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We thank Patil Pillai et al. for preparing a critique on our article (Joy et al., 2018). Patil Pillai et al. contest the analytical procedure utilized for the carbonates and "geological information" documented in our research article and raise concerns on our conclusions. We hereby provide our reply to each of their comments. [ABSTRACT FROM AUTHOR]

The establishment, development and abandonment and/or destruction of ancient civilizations were catalytically controlled by geomorphic features such as lakes and rivers and the climate. This paper examined the possible influence of tectonism and climate on six habitations of the ancient Vaigai River Basin civilization in South India, using multiple proxies such as grain size, geochronology and geochemistry of the sedimentary archives. The tectonic setting of the basin changed between the active margin and passive margin; the discriminant diagrams suggested varying provenance and changing climatic conditions over the mid‐ and‐late Holocene. Tectonic activism and quiescence, base‐level change in the channel morphology led to the burial/marooning of the first habitation surface. Overall, arid conditions were punctuated with catastrophic flooding and peak discharge (flood) destroyed the second, third and fourth habitation sites. These flooding events were characterized by moderate weathering (CIA) and high values of Al, Fe and Rb/Sr and low Ca/Mg in the sediment records. The abandonment/destruction of the fifth habitation also occurred during an arid interval (droughts), possibly caused by weak monsoon. Along with the interactions between tectono‐climatic and fluvial geomorphic factors, the new results provided avenues to (a) check and recognize the archives for 8.2 and 4.2 ka‐like events in this part of the world, and (b) the utility of integrated analyses to constrain on the civilizational histories of the mankind. [ABSTRACT FROM AUTHOR]

The paper presents data on the U–Pb chronology of detrital zircon grains and radiogenic isotopic composition (87Sr/86Sr, ɛNd) from the Proterozoic clastic successions of the Garhwal‐Kumaon Lesser Himalaya representing the extended northern Indian cratonic margin, NW India. The Proterozoic Lesser Himalayan Basin in Garhwal‐Kumaon Himalaya is divided into two sectors, namely, Inner Lesser Himalaya (ILH) and Outer Lesser Himalaya (OLH) by a tectonic boundary, namely the Tons Thrust (TT). Age distribution from inner and outer sectors of the Lesser Himalaya shows that the U–Pb chronology of most of these zircons provides Palaeoproterozoic (between 1.6 and 1.8 Ga) to Neoproterozoic (800 Ma) ages. The age data suggest sedimentation of the Rautgara Formation (Damtha Group) of ILH continued till the Neoproterozoic (~850 Ma), which was earlier regarded as ≤1.6 Ga. Tracking the detrital U–Pb zircon ages in the near adjacent cratonic parts point towards Aravalli Orogen as the major source region. Whole‐rock ƐNd(0) values for ILH rocks range from −37.6 to −14.6 and for OLH it ranges from −19.6 to −6.7. More negative ƐNd values along with dominance of Neoarchean‐Palaeoproterozoic ages in ILH indicates supply from more evolved protolith or recycled sources and less negative ƐNd values with major Neoproterozic zircon ages from OLH supports for less evolved source rock. The change from more negative ƐNd to less negative ƐNd values progressively upward the stratigraphy can be due to a shift in source with time. Both U–Pb zircon and ƐNd supports for a continuous sedimentation model, rule out the presence of ~500 Ma unconformity within the LH and argues for separate evolution of the Lesser Himalayan Basin on the trailing edge of the extended north Indian craton in "Columbia" configuration. [ABSTRACT FROM AUTHOR]

This paper discusses the porphyry copper mineralization in A‐type granitoids from the Precambrian shield of the Karbi Hills (Mikir Hills), NE India. The prospective zone lies in the Kuthori‐Bagori of Kaziranga locality of the north Karbi Hills. The host granitoids are characterized by intermediate to high SiO2 (66.30–72.97 wt.%), Na2O (up to 4.90 wt.%), Ba (up to 1,943 ppm), Zr (up to 410 ppm), Y (up to 70 ppm) and Al2O3 (up to 14.77 wt.%) with low concentrations of CaO (up to 1.53 wt.%), and Cu (up to 32.41 ppm) which suggest a consistent granodiorite‐monzogranite host composition, an intraplate emplacement, A‐type chemistry, shoshonitic to high‐K calc‐alkaline and a predominant metaluminous character. Minerals in the investigated granitoids show hypogene alteration features similar to ideal porphyry style mineralization. Remnants of early chalcopyrite‐bornite‐magnetite (Magnetite‐I) veins have been preserved in the distant propylitic zone. The central core zone of potassic alteration shows the dominance of pyrite‐chalcopyrite‐magnetite (Magnetite‐II) assemblages. Mineral chemistry confirms the presence of two types of magnetites: magmatic (Mag‐I) and hydrothermal (Mag‐II). Mag‐I is octahedral, less commonly cubic, or irregular. It has a porous core with trellis‐type ilmenite exsolution lamellae. Mag‐II is non‐porous, devoid of ilmenite exsolution lamellae, has irregular to distinctly octahedral crystal habit and contains micro‐inclusions of pyrite, chalcopyrite, aluminosilicates, manganite and apatite. The progressive chemical purification of igneous magnetite, exacerbated by hydrothermal re‐equilibration, has resulted in a significant reduction in trace element contents such as Ti, Al, Mg, Zn and Cr, and a significant increase in iron content from 89 to ~94 wt.%. A combination of [Ni/(Cr + Mn) vs. Ti + V], and [(Ca + Al + Mn) vs. Ti + V] variation diagrams and upper threshold concentrations for the Kuthori‐Bagori ore effectively separates Mag‐I and Mag‐II. Our field, petrographic and geochemical data indicate that the Kuthori‐Bagori of Kaziranga granitoid of the Karbi Hills (Mikir Hills) in NE India is an ideal location for porphyry copper mineralization. [ABSTRACT FROM AUTHOR]

Among several devastating natural hazards, flooding is a common and serious threat to society causing huge loss of lives, properties, and infrastructure throughout the world. The intensity and frequency of this extreme weather event are expected to increase due to significant changes in the present‐day climate and land use and land cover (LULC) pattern. India has a very systematic and organized structural program and policies but lacks proper implementations, and adverse effect of climate change and the extreme event goes on in society. This paper is an analysis of floods in India and hazards due to climate change and LULC change patterns. Three models, namely "Eco‐biogeography‐based optimization (EBO), Random forest (RF), and Support vector machine (SVM)" were used to obtain the final output to prepare a "Flood susceptibility map". The result was validated through the "Receiver operating characteristics (ROC)" with "Area under curve (AUC)" values. The future rainfall scenario has been estimated by considering the "General circulation models" through different "shared socioeconomic pathways (SSPs)". The values of AUC are 0.915 (EBO), 0.887 (RF), and 0.869 (SVM), respectively. After consideration of different SSPs, the result shows that there is an increasing tendency of flood hazards in the projected period. Among all the employed modelling approaches, the EBO model has notable potential in delineating the possible flood‐prone regions for effective flood planning and management. Decision‐makers can benefit from country‐specific information and regional planner to implement sustainable and long‐term measures to overcome this type of hazardous situation. [ABSTRACT FROM AUTHOR]

Studying granitoids can provide important knowledge on the composition of continental crust and the geodynamic processes of continental growth. Nevertheless, the mechanisms of granitoids formation during continental collision remain uncertain. In this paper, we present new zircon U–Pb–Hf isotope and whole‐rock Sr–Nd isotope compositions, and major‐ and trace‐element data for granitoids from the Chacangka area of the central Lhasa Terrane, southern Tibet. The Chacangka quartz monzonites crystallized at ca. 61 Ma, whereas the monzonites and granites were emplaced at ca. 51 Ma. The quartz monzonites are peraluminous and have high 87Sr/86Sri ratios (0.7129–0.7131), and their low εNd(t) (−7.65 to −7.10) and zircon εHf(t) (−9.3 to −7.5) values are more depleted than those of ancient crustal basement beneath the central Lhasa Terrane, which suggests that they originated from a mixed source of juvenile and ancient lower crust. Compared with the quartz monzonites, the monzonites have much higher contents of MgO (2.34–3.62 wt%) and values of Mg# (42.3–46.3) and zircon εHf(t) (−6.9 to 1.9) and show more depleted Sr–Nd isotopes, indicating that more juvenile materials were involved in their source. The granites have Sr–Nd isotope compositions that are similar to those of the coeval monzonites but have higher SiO2 contents, lower CaO and MgO contents, and lower values of Mg#, suggesting that they were differentiates of the monzonites. The elemental and isotopic compositions of the Chacangka granitoids exhibit a marked transformation from 61 to 51 Ma, probably indicating breakoff of the Neo‐Tethyan oceanic slab. The Neo‐Tethyan slab breakoff not only induced the upwelling of deep material and eruption of magma but also caused re‐melting and destruction of ancient crustal basement of the central Lhasa Terrane. [ABSTRACT FROM AUTHOR]

