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In this report we describe 32 species belonging to 26 genera of Caenogastropoda from the early Eocene Cambay Shale of the Cambay Basin, western India. This is the first report of gastropod fossils from this basin, and introduces 24 new species, 2 new subgenera and 3 new genera. The new genera, Eopreangeria, Indobatillaria and Pachycerithium, include new species Eopreangeria mangrolensis, Indobatillaria ismatae and Pachycerithium richardi. The new subgenera are Lyrispina in the genus Lyria and Carinotoma in the genus Apiotoma, including new species Apiotoma (Carinotoma) rammohani. The remaining new species are: Amaurellina cambayensis, Ampullina vastanensis, Amp.? eocenica, Ptychocerithium shamukum, Bittium purnimae, Bi. kamalae, Pseudobellardia sitae, Serratocerithium indicum, Potamides mosaliensis, Pot. shahensis, Sandbergeria khanae, Benthonella prosoclinata, Teinostoma maryae, Natica naroliensis, Involuta? ishwari, Rimella rokeyae, Siphonalia kalpanae, Si. pritilatae, Strepsidura reticulata and Amalda bibhae. A palaeoenvironmental analysis and the diversity–abundance pattern of this fossil fauna provide evidence of an overall marginal marine environment that experienced the Ypresian marine transgression and a gradual increase in marine influence. [ABSTRACT FROM AUTHOR]

The Paleogene coal deposits of the Jaintia Hills of Meghalaya have undergone examinations by various researchers, primarily focusing on organic petrography and geochemistry and highlighting the rank, type, and grade, with perspectives on potential utilization. However, the genesis of these coals has received limited attention from the researchers. This research article addresses this gap by conducting a comprehensive examination of the geochemical and mineralogical aspects of these coals. Coal samples from two coal seams at nine locations in the Sampar coalfield in Jaintia Hills were collected and studied. The samples are subjected to X-ray fluorescence spectroscopy, X-ray diffraction analyses, Fourier transform infrared spectroscopy, proximate, and ultimate analysis to study geochemical and mineralogical composition and ash yield. The study utilizes various geochemical proxies based on the inorganic constituents, providing insights into the paleo-depositional conditions and contributing to a deeper understanding of the unique characteristics of Meghalayan coals. The research indicates that these coals were formed in coastal swamps and lagoons on stable platforms, experiencing minimal tectonic activity, influenced by seawater incursions. These coals were deposited in reducing to significantly reducing conditions and warm and humid to semi-arid climatic conditions. No signature of a geothermally active fluid has been recorded. [ABSTRACT FROM AUTHOR]

A new nyctitheriid (Indonyctia cambayensis gen. et sp. nov.) is described from an early Eocene (~55 Ma) marginal marine sequence (Cambay Shale) at Vastan Lignite Mine, Gujarat, western India. The new taxon is diagnosed by a unique combination of several characters including a single-rooted p2; a p4 with a tiny paraconid at the base but without a metaconid; weakly developed talonid basin; reduced p3 relative to p2 and p4; molar trigonid wider and much higher than talonid; hypoconulid nearly on midline; entoconid positioned anterolingual to hypoconulid; presence of precingulid and a larger and taller protoconid than metaconid. The Asian affinities of the Indian nyctitheriid are indicated by its structurally reduced, premolariform p4 with a weakly developed unicuspid talonid. In several respects, the Indian nyctitheriid is similar to Voltaia, a late Palaeocene taxon from Kazakhstan originally assigned to the Palaeoryctidae but later classified as a nyctitheriid. The presence of a nyctitheriid in the basal Eocene of India suggests a wider palaeogeographic distribution and complex dispersal of this Holarctic family. The Asian affinities of the Indian nyctitheriid suggest faunal exchanges between India and the Mainland Asia possibly via the Dras-Kohistan island arc around the Palaeocene-Eocene boundary (~56 Ma). [ABSTRACT FROM AUTHOR]

