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The study of several Paleogene sections in the south of the Russian Plate allowed the refinement of the taxonomic list of diatom and silicoflagellate assemblages. Using an integrated biostratigraphic approach, the stratigraphic range of the Bipalla oamaruensis diatom Zone was defined. The high degree of taxonomic diversity of the studied assemblages is associated with the shallow-water environments of the marginal part of the basin inhabited by various ecological groups of diatoms. The zone was established in the Tishki and Kasyanovka formations and, based on direct comparison, corresponds to the Bartonian–Lower Priabonian Cyrtophormis alta–Etmosphaera polysiphonia–Theocyrtis andriashevi radiolarian interval-zones. The Priabonian age of the Kasyanovka Formation is also confirmed by dinocyst data. The Bartonian-Priabonian boundary approximately coincides with the first appearance of the silicoflagellate Corbisema hexacantha. [ABSTRACT FROM AUTHOR]

The fossil mammalian assemblage of the Itaboraí Basin, located in the state of Rio de Janeiro, Brazil, was recovered from fissure fill deposits that vertically cut its limestone beds. Previous studies have considered the abundant and diversified fossil mammals excavated from such deposits of this small basin to have been deposited synchronously. An analysis comparing the whole Itaboraí mammalian assemblage with that of the Las Flores Formation, Argentina, estimated its age as early Eocene. The purpose of this study is to test the hypothesis of an asynchronous formation and infilling of the fissures and to conduct faunistic comparisons with other South American local faunas, considering the mammals of each Itaboraí fissure (MN, MCT-1 and MCT-2) separately, as these fissures were formed in distinct areas of the basin and in different topographic levels. To evaluate the faunal similarities between the Itaboraí fissures and other South American local faunas, cluster analysis and parsimony analysis of endemicity were undertaken. Both methods nest all three Itaboraí fissures with the Yacimiento Las Flores fauna, but some analysis show two fissures (MN and MCT-1) to be closer to it than the third. Based on the topographic levels of the fissures, their fossil mammals (diversity, presence/absence, and abundance), marsupial trophic structure and evolutionary stage, we conclude that the Itaboraí mammal assemblage is composed of faunas of different ages/stages: the fauna of the fissure discovered in 1968 (MCT-2) is the oldest (probably late Paleocene to earliest Eocene), and the fissure discovered in 1949 (MCT-1) is the youngest (early Eocene). [ABSTRACT FROM AUTHOR]

This is the second part of the paper on the Cretaceous of the Mountainous Crimea. A lot of new data has been received during last ten years. This paper summarizes the state of knowledge of the Upper Cretaceous stratigraphy, selected biostratigraphic groups (ammonites, belemnites, ostracods, foraminifers, gilianelles, nannoplankton) and magnetostratigraphy. Ammonite and belemnite biostratigraphic subdivisions are proposed for the first time for the Crimean Upper Cretaceous. Foraminifera-based biostratigraphy is updated, and new biostratigraphic units are proposed and correlated with the European scale. Stratigraphic hiatuses are recognised in the succession of southwestern Crimea: the base and the top of lower Cenomanian, upper Coniacian–lower Santonian, Campanian/Maastrichtian and Cretaceous/Paleogene boundary intervals. [ABSTRACT FROM AUTHOR]

The aim of the currrent investigation is to date the final closure of Pakistan's portion of the northern Tethys rim in Kohat-Potwar Basin by using integrated bio-sequence stratigraphy and facies information. The Paleogene strata is divided into six biozones while its depositional profile resembles a distally steepened-homoclinal platform. Paleogene deposits in the Kohat Basin include two depositional cycles, two transgressive-highstand systems tracts, one lowstand systems tract, and separated by two sequence boundaries. Three transgressive-highstand systems tracts were observed in the Potwar Basin, which are separated by two tectonically controlled and one eustatic sequence boundary. The sequence boundaries in both basins are synchronous at 50–49.5 Ma and mark a period of drastic change in sediment character, which may have been caused by the combined effects of uplift and eustatic sea level fall. This suggests that the proto-closure of the northern rim of Tethys occurred between 50 and 49.5 Ma. Only the Kohat Basin experienced the restoration of marine conditions, which happened in the Middle Lutetian at around 45.8 Ma and may have been brought on by a combination of flexural loading of the Indian Plate and eustatic sea-level rise that persisted until the Kohat Basin's closure in the Upper Lutetian at around 41.2 Ma due to India-Asia collision. [ABSTRACT FROM AUTHOR]

The Order Pyrotheria is one of the most bizarre and least-known groups of South American native ungulates, and its biochron extends from the early? Eocene to the late Oligocene. The emblematic genus of this order is Pyrotherium, which is known by several maxillae, mandibles, and postcranial bones of adult individuals. In this paper, we describe the most complete juvenile mandible of Pyrotherium found to date, MPEF-PV 2581, which bears dp3–m1 and alveoli of di1–di2. The study of this specimen, re-study of previously published specimens (MACN-A 52-290 and MNHN-F-DES 104), and study of unpublished deciduous upper and lower cheek teeth from several collections allows us to designate MLP-PV 13-3 as the lectotype of P. romeroi, to establish dental age stages for Pyrotherium, to differentiate two juvenile stages (early and late), and to define differences between deciduous and permanent upper premolars. Our observations show that adult individuals of Pyrotherium have a narrower and posteriorly expanded mandible (due to the increase in the size of the tusk-like teeth) and a straighter mandibular incisura. We also observe that di1, di2, and dp2 are present in juveniles but not in adults, except for the i2. X-ray imaging suggests that delayed dental eruption is not present in the juvenile mandible, whereas cheek tooth wear suggests an anteroposterior eruption sequence in p3 through m3. This work adds new information about the dental age stages of Pyrotherium and proposes the following modified deciduous dental formula: dI ?/2, dC ?/0, dP 3/3. [ABSTRACT FROM AUTHOR]

The present study evaluated the Paleogene Sokor-1 clastic reservoirs in the Fana Field on the Agadem Block, Termit Basin, Niger Republic. The evaluation of the hydrocarbon prospect of the Field, which involved petrophysical analysis of six wells namely Fana_2, Fana E_1, Fana N_2, Fana W_1, Fana S_1, Fana SW_1, and sidewall core sample description of Fana_2 well. The petrophysical interpretation of the well-log data was carried out using Interactive Petrophysics software. The petrophysical properties of the hydrocarbon-bearing reservoirs were rated to be suitable reservoirs with average effective porosities varying from 25.8 to 31.6%, permeability varying from 123.6 to 427.7 mD, average water saturation values ranging from 15.2 to 33.0%, and the average range of hydrocarbon saturation is 67.0 to 84.8%. The values of volume of shale (Vsh) of the identified reservoirs indicated that the reservoirs are generally shaly to a high shale/clayey content. The dia-porosity and M-N cross plots revealed that the reservoirs of the Sokor-1 Formation are predominantly sandstone with shale/clay intercalations. The shale structural behaviour of the reservoirs revealed that the dominant shale was mainly dispersed and laminated shale volumes that could impact on the reservoir qualities. The spatial variations of petrophysical parameters indicated that lower N/G values favour the northeast and southern part of the map while the south area has a higher average effective porosity value. This study identified the southern part of the Fana Field as the most prospective and should be considered for the future exploration and development of the Fana field. [ABSTRACT FROM AUTHOR]

The diversity of the tholeiitic, alkali or calc-alkali, high-silica, and adakitic rocks (I-, FG- and А-types) in the northeastern margin of Asia often leads to controversial conclusions about the character of magmatism and the active margin evolution in the West Pacific during the Late Mesozoic–Cenozoic. In addition, paleogeodynamic reconstructions of the Asia-Pacific region can only be made based on the synthesis of patterns identified in compositions of magma sources, evolution and character of magmatism, and strain and kinematic analysis of fault tectonics of all parts of the eastern margin of the paleo-Asian continent. The paper presents new isotopic, geochemical, and structural data on one of the largest early Paleogene structures located at the continental margin of the southern Sikhote-Alin. Based on the new and previously published data we have concluded that the tectonic and magmatic settings of the region were shaped by oblique interaction of continental and oceanic plates during the Late Cretaceous-early Paleogene. The igneous products of the frontal (FG-type), in respect to the trench, and intracontinental (А-type) parts of the area are characterized by isotopic-geochemical variations caused by thermal changes in upwelling asthenosphere and by interaction with lithospheric components. These processes accounted for the formation of initial magmas similar to the IAB- or OIB-type mantle source, respectively. [ABSTRACT FROM AUTHOR]