The Mahanadi river basin (MRB) is one of the eight major fluvial basins of India. This paper presents a very first systematic study of geochemical characteristics, including rare earth elements of surface sediments collected from the riverbed at different parts of this basin to infer the chemical weathering, provenance, and tectonic settings. Lower mean values of major elements (except for SiO2 and K2O) are observed compared with that of the upper continental crust (UCC). It is attributed to the dominance of quartz and orthoclase in sediments and removal of mobile elements from the sediment during the transportation. The concentrations of Rb, Ba, Cu, Th, and Pb are elevated with respect to the UCC. The higher concentration of K2O and Rb, the ratio of Al2O3 to TiO2, and other bivariant plots indicate that the sediments are derived mostly from acidic to intermediate igneous rock. Majority of the sediments have geochemical similarity with the arkose and litharenite sandstones. The chemical index of alteration (CIA) values of the MRB sediments varies between 52 and 69 with most of the samples having CIA < 60 suggesting the lower degree of weathering which is further supported by the mineralogy. The eroded sediments have compositional maturity comparable to sediments deposited under semi‐arid climatic conditions. Sediments show both positive and negative Eu anomalies based on the source rock. Based on the commonly used discrimination diagrams, it is concluded that the MRB has a tectonic setting similar to the passive continental margin. [ABSTRACT FROM AUTHOR]

The Singhbhum cratonic block, eastern India, unlike other Indian cratonic blocks, bears a continuous geological record from the Palaeoarchaean to Mesoproterozoic. The Palaeoarchaean Iron Ore Group of rocks are exposed along three distinct belts (the eastern, western, and southern) encircling the Singhbhum granitoids. The economic geological aspects of the BIF and the gold mineralization aspects of the quartz‐pebble conglomerates of the Eastern Iron Ore Group (EIOG) have been discussed by a number of authors. Komatiites and basalts of the EIOG have been studied by earlier authors. However, no effort has yet been made to infer the volcano‐sedimentary processes in the Eastern Iron Ore belt. This paper presents a brief overview of the sedimentation and magmatic processes in the EIOG belt. The EIOG sedimentary succession is characterized by a basal terrestrial to shallow marine deposits that progressively became deeper up section. The EIOG clastics bear carbonaceous matter. The basal terrestrial deposits (conglomerate‐sandstone association) of the EIOG provide a rare opportunity to undertake fluvial architectural analysis and may enable us to unlock the peculiarities of Palaeoarchaean fluvial systems. [ABSTRACT FROM AUTHOR]

The spatial and temporal association between lamprophyres and kimberlites provides unique opportunities to explore their genetic relationships. This paper explores such a relationship by detailing mineralogical and geochemical aspects of Korakkodu lamprophyre dykes located within the well‐known Mesoproterozoic diamondiferous Wajrakarur Kimberlite field (WKF), towards the south‐western margin of Paleo–Mesoproterozoic Cuddapah Basin, Eastern Dharwar Craton, southern India. Mineralogy reveals that these dykes belong to calc‐alkaline variety of lamprophyres, but their geochemistry display mixed signals of both alkaline and calc‐alkaline lamprophyres. These lamprophyres are highly potassic, and their high Al2O3 and low‐TiO2 content implies a shoshonitic character. Low Mg#, Ni, and Cr concentration highlight their evolved nature. High (La/Yb)N and (Gd/Yb)N content is consistent with their derivation from low degrees of partial melting, whereas highly fractionated nature suggests the presence of garnet in their source. Absence of prominent Nb‐Ta anomaly implies to the dilution of lithospheric mantle source by melts rich in HFSEs and low La/Nb ratio compared to those of the calc‐alkaline island arc volcanics and suggests an asthenospheric overprint on lithospheric mantle source. Carbonatite metasomatism in the source region of these lamprophyres is apparent from conspicuously high‐Zr/Hf ratio, and the HFSE budget of these lamprophyres are principally controlled by the presence of phlogopite veins in their lithospheric source. An extremely heterogeneous and layered lithospheric mantle beneath Eastern Dharwar Craton has been inferred from the divergent genetic history of Mesoproterozoic lamprophyres and kimberlites in the Wajrakarur field. [ABSTRACT FROM AUTHOR]

The Bangong–Nujiang Suture Zone (BNSZ) is one of the main suture zones in the Tibetan Plateau and indicates the existence of the Bangong–Nujiang Neo‐Tethys Ocean (BNO). It was formed by the collision between the Qiangtang and Lhasa blocks after the closure of the BNO. However, its evolutionary processes and subduction polarity remain controversial. Research on the BNSZ is of great significance for exploring plate tectonic evolution and ocean–continent connection. The scarcity of the BNSZ structural data is one of the most important reasons for the debate of the BNO tectonic evolution. Based on structural analysis in the field and combined with previous petrology and palaeomagnetic data, this paper has determined that the closure time of the BNO is progressive and scissor‐like, from Middle Jurassic in the east to Early Cretaceous in the middle and late Early Cretaceous to early Late Cretaceous in the west. There was a three‐stage deformation in the BNSZ: (a) N–S‐directed compression induced by the initial collision; (b) WNW–directed transpression related to the stress adjustment; and (c) NE–SW‐directed compression caused by the low‐angle NE‐directed subduction of the Indus–Yarlung Zangbo Ocean. The different structural pattern along the eastern segment of the BNSZ may have resulted from orogenic bending due to the later Himalayan Orocline caused by the India–Eurasia collision in the Cenozoic. [ABSTRACT FROM AUTHOR]