A small vertebrate faunal assemblage of late Middle Eocene (Bartonian) age is described from the Bandah Formation, a shallow marine deposit in the Jaisalmer Basin of Rajasthan state, Western India. The Bandah assemblage comprises representatives of selachians (sharks, rays), crocodilians, turtles and archaeocete cetaceans (archaic whales). The mammalian component of this fauna, though represented by fragmentary specimens, allows identification of two archaeocete taxa for the first time from the Palaeogene of Rajasthan: an unnamed protocetid close to Babiacetus and an andrewsiphiine remingtonocetid (Kutchicetus sp.). Occurrence of Eocene cetaceans in the Jaisalmer Basin brings to light a new, potentially rich cetacean-yielding horizon in India, and has the potential to allow a better understanding of early whale evolution in the Indian subcontinent. [ABSTRACT FROM AUTHOR]

This study presents results of integrated larger foraminiferal biostratigraphy, lithofacies and stable carbon isotope (S13Corg) analysis carried out in the Sylhet Limestone of Dillai Parbat Limestone Mine succession, Karbi Anglong District, Assam. Larger foraminiferal assemblages assign a middle Eocene age to the studied succession of Sylhet Limestone. The Shallow Benthic Zone (SBZ) 13 and SBZ 16-18 and abarren interval in between is recognized in the studied part of the Sylhet Limestone. The SBZ 13 Zone (early Lutetian) is represented by fossiliferous limestone at the base of the section and is inferred to have been deposited in a subtidal environment. The overlying barren interval lies in the arenaceous interval and was likely deposited in a subtidal channel sand shoaling bars. The upper part of the section is marked by SBZ 16-18 (late Lutetian to Bartonian) and was deposited in subtidal channel sand inner neritic zone environments, followed by intertidal marl to subtidal limestone. The organic carbon stable isotopic data reveals a sharp negative excursion at about 34-35 m of the succession, which may be correlated with Middle Eocene Climatic Optimum (MECO) and/or vegetation types. This and earlier studies from India and elsewhere indicate that during the middle Eocene, the Neo-Tethys Sea was open and connected through the East and West coasts of India, Northeast India, western Himalaya, and most of the Middle East and southeast Europe. This vast area produced enormous amount of petroleum. [ABSTRACT FROM AUTHOR]

Dwarf males of Ostrea jibananandai sp. nov. from the lower Eocene rocks of the Cambay Basin, western India, are found attached inside the anterior end of the hinge of large females. Commonly, one male is found inside a female shell. Equivalent associations are known in the extant oyster Ostrea puelchana and the Neogene "Cubitostrea" alvarezii from Argentina. This association increases successful fertilization of eggs by reducing sperm loss in these spermcasting/brooding oysters. The sperms, released into water, are normally brought in with the inhalant water current before fertilization inside the body of the female in brooding oysters. This male-female association reduces the uncertainty involved in fertilization because sperms are released directly inside the female shell. The phenomenon is christened here as facultative monogamy. With this discovery, its evolution in oysters is pushed back more than 40 myr to over 54 Ma. Facultative monogamy evolved only in these three species over its long history in spite of its obvious advantages. Facultative monogamy reduces evolutionary flexibility by decreasing phenotypic variability. It is argued here that the phenomenon evolved by trading off morphological variability in favour of successful fertilization in response to environmental perturbations that tend to disrupt sperm transport in open water. Rapid global warming is hypothesized to potentially cause environmental perturbation, because two of the three cases of facultative monogamy in oysters, Eocene O. jibananandai sp. nov. and Recent O. puelchana, occurred at the early stages of hyperthermal events. [ABSTRACT FROM AUTHOR]