Peradectidae are Paleogene ‘opossum-like’ stem-metatherians, largely Laurasian, whose evolutionary history remains unclear. Based on new remains (mainly dental) discovered in several French localities, we carry out a comprehensive systematic revision of all early Eocene peradectids from Europe (~MP7 reference level to MP10-11 interval). We describe well-preserved specimens from Palette (Southern France, MP7-MP8 + 9 interval) documenting the earliest European peradectid, Peradectes crocheti sp. nov. This new species exhibits an interesting mosaic of characters, including plesiomorphic traits found in the North American type species, Peradectes elegans Matthew and Granger, 1921. Molars allocated to the strikingly ubiquitous Peradectes crocheti sp. nov. are found in eight additional localities from northwestern and southwestern Europe, all limited to the time interval MP7-MP8 + 9. Moreover, the study of unpublished material of the MP8 + 9 and ~MP8 + 9 peradectids allows us to recognize two younger coeval species (Peradectes louisi Crochet, 1979, and Peradectes russelli Crochet, 1979). Our taxonomic conclusions are supported a posteriori by the first quantitative assessment of the variation in height of metatherian stylar cusps. The holotype of Peradectes louisi is reinterpreted, and Peradectes ‘mutigniensis’ Crochet, 1979 appears to be a junior synonym of Peradectes russelli. In addition to size, the otherwise similar Peradectes louisi and Peradectes russelli can be distinguished based on subtle yet consistent differences, such as lower molar proportions. Phylogenetic analyses using a novel matrix of dental characters shed new light on the relationships among Eocene peradectids, confirming the paraphyly of Peradectes with respect to Armintodelphys and Mimoperadectes. Our results suggest a single dispersal from North America to Europe in the evolutionary history of peradectids, which likely occurred immediately after the Paleocene-Eocene Thermal Maximum, Peradectes crocheti sp. nov. being recovered as the earliest offshoot of the European clade. Scarce lower molars from the MP10 reference locality and ~MP10 localities analyzed within this constrained phylogenetic framework reveal a trend towards shrinking of the entoconid in the European lineage throughout the early Eocene. [ABSTRACT FROM AUTHOR]

The aim of this work is to reveal correlation between the spectral characteristics of the open soil surface on the Pleiades image (April 25, 2020) and soils of a key site with a complex soil cover pattern in the south of the Volga Upland (Volga–Don irrigation system, Volgograd oblast). The study area is specified by the lithological heterogeneity: Paleogene and Neogene sands and loams are overlain by a mantle of Quaternary brown loams of variable thickness from 1–2 m to complete thinning out. The soil cover is represented by light chestnut solonetzic complexes complicated by a mosaic of lithological variants and erosion–accumulative combinations. Eight soil groups have been specified, and a map of their distribution has been developed for the key site of 343 ha with the use of digital methods of processing the spectral characteristics of the satellite image and ground-based soil information. Soil groups differ in general features of the soil surface due to differences in the contents of gravel and stones, texture of the surface horizon (from sand to silt loam), occurrence of brightened crusts, and surface effervescence depending on the thickness of the upper lithological layer. Soils with different horizonation of the profile—agrochestnut soils, agrozems, and agrosolonetzes—fall within the same groups of surface spectral characteristics; vice versa, soils of the same genetic type and, sometimes, subtype fall into different groups. This is explained by the incomplete correspondence of the properties of the soil surface affecting the spectral characteristics to the internal structure of the soil profile as a whole. [ABSTRACT FROM AUTHOR]

The predation-driven Mesozoic marine revolution (MMR) is believed to have induced a dramatic change in the bathymetric distribution of many shallow marine invertebrates since the late Mesozoic. For instance, stalked crinoids – isocrinids (Isocrinida) have undergone a striking decline in shallow-sea environments and today they are restricted to deep-sea settings (below 100 m depth). However, the timing and synchronicity of this shift are a matter of debate. A delayed onset of MMR and/or shifts to a retrograde, low-predation community structure during the Paleogene in the Southern Ocean were invoked. In particular, recent data from the Southern Hemisphere suggest that the environmental restriction of isocrinids to the deep-sea settings may have occurred at the end of the Eocene around Antarctica and Australia, and later in the early Miocene in New Zealand. Here, we report the anomalous occurrence of the isocrinids in shallow nearshore marine facies from the middle Miocene of Poland (Northern Hemisphere, Central Paratethys). Thus, globally, this is the youngest record of shallow-sea stalked crinoids. This finding suggests that some relict stalked crinoids may have been able to live in the shallow-water environments by the middle Miocene, and further confirms that the depth restriction of isocrinids to offshore environments was not synchronous on a global scale. [ABSTRACT FROM AUTHOR]

The northward subduction of the Neo-Tethys oceanic crust triggered multiple magmatic activities in the West Myanmar Arc, which in turn influenced the deposition of sedimentary pyroclastic rocks from the Cretaceous to Eocene strata in the Central Myanmar Basin (CMB). The pore structure of these lithologic reservoirs is complex and rich in tuffaceous sandstone, which plays an adverse role in reservoir development in this region. To understand the development characteristics and genetic mechanism of the pyroclastic rocks within three sets of reservoirs in this area, a comprehensive analysis was conducted through borehole core observations, thin section identification, scanning electron microscope analysis, and mercury injection tests. The tuffaceous sandstone from the upper Cretaceous to the Eocene is dominated by intermediate-acid volcanic rock debris. The pyroclastic rocks exhibit evident chloritization and ironization, with residual intergranular pores being the principal type accompanied by a smaller amount of intergranular dissolved pores and intragranular dissolved pores. The highest porosity is observed in the Eocene tuffaceous sandstone, ranging from 8% to 12%. The Late Cretaceous to Paleocene sandstones exhibit lower porosity levels of only 4%–6%. These reservoirs are characterized by their low-porosity and low-permeability. Despite the presence of a good source rock in this area, the volcanic debris particles filling the pores, as well as their subsequent devitrification, chloritization, and limonite mineralization, result in pore throat blockage and narrowing. The reservoirs in this area are small in size, exhibit poor reservoir connectivity and lateral continuity, and fail to meet the necessary conditions for commercial-scale hydrocarbon accumulation and migration. [ABSTRACT FROM AUTHOR]

Palaeontologists have long sought to explain the diversification of individual clades to whole biotas at global scales. Advances in our understanding of the spatial distribution of the fossil record through geological time, however, has demonstrated that global trends in biodiversity were a mosaic of regionally heterogeneous diversification processes. Drivers of diversification must presumably have also displayed regional variation to produce the spatial disparities observed in past taxonomic richness. Here, we analyse the fossil record of ammonoids, pelagic shelled cephalopods, through the Late Cretaceous, characterised by some palaeontologists as an interval of biotic decline prior to their total extinction at the Cretaceous-Paleogene boundary. We regionally subdivide this record to eliminate the impacts of spatial sampling biases and infer regional origination and extinction rates corrected for temporal sampling biases using Bayesian methods. We then model these rates using biotic and abiotic drivers commonly inferred to influence diversification. Ammonoid diversification dynamics and responses to this common set of diversity drivers were regionally heterogeneous, do not support ecological decline, and demonstrate that their global diversification signal is influenced by spatial disparities in sampling effort. These results call into question the feasibility of seeking drivers of diversity at global scales in the fossil record. Global trends in biodiversity are subject to regionally heterogeneous diversification processes. Here, the authors examine Late Cretaceous ammonoids, modelling the impact of sampling bias and potential biotic and abiotic drivers on our understanding of their biodiversity trends towards the Cretaceous-Paleogene boundary. [ABSTRACT FROM AUTHOR]

The quantitative estimation of key parameters of paleotemperature and paleoprecipitation is crucial for paleoclimate reconstruction. Geochemical data from modern sediments are highly consistent with climate data, and their relationship can provide an important reference for the quantitative reconstruction of the paleoclimate. In this study, detailed inorganic geochemical analysis was carried out using high-precision sampling of the Paleogene (LFD-1 well) Guchengzi, Jijuntun and Xiloutian Formations in the Fushun Basin located in the mid-latitudes of the Northern Hemisphere. The Eocene Guchengzi Formation (54.51–47.8 Ma) and Jijuntun Formation (47.8–41.2 Ma) in the Fushun Basin were found to have been deposited under a humid climate. The lower (41.2–40.1 Ma) and upper (40.1–37.8 Ma) parts of the Xiloutian Formation were characterized by semiarid and semihumid–semiarid climates, respectively, which is very similar to the paleoclimatic information reflected by organic carbon isotopes. The Eocene Thermal Maximum 2 (ETM2, ~ 53.7 Ma), Early Eocene Climatic Optimum (EECO, ~ 53.1–46.5 Ma, Eocene Thermal Maximum 3 (ETM 3, ~ 52.8 Ma), and Middle Eocene Climatic Optimum (MECO, ~ 40.7–40.1 Ma) events significantly enhanced chemical weathering during these periods. The rapid increase in pCO2 concentration leads to an increase in temperature, precipitation, and surface runoff, exhibiting strong chemical weathering. The mean annual temperature (MATa) and mean annual precipitation (MAPa, MAPb, and MAPc) were estimated using parameters, such as the corrosion index without potassium (CIA-K), CaO/Al2O3, and (Na2O + K2O)/Al2O3. Comparing MAPa, MAPb, and MAPc with the MAP estimated using pollen data, MAPa and MAPb were found to be more sensitive to the climate during high precipitation periods (precipitation > 1000 mm, Guchengzi Formation), and the recovered average precipitation was similar to MAP. In contrast, MAPc was more sensitive to the climate during low precipitation periods (precipitation < 1000 mm, Jijuntun, and Xiloutian Formations), with higher accuracy. To fully consider the influence of soluble inorganic salts Ca2+ and Na+, multivariate linear equations of CIA-K and CaO/Al2O3 with CIA, and CIA-K and CaO/Al2O3 with MAP were constructed, namely MAPd and MAPe. The results show that MAPe has the highest performance and can be effectively used to estimate the change of paleoprecipitation in Northeast Asia. [ABSTRACT FROM AUTHOR]