This paper presents the sedimentological analysis of about 1.3 km succession of Neogene Siwalik Group exposed in the Gish River section, Darjeeling foothills. Contrary to the existing alluvial fan‐braided stream depositional model, the facies analysis shows that the succession accumulated in a shallow marine deltaic setting. Nine facies identified represent deposition from various processes related to unidirectional and oscillatory current, suspension settlement in quiet water and also to processes related to soil formation. Abundant trace fossils of marine affinity occur throughout the succession and include Cylindrichnus, Rosselia, Teichichnus, Rhizocorallium, Chondrites and Zoophycos. The studied succession has been subdivided into seven facies associations that can be interpreted in terms of the different sub‐environments of a river‐dominated delta. The lower ~550 m of the succession comprises sand–mud alternation of delta front, delta mouth and delta plain deposits (FA3, 4, 5 and 6), organized in stacked, 10–30 m coarsening‐upward units, and is inferred to represent progradation of the delta lobes. The overlying 300 m mud‐dominated interval is dominated by prodelta to open marine bay‐fill succession (FA1 and 2); the pebbly sandstones and conglomerates of the uppermost ~500 m represent a braidplain delta environment. A kilometre‐scale coarsening‐upward trend of the Siwalik deposits of this section is attributable to southward propagation of the thrust front related to the activity of the Main Boundary Thrust (MBT). The sedimentological analysis shows that a marine embayment existed in the Eastern Himalaya during the Siwalik time and the deltaic succession reported here provides the link between the upland transverse drainages recorded from Western Himalaya and the deep marine Bengal Fan succession. Copyright © 2017 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Detailed facies architecture study of the Late Cretaceous (Cenomanian) Nimar Sandstone (Bagh Group), from Son-Narmada rift valley, Central India, reveals deposition in a fluvial-marine environment. The lower part of the Nimar Sandstone succession depicts deposition in predominantly fluvial setting, whereas the middle-upper part of the succession manifests sedimentation under a tide-dominated estuarine to a tide-wave influenced shoreface environment. Retrogradational nature of the successions in the upper part and lateral facies change from west to east signifies an eastwardly decreasing marine influence. This attests to a sustained event of marine transgression from the west affecting the Son-Narmada rift valley during the Late Cretaceous time. Beds with various soft-sediment deformation structures (SSDS), viz., convolute laminae, load and flame structures, pseudonodules, contorted beddings, syn-sedimentary faults, and sand/silt dykes, occur in distinct stratigraphic levels within the middle part of the succession. These beds are separated by thick successions of undeformed beds. This paper reports these beds as seismites for the first time from the Son-Narmada rift valley. The seismites signify instantaneous liquefaction and fluidization of unconsolidated sediments triggered by passage of repetitive earthquake shock waves during sedimentation in fault-bound rift basin. These seismites are important as they mark a new phase of reactivation of the Son-Narmada South Fault within the Son-Narmada rift valley during the Cenomanian time. This reactivation of the Son-Narmada South Fault led to basinal subsidence under prevalent extensional tectonism, which controlled the sedimentation during the Late Cretaceous time. Copyright © 2016 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Petrographic, whole‐rock geochemical and geochronological analysis of polymictic conglomerate, associated siltstone and greywacke in the Neoarchean Gadag Greenstone Belt in the Western Dharwar Craton, India, provides new insights into sedimentary provenance and tectonic setting. The polymictic conglomerate contains granitic, gneissic, felsic and mafic volcanic, quartzite and banded ferruginous chert clasts within a quartzo‐feldspathic matrix. Framework grains in the siltstone and greywacke are quartz, feldspar with rock fragments, embedded in a chlorite‐dominant matrix. The chemical index of alteration values (~70) and A‐CN‐K plot for the rocks suggest a low‐to‐moderate degree of weathering. Rare earth element (REE) patterns show moderate fractionation (LaN/YbN ~ 12.31) with a weak negative europium anomaly (0.82). Enrichment in transition elements (Ni, Cr, Co, Sc) and depletion in high‐field‐strength elements, as well as relatively low La/Co (0.62), moderate to high Th/Yb (3.06), La/Th (5.16), La/Yb (17.5), and La/Sc (~2.37) ratios, suggest a mixed felsic‐mafic provenance. U–Pb dating of detrital zircon from the conglomerate and greywacke revealed major age peaks at ca. (3.2, 2.9, 2.8, 2.6, 2.5 Ga) and a maximum age of deposition of 2,508 ± 26 Ma, 2,493 ± 20 Ma, respectively. The above data suggest low to moderately weathered proximal sources for both conglomerate and greywacke, indicating that these two rock types were not deposited simultaneously, but rather separately. The association of these conglomerates and greywacke with continental arc‐related volcanics indicates the closing of an arc at the time of sedimentation. Complex provenance consisting of recycled and magmatic arc during basin closure confirm the notion of modern style plate tectonics operating during Neoarchaean. [ABSTRACT FROM AUTHOR]

In this study, textural relations coupled with mineral chemistry of hydrothermal magnetite, fluorapatite, monazite and allanite from the Mohuldih uranium deposit in the Singhbhum Shear Zone (SSZ) is used to characterize the nature of the fluid during various events of alteration and uranium precipitation. These minerals have two distinct textural types, the earlier of which are coeval with the uraninite mineralization. The later type formed during subsequent hydrothermal overprint as a result of coupled dissolution‐reprecipitation of earlier fluorapatite and mobilization of light rare earth elements. Uranium‐lead dating of texturally‐constrained hydrothermal monazite grains yields two major concordant age clusters at 1855 ± 7 Ma and 963 ± 10 Ma and several discordant analyses. Two spot analyses furnish concordant ages of 1656 ± 33 Ma and 1438 ± 35 Ma that are identical within error of the 207Pb/206Pb ages (1628–1643 Ma and ca. 1392 Ma) of several discordant data points. Similar ages have been reported by other studies from the rocks of the SSZ and are therefore considered to be geologically meaningful. The oldest age of ca. 1855 Ma obtained from the texturally early core regions of monazite corresponds to the earliest stage of uraninite mineralization. The two main alteration types can be interpreted based on the known metamorphic events in the SSZ. A combination of high‐temperature calcic iron ± sodic and high‐temperature potassic iron alteration accompanied the M1 metamorphic event and the low‐temperature silicification/K‐Al alteration during the M2 metamorphic event. A comparative study between our data on magnetite and fluorapatite compositions with those from global iron oxide‐Cu‐gold (IOCG) and iron oxide‐apatite deposits classifies Mohuldih as an IOCG‐type deposit. [ABSTRACT FROM AUTHOR]

Packages of fluvial systems in the Lower Ganga plains (LGP) archive the changes in stratigraphic architecture induced by perturbations in the climatic system. In some parts of this landscape, where the fluvial sequences predominate, the role of climate in landsculpting is strongly indicated by the presence of sediment architecture. The present study is focused on the formation of alluvial plains of the Ajay River in the Rarh region that represent a region's environmental templates for understanding the landscape of LGP. The sedimentological, geomorphological, and optically stimulated luminescence (OSL) chronological investigations were attempted to document sedimentation patterns and the timing of deposition. The stratigraphic data from two exposed cliff sections and three boreholes are compared with proxy records to understand the Indian Summer Monsoon (ISM) controls on alluvial sedimentation for the last ~2.4 ka. The fluvial packages in the study area correspond to two significant channel phases: Period‐I (2.4–1.3 ka) and Period‐II (800–200 years ago). Period‐I is characterized by the episodes of floodplain development and lateral migration of the trunk river during Marine Isotope Stage (MIS) I, especially around 2 ka corresponding to the Roman Warm (RW) period in the Indian subcontinent. The sediment filling was high during ~2.4 ka due to ISM intensification, but in the later stage, the sedimentation was at a fairly steady rate. Conversely, Period‐II is characterized by flooding phenomena and aggradation of channel bodies across much of the present valley area during the last 800 years. The distinct flood events occurred during the times of significant shifts in ISM, from fluvial dormancy to sudden outbursts of monsoons (end of Little Ice Age [LIA] ~ 19th century), indicating that climatic patterns can be associated with the occurrences of abrupt flood events. The alluvial records fit well with the historical, instrumental, and published proxy data on the ISM validating the chronology and the potential of sedimentary archives for further studies related to the palaeoenvironment and palaeogeography. [ABSTRACT FROM AUTHOR]

The Zn‐Cd‐S critical minerals system is a significant mineralogical indicator of hydrothermal ore‐forming processes. The understanding of greenockite (CdS) formation in natural mineral systems is very restricted due to low crustal abundances (Cd <0.2 ppm). We report the first occurrence of greenockite from the Bagada orogenic gold prospect, Paleoproterozoic Mahakoshal belt, Central Indian Tectonic Zone (CITZ). This provides an ideal opportunity to access the occurrence and its genesis. Greenockite occurs in discrete sheared quartz veins hosted in phyllites. Sulphide mineralization is closely associated with hydrothermal chlorite alterations. Pyrrhotite, arsenopyrite, pyrite, and chalcopyrite assemblages are formed at high temperatures, while sphalerite and galena precipitated when the temperature decreased. Greenockite, native silver and bismuth with gold precipitated during the breakdown of arsenopyrite to scorodite in progressively oxidizing conditions. Greenockite precipitation occurred in a transforming hydrothermal environment from a reducing to an oxidizing one during late‐stage hydrothermal alteration. Sphalerite and chlorite thermometry yielded temperatures in the range from 266 to 366°C for this late‐stage hydrothermal alteration. Textural relations show two modes of occurrence of greenockite, one (Gck‐1) as exsolution within sphalerite (Sp‐2) and the other (Gck‐2) occurring as a discontinuous rim replacing the Cd‐rich sphalerite (Sp‐3). The Gck‐1 contains high Zn and low Cd, while as compared to Gck‐2. Zinc and Cd in greenockite show diadochy relation (Zn2+ ↔ Cd2+). Laser ablation ICPMS analyses of sphalerite (Sp‐2) reveal remarkably high Cd contents (1.9–12 wt%). Cd >0.02 ppm suggests possible Cd derivation from sphalerite (Sp‐2) under variable fS2, T, pH, fO2 conditions, fluid–rock interaction, and change in the Zn/Cd ratio. Sphalerite compositions display a low Zn/Cd (av.22) ratio and high temperature of formation, with characteristics intermediate between volcanogenic massive sulphides (VMS) and magmatic‐hydrothermal Cu‐Pb‐Zn system. [ABSTRACT FROM AUTHOR]