We report a new genus and species of herbivorous mammal, Pahelia mysteriosa, from the early Eocene Cambay Shale Formation, Tadkeshwar Lignite Mine, Gujarat, India. The new taxon, approximately the size of a small phenacodontid (e.g. Ectocion parvus), is represented by three mandibular fragments, the most complete of which documents nearly the entire symphysis and mandibular body plus P3–M3. Pahelia has incipiently selenolophodont molars with strong exodaenodonty, absent paraconids, weak but distinct entolophids, and prominent ectostylids. Molar size increases distally, but M3 does not develop a prominent third lobe. Premolars are simple, with prominent protoconids and short talonids but little development of other trigonid cusps. The mandibular symphysis is strongly fused, and there is an enlarged alveolus for an anterior tooth. The combination of features present in the new taxon does not closely match that of any known mammal, but there are some similarities to a diversity of ungulates from Africa, Asia, Europe and North America. Preserved morphology is insufficient to assess the affinities of the new taxon with confidence, but a link to Quettacyonidae, also endemic to the Indian subcontinent, is morphologically and biogeographically plausible. If this scenario is correct, it suggests that P. mysteriosa could be a part of the endemic mammalian fauna of India prior to its initial faunal contact with Asia. [ABSTRACT FROM AUTHOR]

Palar basin is located between Pennar and Cauvery sedimentary basins of East coast of India in Bay of Bengal, northeast Indian Ocean. Sea floor drill (Wire-line Autonomous Coring System – WACS) with operational capability of up to 3000 m water depth was developed to collect long cores from deep sea floor for geotechnical and ocean resource assessment studies. During the drilling operation it encountered Nummulitic coralline limestone of Lower Eocene age at 18 meters below the seafloor (mbsf) at 850 m water depth indicating carbonated platform presence for the first time at the study region. Bathymetry contour from Naval Hydrography Chart and General Bathymetric Chart of the Oceans (GEBCO) has revealed the presence of shallow mounds from 50 to 200 m depth closure contour near the sampling site at 850 m water depth which might be a submerged carbonated structure. Since, Nummulites are shallow water dwelling fauna (<20 m depth) but its occurrence at 18 mbsf in 850 m water depth is recorded because of the advancement in technology tool for long core sampling by means of sea floor drill. [ABSTRACT FROM AUTHOR]

The 8.5 m thick, 1.4 km long and 0.35 km wide, ESE–WNW oriented cliff section (N 23°31′32″ E 68°41′00″) exposed across Harudi–Baranda road is extensively studied for its facies characteristics and based on that depositional environments of the middle Eocene (Lutetian) Harudi Formation are deciphered in the present study. Two cycles of grey mudstone alongwith nodular limestone–coquina limestone-gypsiferous mudstone facies in the lower part of the succession suggest sedimentation in coastal quiet-water lagoonal to tidal flat environments, while glauconitic shale, bioclastic packstone and gypsiferous foraminiferal packstone facies in the upper part suggest sedimentation on middle- to inner-shelf and tidal flat depositional environments. In all, three shallowing upward cycles have been identified in the studied outcrops and based on that lagoonal-middle shelf-inner shelf-tidal flat depositional environments are suggested for the middle Eocene Harudi Formation. [ABSTRACT FROM AUTHOR]