The Antarctic Digital Magnetic Anomaly Project is an international research effort to construct a magnetic map of the continent based on ground, satellite, marine, and aeromagnetic surveys. This paper reports the magnetic mapping of the shelf zone in the SE part of the Wilhelm Archipelago, West Antarctica, based on magnetic surveys conducted with Zodiac boats. A spectacular feature of this area is the strong magnetic anomaly of the Antarctic Peninsula (AP) batholith, which was the product of subduction-related Mesozoic–Cenozoic arc magmatism on the former margin of Western Gondwana. We constructed and analyzed a detailed magnetic map of magnetic field anomalies using field observations of rock exposures on the islands and magnetic properties of rocks from laboratory data. The oldest volcanic rocks of Jurassic to Lower Cretaceous age relate to N-NE trending bands of negative magnetic field. The largest feature in the study area is an Upper Cretaceous/Paleogene granodiorite complex that produces a positive magnetic anomaly. Many smaller anomalies are also present over gabbroid bodies of Cretaceous age. Two-dimensional magnetic modeling shows that heterogeneities in the upper crust may have magnetic susceptibilities in the range of 0.005–0.13 SI. Magnetic field anomalies also delineate an orthogonal system of tectonic faults, including the main NE fault along the Penola Strait (sub-parallel to the AP coastline) and four intersecting faults. These fault systems may be associated with different stages of continental margin evolution along the Antarctic Peninsula. [ABSTRACT FROM AUTHOR]

The Paleogene is a crucial period when terrestrial and marine ecosystems recovered from major disruptions and gradually approached their modern states. In the Qinghai-Tibetan Plateau and its surrounding regions, the Paleogene also represents a significant phase of tectonic evolution in the Qinghai-Tibetan Plateau-Himalaya orogeny, reorganization of Asian climates, and evolution of biodiversity. Due to limitations in research conditions and understanding, there are still many controversies regarding stratigraphic divisions in the Qinghai-Tibetan Plateau and its surrounding regions In recent years, extensive studies on sedimentary petrology, magnetostratigraphy, and isotope dating have been conducted in the region. Numerous fossils have been discovered and reported, contributing to a more systematic understanding of biostratigraphy. These studies have laid a solid foundation for the comprehensive investigation of the stratigraphy, biotas and paleogeographic evolution of the Qinghai-Tibetan Plateau and its surrounding regions during the Paleogene. In this paper, we integrate recent research on fossils, isotopic dating, magnetostratigraphy, and geochemistry to refine the stratigraphic divisions and correlation framework of different tectonic units in the region, building upon previous studies. Since the Second Tibetan Plateau Scientific Expedition and Research, the knowledge of Paleogene floras has gradually expanded. This paper discusses the biostratigraphic significance of extinct and newly appeared taxa based on the latest dating results of these plant species. The new understanding of fossil species such as the "Eucalyptus" and Arecaceae establishes connections between the Paleogene flora of the Qinghai-Tibetan region and the biotas of Gondwana, specifically Oceania and South America. The evolutionary history of key taxa near the Yarlung Zangbo suture zone indicates that the collision between the Indian and Eurasian plates occurred approximately 65–54 Ma. Paleoelevation reconstructions, based on plant fossils, suggest that the Hengduan Mountain had already formed their current topographic pattern prior to the Early Oligocene. The warm and humid lowlands adjacent to the main suture zones in the Paleogene Qinghai-Tibetan Plateau served as the primary pathway for biota exchanges. The relatively low elevation of the Himalaya during the Paleogene did not effectively block the moisture from the Indian Ocean. [ABSTRACT FROM AUTHOR]

The Western Xihu Basin (WXB), part of the East China Sea Shelf Basin (ECSSB), demonstrates distinct structural differences between different sub-areas. Understanding the origin and mechanism of these differences is critical for unravelling the formation and evolution of the Western Xihu Basin and the ECSSB. Based on high-resolution 2D and 3D seismic data, we investigate the structural characteristics and evolution of the hinged margin and discuss the underlying formation mechanisms. The results suggest that, while controlled by NNE-, NE- and NW-striking major faults, there are distinct differences in the fault geometry, margin structure, fault displacement rate, and margin evolution in different basin areas. In contrast to the conventional division scheme which divides the WXB into three general sub-areas, our results suggest that the WXB should be divided into seven sub-areas with different tectonic structures and stress histories. The evolution of the WXB can be divided into three stages: (1) the synrift stage in the Palaeocene and early Eocene, when NNE-, NE- and NW-striking major faults were highly active and controlled the initial formation of the hinged margin structure; (2) late synrift stage in the late Eocene, when the faulting activity diminished, and the control of faults on the margin evolution decreased; (3) postrift stage from the Oligocene onwards, when active faulting ceased and sedimentation and differential basement subsidence became the main factors controlling basin evolution. The formation and reactivation of NW-striking faults under influence of the Izanagi-Pacific ridge subduction during the Mesozoic provided the basis for the differential evolution of the WXB in Cenozoic. [ABSTRACT FROM AUTHOR]

Multiple borehole samples are collected from the Baiyun Depression in deep-water area of the northern South China Sea (SCS) in an effort to reconstruct transgression processes during the Paleogene based on palynalgal analysis. This study indicates that the Baiyun Depression generated a large group of palynopore assemblages and fluvial/lacustrine-related algae during the early and middle Eocene when the Wenchang Formation was deposited. The entire depression was dominated by fluvial and lacustrine facies before transgression. Its eastern and southeastern sags transitioned to shallow marine environment by generating a large abundance of marine dinoflagellates during the Enping deposition of the late Eocene. Meanwhile, the southern uplift zone simply yielded fluvial/lacustrine-related palynopores and algae, and was dominated by the fluvial and lacustrine environment during the early stage of the Enping Formation, prior to shifting into transitional setting in the later period. Northwestern sags remained extensive fluvial and delta facies without existence of marine dinoflagellates. It was until the depositional stage of the Zhuhai Formation (Oligocene) that the overall depression was strongly impacted from transgression process. Both eastern and southeastern sags were mainly under deep marine setting on a continental slope while northwestern and southern areas developed transitional facies. Although distribution and accumulation patterns varied greatly among sub-sags, the overall Baiyun Depression was characterized by widespread development of marine dinoflagellates. It should be noted that the northwestern sag also partly generated large-scale river delta deposits. Due to the eustatic rise and change of SCS spreading axis, the overall Baiyun Depression was mostly influenced by the deep marine environment on a continental slope during the early Miocene. Both northwestern sag and southern uplift zone were found plentiful marine dinoflagellates. In summary, transgression initiated from the eastern and southeastern Baiyun Depression before subsequently progressing into the farther west. Evolution of transgression process is also greatly consistent with the gradual westward expansion of the SCS. [ABSTRACT FROM AUTHOR]

The coal-measure source rock in the Chinese sea area plays a significant role as a hydrocarbon source rock, with its genetic environment, development and distribution, and hydrocarbon generation potential serving as essential factors for the exploration of coal-type oil and gas fields. This study focuses on the coal-measure source rock of the Paleogene Enping Formation in the Zhu I Depression, located in the northern South China Sea. The main geological insights obtained are as follows. The coal measures of the Enping Formation are developed in a warm and wet tropical-subtropical climate. The development environment of the coal-measure source rock in the Enping Formation includes the braided river delta upper plain peat swamp, characterized by dry forest swamp coal facies with relatively thick coal seams and a small number of layers. The braided river delta lower plain swamp-interdistributary bay of braided river delta front represents a forest edge-wetland herbaceous swamp coal facies with numerous layers of thin coal seams and poor stability. The shore swamp corresponds to an open water swamp coal facies with multiple layers of thin coal seams and poor stability. The organic matter abundance in the braided river delta upper plain is the highest, followed by the braided river delta lower plain-braided river delta front, and the shore-shallow lake. The organic matter type is predominantly type II1. Thermal evolution analysis suggests that the organic matter has progressed into a substantial oil generation stage. The hydrocarbon generation potential of the coal-measure source rock in the Enping Formation is the highest in the braided river delta upper plain, followed by the braided river delta lower plain-braided river delta front and the shore-shallow lake. Overall, this study proposes three organic facies in the coal-measure source rock of the Enping Formation: upper-plain swamp-dry forest swamp facies, lower plain-interdistributary bay-forest-herbaceous swamp facies, and lake swamp-herbaceous swamp facies. [ABSTRACT FROM AUTHOR]

