ocean Discovery Program (IODP) Expedition 364 coredthrough the post-impact strata of the end-Cretaceous Chicxulub impact crater, Mexico. Core sampleswere collected from the post-impact successions for terrestrial palynological analysis, yielding a rareDanian to Ypresian high-resolution palynological assemblage. This record constitutes one of the firstPalaeocene and Ypresian palynological assemblages from Central America or Mexico, representing amore coastal lowland palaeoenvironment than previous studies from mainland Mexico. Although theabundance of pollen and spores is very low in the Palaeocene carbonates, abundance increases in themore organic-rich shale layers representing the Palaeocene–Eocene Thermal Maximum (PETM) andlater Ypresian. The spores and gymnosperm pollen identified from IODP 364, although rare comparedto the angiosperm pollen, are a diverse mix of cosmopolitan taxa, as well as some characteristic of fossilCentral American assemblages (e.g. Selaginellaceae), and others previously identified from thePaleogene northern Gulf of Mexico coastal plain. The assemblage generally indicates the presence ofnearby moist to seasonally dry lowland tropical forest, with some taxa suggestive of higher elevationforests. Ephedroid pollen grains may be indicative of the presence of more arid conditions.

The relevance of the work. This paper is devoted to topical issues of identifying promising intervals favorable for petrophysical properties for hydrocarbon accumulations using 3D seismic data. The purpose of these studies is to establish the effective attributes of the seismic-wave motion to determine the petrophysical properties of Maikop sediments aimed at restoring oil and gas production in the Gazanbulak area. The subjects of research are core materials, well geophysical survey data and seismic attributes, as well as relationships between core data and mathematical transformations of petrophysical properties data. The PP curves were transformed into the porosity values of the sediments of the target interval, and a regression equation was obtained for the research area, which establishes a relationship between the porosity coefficient and �PP. The object of research is the Gazanbulak field. The paper gives a brief geological and geophysical characteristic, stratigraphic and lithological description of the rocks composing the section of this field. Despite the fact that this field has been repeatedly studied by various geological and geophysical methods, many features of its structure are not fully clarified; in 2014, 3D seismic surveys were carried out. Result of the studies. The main results of studies on the petrophysical properties of the Gazanbulak horizon II of the Maikop suite using 3D seismic and GIS seismic data are presented. The cubes, reservoir maps, and porosity maps were constructed according to which it was found that the percentage of sands is high and reaches 62% in the target interval; the average values of apparent resistivity vary from 3.0–8.4 ohm m. It is shown that the calculated �PP values by area increase in the southern and eastern parts of the Ziyadkhan area, and the predicted porosity data are observed in the central part of the Ziyadkhan area, in the northern and central parts of the Gazanbulak area. The values of the porosity coefficient calculated for the research interval are approximately 10–22%. The results of the forecast of porosity using the seismic attribute RMS Amplitude are given. Comparison of maps constructed by different methods (GIS and RMS amplitude analysis) shows that the data obtained by different computation methods are similar and coincide quite well and can be used in determining the location of the next production well. Conclusion. RMS Amplitude can be successfully used to determine the petrophysical properties of individual sediments of deposits with similar seismic and geological conditions

A new fossil species from the Eocene Baltic amber of the extinct tribe Mimoplatycini Kazantsev, 2013 (Cantharidae Malthininae), is illustrated and described here. Mimoplatycis marchettii sp. nov. is characterized by a transverse but interrupted carina in the middle of pronotum. The tribe is known from Baltic and Rovno amber, and the pronotum with carinae similar to Lycidae could be interpreted as mimicry. The pronotal shape is here indicated as a diagnostic character of the species level.

The authors studied the isotope-geochemical composition of the Eocene volcanic rocks from the Kinkilsk complex of Western Kamchatka. The peculiarities of the distribution of high field strength and heavy rare-earth elements and their ratio, as well as the isotopic composition of Sr, Nd and Pb suggest the formation of primary melts from depleted or poorly enriched in isotopic composition of the mantle wedge sources in different contaminated quartz-feldspathic sialic sediments. Two types of dependences of εNd in volcanic rocks of the complex on the degree of differentiation of rocks and inter-element relations are revealed. The first is associated with strong contamination of igneous melts with quartz-feldspathic sediments, the second relates to the fractionation of an isotopic (Nd)-enriched magmatic source with weak contamination of the melts with a crustal terrigenous material. The distribution of large-ion (LILE) elements is typical for sources of melts enriched with aqueous fluid and formed with the participation of a substance of a metasomatized mantle wedge.