The recognition of pyroclasts preserved in sedimentary environments far from its source is uncommon. We here describe occurrences of several centimetres-thick discontinuous basaltic pumice lenses occurring within the Early Eocene Vastan lignite mine sedimentary sequence, western India at two different levels - one at ∼5 m and the other at 10 m above a biostratigraphically constrained 52 Ma old marker level postdating the Deccan Volcanism. These sections have received global attention as they record mammalian and plant radiations. We infer the repetitive occurrence of pumice have been sourced from a ∼52-50 Ma MORB related to sea-floor spreading in the western Arabian Sea, most plausibly along the Carlsberg Ridge. Pyroclasts have skeletal plagioclase with horsetail morphologies ± pyroxene ± Fe-Ti oxide euhedral crystals, and typically comprise of circular polymodal (radii ≤10 to ≥30 μm), non-coalescing microvesicles (>40-60%). The pumice have undergone considerable syngenetic alteration during oceanic transport and post-burial digenesis, and are a composite mixture of Fe-Mn-rich clay and hydrated altered basaltic glass (palagonite). The Fe-Mn-rich clay is extremely low in SiO , Al O , TiO , MgO, alkalies and REE, but very high in Fe O , MnO, P, Ba, Sr contents, and palagonitization involved significant loss of SiO , Al O , MgO and variable gain in Fe O , TiO , Ni, V, Zr, Zn and REE. Bubble initiation to growth in the ascending basaltic magma (liquidus ∼1200-1250 C) may have occured in ∼3 hr. Short-distance transport, non-connected vesicles, deposition in inner shelf to more confined lagoonal condition in the Early Eocene and quick burial helped preservation of the pumice in Vastan. Early Eocene Arabian Sea volcanism thus might have been an additional source to marginal sediments along the passive margin of western India. [ABSTRACT FROM AUTHOR]

Background: The Indian Tectonic Plate split from Gondwanaland approximately 120 MYA and set the Indian subcontinent on a ~ 100 million year collision course with Eurasia. Many phylogenetic studies have demonstrated the Indian subcontinent brought with it an array of endemic faunas that evolved in situ during its journey, suggesting this isolated subcontinent served as a source of biodiversity subsequent to its collision with Eurasia. However, recent molecular studies suggest that Eurasia may have served as the faunal source for some of India's biodiversity, colonizing the subcontinent through land bridges between India and Eurasia during the early to middle Eocene (~35-40 MYA). In this study we investigate whether the Draconinae subfamily of the lizard family Agamidae is of Eurasian or Indian origin, using a multi locus Sanger dataset and a novel dataset of 4536 ultraconserved nuclear element loci. Results: Results from our phylogenetic and biogeographic analyses revealed support for two independent colonizations of India from Eurasian ancestors during the early to late Eocene prior to the subcontinent's hard collision with Eurasia. Conclusion: These results are consistent with other faunal groups and new geologic models that suggest ephemeral Eocene land bridges may have allowed for dispersal and exchange of floras and faunas between India and Eurasia during the Eocene. [ABSTRACT FROM AUTHOR]

Analysis of lithofacies, paleoflow directions, and sandstone petrography of upper Paleocene-lower Eocene paralic and continental sediments exposed along the transpressional suture zone of the western margin of the Indian plate indicate that the process of deformation and uplift of the carbonate shelf in this area had started by late Paleocene time. This tectonic uplift and deformation is documented by: (1) an overall shallowing upward synorogenic sequence of sediments, (2) proximal conglomerate facies (consisting of lower Paleocene and Mesozoic clasts) dominating in the western part of the study area and distal facies of sandstone and shale dominating in the eastern part of the study area, (3) the existence of an unconformity of late Paleocene-early Eocene age in the Quetta and Kalat regions, (4) paleocurrent directions in deltaic and fluvial deposits indicating southeastward flowing sediment dispersal paths during late Paleocene-early Eocene time, which is opposite to that found in the late Cretaceous, suggesting a reversal in the depositional slope of the Cretaceous shelf, and (5) petrographic study of sandstones indicating a collision suture/fold thrust belt provenance. This episode of uplift and deformation could be the result of India-Arabian transpression with associated ophiolite obduction or, more likely, to represent the local response to initial India-Asia contact. The unroofing pattern and uplift geometry of the western Indian shelf suggests that this tectonism first started in the southern part of the study area (Kalat-Khuzdar area) during the late Paleocene-early Eocene and proceeded northward in a time-transgressive fashion. [ABSTRACT FROM AUTHOR]