The development of the Paleogene coal seams in China's offshore basin areas generally had the characteristics of coal measures with large thicknesses, large numbers of coal seams, thin single coal seams, poor stability, scattered vertical distribution, and a wide distribution range. This study selected the Enping Formation of the Zhu I Depression in the northern section of the South China Sea as an example to determine the macro-control factors of the development of the Paleogene coal seam groups. An analysis was carried out on the influencing effects and patterns of the astronomical cycles related to the development of the thin coal seam groups in the region. A floating astronomical time scale of the Enping Formation was established, and the sedimentary time limit of the Enping Formation was determined to be approximately 6.15 Ma±. In addition, the cyclostratigraphy analysis results of the natural gamma-ray data of Well XJ in the Enping Formation of the Xijiang Sag revealed that the development of the thin coal seams had probably been affected by short eccentricity and precession factors. The formation process of coal seams was determined to have been affected by high seasonal contrast, precipitation, and insolation. During the periods with high values of short eccentricity, the seasonal contrasts tended to be high. During those periods, fluctuations in the precession controls resulted in periodic volume changes in precipitation and insolation of the region, resulting in the development of thin coal seams. It was also found that the periods with low precession were the most conducive to coal seam development. On that basis, combined with such factors as sedimentary environmental conditions conducive to the development of thin coal seam groups, this study established a theoretical model of the comprehensive influences of short eccentricity and precession on the development and distribution of Paleogene thin coal seam groups in offshore lacustrine basins. The patterns of the Paleogene astronomical periods and paleoclimate evolution, along with the control factors which impacted the development of thin coal seam groups in offshore lacustrine basins, were revealed. [ABSTRACT FROM AUTHOR]

Unraveling the Paleo-Kuril Arc's origins is key to understanding northwest Pacific tectonics. The Paleo-Kuril Arc is viewed as an intraoceanic arc from trench subduction between the Izanagi and Pacific Plates. Alternatively, several studies suggest the Paleo-Kuril Arc as a continental magmatic arc, hypothesizing the existence of a mid-oceanic ridge and Paleogene subduction, placing the Paleo-Kuril Arc near the Okhotsk Block's southern edge. This study clarifies these hypotheses, previously clouded by limited geochronological data on deposits in the Paleo-Kuril Arc. We conducted U–Pb dating to examine the origins of detrital zircons from the Cretaceous–Paleogene Tokoro and Nemuro Belts of the Paleo-Kuril Arc. Cluster analysis, merging new and existing data, identified two unique detrital zircon age clusters. The abundance of Precambrian zircons in Cretaceous–Paleocene Paleo-Kuril Arc sandstones (Type 1 Cluster) suggests a continental magmatic origin, supporting the ridge subduction model. However, an early Eocene shift to a consistent local volcanic source (Type 2 Cluster) highlights a significant provenance change. This geochronological evidence, indicating a separation from continental sources, calls for further research to decode the simultaneous development of sediment sources in different geological belts, potentially tied to the ridge subduction event. [ABSTRACT FROM AUTHOR]

During the re-mapping of the area for the Geological Atlas of Switzerland, a significant stratigraphic unconformity was discovered in the North Penninic (Valais) Bündnerschiefer and the Flysch series of the northern Prättigau. It separates different units of the Cretaceous Bündnerschiefer from the Palaeogene Flysch. We explain this observation by a basin conversion from extension to compression, which caused the initial deformation of the Bündnerschiefer in an accretionary wedge. Interlinked return-flow has created a new heterogeneous substrate for the flysch sediments and explains the different types of unconformities. The basin conversion coincided with high-grade metamorphism in the vicinity of the the South Penninic suture and the Austroalpine units, and the increased exhumation in the Austroalpine nappe stack. Detrital zircon dating confirms also a change from European to Austroalpine detrital sources in the flysch sandstones. We discuss a palaeotectonic model leading to hP/lT metamorphism of the Bündnerschiefer in the Late Eocene (c. 42 Ma). It appears that the flysch formations were also involved, but to a lesser degree by tectonic deformation from the late Early Eocene onwards, as the pervasive folding characteristic of the Bündnerschiefer is absent. This has been followed by a phase of S-directed backfolding. During the Oligocene and Miocene, more extensive deformation occurred by SE to NW compression and finally by probable westward thrusting and folding. Our main theme is the transition from passive to active continental margins, which in Alpine plate tectonic framework corresponds to the transition to flysch sedimentation by basin conversion. Our results show that the simultaneity of the transition from extension to compression, as indicated by the accumulation of flysch, shifted in time from south to north in the Alpine Tethys. [ABSTRACT FROM AUTHOR]

There are few studies focused on spore and pollen clumps in paleopalynological samples, and these are only reports from the Northern Hemisphere. These aggregates may be of animal or floral origin. The goal of this contribution is to provide the first detailed study of spore and pollen clumps from the Southern Hemisphere, and to discuss their possible origin, botanical affinities, and pollination modes, based on their morphological characteristics, preservation and comparison with putative living representatives. Three fern spore clumps and 18 angiosperm pollen clumps were recognized in Maastrichtian-Danian La Colonia Formation sediments that outcrop at Chubut Province, Patagonia, Argentina. Most clumps are monospecific and composed of undamaged elements but some of them have two types of spore/pollen with corroded and/or fragmented exines. These findings represent the most diverse and abundant record of fern and angiosperm clumps from the Late Cretaceous and early Paleocene so far known from South America and the Southern Hemisphere. These results are indicative of the need for comprehensive large-scale studies on pollination of modern taxa and careful processing of palynological samples to lessen the already large bias in paleopalynological interpretations. The paucity of information on clumps in the fossil record has impaired our comprehension of dispersion/pollination in deep time. [ABSTRACT FROM AUTHOR]

The Musandam peninsula (northern part of the Oman thrust-and-fold belt), although flanked by a foreland basin rich in petroleum resources, has remained so far without a proven play. As part of an exploration project that covered partly the exposed external part of the peninsula made up of mainly Mesozoic carbonate platform, i.e., Arabian (including the equivalents of the producing reservoirs), the study of its outcrops, easily accessible along existing valleys, became the best opportunity to record details far beyond the resolution allowed by seismic surveys or wells and thus, to refine the structural model. The purpose of the paper is to update the general tectonic framework based on novel observations presented as series of outcrop pictures, supplemented with two interpreted seismic lines imaging the subsurface structure. These observations were made in around two hundred points where bed and/or fault/fold axis positions were measured or estimated, eventually modifying an existing geological map. Although it has been generally considered that in Musandam peninsula the fault systems affecting the Arabian platform were related in essence only to the continuing shortening since Late Cretaceous (after the obduction of the Semail ophiolite), the first outcomes of the fieldwork refer to those tectonic events pre-dating the contraction in the foreland plate which have not been previously noticed, namely a widespread Upper Triassic extension followed by inversion and development of a major angular unconformity at the Jurassic base (an equivalent of the "Old Cimmerian phase" encountered elsewhere along former Neo-Tethys margins). Within the newly installed carbonate platform, a second but milder angular unconformity occurs at the Dogger/Liassic boundary. Surprisingly, two ubiquitous ~ 20-m-thick reservoir beds—Upper Triassic and Lower Jurassic—leaked (everywhere accessible) hydrocarbons or hydrogen sulfide odor upon hammering. Other new outcomes are related to the structures and tectonic displacements induced during the shortening period, which appear far more complex and significantly larger than usually interpreted, as documented by series of thrusts making a duplex system, farther coupled within the foredeep to a triangle zone as supported by seismic data; these data also allowed to depict an offshore canyon initiated roughly at the Oligocene base which lies in continuity with a few small Paleogene clastic units cropping out just downstream the northern Musandam valleys (in UAE). The last (Late Miocene) major outcropping structure is a NW–SE-trending long and steep reverse fault running from near the confluence of valleys Shah and Bih in the south, up to at least the western parts of the Tibat and Bukha offshore hydrocarbon fields (Sultanate of Oman) in the north (called herein Bukha-Tibat-Ghalilah-Rahbah fault), which cuts obliquely the former nappe pile. As it appears to be synchronous with the orthogonal, also major, Dibba fault (SE margin of the Musandam platform), but of opposing kinematics (the latter is normal), one can infer that ~ E-W sinistral wrenching had acted upon the peninsula before the shortening was transferred to the Zagros system. Coeval with them or younger, a system of normal faults trending variously around N-S, with throws up to 100 m, was mapped. The main fieldwork results reported in the paper bring significant improvements to the understanding of the Musandam belt by highlighting previously overlooked tectonic events (particularly the early rifting), refining the structural geometry of the successive fault systems and adding new constraints on the regional kinematics and evolution. Furthermore, the onset of the Musandam nappe pile erosion can be placed confidently at around the beginning of the Oligocene, older than previously considered. Through the depiction of the aforementioned reservoir beds and a direct indication of a new perspective in terms of viable source rocks in the subsurface, the accompanying suggestions may trigger a rejuvenation of the prospectivity-oriented research. [ABSTRACT FROM AUTHOR]