The Narmada‐Son lineament is a major tectonic feature in Central India. Here we employ data from geodetic measurements of crustal deformation and upper mantle P‐wave travel time tomography and propose that the Narmada‐Son palaeo‐rift is a present‐day diffuse plate boundary that segments the continental part of the Indian "composite" plate into two component plates, the North and South‐Indian plate. Tomographic images reveal that the collision of an indenter, associated with the relatively faster moving South‐Indian plate, with the Narmada‐Son diffuse plate boundary acted as a pivot point exerting a torque on one of the component plates along with mechanical rotation. This new proposal along with a new identity of the Narmada‐Son diffuse plate boundary is in better agreement with the estimated location of the relative Euler pole across two respective component plates. Our model is also able to better explain the Indian "composite" plate hypothesis, diversity in the topographic architecture along the rift, and contrasting deformation styles on either side of the diffuse plate boundary. [ABSTRACT FROM AUTHOR]

The Raageshwari Volcanic Formation (RVF) is a volcanic complex in the southern part of the Barmer Basin, NW India, localized around a large rift centre horst block, the Central Basin High. The RVF comprises an initial sequence of acid igneous rocks, which are of ignimbritic origin, termed the Agni Member, overlain by a stacked sequence of basaltic lava flows interbedded with subordinate pyroclastic deposits, the Prithvi Member. Seismic data confirms that the volcanic complex has a conical overall geometry and a layered internal structure produced by successive and extensive flows of basalt and ignimbrite, very similar to that observed in the main Deccan lava outcrops along the western margin of India. U–Pb zircon ages near the top of the Agni Member in the Raageshwari‐26 well give an age of 68+/−2 Ma for a tephrite pyroclastic unit, whilst Ar–Ar analysis of a distal basalt containing phenocrysts of biotite from the Saraswati‐4 well gave an older robust Ar–Ar plateau age of 73.7 ± 1.4 Ma. A typical Deccan age of 67.9 ± 1.7 Ma was obtained from the isolated unaltered basaltic andesite in well NE‐South‐1. Due to depositional on‐lap onto the Central Basin High, the overlying alluvial Dandlawas and Fatehgarh formations are absent on the crest of the Central Basin High and Barmer Hill Formation lake sediments rest directly on the basalts. This relationship indicates that the volcanic cone was a structural or topographic high during deposition onto which the Fatehgarh and Barmer Hill formations lake sediments eventually on‐lapped. The RVF of the Barmer Basin along with the Deccan volcanics in the Cambay Basin, Narmada Rift and in Saurasthra are all developed within fault‐bounded rift basins, in which deep seated faults extend beneath the Deccan volcanic sequence. They are associated with thermal anomalies and thinned continental crust and the presence of a linear low velocity zone at ~100 km depth in the upper mantle region beneath the Barmer and Cambay basins. This is interpreted to be the position of the "conduit" through which plume head material passed through the upper mantle before arriving at the base of the Indian lithosphere. The RVF therefore appears to be an early eruption of differentiated ultrabasic magma from a shallow, secondary magma chamber produced by partial crustal melting. [ABSTRACT FROM AUTHOR]

The Cenozoic Himalayan Orogeny is a manifestation of subduction and subsequent collision of the Indian lithosphere with the Asian Plate in the Eocene, resulting in the formation of intra‐terrane shear zones and regional metamorphic belt along the strike of the entire orogen. This metamorphic belt contains high‐pressure (HP) metamorphic rocks (garnet‐amphibolite, late‐stage granulite, and host gneisses) at various structural levels in the Himalayas. In the present study, we carried out geochemical, chronological, and metamorphic modelling of an exotic tschermakite‐bearing garnet‐amphibolite unit exposed within the Tethyan Himalayan Sequence of Western Garhwal Himalaya of India. Bulk‐rock geochemistry suggests the protolith's tholeiitic fractionation trend and trachy‐andesitic nature. U–Pb geochronology of zircon reveals an age spectrum with pronounced clusters at ~1,550 Ma, ~1,350 Ma, 1,100–1,150 Ma, 900–930 Ma, and ~550 Ma. There is a possibility that the protolith of the HP garnet amphibolite is magmatic. However, near‐concordant ages at certain intervals might suggest crustal components from multiple sources. Integrated geothermobarometry and P–T pseudosection modelling indicate high‐P/medium‐T conditions (~1.65 GPa and 650°C) of peak metamorphism. Based on these results, we infer that this garnet‐amphibolite represents pre‐Himalayan Indian lower crust and during India–Asia collision. The leading edge of the Indian continental lithosphere subducted where mafic and some of the felsic lithologies underwent HP garnet‐amphibolite facies metamorphism, and after a possible slab break‐off, these rocks exhumed during the Himalayan orogeny. [ABSTRACT FROM AUTHOR]

Regular monitoring of drought events, watershed characterization, management, and development efforts is crucial for future disaster predictions and mitigation strategies. The drought susceptibility investigation has been carried out in the Ken River Basin of Bundelkhand region, one of the most drought‐prone areas in India. Proxies used in the present study are long‐term climatological data (rainfall, standardized precipitation index, and aridity index), satellite data (slope, drainage density [DD], distance to river, and normalized difference vegetation index), lithology, lineament density, and groundwater depth. By the analytical hierarchy process, weightage of each factor is assigned according to its importance. Study shows that nearly 48% of the area of the basin experiences moderate to severe drought conditions. In the last five decades, there have been 22 years of extreme drought, with the most extended period being 1972–1974 and the driest year being 2006–2007. Sensitivity analysis reveals that lithology, slope, and DD are the most significant parameters in the susceptibility analysis. Model validation through an artificial neural network demonstrates the model's high accuracy (0.9) and sensitivity with minor errors. An integrated study of drought susceptibility and morphometry is useful for identifying the drought risk hotspots in the basin. The investigation will be helpful in river basin management and disaster management strategies. [ABSTRACT FROM AUTHOR]

Geochemical study in the siliciclastic sediments of a basin provides an understanding of palaeoclimate, provenance and subsequently, it can be used to reconstruct the palaeo‐tectonics and evolution of the basin. Sedimentation in the Gondwana basins, worldwide, generally provides a record of climatic fluctuations and evidences of the Permo‐Triassic mass extinction. In spite of its global importance, our knowledge about the nature of sedimentation, basin development and conceptual regional tectonic model in the Satpura Basin, one of the Gondwana basins of India is limited. Major and trace element concentrations of the mudstones from the Denwa Formation along with the existing geochemical data of other formations are studied here for establishing a comprehensive idea about the palaeoclimate, tectonic settings, provenance and basin evolution. The composition of the sediments in the lowermost Talchir Formation revealed cold and dry climatic conditions at the sources, whereas the sources of the sediments for the overlying formations have experienced warm, humid and semiarid climates. The contributions of the mafic rock‐derived sediments are relatively higher in the Talchir, Barakar and Motur formations compared to the overlying formations. Approximately 60% of the sediments in the overlying Bijori, Pachmarhi and Denwa formations were derived from the felsic volcanic rocks and granites of the Sausar Mobile Belt and Betul‐Chindwara Mobile Belt (BCMB) with minor inputs from mafic volcanic rocks of the BCMB. Furthermore, the sediments of the Talchir Formation were derived from the BCMB when they became tectonically active, whereas the sediments in the younger formations have been derived from a passive tectonic setting. [ABSTRACT FROM AUTHOR]