Abstract: Eocene is a critical time for the elevation of Tibetan Plateau and global climate change, and previous studies suggested that the Eocene elevation was caused by intra-continental subduction of the Songpan–Garze block beneath the Qiangtang block. This paper reports zircon U–Pb age and geochemistry of the Eocene volcanic rocks from the Zuerkenwula mountain area in the northern part of Qiangtang block, and proposes that both slab break-off of the Neo-Tethys oceanic slab along the Bangong–Nujiang suture and intra-continental subduction of the Songpan–Garze block beneath the Qiangtang block caused the extensive partial melting of lithospheric mantle and subducted Songpan–Garze continental crust, which resulted in the significant elevation of the Tibetan Plateau. The volcanic rocks have LA-ICP MS U–Pb zircon age of 40.25±0.15Ma (MSWD=2.1, 2σ), which is contemporaneous with the Eocene eclogites in the Great Himalayan and K-rich lavas in the southeastern Tibet. They display some adakitic characteristics with SiO2 =57.44 to 68.72%, TiO2 =0.38 to 0.81%, Na2O=2.89 to 4.35%, K2O=2.77 to 4.48%, Al2O3 =13.92 to 18.22%, A/CNK=0.69 to 1.03, MgO=0.27 to 5.86% with Mg# ranging from 13.2 to 72.0, strongly depleted in heavy rare earth elements (HREEs) (Yb=0.92 to 1.51ppm and Y=10.1 to 24.1ppm), in combination with their positive Sr anomalies, high Sr/Y ratios and no significant Eu anomalies, which suggest a garnet-in and plagioclase-free source residue. These volcanic rocks can be divided into high-Mg# (>45) and low-Mg# (<45) groups. Both of the two groups share evolved Sr–Nd–Pb isotopic compositions with 87Sr/86Sr=0.707412–0.708284; εNd(t)=−4.0 to −5.7; 206Pb/204Pb=18.7499–18.8189, 207Pb/204Pb=15.7189–15.7384; 208Pb/204Pb=39.166–39.262. The geophysical data and regional geological setting suggest that the low-Mg# adakitic rocks were derived from the decompression melting of a subducted lower continental crust, when low-Mg# adakitic melts in the overlying peridotite mantle wedge captured some olivine crystals, resulting in their elevated Mg# and MgO values. [Copyright &y& Elsevier]

Three successive subspecies of Nummulites burdigalensis evolved from N. solitarius. These include N. burdigalensis keupperi, N. burdigalensis burdigalensis and N. burdigalensis cantabricus. The evolving lineage is traced in a borehole drilled through the Naredi Formation of Kutch. The associated taxa include N. solitarius and N. fraasi in the lower part and Assilina laxispira and A. spinosa in the upper part of the formation. The better stratigraphic resolution achieved by subspecies identification and the lately redefined Ilerdien Stage in the background of Early Eocene carbon isotope excursion marker, lead to constrain the age of Naredi Formation as Early Eocene, ranging from shallow-benthic zones SBZ6 to SBZ11. [ABSTRACT FROM AUTHOR]

During the Paleocene and Eocene the extratropical Central Eurasia was the main seaway link of the contiguous south to north seaway system connecting the Tethys and Arctic oceans. The seaway extended from North Pakistan and India to North Siberia through a system of inland seas and straits and acted as a kind of heat transfer to the Arctic during this time. Before the emergence of the latitudinal Alpine-Himalayan orogenic belt, the Tethys and its marginal seas to the north formed a continuous shelf area. The closest linkage of the water masses and exchange of biota between the Tethys and the Arctic ocean existed during the Thanetian and Ypresian. Latest Paleocene - Early Eocene heat transfer developed both by water- and atmospheric currents at the mid- latitudes of Central and Eastern Eurasia. From the end of the Paleocene or earliest Eocene onwards this system was complicated by latitudinally oriented straits that ensured the connection of the Northern Peri-Tethys with the Atlantic through the North Sea basin. The combination of two sea systems controlled the climatic history of the Central Asia regions from the Late Paleocene until the Late Eocene. During the Bartonian and Priabonian the West Siberian inland sea was isolated completely from the Arctic Basin during the last phase of marine sedimentation. It was connected with the Turan sea through the Turgai strait. Azolla beds accumulated periodically during eustatic sea level lowstands in fresh-water surface waters, and in dysoxic bottom waters inhabited stunted benthos during the Bartonian - earliest Late Eocene. During the Late Eocene eustatic rise of sea level the input of saline water from the Peri- Tethys increased and the West Siberian basin became normally marine again. The monsoonal subtropical climate during Ypresian - Early Lutetian was transformed to subtropical seasonal with semi-arid features during the Late Lutetian - Early Priabonian, up to subtropical to warm-temperate with alternations of humid and arid phases in the Late Priabonian. [ABSTRACT FROM AUTHOR]