Hydrocarbon exploration and exploitation have been going on in the Jaisalmer Basin, Western Rajasthan, India, for over a decade. The Cretaceous sequences are the potential source rocks in the basin; however, Mesozoic and Tertiary clastics and carbonates form the reservoirs. This study aims to investigate the quality of the source rock, hydrocarbon generative potential along with the thermal maturity of the Paleocene–Eocene clastics and carbonate sequences in Jaisalmer Basin, Rajasthan, India, using geochemical methods. Results of pyrolysis show that the Sanu Formation possesses poor hydrocarbon generative potential, as the values of generative potential range between 0.03 and 1.29 mg HC/g rock with an average of 0.26 mg HC/g rock, and poor to fair organic richness, with TOC ranging from 0.03wt% to 1.32 wt% with an average of 0.42%. Sediments of the Khuiala Formation also possess poor to fair organic content, with average TOC content ranging from 0.04 to 1.34 wt%. However, the generative potential of sediments ranges from 0.03 to 3.02 mg HC/g rock, with an average of 0.41 mg HC/gm rock, suggesting that the sediments have poor generative potential with fair remaining hydrocarbon generating potential as depicted from S2 values (max S2 values of 2.92 mg HC/gm rock) at selected depth intervals. The sediments from the Sanu and Khuiala Formations primarily contain type III and type IV kerogens. The prevalence of kerogen types III and IV is indicative of terrestrial organic input derived from terrestrial plants along with highly degraded or metamorphosed organic matter. The thermal maturity parameters reveal that the sediments are immature to early mature in nature and can generate only wet gas at present. [ABSTRACT FROM AUTHOR]

The Imini mining district (southern foreland of the intraplate Atlasic belt of Morocco) hosts the largest Mn resources of North Africa, consisting of two laterally extensive bodies of high-grade pyrolusite-rich manganese ore and a third discontinuous medium-grade coronadite-rich Mn ore in a ~ 10–15-m-thick Cenomanian–Turonian dolostone unit. Until now, the origin and timing of the Mn ore have been poorly constrained. New Pb isotopic ratios show that Triassic series (basalts and ferruginous sandstone) are likely the source of the metals. 40Ar/39Ar dating of K-Mn oxides shows that the Mn-rich orebodies formed during at least three periods: late Cretaceous to late Paleocene (> 58 Ma), late Eocene (ca. 36.3 Ma), and early Burdigalian to early Serravalian probably in two pulses at ca. 19–20 Ma and ca. 13 Ma. These periods coincide with three known building phases of the Atlasic relief during late Cretaceous, late Eocene, and the Early(?)-Middle Miocene. We therefore propose the Atlasic tectonics as the first-order control of the Mn mineralization. Periods with regionally high elevations modified the climate to wetter conditions that supplied meteoric water to feed temporary aquifers. Relief building created the required hydraulic head to sustain (1) fluid-rock interaction between O2-poor acidic fluids and the Triassic series, (2) migration of the metal-rich fluid, and (3) to overpressure fluid in the Imini depositional site. The decreasing thickness of Triassic series in front of the Imini anticline forced these low-temperature (< 100 °C) fluids to mix with oxygenated and alkaline ground waters in the karst system and precipitate Mn oxides. The N70°-oriented Atlasic tectonic structure controls the orientation of the Mn deposits. The late Eocene–Early/Middle Miocene uplifts generated additional supplies and/or in situ remobilization of the primary late Cretaceous medium-grade ore to form the high-grade pyrolusite-rich ore. [ABSTRACT FROM AUTHOR]

The Eocene biota from the pre-rifting stage of the Upper Rhine Graben (southwest Germany) is, with exception of the world-famous fossil sites Messel and Bouxwiller, poorly known. While from these localities exclusively terrestrial and freshwater fossils were recovered, here we present floral and faunal assemblages from the middle Upper Rhine Graben which clearly indicate a temporarily brackish water environment and consist of a diverse palynomorph association, calcareous nannoplankton, foraminifers, ostracods and some fish and reptile remains. Based on the occurrence of Trochastrites hohnensis, a Lutetian age is assumed. Organic-walled dinoflagellate cysts, in particular Phthanoperidinium comatum, Phthanoperidinium echinatum, Apectodinium homomorphum and Apectodinium quinquelatum, suggest a late Ypresian to Lutetian age. The pollen and spores assemblage includes typical mid Eocene species, such as Tegumentisporis villosoides, Tricolporopollenites crassostriatus and representatives of Bombacaceae, but a late Ypresian to Priabonian age cannot be excluded. Foraminifers and ostracods do not further refine the biostratigraphical assignment. Hence, a Lutetian age is most probable. The mass occurrence of Neocyprideis, various foraminifer taxa and an organic-walled dinoflagellate cyst assemblage of very low diversity are indicative of a brackish water environment. Disarticulated vertebrate remains include fish teeth of Lepisosteidae, turtle plates and alligatoroid teeth of Diplocynodon and Hassiacosuchus. The present palaeogeographical scenarios do not consider a connection from the Upper Rhine Graben to the North Sea Basin, Alpine Sea/Paratethys or Paris Basin during the mid Eocene. Provided that the middle Upper Rhine Graben was land-locked and definitely not reached by a marine ingression during this time interval, we tentatively suggest that the brackish water taxa may have been accidentally introduced into a brackish inland sea by wind (anemochory), rain, highly mobile insects or vertebrates such as fish, birds and mammals (endozoochory/ectozoochory). The presumably freshwater calcareous nannoplankton species Nannoserratolithus minutus Martini is newly described. [ABSTRACT FROM AUTHOR]

Atera Fault clay gouges were collected for age dating near Kawaue, Nakatsugawa City, Central Japan, and the results integrated within its complex geological history. The results form an internally consistent data set constrained by extensive geochronological data (AFTA, ZFTA, CHIME) and support the application of gouge dating in constraining timing of brittle deformation in Central Japan. The Atera illite age data complete recently obtained limited illite fault gouge age data from underground exposure in the Toki Granite; the new illite age data are identical within error. The age of the heterogenous welded tuff breccia zone (Atera 1) ranges from 40.6 ± 1.0 Ma to 60.0 ± 1.4 Ma, whereas ages of the fault core gouge sample (Atera 2) range from 41.8 ± 1.0 Ma to 52.7 ± 1.2 Ma. The finest < 0.1 µm fraction of the fault breccia and fault core gouge yield ages around 41 Ma, identical within error. The new illite age data indicate brittle faulting and a following geothermal event occurring in the Paleogene–Eocene, similar to the nearby Toki Granite area and confirm they were both synchronous with a post-intrusive pluton exhumation. The Atera Fault illite age data provide additional insights into an integrated, regional-scale record of the tectonic displacement of Central Japan and might be influenced by large-scale tectonic processes such as the Emperor sea mount kink around 55 to 46 Ma with fault initiation around 50 Ma and brittle fault cessation or reactivation around 40 Ma in the Eocene. [ABSTRACT FROM AUTHOR]

Previous research shows that the origin and distribution of formation overpressure are governed by several dominant factors including disequilibrium compaction, hydrocarbon generation, tectonic compression and diagenesis, influenced by salt components and their concentration, but it is unclear how salts affect formation overpressure in saline lacustrine basins. This paper investigated the effect of salts on formation overpressure based on organic geochemistry, rock mineralogy, logging curve comparison and wave velocity-density cross-plot by combining the sedimentary and structural background. In the Western Qaidam Basin, the proportion of abnormally high pressures rises from the Neogene to the Paleogene. The top surface of the overpressure is between 2300 and 2500 m deep. As the subsidence and sedimentary centers of the basin moved eastward, the centers of the overpressure migrated from west to east. In the Upper Oligocene, the overpressure is developed in the deep and semi-deep lacustrine facies, and the pressure coefficient is 1.8–2.0. Disequilibrium compaction is the primary control factor with a contribution rate of more than 60% in the intersalt and subsalt strata, followed by tectonic compression with a contribution rate of 20–30%. Fracture reducing by salt filling and fluid volume expanding by gypsum dehydration increase the fluid volume in the formation, which promotes formation overpressure. The gypsum salt rocks also have strong plasticity and sealing effect, thus providing a closed environment for the formation overpressure. Through providing the primary migration driven force and sealing conditions for oil and gas, the overpressure is meaningful to petroleum accumulation and preservation in saline lacustrine formation of the Paleogene and Neogene in the Western Qaidam Basin, NW China. [ABSTRACT FROM AUTHOR]

Lamiinae (Cerambycidae, Coleoptera) is a striking subfamily due to its members' economic importance and role in the forest ecosystem. Morphological diversity, worldwide distribution and species richness complicate its already intricate phylogenetic relationships. We implemented Maximum Likelihood (ML) and time-scaled Bayesian Inference (BI) analyses to the species from East of Marmara Basin, Türkiye, from the tribes Acanthocinini, Acanthoderini, Agapanthiini, Batocerini, Dorcadionini, Lamiini, Mesosini, Monochamini, Phytoeciini, Phrynetini, Pogonocherini (including Exocentrini) and Saperdini using partial mitochondrial cytochrome c oxidase-I (COI) and 16S rRNA and nuclear 28S rRNA gene regions (2257 base pair alignment length) and Neighbor-Joining (NJ) and ML analysis to the global COI gene region dataset (658 bp). The most recent common ancestor (MRCA) of Lamiinae members included in the analyses was dated ~ 127 million years ago (Mya) in the Cretaceous. The MRCA of Dorcadionini, Lamiini and Monochamini was younger than the common ancestors of the other close tribes. There was a concurrence between resolutions of ML and BI on the affiliations of Dorcadionini and Monochamini to Lamiini and the proximity of Batocerini to Lamiini, Acanthocinini to Acanthoderini, Phrynetini to Pogonocherini, and Phytoeciini to Saperdini. The COI-based NJ and ML gene trees suggest that the closest relatives of most of the sampled Lamiinae species from the East of Marmara Basin were the European conspecifics or congeners. Our results support Dorcadionini and Monochamini as synonyms of Lamiini; and Phytoeciini of Saperdini. Also, they suggest that the emergence of the living tribes included in this study was during the Paleogene, and their intrageneric diversifications occurred during the Cenozoic, mostly the Neogene. [ABSTRACT FROM AUTHOR]