We present the stable carbon (δ13C) and oxygen (δ18O) isotopic composition of 75 serial samples (tooth enamels) from five mammalian fossil groups, which include giraffids, equids, bovids, tragulids, and suids, to reconstruct their diet and habitat. These mammalian faunas were recovered from a late Miocene Middle Siwalik succession exposed in Nurpur, Himachal Pradesh, India (8.14–5.26 Ma). The average δ13C data of the studied mammals, that is, −13.30 ± 0.71 (giraffids), −11.29 ± 0.63 (equids), −12.68 ± 0.49‰ (bovids), −12.97 ± 1.11 (tragulids), and −12.01 ± 0.47 (suids) indicates a mainly C3 diet with a minor component of C4 grass (up to 17%) and a habitat dominant by forest/woodland. The average δ18O value of giraffids (−5.83 ± 0.85) is slightly enriched as compared to other herbivore mammals, such as equids (−8.85 ± 1.71), bovids (−7.86 ± 0.62‰), tragulids (−8.26 ± 1.92), and suids (−10.65 ± 0.23). It suggests that the browsing giraffids could likely intake water from enriched 18O sources, whereas the other browsing mammals consume water from depleted 18O sources in the local ecosystem. However, the δ18O values indicate the existence of a warm, humid climate and more precipitation in the Siwalik during the late Miocene. [ABSTRACT FROM AUTHOR]

The carbonates of the Dodguni area of the Chitradurga greenstone belt, Dharwar Craton, India were studied to understand the Archean diagenetic and palaeo‐depositional conditions using carbon and oxygen isotopes along with whole‐rock geochemistry. These carbonates show significant variation in δ13C and δ18O (−1.73‰ Vienna Peedee Belemnite [VPDB] to −0.45‰ VPDB and δ18O vary from −13.51‰ VPDB to −8.46‰ VPDB, respectively). The rare earth element (REE) + Y (rare earth elements and yttrium) of the studied carbonate rocks exhibit flat and uniform patterns (PrSN/YbSN = 0.4–1), slight positive La, Eu and Gd anomalies (CeSN/CeSN* = 0.8–0.9; EuSN/EuSN* = 0.7–1.4 and GdSN/GdSN* = 2–2.3, respectively) with slight positive Ce anomalies (PrSN/PrSN* = 0.84–0.86) and superchondritic Y/Ho ratios (Y/Ho = 29–45; chondritic Y/Ho = 28). Their negative δ13C (−1.75‰ to −0.45‰) values are attributed to the influence of higher bio‐productivity during their deposition and oxidation of organic carbon. The geochemical and isotopic systematics suggest that the Dodguni limestones are not affected by the diagenetic and metamorphic processes and record the REE geochemistry of the ancient seawater in which they were precipitated. The comprehensive geochemical including the isotopic studies of the Archean carbonate rocks of the Dharwar Craton, indicate their deposition in shallow marine conditions, precipitation in high temperatures with significant hydrothermal input under the influence of high bio‐productivity, thereby providing valuable constraints on the palaeoceanography and geochemical evolution of the Archean sea. [ABSTRACT FROM AUTHOR]

In this study, the variation in frequency magnitude distribution factor (b‐value) before the main shock has been assessed for the 26 November 2021 Mizoram earthquake (Mw 6.1) in northeast India. The study area covering the Indo‐Burma Ranges is divided into square grids of equal dimension and spatial mapping of the b‐value for each square grid has been carried out. The maximum likelihood method is implemented for the estimation of the b‐value of each grid. The epicentral location of the 26 November 2021 Mizoram earthquake (Mw 6.1) is found to be in the intermediate b‐value square grid. The temporal variation in the b‐value indicates a considerable decline in the b‐value before the occurrence of the main event. The depth‐wise variation in the b‐value suggests an antithetical relationship between the b‐value and crustal stress. The spatio‐temporal and depth‐wise fluctuation in the b‐value results have been strengthened by employing a non‐parametric Kolmogorov–Smirnov (K–S) test. Based on our study, we infer that interplate earthquakes occur mostly in the upper crust of the study region. [ABSTRACT FROM AUTHOR]

The along‐strike heterogeneity in the tectonics of Himalaya is well recognized; however, the eastern segment of Himalaya is less studied compared to the other segments. This study combines the comprehensive field data, as well as the U–Pb geochronology of sandstone samples from the Indo‐Burma Range (east India). The study shows that the Lower Disang Formation was deposited in an open marine environment with a steep gradient during the Late Cretaceous to Mid‐Eocene, accommodating the detritus solely from an Indian source. Furthermore, during the Early to Late Eocene interval, the sedimentary basin changed to a shallow marine shelf when the sediments from Himalayan as well as trans‐Himalaya were deposited. The Upper Disang Formation must have been deposited just before or during the collision process between the Indian and Asian plates. After the India‐Asian collision, there was a remnant ocean, in which the sediments of the Barail and Surma groups were deposited in the shallow marine to deltaic environments. The Tethys Ocean completely dried out in the Late Miocene resulting in a change from marine to fluvial environments, which facilitated the deposition of the sandstones of the Tipam Formation. Based on the U–Pb ages, the Palaeogene basin history in the Indo‐Burma Range was unlike the central Himalaya, that is, the detritus were mainly sourced from the Burmese Plate and adjoining magmatic rocks. [ABSTRACT FROM AUTHOR]

The increasing frequency of landslides has become a matter of concern in Nagaland, a north‐eastern state of India. Noklak town, the administrative headquarter of the Noklak district in the eastern part of Nagaland bordering Myanmar, is also affected by slope stability issues. A major landslide in 1980 caused major damage to parts of the township. The problem has grown in magnitude and influence over the last four decades, damaging an area of about 1.84 km2 and several households. Slope movements have caused immense distress to the local populace by posing a constant threat to nearly one‐fourth of the town's built‐up area, roads, and cultivated tracts. Surface instability has also hampered India's Act East policy with South‐east Asian countries by disrupting the sole motorable route to the International Trade Centre at Dan (Pangsha), between India and Myanmar. A landslide susceptibility map (LSM) was generated using the Bivariate Yule coefficient (Yc) method. The LSM delineates the study area into three categories, with 23%, 23%, and 54% in high, moderate, and low susceptible zones, respectively. This was superimposed with elements such as buildings, population, roads, and cultivated tracts to assess the effects of landslides on the population and infrastructure. From the present study, it is estimated that 334 buildings, 1235 people, 2.99 km of roads, and 8 ha of cultivated landfall lie within the moderately and highly susceptible zones. Considering the rapid developmental activities that will ensue with the recent upgradation of the subdivision to that of the district, the data generated will be useful for urban sprawl and land use planning, to minimise and mitigate the loss of life and property due to landslides. [ABSTRACT FROM AUTHOR]

The Naga Hills Ophiolite (NHO) of Late Jurassic to Eocene age is one of the well‐exposed domains of Tethyan ophiolites, located in the northern margin of the Indo‐Myanmar Orogenic Belt, north‐east India. It is composed of suites of tectonite peridotite and cumulative ultramafic, mafic intrusive‐extrusive rocks, felsic intrusive, radiolarian, and marine pelagic sediments. The mafic intrusives of the NHO exhibit rhythmic to cryptic layering and isotropic in nature. Based on their mineralogy, the mafic intrusives are identified as gabbro, gabbronorite, hornblende gabbro, and olivine gabbro. The gabbros are adcumulate and mesocumulate and essentially composed of plagioclase feldspar, clinopyroxene, orthopyroxene, hornblende, with minor olivine, serpentine, chlorite, and magnetite. These mafic intrusive rocks show affinity to tholeiitic parental magma and fractionated trends in the multi‐elemental diagram, with negative anomalies at Zr, P, Ce and positive anomalies at Sr, Nb, and Ti suggesting that the magmatism was influenced by subduction zone components. The majority of the samples represent light rare earth elements (LREE) depletion (LaN/SmN = 0.28–0.86), except two samples that display LREE enrichment (LaN/SmN = 2.11–3.03), with negligible negative Eu anomaly. Petrogenetic modelling suggests 5%–20% partial melting of a depleted mid‐ocean ridge basalt‐type mantle source, within the spinel lherzolite stability field, as well as low degree partial melting (<10%) of an enriched mantle source probably metasomatized by sediment‐melt from a subducted slab. Therefore, based on mineralogical and geochemical data, we propose that the mafic intrusive of the NHO were generated in the intra‐oceanic arc system within the Neotethys Ocean with the active participation of possible wet basaltic melt from spinel‐lherzolite source‐mantle, subsequently modified by melts derived from sediments in a subduction zone. [ABSTRACT FROM AUTHOR]