The fauna of termites (Isoptera) preserved in Early Eocene amber from the Cambay Basin (Gujarat, India) are described and figured. Three new genera and four new species are recognized, all of them Neoisoptera - Parastylotermes krishnai Engel & Grimaldi, sp. n. (Stylotermitidae); Prostylotermes kamboja Engel & Grimaldi, gen. et sp. n. (Stylotermitidae?); Zophotermes Engel, gen. n., with Zophotermes ashoki Engel & Singh, sp. n. (Rhinotermitidae: Prorhinotermitinae); and Nanotermes isaacae Engel & Grimaldi, gen. et sp. n. (Termitidae: Termitinae?). Together these species represent the earliest Tertiary records of the Neoisoptera and the oldest definitive record of Termitidae, a family that comprises >75% of the living species of Isoptera. Interestingly, the affinities of the Cambay amber termites are with largely Laurasian lineages, in this regard paralleling relationships seen between the fauna of bees and some flies. Diversity of Neoisoptera in Indian amber may reflect origin of the amber deposit in Dipterocarpaceae forests formed at or near the paleoequator. [ABSTRACT FROM AUTHOR]

The Paleocene-Early Eocene carbonate successions of the Indus Basin in Pakistan formed on the northwestern continental shelf margin of the Indian Plate in the eastern Tethys Ocean. Based on larger benthic foraminifera (LBF), eight Tethyan foraminiferal biozones (SBZ1-SBZ8) spanning the Paleocene to Early Eocene interval are identified. The base of the Eocene is identified by the first appearance of Alveolina sp. Other stratigraphically important LBFs that are characteristic of the earliest Eocene are Ranikothalia nuttalli, Discocyclina dispansa and Assilina dandotica. Stable isotope analysis through the Paleocene-Eocene (P-E) boundary interval identifies more positive δ13C values for the Late Paleocene (+3.4‰ to +3.0‰) and lower values (+2.7‰ to +1.6‰) for the earliest Eocene. However, there is insufficient sampling resolution to identify the maximum negative δ13C excursion of the Paleocene-Eocene Thermal Maximum. During Late Paleocene times LBF assemblages in the Indus Basin were taxonomically close to those of west Tethys, facilitating biostratigraphic correlation. However, this faunal continuity is lost at the P-E boundary and the earliest Eocene succession lacks typical west Tethys Nummulites, while Alveolina are rare; LBFs such as Miscellanea and Ranikothalia continue to dominate in the Indus Basin. The absence of Nummulites from the earliest Eocene of Pakistan and rarity of Alveolina, elsewhere used as the prime marker for the base of the Eocene, may imply biogeographical barriers between east and west Tethys, perhaps caused by the initial stages of India-Asia collision. Later, at the level of the Eocene SBZ8 Biozone, faunal links were re-established and many foraminifera with west Tethys affinities appeared in east Tethys, suggesting the barriers to migration ceased. [ABSTRACT FROM AUTHOR]

This paper presents a brief review of recent advances in the classification of mammals at higher levels using fossils and molecular clocks. It also discusses latest fossil discoveries from the Cretaceous — Eocene (66–55 m.y.) rocks of India and their relevance to our current understanding of placental mammal origins and diversifications. [ABSTRACT FROM AUTHOR]

