Geology

University of Calcutta (informally known as Calcutta University or CU) is a collegiate public state university located in Kolkata, West Bengal, India.&nbsp;Within India it is recognized as a &quot;Five-Star University&quot; and accredited &quot;A&quot; Grade by National Assessment and Accreditation Council.

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The University of Calcutta has secured the Fifth position among the Universities of India in the prestigious &quot;Indian University Ranking 2019&quot; list, released by the NIRF of the Ministry of Human Resource Development, Government of India.

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It was established on 24 January 1857, and was one of the first institutions in Asia to be established as a multidisciplinary and Western-style university. Its alumni and faculty include several heads of state, heads of government, social reformers, prominent artists, only academy award winner and Dirac medal winner in India, many Fellows of the Royal Society and five Nobel laureates as of 2019 which is highest in South Asia.

University Of Calcutta

The Paleoproterozoic-Mesoproterozoic boundary is associated with onset of supercontinental cycle and global thermal perturbation. In the Singhbhum cratonic province, the 1600 Ma felsic volcanics and metasedimentary successions of the Chandil Formation conformably overlies the mafic volcanic and volcaniclastic successions of the Dalma Formation. Unlike the Dalma Formation and the underlying Singhbhum Group of rocks, the sedimentary facies and provenance characterization of the Chandil Formation has been long overdue. Herein we present sedimentary facies and geochemical characterization of the Chandil Formation. The Chandil Formation has been divided into three distinct sedimentary facies associations: the bottommost trough cross-stratified, poorly sorted and texturally immature, coarse- to medium-grained sandstone-shale facies association formed in a fluvial setting. The overlying fine-grained, well-sorted and well-rounded sandstones of the sandstone-siltstone-mudstone (volcanic ash) facies association is characterized by aeolian dunes and pinstripe laminations, and thus formed in an aeolian environment. The medium-grained, moderately sorted, cross-bedded sandstones of the topmost facies association bear alternate thick-thin sandy foresets that are bounded by mudstone drapes and hummocky-cross stratification, indicating a marine depositional setting. The Chandil sedimentation pattern is remarkably similar to the very well-known and 1000 million years younger Potsdam Group clastics, USA that formed in an intracratonic rift setting with similar sedimentary facies characteristics. Comparative provenance studies of the clastic rocks of the Chandil Formation and the lowermost Potsdam Group reveal that the protoliths of both rock successions were arkosic to litharenitic composition. Trace element studies of the sedimentary units of both rock successions confirm the provenance interpretation and indicate reworking of early rift and/or granitic basement rocks. The similarities between these sedimentary successions including sedimentary facies, basin development, and geochemical trends, although differing in age by ca. 1 billion years, indicate overwhelming influence of provenance on sediment generation, transportation and deposition that muted other controlling factors of sedimentation like paleoclimate, changes to Earth magmatism and consequent changes in tectonic regime etc. Sedimentological and geochemical analysis, following the methodology adopted in this paper, from other sedimentary successions will help to infer the interplay between contemporary basin tectonics and consequent sedimentation. Our analyses further indicate major terrestrial sedimentation, higher continental freeboard and felsic magmatism around 1600 million years in the Singhbhum craton similar to the adjoining Cuddapah basin (Dharwar), Pranhita-Godavari basin (Bastar) in the southern Indian block, in the Central Indian Tectonic Zone, and in the Vindhyan basin of the north Indian block. © 2021 Elsevier B.V.

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Earth-Science Reviews

Influence of continental rifting on sedimentation and its provenance and geodynamic implications: An example from late Paleoproterozoic Chandil Formation, eastern India

Palaeobiodiversity and Palaeoenvironments

Palaeobiogeographic analysis of Late Permian marine invertebrates from the Arunachal Himalaya, NE India