The Lichi volcanic rocks crop out along the Main Boundary Thrust (MBT) of the Arunachal Himalaya, northeast India are comprised primarily of sub‐alkaline basalt (SiO2 ranges from 48.66 to 50.62 wt%), with minor trachy‐andesite (SiO2 ranges from 57% to 61.42 wt%). The distribution of incompatible trace elements, low concentrations of large‐ion lithophile elements, and REE behaviour suggests an enriched nature of the studied rocks and limited influence of the crustal contamination during their evolution. Linear distribution trends of major oxide, consistent patterns of trace elements, and REEs on primitive mantle‐ and chondrite‐normalized diagrams suggest the cogenetic nature of mafic basaltic rocks and intermediate trachy‐andesite. The variation in Ti/Y (256.00–469.95) and Zr/Y (7.65–36.96) ratios indicates that garnet was present in the source. The well‐defined geochemical trends on variation diagram and the sub‐parallel trends on the chondrite‐normalized REE patterns suggest that fractional crystallization processes have played a major role in the evolution of parental magma. Petrogenetic modelling implies that the sub‐alkaline basalts and intermediate rocks were derived from low‐degree partial melting (1%–5%) of a garnet bearing peridotite source. The melt further evolved by fractional crystallization. We conclude that the geochemical attributes of the Lichi volcanics of the Arunachal Himalaya imply their emplacement in a continental extensional regime and possibly resulted from the Cretaceous Kerguelen plume activities. [ABSTRACT FROM AUTHOR]

A comprehensive data of whole‐rock and stable isotopic geochemistry along with microfossil assemblages of the carbonate rocks of the ophiolite mélange zone of the Indo–Myanmar orogenic Belt (IMOB), north‐east India are discussed, to determine the influence of terrigenous contamination during the formation of these carbonate rocks and also to understand their depositional environment and ages. These carbonate rocks contain a diverse fauna with the dominance of foraminiferal assemblages of planktonic foraminifera (Globotruncana sp. and Heterohelix sp., etc.) which indicates they were formed during the Santonian to Maastrichtian age. Based on chemical compositions, these carbonate rocks have been identified as limestone (CaO/MgO > 50.1) to slightly dolomitic limestone (9.1 < CaO/MgO < 50.1). Total rare earth element (REE) contents in these carbonates are variable (22.39–146.05 ppm). The Post‐Archean Australian Shale (PAAS)‐normalized REE + Y patterns of these carbonates exhibit seawater‐like REE patterns with LREE depletion and relative HREE enrichment with negative Ce anomalies (Ce/Ce* = 0.32–0.79) and positive Y (4.42–27.81 ppm) and Eu anomalies (Eu/Eu* = 1.11–1.86), suggesting that they were deposited under an oxygenated environment with contamination by hydrothermal activity. They are also depleted in δ13C 0/00 (PDB) (1.02–1.570/00) and δ18O 0/00 (PDB) (−6.37 to −9.00%) values which characterize marine precipitates. Eu anomalies and spread in negative δ18O 0/00 (PDB) values to a lesser extent of δ13C 0/00 (PDB) values of these carbonates suggest their formation was altered by diagenesis in the shallow marine environment. Our new whole‐rock and stable isotope geochemical characteristics, in conjunction with microfacies, suggest that the investigated carbonate rocks might have been formed in low‐energy environments, and deposited in neritic to bathyal palaeoenvironments during the Santonian to Maastrichtian interval. [ABSTRACT FROM AUTHOR]

The study of brittle deformation of the collisional mountains can explain its shallow crustal tectonic evolution and the palaeostress regime. The Main Boundary Thrust (MBT) zone in the western Arunachal Himalaya displays imbrication in the Permian Gondwana sequence between the MBT‐1 (/Bome Thrust/MBT‐Upper) in the north and MBT‐2 (/MBT‐Lower) in the south with consistent northerly dip. The Lower Gondwana rocks occur in the footwall of the MBT‐1 with the Proterozoic Bomdila Group in the hangingwall. The upper Gondwana rocks constitute the hangingwall sequence for the MBT‐2 with Neogene Siwalik rocks in the footwall. This article analyses palaeostress using brittle fractures in the Gondwana rocks that crop out for ~120 km2 in the study area. The fault‐bounded imbricate zone depicts eight brittle shear indicators and four sets of joints (J1 and J2: inclined and J3 and J4: subvertical). The signatures of the inherited pre‐Himalayan extensional deformation are preserved in the Lower Gondwana Miri Formation. The Bichom and Bhareli rocks exhibit brittle deformation features of the Himalayan Orogeny under strong ~N‐S compression. The palaeostress analysis of all joint sets indicates three phases of brittle deformation in the Gondwana and Siwalik rocks of the area. The subvertical joint sets and normal faults in the Miri Formation indicate a north‐northwest (NNW)‐directed extensional phase of the pre‐Himalayan origin. The inclined joint sets of the Bichom and Bhareli formations of the Gondwana sequence depict Himalayan orogeny with ~N‐S compressional phases. The third phase of brittle deformation in the Siwalik sequence depicts an east‐west (~E‐W) extension. The arc‐parallel extension in the frontal fold belt of the Arunachal Himalaya may be due to oblique India‐Asia collisional tectonics. [ABSTRACT FROM AUTHOR]

Water quality index (WQI) and irrigational indices for surface water and groundwater in the southeastern part of Manipur Valley in north‐east India has been examined. The water samples were collected during the pre‐monsoon season in the year 2016. Geologically, the Manipur Valley occurs as an intermontane piedmont‐alluvial plain filled with Quaternary alluvium of fluvio‐lacustrine origin. The basic chemical parameters of pH, total dissolved solids, electrical conductivity, total hardness, Cl−, HCO3−, Na+, Ca2+, Mg2+, Fe, Mn, and Zn were considered for computing water quality index for drinking water. Irrigational indices such as sodium absorption ratio, sodium percentage, Kelly's index, magnesium hazard, and residual sodium carbonate were calculated for determining the suitability for irrigational use. WQI, SAR, %Na+, KI, MH, RSC suggest that majority of the water samples are suitable for drinking and irrigational uses. They exhibit positive relations among them suggesting that these parameters are dependent over one another. About 20% of the piedmont zone groundwater are unsuitable for both drinking and agricultural purposes. The encrustation of gypsum, halite, and evaporite into the Disang shales enhances the dissolution process of ions such as Cl−, Na+, Ca2+, Mg2+ in the piedmont water leading to quality deterioration. Gibb's plots suggest that the chemical origin of water dominates with rock‐weathering process, while hydrochemical facies evolved from the initial stage to intermediate stage. Therefore, proper integrated management and development of water resources is necessary for the effective utilization water resources particularly around the piedmont zone. [ABSTRACT FROM AUTHOR]

The spatial distribution of the b‐value has been determined using a homogeneous earthquake catalogue from 1964 to 2018 to examine the characteristics of structural heterogeneities and their bearing on the style of faulting in the Indo‐Burma region of Northeastern India. The study region is associated with an uneven distribution of structural heterogeneities and demonstrates the mixed type of faulting, nature where the majority of earthquakes resulted mainly by thrust and strike‐slip fault. Our critical analysis demonstrates that the existence of two prominent zones is associated with high b‐values and low b‐values where the mixed type of faulting resulted in the genesis of seismicity in the study area. The high b‐values in the study area contain a large number of smaller earthquakes whilst the low b‐values comprise a smaller number of larger earthquakes distributed along with the Naga‐Disang Thrust, Kabaw Fault, and Sagaing fault systems. A close comparison between b‐values and different faulting styles reveals that the area containing a low b‐value suggests stronger seismogenic zones, where an accumulation of strain energy leads to the genesis of seismicity by thrust faulting with slight slip component whilst Indo‐Burma Ranges regions connected with b‐values (0.5–0.9) demonstrate strike‐slip to the normal mode of faulting, indicating relatively weak seismogenic zones where tensional forces are prevalent. The depth sections illustrate that lower b‐values for the upper part of the subducting slab correspond to more stress generated by tectonics compared to that of the lower part, and interestingly the deeper part of the subducting Indian slab is coupled with conspicuously very high‐b values, suggesting the weakening of the Indian subducting slab through dehydration. [ABSTRACT FROM AUTHOR]