Abstract: The oldest euprimates known from India come from the Early Eocene Cambay Formation at Vastan Mine in Gujarat. An Ypresian (early Cuisian) age of ∼53Ma (based on foraminifera) indicates that these primates were roughly contemporary with, or perhaps predated, the India-Asia collision. Here we present new euprimate fossils from Vastan Mine, including teeth, jaws, and referred postcrania of the adapoids Marcgodinotius indicus and Asiadapis cambayensis. They are placed in the new subfamily Asiadapinae (family Notharctidae), which is most similar to primitive European Cercamoniinae such as Donrussellia and Protoadapis. Asiadapines were small primates in the size range of extant smaller bushbabies. Despite their generally very plesiomorphic morphology, asiadapines also share a few derived dental traits with sivaladapids, suggesting a possible relationship to these endemic Asian adapoids. In addition to the adapoids, a new species of the omomyid Vastanomys is described. Euprimate postcrania described include humeri, radii, femora, calcanei, and tali, most of which show typical notharctid features and are probably attributable to asiadapines. Anatomical features of the limb elements indicate that they represent active arboreal quadrupedal primates. At least one calcaneus is proximally shorter and distally longer than the others, resembling eosimiids in this regard, a relationship that, if confirmed, would also suggest an Asian or southeast Asian faunal connection. Isolated teeth from Vastan Mine recently attributed to a new eosimiid, Anthrasimias gujaratensis, appear to provide that confirmation. However, their attribution to Eosimiidae is equivocal. They are similar to teeth here tentatively referred to Marcgodinotius, hence A. gujaratensis may be a junior synonym of M. indicus. Corroboration of eosimiids at Vastan requires more compelling evidence. Although definitive conclusions are premature, available evidence suggests that the Vastan adapoids, at least, were derived from western European stock that reached India near the Paleocene-Eocene boundary. [Copyright &y& Elsevier]

Successive indentations of Eurasia by India have led to the Tibet-Himalaya E–W orthogonal collision belt and the SE Tibetan Plateau N–S oblique collision belt along the frontal and eastern edges of the indenter, respectively. The belts exhibit distinctive lithospheric structures and tectonic evolutions. A comprehensive compilation of available geological and geophysical data reveals two sudden tectonic transitions in the early Eocene and the earliest Miocene, respectively, of the tectonic evolution of the orthogonal belt. Synthesizing geological and geochronological data helps us to suggest a NEE–SWW trending, ~450 km-long, ~250 km-wide magmatic zone in SE Tibet, which separates the oblique collision belt (eastern and SE Tibet) into three segments of distinctive seismic structures including the mantle and crust anisotropies. The newly identified Yongping basin is located in the central part of the magmatic zone. Geochronological and thermochronological data demonstrate that (1) this basin and the magmatic zone started to form at ~48 Ma likely due to NNW–SSE lithosphere stretching according to the spatial coincidence of the concentrated mantle-sourced igneous rocks on the surface with the seismic anomalies at depth; and (2) its fills was shortened in the E–W direction since ~23 Ma. These two dates correspond to the onset of the first and second tectonic transitions of the orthogonal collision belt. As such, both the orthogonal and oblique belts share a single time framework of their tectonic evolution. By synthesizing geological and geophysical data of both collision belts, the indenting process can be divided into three stages separated by two tectonic transitions. Continent–continent collision as a piston took place exclusively during the second stage. During the other two stages, the India lithosphere underthrust beneath Eurasia. [ABSTRACT FROM AUTHOR]