This study is aimed at comparing ostracod assemblages during the Eocene-Oligocene transition that were identified in the Paleogene succession at twenty-two previously studied locations across the seven geographical regions of Turkey. The formations deposited in the Eocene-Oligocene and the paleogeographic distribution and paleoenvironmental properties of the ostracods that were identified in these formations were investigated in the following different geographical regions of Turkey: the Aegean (Denizli), the Eastern Mediterranean (Mut, Karsantı Baseni), Southeastern Anatolia (Adıyaman), Eastern Anatolia (Malatya-Darende, Elazığ), Central Anatolia (Karaman, Ulukışla, Sivas, Ankara), Northern Anatolia (Batı Pontidler/Kastamonu) and Northwestern Anatolia (İstanbul, Çatalca/GD Trakya, Kırklareli, Tekirdağ). The ostracod biozones in the acme-zone category were studied in these geographical regions. The zones were identified and chosen by successions or rock assemblages. The study revealed that the Eocene-Oligocene ostracod species demonstrated lacustrine, lagoonal, lagoon-littoral, epineritic, epineritic-infraneritic and infraneritic-bathyal environmental conditions. It was observed that, especially in the Aegean, Northwestern Anatolia and Southern Anatolia/Eastern Mediterranean regions, marl and silty sandstone in the upper and bottom levels of the Oligocene, in which coal settlement is observed, were usually deposited in lagoons containing ostracods. Furthermore, in the studied regions the co-occurrence of ostracod species living in maritime conditions with ostracod species living in lagoonal conditions can be explained by sea-related excessive shoaling in the basins. In Turkey, judging from environmental properties of the ostracod species, the transgression of the sea declined from northeast to northwest during the Eocene–Oligocene. © 2018, Pleiades Publishing, Ltd.

Future global warming is widely anticipated to increase the occurrence of extreme precipitation events, but such hydrological changes have received limited attention within paleoclimate studies. Several proxy studies of the hydrological response to the Paleocene–Eocene Thermal Maximum hyperthermal, ∼56 Ma, have recently invoked changes in the occurrence of extreme precipitation events to explain observations, but these changes have not been studied for the geologic past using climate models. Here, we use a coupled atmosphere–ocean general circulation model, HadCM3L, to study regional changes in metrics for extreme precipitation across the onset of the PETM by comparing simulations performed with possible PETM and pre-PETM greenhouse gas forcings. Our simulations show a shift in the frequency–intensity relationship of precipitation, with extreme events increasing in importance over tropical regions including equatorial Africa and southern America. The incidence of some extreme events increases by up to 70% across the PETM in some regions. While the most extreme precipitation rates tend to relate to increases in convective precipitation, in some regions dynamic changes in atmospheric circulation are also of importance. Although shortcomings in the ability of general circulation models to represent the daily cycle of precipitation and the full range of extreme events precludes a direct comparison of absolute precipitation rates, our simulations provide a useful spatial framework for interpreting hydrological proxies from this time period. Our results indicate that changes in extreme precipitation behaviour may be decoupled from those in mean annual precipitation, including, for example in east Africa, where the change in mean annual precipitation is small but a large increase in the size and frequency of extreme events occurs. This has important implications for the interpretation of the hydrological proxy record and our understanding of climatic, as well as biogeochemical, responses to global warming events.

Triple oxygen isotope measurements are an emerging tool in paleoclimate reconstructions. In this contribution we develop the application of triple oxygen isotope measurements to lacustrine sediments to reconstruct past elevations. We focus on a well-constrained sample set from the Eocene North American Cordillera (Cherty Limestone Formation, Elko Basin, NV, United States, 42–43.5 Ma) on the east side of the elevated Nevadaplano. We present triple oxygen isotope measurements on freshwater lacustrine chert samples from the Cherty Limestone Formation. Across an evaporation trend spanning 6.5‰ in δ18O values we observe a negative correlation with Δ′17O ranging from −0.066 to −0.111‰ (λRL= 0.528), with an empirical slope (λchert, δ′17O vs. δ′18O) of 0.5236. Additionally, we present new carbonate clumped isotope (Δ47) temperature results on the overlying fluvial-lacustrine Elko Formation, which indicate an error-weighted mean temperature of 32.5 ± 3.8°C (1σ), and evaporatively enriched lake water spanning δ18O values of −3.7 to +3.5‰ (VSMOW). Paired chert and carbonate δ18O values demonstrate that co-equilbrium among the carbonate and chert phases is unlikely. Thus, as also previously suggested, it is most likely that Elko Basin chert formed during early diagenesis in equilbirium with pore waters that reflect evaporatively18O-enriched lake water. Using this scenario we apply a model for back-calculating unevaporated water composition to derive a source water of δ′18O = −16.1‰ (VSMOW), similar to modern local meteoric waters but lower than previous work on paired δ18O- δD measurements from the same chert samples. Further, this back-calculated unevaporated source water is higher than those derived using δD measurements of Late Eocene hydrated volcanic glass from the Elko Basin (average δ′18O equivalent of approximately −18.4‰, VSMOW). This suggests, assuming Eocene meteoric water Δ′17O values similar to today (∼0.032‰), either that: (1) the hypsometric mean elevation recorded by the lacustrine Cherty Limestone was lower than that derived from the average of the volcanic glass δD measurements alone; or (2) there was hydrogen exchange in volcanic glass with later low δD meteoric fluids. Nonetheless, our new findings support a relatively high (∼2.5–3 km) plateau recorded in the Elko Basin during the mid-Eocene.