Cratonic stabilization was a critical crustal process during the Hadean to Archean for the formation of cratons. The understanding of how and where this process took place is significant to evaluate the architecture of continents. The Singhbhum Craton of eastern India has well preserved Precambrian volcano-sedimentary sequences. The Simlipal volcano-sedimentary complex of Singhbhum Craton consists of circular bands of mafic volcanic rocks interlayered with quartzites/ shales/phyllites. In the present study, we report petrographic and geochemical characteristics of quartzites from Simlipal Complex coupled with U–Pb ages of detrital zircons and zircon geochemistry to understand the provenance and depositional conditions and its connection with the crustal stabilization in the Singhbhum Craton. The quartzites are texturally mature with sub-angular to sub-rounded quartz grains followed by feldspars embedded in a silty matrix. Based on modal compositions and major element ratios, these quartzites are categorized as quartz arenite and sub-lithic arenites. Trace element abundances normalized to Archean Upper Continental Crust (AUCC) display positive anomalies at U, Zr, Hf and negative anomalies at Nb. REE patterns are characterized by negative Eu anomalies (Eu/Eu* = 0.47–0.97) and flat HREE suggesting felsic provenance. These quartzites show depletion of LILE, enrichment of HFSE and transition metals relative to AUCC. High weathering indices such as CIA, PIA, and ICV are suggestive of moderate to intense chemical weathering. Low trace element ratios such as Th/Cr, Th/Sc, La/Sc, La/Co and Th/Co indicate a predominantly felsic source for these rocks. The overall geochemical signatures indicate passive margin deposition for these quartzites. Detrital zircons from the Simlipal quartzites yield U–Pb ages 3156 ± 31 Ma suggesting Mesoarchean crustal heritage. The trace element geochemistry of detrital zircons suggests that the zircons are magmatic in origin and possibly derived from the 3.1 Ga anorogenic granite/granitoid provenance of Singhbhum Craton. These observations collectively indicate the Mayurbhanj Granite and Singhbhum Granite (SBG-III) provenance for these quartzites, thereby tracking the stabilization of the eastern Indian Shield/Singhbhum Craton back to Mesoarchean. © 2021 China University of Geosciences (Beijing) and Peking University

Geoscience Frontiers

Crustal stabilization: Evidence from the geochemistry and U–Pb detrital zircon geochronology of quartzites from Simlipal Complex, Singhbhum Craton, India

Gondwana Research

Paleogeography of the West Burma Block and the eastern Neotethys Ocean: Constraints from Cenozoic sediments shed onto the Andaman-Nicobar ophiolites

Journal of Earth System Science

Multistage evolution of subcontinental lithospheric mantle of northwestern Deccan volcanic province, India: Constraints from the ultramafic xenoliths in alkali magma

The soda granite (~Paleoproterozoic) of the Singhbhum Craton (SC) of eastern India occurs along the entire stretch of the Singhbhum Shear Zone (SSZ; or Copper Belt Thrust Zone). The SSZ (marking a thrust contact between the adjacent North Singhbhum mobile belt and SC) serves as the important locale to host apatite-magnetite, copper sulphide, and uraniferous mineralization. Typical field occurrence of soda granite is either as tongues (or patches) within a shear zone or as lit-per-lit style injections into surrounding country rocks which are generally highly sheared and mylonitized. Experimental studies on granite bodies can potentially throw light on their mineralogical and petrogenetic aspects; however, these studies are hitherto unreported in case of soda granites for almost the last 60 years. In this view, during the present research, experimental studies on soda granites have been carried out and these decipher the nature of the stability relationship of K-feldspar (and transgression to more disordered anorthoclase), amphibole (both Ca-amphibole and Fe–Mg–Mn amphibole and breaking down of Ca-amphibole to Fe–Mg–Mn amphibole + non-quad pyroxene + quartz at an appropriate temperature), biotite, muscovite, and albite (high albite- low albite displacive transformation). Whole-rock chemistry (deduced from homogenized glass compositions) indicates its peraluminous, S-type nature with an affinity towards Caledonian post-collisional plutons. Characteristic geochemical plots suggest a pelitic source material for melting (and subsequent internal differentiation of the melt) and this has given rise to both migmatite as well as patchy soda granite exposures in the field. It is suggested that partial melting of mainly metapelitic (and minor mafic magmatic rocks) source (belonging to Singhbhum Series) gave rise to soda granites in this region. © 2021 John Wiley &amp; Sons Ltd.