India's northward flight and collision with Asia was a major driver of global tectonics in the Cenozoic and, we argue, of atmospheric CO2 concentration (pCO2) and thus global climate. Subduction of Tethyan oceanic crust with a carpet of carbonate-rich pelagic sediments deposited during transit beneath the high-productivity equatorial belt resulted in a component flux of CO2 delivery to the atmosphere capable to maintain high pCO2 levels and warm climate conditions until the decarbonation factory shut down with the collision of Greater India with Asia at the Early Eocene climatic optimum at ≈50 Ma. At about this time, the India continent and the highly weatherable Deccan Traps drifted into the equatorial humid belt where uptake of CO2 by efficient silicate weathering further perturbed the delicate equilibrium between CO2 input to and removal from the atmosphere toward progressively lower pCO2 levels, thus marking the onset of a cooling trend over the Middle and Late Eocene that some suggest triggered the rapid expansion of Antarctic ice sheets at around the Eocene-Oligocene boundary. [ABSTRACT FROM AUTHOR]

A small collection of fossil pteropods, including some unidentified species, provisionally referable to the families Limacinidae, Creseidae, and Clioidae (?) is reported from the late Middle Eocene-Late Eocene beds of the Upper Disang Formation exposed near the town of Pfutsero, Phek District, South Central Nagaland (Assam-Arakan Basin, northeastern India). This is the first record of fossil pteropods from this part of India. Although based exclusively on juvenile or incompletely preserved adult shells, documentation of this collection is important from the viewpoint of biostratigraphy as well as palaeoecology. The occurrence of pteropods in the Upper Disang Formation indicates deposition in an open marine basin above the aragonite compensation depth. The combined assemblages of pteropods and previously reported uvigerinid foraminifers from the Upper Disang Formation indicate a palaeobathymetry of ~500 m, i.e. upper bathyal zone, and a tropical-subtropical climate. [ABSTRACT FROM AUTHOR]

This communication highlights the level of atmospheric CO2 and the climatic conditions during Eocene (36 ± 5 Ma) based on measurements of stable carbon and oxygen isotopes of late Eocene soil carbonate (calcretes) occurring in the Himalayan foreland basin sequences. The atmospheric pCO2 is estimated to be about 930 ppm V at high productivity and about 465 ppm V at low productivity. The covariance of δ18O and δ13C suggests that the higher atmospheric CO2 may be responsible for higher temperature. Moderate weathering intensity (CIA value 70-82) of the host mudstones suggests warm climate associated with reasonable wetness that became dry-subtropical, resulting in calcrete development in the northern part of the Indian subcontinent during late Eocene. Wet subtropical climate demonstrates considerable rainfall at this time interval in the region long before the uplift of the Tibetan plateau. Alternatively, it can be suggested that uplift of the Tibetan plateau began much earlier than presently considered. [ABSTRACT FROM AUTHOR]

The Hazad Member (Middle Eocene) of the Ankleswar Formation in Cambay Basin, India, is traditionally reported as deltaic system. Present work documents three major facies associations, namely, (i) sandstone-rich upper delta plain (FA-1) deposits, (ii) sandstone-mudstone heterolithic lower delta plain-delta front (FA-2) deposits, and (iii) shale-dominated prodelta (FA-3) deposits, in an overall coarsening-up to fining-up succession. Tidalites are well preserved in FA-2 and are represented by laterally accreted tidal bundles, tidal beddings and vertically accreted tidal rhythmites, described from drill core samples in this communication. Laterally accreted tidal bundles with reactivation surfaces in sand-dominated heterolithic units indicate time-velocity asymmetry in subtidal condition. Tidal beddings and tidal rhythmites in mud-dominated heterolithic units, associated with asymmetric/symmetric ripple forms and desiccation cracks, indicate periodic subaerial emergence in intertidal flat depositional setting. Systematic analysis of the architecture of the tidalites in different parts of the basin signifies rapid shift in sedimentation from subtidal to intertidal flat within the lower delta plain. Transitions from prodeltaic to tidally (subtidal-intertidal) affected delta front to lower delta plain and fluvial-dominated upper delta plain depositional systems attest to high frequency transgressive-regressive cycles in response to changing accommodation, as a result of sea level fluctuations and basinal tectonisms in the Cambay Basin. [ABSTRACT FROM AUTHOR]