Gahnite occurs in diverse rock types and metamorphosed mineral deposits. The gahnite geochemistry is being used as an exploration tool for zinc sulfide deposits. In the present study, the geochemistry of gahnite and associated minerals viz. sphalerite, garnet, sillimanite, staurolite, anthophyllite, biotite, ilmenite, and chlorite, and their petrography have been used in studying the genesis, metamorphic evolution, deposit characterization, and exploration significance of seven Palaeoproterozoic volcanogenic massive sulfides (VMS) deposits in the Betul belt in the Central Indian Tectonic Zone, India. Different textural types of gahnites are recognized in the Betul belt. Field investigations of textural and geochemical characteristics suggest that the gahnites were formed by multiple geological processes: desulfidation of sphalerite, breakdown of almandine garnet, and zincian staurolite, and chloritization of zincian biotite corresponding with regional metamorphism. The temperature conditions of gahnite formation are estimated to be ~600–650°C using empirical Ti in biotite thermometry. The elemental concentrations in gahnites vary from Zn/Fe ratio 2–4; Co 1–30 ppm; Ga 14–573 ppm and Mn 126–3422 ppm, indicating that bimodal volcanics and volcano‐sedimentary rocks as protolith. High Mn content in gahnite suggests an influx of magmatic‐hydrothermal fluid in the protolith. Variations of trace elements (Mg vs. Al/V, Ti vs. Co/Mn, Co vs. V/Ga, Mn vs. Zn/Fe) and high‐temperature of gahnite formation attest to sensu stricto VMS type mineralization in Betul belt, which is entirely different from SEDEX, Broken Hill‐type, and non‐sulfide deposits. Principal component analysis of trace elements shows the geochemical variations at a few deposits and reveals that gahnites were formed as a result of the competing effect of fS2‐fO2 and governed by bulk rock composition. [ABSTRACT FROM AUTHOR]

The Jhilmili intertrappean beds (Chhindwara District, Madhya Pradesh) of Central India are studied from a palaeoenvironmental, palaeoecological, and palaeobiogeographical perspective using fossil charophytes. These beds have yielded a diverse charophyte assemblage, consisting of Platychara perlata, Platychara raoi, Platychara sahnii, Peckichara cf. varians, Nemegtichara cf. grambasti, and Chara sp. 1. These charophytes were recovered from a 60 cm thick clayey and nodular limestone unit that is underlain by claystone and overlain by laminated claystones deposited on fluvial floodplains. This charophyte assemblage suggests a Late Cretaceous–Early Danian age, which agrees with the previous dating carried out using freshwater to brackish water ostracods and planktic foraminifera found in the same beds, together with dasycladalean and halimedacean chlorophytes. The Jhilmili intertrappean charophyte assemblage resembles those found in other infra‐and intertrappean sections of western, central, and southern India. The charophyte assemblage indicates that during the Cretaceous–Palaeogene timespan the Indian subcontinent mainly experienced interchange with Laurasia (China, Europe, and North America) but also with Gondwana (North Africa and South America). In the opposite sense, Laurasian species might have dispersed to India by means of a sweepstakes route across the Kohistan–Dras volcanic arcs. [ABSTRACT FROM AUTHOR]

The Southern Granulite Terrane (SGT) in India hosts granulite facies rocks metamorphosed at ultra‐high temperature (UHT) conditions in the various crustal blocks, as well as within the Palghat‐Cauvery Suture Zone (PCSZ), that is considered as a trace of the Late Neoproterozoic—Cambrian Gondwana suture. Here we investigate UHT granulites from the northern margin of the Madurai Block adjacent to the PCSZ where Mg‐Al‐rich granulites are exposed. We identify sodic gedrite + kyanite in these rocks as the high‐pressure prograde stage assemblage, followed by sillimanite‐garnet‐orthopyroxene that formed during pressure decrease and temperature increase. The rare remnant gedrite is also stable at the near‐peak UHT metamorphism until it was replaced by sapphirine. The rocks subsequently underwent decompression that formed sapphirine + cordierite and sapphirine + plagioclase symplectite around sillimanite. Dehydration during decompression generated orthopyroxene‐sillimanite‐quartz assemblage with the appearance of sapphirine, defining the diagnostic mineral assemblage indicative of peak UHT metamorphism (T > 900°C) at relatively high‐pressure (P > 9 kbar). The UHT peak metamorphism in this region is consistent with the results of P–T calculations using conventional geothermometers and phase equilibrium modelling (T up to 1,050°C, P over12 kbar). Zircon and monazite geochronology on the UHT metapelites indicate distinct stages. Detrital zircon grains in the metasediments indicate protolith from ca. 2.5 Ga igneous source and the metamorphic overgrowths yield 206Pb/238U mean ages concentrated at ca. 550–520 Ma. Monazite ages define another younger group 206Pb/238U mean ages at ca. 450 Ma. The prograde high‐pressure granulite‐facies metamorphism and following UHT event correlate with the subduction‐collision tectonics at 550–500 Ma associated with the final stage of amalgamation of the Gondwana supercontinent, while the 420–460 Ma monazite age records a later hydration at the post‐orogenic stage, possibly associated with deep shearing and fluid influx. [ABSTRACT FROM AUTHOR]

The spatially widely distributed and temporally protracted Santonian–Campanian stratigraphic records of the Sillakkudi Formation of the Ariyalur Group, Cauvery Basin, southern India represent an onland exposure of a Gilbert‐type delta. Here, we present geochemical, mineralogical, and petrographic analyses of two composite stratigraphic sections, and evaluate the climatic, tectonic, and other factors that contributed to the spatio‐emporal uniqueness of this formation. A range of low to intensive weathering, simultaneous exhumation/erosion, physical transport, and chemical weathering, prevalent at different parts of the source region and or the existence of multiple channels that drained varied source regions and hence varied lithologies at exhumation surfaces which in turn experienced seasonally varied flow conditions were interpreted. The prevalence of physical erosion during the initial stages of the deposition of the Sillakkudi Formation that progressed towards higher intensities of chemical weathering, in tune with the increase in atmospheric temperature and sea‐level rise during the later stages of the formation, is evidenced. Occurrences of positive and negative Eu anomalies and a progression from active to passive tectonic setting of samples, concomitant with change from tectonic control to relative sea‐level and the sediment influx controlled nature of deposition from Santonian–Campanian is recorded. Together, three sets of related factors namely, tectonics, increase of atmospheric temperature and sea‐level rise operated independently, and the enforced transience of transformation of the source terrain from active to passive margin, the transformation of depositional setting from fluvial to estuarine/intertidal to open marine, and shifting of principal loci of deposition from onland to offshore, are documented. The causal link between the progressive increase of sea‐level control over the depositional system during the Santonian–Campanian as recorded by this study could be due to the rise in atmospheric temperature that in turn might have been influenced by the movement of the Indian Plate from low latitudes towards the equatorial region. The second implication of the results is that the studies attempting to document tectonic setting, provenance, and weathering, with the help of geochemical discriminant diagrams, should also consider the spatial and temporal changes in the source area as well as depositional setting. [ABSTRACT FROM AUTHOR]