Bioerosion structures, including holes, pits, and grooves, on the surface of benthic foraminiferal tests from the Upper Cretaceous and Paleogene of Western Siberia are studied. Their morphology is examined, their possible origin and the paleogeographic and stratigraphic distribution in sections representing marine basins of Western Siberia are discussed. The ichnospecies assemblage studied includes Oichnus simplex Bromley, 1981, O. paraboloides Bromley, 1981, O. gradatus Nielsen et Nielsen, 2001, and O. ovalis Bromley, 1993. [ABSTRACT FROM AUTHOR]

This paper discusses the current state of knowledge of Paleogene stratigraphy of Kaliningrad Oblast, the age of local stratigraphic units and the duration of possible gaps in deposition and proposes trends for future regional Paleogene stratigraphy. The Paleocene Chistoozerskaya and Lubava formations in total probably correspond to the Danian–Selandian on the basis of foraminiferal zonation, but their relationship is not entirely clear. The Zaostrovskaya Formation probably corresponds to the upper Thanetian, but its fossil record is very poor. The Sambian Formation corresponds to the Ypresian according to foraminifera, but its precise stratigraphical interval remains insufficiently substantiated. The Alka Formation is presumably late Lutetian–early Bartonian. The age of the Prussian Formation is emended based on dinocysts as early–late Priabonian, while the Palvé Formation is now dated as the latest Priabonian. The Kurshskaya Formation corresponds to the uppermost Eocene–Oligocene–?lower Miocene. The problem of the recognition and duration of hiatuses between formations remains relevant. [ABSTRACT FROM AUTHOR]

Paleogene strata in Southwest Tarim Basin are important hosts of hydrocarbons with the highest quality reservoirs, a product of depositional environment, diagenesis and tectonics. The Paleogene interval is composed, in ascending order, of the Altash, Zimugen, Karatar, Wulagen and Bashbluk formations. Five facies associations are interpreted, respectively, as gypsum bay, alluvial fan-braided river, intertidal flat, supratidal flat and restricted platform. Stratigraphic evolution of Paleogene is recorded in vertical changes of sedimentary environment and climate. At least four transgressive–regressive cycles are recognized that can be correlated with the global eustatic changes. Detailed paleoenvironmental analysis laid a foundation for predicting the reservoir rocks in this mixed clastic–carbonate sequence. Braided channel sandstone and restricted platform grainstone constitute the best reservoirs in Paleogene. The most important diagenetic processes in sandstones that resulted in porosity and permeability changes are mechanical compaction, cementation, and dissolution of unstable clastic grains and cements, whereas in carbonate rocks, the dominant factors are cementation and dissolution. Tectonic fracturing developed in multiple stages in Paleogene has played an important role in improving the quality of reservoir rocks. Stratigraphic evolution of the Paleogene resulted in stacking of seal rocks above reservoirs during the late transgressive and regressive phases of sedimentation. [ABSTRACT FROM AUTHOR]

Two new specimens of the anatoliadelphyid metatherian Orhaniyeia nauta are described from the middle Eocene Uzunçarşıdere Formation in the Orhaniye Basin, north-central Turkey. These specimens augment our knowledge of the dentition of this taxon, revealing that P3 and p3 of Orhaniyeia resemble those of its sister taxon Anatoliadelphys in being enlarged and highly inflated, suggesting that both taxa consumed a durophagous diet. The ancestral dental morphology of anatoliadelphyids likely approximated that of Orhaniyeia nauta, whereas the dentition of Anatoliadelphys is autapomorphous. A phylogenetic analysis incorporating the new data for Orhaniyeia reconstructs anatoliadelphyids as nested among a diverse, but generally poorly documented, assemblage of early Paleogene bunodont Gondwanan marsupials that are typically allied with polydolopimorphians. Alternative phylogenetic reconstructions based on Anatoliadelphys alone have suggested either peradectid or protodidelphid affinities for anatoliadelphyids, but these hypotheses are not supported by the new data from Orhaniyeia. Anatoliadelphyids likely colonized Balkanatolia from the south (Africa/Arabia), even though there is no current fossil record indicating that this Gondwanan bunodont marsupial clade ever inhabited Africa/Arabia. The durophagous diet of Orhaniyeia was probably eclectic, but with an emphasis on gastropods. A similar dietary reconstruction has been proposed for the Australian Miocene marsupial Malleodectes, the dentition of which is remarkably convergent with that of Orhaniyeia. Orhaniyeia and Anatoliadelphys appear to have exploited distinct ecological niches, because the autapomorphous dentition of Anatoliadelphys includes multiple specializations for enhanced carnivory. The colonization of Balkanatolia by anatoliadelphyids instigated a small endemic radiation, a pattern that was replicated by multiple other Balkanatolian mammal clades. [ABSTRACT FROM AUTHOR]

With a few exceptions, crown-clade Primates differ from other arboreal mammalian clades by having nails instead of claws on most post-axial digits. Distal phalanx morphology of close extant and fossil relatives of crown-clade Primates provides a context in which to study the evolution of this characteristic feature. Plesiadapiforms are a diverse group of extinct arboreal mammals closely related to crown-clade Primates (together classified as total clade Pan-Primates) that have distal phalanges that are indicative of having supported keratinous claws, with the only documented exception being that of Carpolestes simpsoni which may have had a nail on its hallucal phalanx. To contextualize morphological variation among plesiadapiform distal phalanges, we investigated the influence of behavior and phylogeny on post-axial distal phalanx morphology using a broad sample of extant mammalian taxa (273 distal phalanges from 67 species) compared to those known for plesiadapiforms (26 specimens from 9 species). Results show that plesiadapiform distal phalanges share characteristics with those of both extant generalized arborealists/scansorialists and antipronograde specialists, consistent with previous behavioral reconstructions of frequent vertical clinging and climbing based on other regions of the skeleton. Distal phalanges of Plesiadapis cookei, Plesiadapis tricuspidens, and the "Le Quesnoy plesiadapid" are most similar to those of extant species that clasp branches between claws and the rest of the autopod when climbing. In contrast, known distal phalanges of micromomyids and the plesiadapoid C. simpsoni share some similarities with those of extant taxa that rely more heavily on grasping with digital pads when climbing. [ABSTRACT FROM AUTHOR]

Lumbar vertebrae are an important functional unit of the spine in mammals. Although the correlation between lumbar morphology and function in extant mammals is well known, the evolution of disparate lumbar morphology through the fossil record has remained unexplored. I sampled lumbar vertebrae from 100 fossil and extant mammals across a wide taxonomic range and categorized the morphology of these vertebrae with discrete morphological characters. I used marginal ancestral state reconstruction to model the evolutionary history of each character and calculated a retention index to assess homoplasy. I then compared these results to correlations between each character and body size, as a functional metric. Presence of anapophyses, a postzygapophyseal lamina, and xenarthrous articulations all showed high retention, indicating strong phylogenetic signal. Centrum length and transverse process angle showed low retention and strong correlation with body size. These results demonstrate that, although lumbar morphology is strongly controlled by function, phylogeny does have a notable influence. Furthermore, these data support the evolution of lumbar vertebrae along the stem to Theria, with ancestral therian vertebrae having had transverse processes rooted to the neural arch, posteriorly angled neural spines, and flat, horizontal zygapophyses. [ABSTRACT FROM AUTHOR]

The Cenozoic India-Eurasia collision has had profound impacts on shaping the Tibetan plateau, but its early history remains controversial due to uneven availability of constraints. Recent plate reconstructions reveal two prominent counterclockwise rotation (azimuthal change) rate peaks of the Indian plate at 52-44 and 33-20 Ma, respectively, which could bear key information about this collision history. Using fully dynamic three-dimensional numerical modeling, we show that the first rotation rate peak reflected the initial diachronous collision from the western-central to eastern Indian front, and the second peak reflected the full collision leading to strong coupling between India and Eurasia. Further comparison with observation suggests that the initial and complete India-Eurasia collision likely occurred at 55 ± 5 and 40 ± 5 Ma, respectively, an inference consistent with key geological observations. We suggest that this collision history is instructive for studying the tectonic history of the Tibetan plateau and its surrounding areas. Dynamic 3D modelling of counterclockwise rotation of the Indian plate, which peaked at 52-44 and 33-20 Ma, reveals the diachronous India-Eurasia collision from western-centre to east since 55 ± 5 Ma and complete collision since 40 ± 5 Ma. [ABSTRACT FROM AUTHOR]