Geological Journal

Experimental study on soda granites of the Singhbhum Craton, eastern India, and its petrogenetic significance

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PLoS ONE

{High biogeographic and latitudinal variability in gastropod drilling predation on molluscs along the eastern Indian coast: implications on the history of fossil record of {\ldots}}

Evaluation of the petrogenetic history of continental flood basalt using mineral–chemical data has been sparingly used for several flood basalt provinces of the world. For the Deccan flood basalts, such attempts are still rudimentary. The present contribution highlights several facets of petrogenesis of the Eastern Deccan Volcanic Province using details of constituent phases including glass. The present-study area around Khandwa (21°49′N, 76°21′E) indicates the presence of three distinct lava flows, which were identified on the basis of physical volcanological features based on a three-tier classification. Moreover, the occasional presence of chilled dykes and feeder dykes has been documented. The lava succession rests above (apparent) cumulate gabbro basement. The lava flows, in general, are characterized by dominant pyroxene (mostly augite, locally pigeonite) and plagioclase, opaque (magnetite and ilmenite) and glass, whereas olivine is rare. Both of these principal mineral phases (namely, plagioclase and pyroxene) occur both as phenocrysts and groundmass, while opaque phases occur only as groundmass. Pyroxene and plagioclase are generally zoned due to the changing milieu of crystallization conditions. Pyroxene thermometry data show the equilibration temperature range of 1050–1300 °C. Except for two samples of Flow II and one sample of chilled zone, the pyroxene thermometry data are broadly similar to that obtained from magnetite–ilmenite thermometry. As expected, deduced glass thermometric data reveal a relatively higher temperature. Crystallization history of parental magma was quantitatively modeled using Petrolog 3 software. The results indicate that the parental magma underwent both equilibrium and fractional crystallization (for example initially crystallized olivine reacted with ambient liquid to give rise to pyroxene). Phenocrystal and groundmass plagioclase and pyroxene show distinct patterns of compositional zoning corresponding to fluctuating physical parameters within the magma. Some of the glass [especially from the chilled dyke, feeder dyke, and Upper Colonnade Zone (UCZ) of flow II and flow III] represents ‘higher magnitude pressure ambience’ (fossilized glass) which is distinct from ‘surficial glass’ caused by equilibrium quenching. The glass and pyroxene compositions (using tectonic discrimination diagrams) suggest a non-orogenic continental setting of the parent magma. It is concluded that the studied Deccan volcanism shows a complex interplay of repeated pulses of magma ascent, fluctuation of crystallization condition, effervescence, and local magma mixing. © 2021, Geologische Vereinigung e.V. (GV).

International Journal of Earth Sciences

Windowing petrogenesis of continental flood basalts through mineralogical investigations: a case study from the Eastern Deccan Volcanic Province

Ophiolites are widely studied to unravel how new subduction zones form. They may contain crustal and mantle rocks that formed during juvenile stages of intra-oceanic subduction, modifying the pre-existing oceanic lithosphere within which subduction started, and in which a magmatic arc formed upon subduction maturation. Previous geochemical work on the Cretaceous Andaman Ophiolite and its metamorphic sole, located in the forearc of the Sunda subduction zone of south-east Asia, has revealed geochemical signatures that are difficult to reconcile in a single tectonic setting but may rather record different stages in a longer evolution. A recent kinematic reconstruction proposed that the Andaman Ophiolite may have formed during subduction initiation in a former back-arc basin, when the former (Woyla) arc collided with the Sundaland continent. Here, we evaluate whether such a scenario may provide a feasible context to explain the enigmatic geochemical signatures preserved in the Andaman Ophiolite. To this end, we provide new, and review existing geochemical as well as geochronological constraints on the formation of its crustal rocks, as well as the evolution of its mantle portion. We identify mafic magmatic rocks and cogenetic plagiogranites that are consistent with formation in a magmatic arc, whereas other magmatic rocks, as well as metamorphic sole protoliths, have characteristics indicative of a back-arc origin. Three new, and two previous zircon U/Pb ages of arc magmatic rocks give a 99–93 Ma age range, but we also identify an inherited ~105 Ma age. This latter age coincides with Ar/Ar cooling ages of the Andaman metamorphic sole, and with a plagioclase xenocryst age from recent Barren Island volcanics east of Andaman. The geochemical and geochronological constraints of the Andaman ophiolites are straightforwardly explained in the context of the regional kinematic history: (1) The original lithosphere formed in the back-arc basin of the Woyla intra-oceanic arc; (2) Subduction initiation and SSZ ophiolite formation within this basin occurred around or slightly before 105 Ma; (3) This was followed by arc magmatism between 99 and 93 Ma upon subduction maturation. © 2020 Elsevier B.V.