Stromboid gastropods (Superfamily Stromboidea) are one of the most diverse groups of gastropods present in the Neogene marine successions of western India. In the present endeavor, we report eight stromboid species, of which four are described as new, from the early-middle Miocene marine successions of the Dwarka Basin, western India. The species are Conomurex indica n. sp., Persististrombus deperditus, Persististrombus sp., Dilatilabrum mahalonobisi n. sp., Tibia indica, Terebellum obtusum, Hemithersitea kanerus n. sp. and Hemithersitea nadharus n. sp. Paleobiogeographic distribution of most of the stromboid genera reported here reveals a unidirectional migration from the Tethys Region towards the Indo-Pacific Region during the Paleogene and Neogene. Conomurex originated in the western India and further radiated to the eastern Indian-Western Pacific localities with the onset of the Neogene. Persististrombus and Tibia show widespread distribution in the Mediterranean and gradually radiated towards the eastern Africa-western India localities during the Paleogene. However, from the middle Miocene onwards, these two genera further migrated towards the eastern Indian-Western Pacific localities and became more diverse. The remaining two genera, i.e., Dilatilabrum and Hemithersitea originated in the Mediterranean and later migrated to take refuge in western India during the late Paleogene, and ultimately succumbed to extinction during the middle Miocene. [ABSTRACT FROM AUTHOR]

Igneous rocks associated with the Cretaceous to Paleogene volcanic arc in SW Japan show ages that young from west to east in a direction parallel to the Median Tectonic Line suggesting corresponding translation of a heat source traditionally interpreted in terms of oblique subduction of a spreading ridge. However, recent oceanic plate reconstructions suggest ridge subduction may be younger than the main arc activity. Age compilations of 1227 points of felsic to intermediate Cretaceous and Cenozoic igneous rocks from the Japan arc show arc magmatism that can be separated into an early active period 130–60 Ma (stage 1), a subsequent period of quiescence 60–46 Ma (stage 2), which is followed by a resumption of igneous activity from 46 Ma onward (stage 3). In southwest Japan, the orientations of the magmatic arcs of stages 1 and 3 show and angular discordance of about 20°. The lack of active arc magmatism and the occurrence patterns of adakitic and high-Mg andesitic magmas indicate that ridge subduction occurred during stage 2. The arc age distribution pattern of stage 1 is explained by the slab shallowing related to a younging of the subducting slab as the ridge approaches. Furthermore, the obliquity of the arcs formed at stages 1 and 3 is explained by a 20° clockwise rotation of the inner zone of southwest Japan during the ridge-subduction phase. Oceanic plate reconstructions show counterclockwise rotation in the subduction direction after the ridge subduction phase, and coupling of the subducting oceanic plate with the upper plate would support microplate rotation in the inner zone. The new proposed tectonic reconstructions provide a framework to related Paleogene subduction of an active spreading ridge along the east Asia margin not only to the distribution of granitic bodies but also to rift-related basin formation on the eastern margin of the Eurasian continent and to rotation of crustal blocks indicated by paleomagnetic data of Cretaceous terranes. [ABSTRACT FROM AUTHOR]

Data on the principal Cenozoic localities of marine bony fishes (represented by skeletal remains, not otoliths) from the territory of the development of the Tethys and Paratethys are presented. The historical development of many supra-generic taxa of the higher Teleostei (spiny-rayed) in the Cenozoic basins of the Tethys and Paratethys has been traced. The available paleontological data do not confirm the appearance of most lineages of "crown Acanthomorpha" (and even "crown Percomorpha") already at the end of the Cretaceous, as indicated by the time-calibrated molecular phylogeny. [ABSTRACT FROM AUTHOR]

The Shotori mountain range is located along the northern terminus of the Nayband fault on the eastern and western domains of the Tabas and Lut blocks, respectively. This range with NNW-SSE trending and approximately 120 km long includes a series of thrust faults approaching the right-lateral strike-slip Nayband fault. Since the Shotori range has experienced various geological events since the Triassic, our investigations suggest that the basement of the Central Iranian subcontinent of the Shotori range contains the early Triassic deep sedimentary with normal faults which confirms Triassic tensional tectonic stress regime in the region. After the middle Triassic, the mountain range has experienced thrust and strike-slip regimes. Therefore, in this study, we reconstruct the stress regimes for different geological periods using fault-slip data. The inversion of fault-slip data reveals drastic temporal changes in the maximum stress regime (σ1) over the Triassic, Jurassic, Cretaceous, Paleogene, Neogen, and Quaternary. The reconstruction of the stress field based on the age and direction of fault movement reveals that the direction of the maximum horizontal stress axis (σ1) under a tensional stress regime was approximately N129° in the Early Triassic. This stress regime is the cause of thinning and subsidence of the Shotori sedimentary basin. During the middle Triassic, the σ1 direction was about N81° and the upper Triassic, the σ1 direction was almost N115°. The middle Triassic and upper Triassic stress states exhibited two distinct strike-slip and compressive stress regimes. This stress regime led to the uplift of the Shotori sedimentary basin. During the Jurassic, the direction of the maximum horizontal stress axis (σ1) was ∼NW-SE under a compressive stress regime. During the Triassic, the σ1 direction was ∼N-S. This stress regime led to the formation of the high topography of the Shotori Mountain Range. In the Late Cretaceous, the direction of the maximum horizontal stress axis (σ1) under the extensional stress regime was ∼NE-SW. This stress regime led to the uplift of the Paleogen Dacite in eastern Iran. During the Neogene, the σ1 direction was ∼N6o°. The Quaternary tectonic regime is strike-slip and the σ1 direction is ∼N50°, consistent with the current convergence direction of the Arabia–Eurasia plates. Our paleostress analysis reveals four recognized stress in this area, which includes compressional, transtensional, transpressional, and strike-slip regimes. Our findings indicated that the crustal diversity of the tectonic regimes was responsible for the formation of various geological structures, such as folds, faults by different mechanisms, and the present-day configuration of the Shotori sedimentary basin. [ABSTRACT FROM AUTHOR]

The periphery of the Deccan Volcanic Province (DVP) of India comprises sedimentary succession deposited during the waning phase of volcanism across the Cretaceous-Paleogene boundary which preserves the continental biota. The Saurashtra Peninsula, a part of the Saurashtra-Kachchh sub-province, exposes thick intertrappean sedimentary successions, systematically described to understand the stratigraphic framework with respect to the lava flows and their geographic distinctness. The thickness of the exposed sections is measured, and contact and continuities are marked, revealing two different, small geographically isolated but adjacent, coeval basins, named the Ninama Basin and Chotila Basin, initially comprising fine grain sediment, followed by thick conspicuous limestone and chert deposits respectively. Formal lithostratigraphic unit names are proposed for both basins: Ninama Basin comprises lithic arenite, fossiliferous limestone, bedded siltstone, mudstone and claystone, and is divided into Sukhbhadar Formation and Ninama Limestone. Chotila Basin comprises calcareous sandstone, bedded siltstone, silty shale and mudstone, claystone and chert divided into Rangpar Formation, Chotila Chert, and Bamanbor Formation. Lithology and palynofossil evidence suggest restricted continental environments with varying salinities during the Paleogene. [ABSTRACT FROM AUTHOR]

A new concept of the formation of glauconite from the Paleocene deposits of the sedimentary cover of the southwestern part of the Near-Volga monocline is presented. It was formed as a result of halmyrolysis of ash material in lake conditions. Glauconitization is confined to the Paleogene thermal maximum and the periphery of active volcanism along the entire mobile belt. In this connection, it is widely distributed in the Paleogene deposits. Structural and crystal-chemical features of glauconite, stages of crystallization of its aggregates, paragenetic associations with smectite, kaolinite, and zeolite, as well as the presence of ore minerals indicate its authigenic origin. The authigenic origin is confined to the formations of temporary, episodically submerging shallow marine basins. An applied scheme of discrimination of glauconites by their crystallochemical features has been developed. The discrimination diagram can be used to determine the specific conditions of the sedimentation basin, which are expressed in the progradation cycles of glauconite accumulation. The cycles were controlled by induced depressions within the Russian plate. [ABSTRACT FROM AUTHOR]

Sandstone-type uranium deposits (STUDs) are the most important global source of uranium. However, it is unclear why STUDs have a non-random distribution in time and space. It is generally thought that STUDs are formed by the circulation of groundwater in sandstone rocks. The groundwater is typically oxidized and sourced from local precipitation, which suggests the regional climate may have a role in the formation of STUDs. The groundwater circulation is mainly affected by basin evolution, which means that regional tectonism may also control the formation of STUDs. In this study, the author examined STUDs in Asia, and compiled previously reported ages for STUDs and compared these with the uplift history of the major ore-hosting regions and the late Mesozoic–Cenozoic climatic evolution of Asia. Apart from a few uranium deposits in the Transural region, most of the STUDs in Asia were formed during the Late Cretaceous to Quaternary, and can be classified into three stages: Late Cretaceous–early Paleogene (80–50 Ma; stage I), Oligocene–mid-Miocene (25–17 Ma; stage II), and late Miocene–present (8–0 Ma; stage III). The formation of STUDs in Asia was closely related to regional uplift caused by India–Eurasia collision, subduction of oceanic plates, and increased humidity during greenhouse climate periods and intensification of the Asian Monsoon. [ABSTRACT FROM AUTHOR]

The Dinaric–Hellenic mountain belt bends where two fault systems transect the orogen: (1) the dextral Shkoder-Peja Transfer Zone (SPTZ), active sometime between the Late Cretaceous and middle Eocene; (2) the Shkoder-Peja Normal Fault (SPNF), which accommodated NW–SE directed orogen-parallel extension. The SPTZ dextrally offsets the Dinaric–Hellenic nappes by ~ 75 km, a displacement attributed to reactivation of an Early Mesozoic rift transfer zone in the Adriatic margin during Paleogene subduction of the Pindos Ocean. This subduction involved an initial counter-clockwise rotation of the Hellenides with respect to the Dinarides around a pole at the NW end of the Budva–Krasta–Cukali–Pindos Basin. The SPNF overprints the SPTZ and is a composite structure comprising five fault segments: four of them (Cukali–Tropoja, Decani, Rožaje, Istog) were active under ductile-to-brittle conditions. They downthrow the West Vardar Ophiolite in the hanging wall. The Cukali–Tropoja and Decani segments exhume domes with anchizonal-to-greenschist-facies metamorphism in their footwalls. These structures formed during a first-phase of extension and clockwise rotation, whose Paleocene age is constrained by cross-cutting relationships. A second extensional phase was accommodated mainly by the fifth (Dukagjini) segment of the SPNF, a subsurface normal fault bordering syn-rift, mid-late Miocene clastic and lacustrine sediments in the Dukagjini Basin (DB) that are sealed by Plio-Pleistocene strata. This later phase involved subsidence of Neogene basins at the Dinaric–Hellenic junction coupled with accelerated clockwise oroclinal bending. The driving force for clockwise rotation is thought to be bending and rollback of the untorn part of the Adriatic slab beneath the Hellenides. [ABSTRACT FROM AUTHOR]

Nemolestes and Procladosictis are Eocene sparassodonts of controversial affinities. Nevertheless, despite the poor preservation of their holotypes, several other specimens have been tentatively assigned to these genera, as exemplified by some isolated teeth from the Itaboraí and Laguna Fría faunas. Here, we revise specimens referred to Nemolestes and Procladosictis from Itaboraí, Laguna Fría and Ameghino's collection. Nemolestes differs from Patene in its more reduced metaconid, and "carnassialized" m4 (with reduced talonid and talonid cuspids, except the hypoconulid), features that make it possible to identify specimens from Itaboraí and Laguna Fría as Nemolestes. This taxon occurred from the early Eocene (Itaboraian SALMA) to the middle Eocene (Casamayoran SALMA). Nemolestes represents the oldest known hypercarnivorous sparassodont. The inclusion of Nemolestes and Procladosictis in a comprehensive phylogenetic analysis recovered them in a polytomy as the sister taxa of Borhyaenoidea and a new unnamed clade that includes Lycopsis, Dukecynus, Hathliacynidae, Hondadelphys and Stylocynus. Nemolestes shares with these taxa, but not Patene, the presence of a "carnassialized" m4. Nemolestes differs from known borhyaenoids in the absence of a medially positioned protoconid and short anterolabial cingulid. Therefore, Nemolestes is an early lineage of Sparassodonta. "Procladosictis erecta" is a lower premolar of the unnamed clade, as it shows symmetric walls and a small precingulid. "Procladosictis erecta" should be, in fact, referred to Procladosictis. Our phylogenetic analysis indicates that during the early middle Eocene (Laguna Fría and La Barda faunas), the unnamed clade and Borhyaenoidea had already diverged. Therefore, the evolutionary history of these groups is older than previously thought. [ABSTRACT FROM AUTHOR]

The timing, sequence, and scale of uplift of the Himalayan–Tibetan Orogen (HTO) are controversially debated. Many geoscientific studies assume paleoelevations close to present-day elevations and the existence of alpine environments across the HTO already in the late Paleogene, contradicting fossil data. Using molecular genetic data of ground beetles, we aim to reconstruct the paleoenvironmental history of the HTO, focusing on its southern margin (Himalayas, South Tibet). Based on a comprehensive sampling of extratropical Carabus, and ~ 10,000 bp of mitochondrial and nuclear DNA we applied Bayesian and Maximum likelihood methods to infer the phylogenetic relationships. We show that Carabus arrived in the HTO at the Oligocene–Miocene boundary. During the early Miocene, five lineages diversified in different parts of the HTO, initially in its southern center and on its eastern margin. Evolution of alpine taxa occurred during the late Miocene. There were apparently no habitats for Carabus before the late Oligocene. Until the Late Oligocene elevations must have been low throughout the HTO. Temperate forests emerged in South Tibet in the late Oligocene at the earliest. Alpine environments developed in the HTO from the late Miocene and, in large scale, during the Pliocene–Quaternary. Findings are consistent with fossil records but contrast with uplift models recovered from stable isotope paleoaltimetry. [ABSTRACT FROM AUTHOR]

Materials on the Paleogene biostratigraphy of the Lomonosov Ridge in the Arctic Ocean are presented, including new data on foraminifera from the M0004A borehole section (interval 390–391 m) in its polar part. The studied benthic foraminifers are united into the complex with Reticulophragmium coksuvorovae of the upper part of the Selandian Stage to the lower part of the Thanetian Stage, which includes some characteristic species of the North Atlantic and West Siberian basins. Also, information about the connection of these Arctic seas in the Paleocene time is presented. [ABSTRACT FROM AUTHOR]

A 3D model of the Earth's crust for the continental margin of the Laptev Sea and the adjacent part of the Eurasian Basin was developed using the latest seismic and gravity data. The thickness of the consolidated part of the Earth's crust in the study area is estimated at 7–11 km, which corresponds to a highly extended continental or oceanic crust. The formation of the basement and sedimentation in this area most likely began in the Late Jurassic. The southeastern part of the Eurasian Basin is separated from the rest of the basin by a dextral shear zone, the displacement along which during the Paleogene was more than 100 km. [ABSTRACT FROM AUTHOR]

Paleocene–Eocene phosphorite beds from three major outcrops of the Maknassy-Mezzouna basin (Central-Tunisia) were geochemically investigated to improve local stratigraphy, determine their ages, and attempt to constrain ocean circulation. 87Sr/86Sr ratios of phosphate materials from the Chouabine Formation display a large variation even within the same deposit (87Sr/86Sr between 0.707782 and 0.707830). Based on the Sr isotope data obtained in teeth enamels, further supported by the results in coprolites, Sr isotope ages of 57 ± 1.1 Ma were attributed to Layers I and II, and 62 ± 1.4 Ma to Layer III. These results assign a Paleocene Epoch for the principal phosphate series. The 87Sr/86Sr value of teeth enamel sample from the upper phosphate bed suggests an age of 46 ± 1 Ma for this sequence. Furthermore, the Nd isotopic compositions of these samples were used as a tracer for seawater circulation. The 143Nd/144Nd values of the analyzed samples vary between 0.512174 and 0.512202, corresponding to εNdCHUR between – 8.1 and – 8.4. These values are similar to those reported from Gafsa-Metlaoui basin, southern Tunisia and other North African phosphorite deposits. These data are reminiscent of those of the Atlantic Ocean, which is new argument of the overturning of Tethys Circumglobal Current during the Paleogene period. The obtained results suggest water exchange between Tethys and Atlantic Ocean during this period. [ABSTRACT FROM AUTHOR]

The evaluation of geochemical properties of source rocks can provide an important basis for the accurate evaluation of hydrocarbon resources. In this paper, taking the Tanhai area of the Damintun Sag of Liaohe Oilfield as an example, the chemical properties of source rocks of the Dongying and Shahejie Formations of Paleogene are compared using a large number of geochemical and hydrocarbon generation thermal simulation results. The results show that the organic carbon content of the Dongying and Shahejie Formations in the study area ranges from 0.4% to 3.2%. It is considered that the source rock of the She 3 Member in Paleogene is good source rock. The Dong 3 and Sha 1 Members are the relatively good source rocks. While the Dong 2 Member is a relatively poor source rock, and the Dong 1 Member is the non-source rock. The vitrinite reflectance of Paleogene mudstone in the study area ranges from 0.33 to 0.93%, with an average value of 0.57%, which belongs to the immature to mature stage. Considering that the organic matter types in this area are mainly type IIB–III, the oil generation threshold is set at 2850 m. It is particularly noteworthy that thick coal measure strata are developed in the lower part of the Dong 3 Member and the upper part of the Sha 3 Member, although they are of poor type as oil source rocks, however, they are of great potential value as gas source rocks. The Shahejie source rock has the closest affinity with crude oil. Natural gas in the study area is mainly wet gas and a small amount is dry gas. The ratio of isobutane to n-butane (iC4 /nC4) in natural gas increased with decreasing depth, showing a certain migration differentiation effect. It is speculated that the Shahejie Formation source rock is the main source of natural gas in the Taiyangdao – Kuihuadao Structure. [ABSTRACT FROM AUTHOR]