Vermiculite, a clay mineral of economic importance, is reported for the first time from the Bundelkhand Craton. The locales of the vermiculite occurrence are mapped within the Bundelkhand granitoids at several places. The identification of the fracture system and the zones of strain localization within Bundelkhand granitoids are critical for targeting the occurrences of vermiculite. A range of studies including meso‐, micro‐, and sub‐microscopic analyses were used to delineate the characteristic features of vermiculite along the brittle/ductile shear zones in the Bundelkhand Craton. SEM‐based EDS, EPMA, and XRD analyses confirm the ubiquitous dominance of vermiculite as fracture infills and/or channel infill materials along the zones of nucleation of ductile shear zones. It is postulated here that the occurrence of vermiculite is a result of supergene alteration of biotite present in the vein material. The parent material of the fracture infills from which the veins crystallized is genetically derived from the host rock (Bundelkhand granitoid), which later healed the fractures and prompted the nucleation of ductile shear zones in the Bundelkhand Craton. [ABSTRACT FROM AUTHOR]

To understand the palaeoenvironmental changes during the Middle to Late Holocene period, we have carried out multiproxy analysis integrating ichnology, geochemistry, and sedimentology in the Great Rann of Kachchh (GRK). The exposed cliff sections of Rann sediments and overlying Bet sediments are explored and analysed for the characteristics of the sedimentary sequences and ichnological assemblages. Seven recurring ichnotaxa are documented, which comprise of Arenicolites, Paleophycus, Planolites, Psilonichnus, Skolithos, Teichichnus, and Thalassinoides. The ichnological and sedimentological findings were supported by obtained geochemical results, which were then compared with the existing chronological data. The trace fossils associated with the bottom of the Bet Zone and the top surface of the Great Rann sediment units (Middle Holocene) suggest the shallow marine depositional environment. Further, the monospecific occurrence of Teichichnus in the middle units (Middle to Late Holocene period) of the Bet Zone sediments suggests the brackish water environmental conditions associated with the high discharge of fluvial system leading to lowering of salinity. The topmost unit of the Bet Zone sediments shows the disappearance of trace fossils suggesting a terrestrial depositional condition. The present work suggests that the area of the western GRK has witnessed a gradual shifting of shallow marine to the fluvial environment during the Middle to Late Holocene period. [ABSTRACT FROM AUTHOR]

The Banded Gneissic Complex (BGC) of the Aravalli Craton (India) comprises Archean BGC‐I (3.3–2.5 Ga) and Proterozoic BGC‐II. The BGC‐II is a mosaic of amphibolite facies namely, (a) Mangalwar Gneissic Complex (MGC), (b) Mangalwar Metasedimentary Complex (MMC), and (c) granulite‐facies Sandmata Metamorphic Complex. Here we present field, petrography and geochemical study of the Proterozoic amphibolites from the MGC and MMC. Based on field and geochemical data, the amphibolites have been characterized into three types related to rift settings (G1, G2 and G3). The G1 type occurs as dykes in the MGC and bears ocean island basalt‐type rare earth element (REE) patterns along with negative Nb and Ti anomalies, negative to positive values of εNd(t) (−0.02 to +3.96) and slightly variable initial 87Sr/86Sr (ISr) ratios. They are derived from deep mantle sources and correspond to the pre‐rift magmatic phase. The G2 type occurs as isolated patches associated with chert and is characterized by light REE (LREE) depleted and almost flat heavy REE (HREE) patterns suggesting that they were emplaced in an oceanic setting and were derived from a shallower mantle bearing positive εNd(t) (+2.87 to +6.27) and ISr = 0.7002–0.7083. This phase corresponds to the opening of the Mangalwar sedimentary basin (MMC). The G3 type occurs intercalated with metasedimentary rocks of the MMC and marked by LREE‐enriched and HREE‐depleted to flat patterns that resemble Upper Continental Crust signature, their εNd(t) mostly negative values and variable ISr also corroborate this explanation. They are believed to be derived from heterogeneous sources and represent syn‐sedimentary volcanic phases. All these signatures indicate that the amphibolites distinctly represent three phases of magmatism that occurred during pre‐rift (1.72 Ga), opening of basin (1.62 Ga) and syn‐sedimentary volcanism (1.6–1.3 Ga) in the rift‐basin and they were formed during the Proterozoic. These rifting events might have been connected with the fragmentation of Columbia. [ABSTRACT FROM AUTHOR]

A combined geochemical and Sm–Nd isotopic study on the Palaeoproterozoic (1,845 Ma) granites of the Lesser Himalayan Crystalline Sequence (LHCS) in the Garhwal region of NW India has been done in the present study. These granite samples are characterized by high silica, alumina, and potash and belong to a peraluminous to strongly peraluminous series, having molar A/CNK values of 1.01 to 2.4. The low P2O5 contents and its negative correlation with SiO2 presiding out that the granites have S‐type affinity, also supported by various classification diagrams (ACF; SiO2 vs. P2O5, Na2O + K2O‐CaO, and Th). The concentration of trace elements Ba, Sr, Nb, and Ti are low, and Rb, Th, U, and Pb are found to be high. The granites have low total rare earth elements contents of 56.19–229.16 ppm with enrichment in Light rare earth elements (LREE) ([La/Yb]N = 1.61–15.08) and negative europium anomaly (Eu/Eu* = 0.12–0.31). Sm–Nd isotope studies were also performed for three granite samples. Estimated model ages as 2.5–2.7 Ga, indicates the contribution of the Archean crustal substrate as their protolith source. Therefore, we assume that the melting of metasedimentary rocks with Archean protolith can form these peraluminous granites in an accretional–collisional event, during the Palaeoproterozoic on the western flank of the Columbia supercontinent. [ABSTRACT FROM AUTHOR]

The Ib River Basin, located in the south‐eastern part of the Son‐Mahanadi Master Basin, is renowned for its reserve of well‐diversified Lower Gondwana plant megafossils. The remains of Glossopteris flora collected from a Late Permian Gondwana (Lower Kamthi Formation) exposure, near Himgir Village, Ib River Basin, Odisha, has demonstrated a record of different types of insect traces. The structures are compatible with a variety of insect activities on fossil leaves. Different feeding traces such as leaf margin and surface feeding traces, cuspate margin feeding traces, obliterated surfaces and blotch marks are found in the Glossopteris leaves. Egg pouches found along the midrib and on the lamina in the Glossopteris leaves are the traces of egg‐laying. The various traces of insect activities recorded in the present investigation reveal the survival of a diverse insect fauna during the Late Permian Glossopteris flora of India. It is the first report of its kind in the Mahanadi Gondwana Master Basin of India, and also it is the first record of insect traces in the Late Permian sediments of India. [ABSTRACT FROM AUTHOR]

The present work elucidates miofloral records from the Ganmachidam Formation (late Carboniferous–earliest Permian) of Spiti Valley, Tethyan Himalaya. The Ganmachidam Formation was hitherto considered as unfossiliferous, both for the faunal as well as floral records, and has been subjected to contentious age assessment. The present study has been carried out to find out the microfloral remains, assess the palynostratigraphic status, and the age of the Ganmachidam Formation. From the splintery shale sequence, a rich assemblage of palynomorphs has been recovered, having a dominance of monosaccate pollen grains, namely Parasaccites (Cannanoropollis), Crucisaccites, Divarisaccus, Densipollenites, Maculatasporites, followed by diverse bisaccate pollen grains, namely Scheuringipollenites, Crescentipollenites, Faunipollenites (Protohaploxypinus), Lunatisporites, Striatopodocarpites, Striatites, Rhizomaspora, Primuspollenites, and the spores Callumispora (Punctatisporites) and Calamospora in addition to woody fragments and fungal spores. Three palynoassemblages are identified. The recovered palynocomposition is corroborated with known records of palynomorphs from the Tethyan realm of India and from the late Carboniferous–Early Permian records of contemporaneous sequences across the globe. The composition of these palynoassemblages shows close correlation with the Crucisaccites monoletus Zone and Vittatina costabilis Interval Zone in the northeastern area of the Paraná Basin, Brazil, and lower Barakar palynozone (Scheuringipollenites barakarensis Assemblage Zone) of Peninsular India which indicates the studied section of the Ganmachidam Formation is late Pennsylvanian to early Permian in age. Moreover, occurrences of palynomorphs from the Carboniferous sequences having a glossopterid affinity further strengthen the idea that glossopterids might have originated in Carboniferous time. [ABSTRACT FROM AUTHOR]

This study aims to determine variations in the terrigenous influx, the intensity of chemical weathering, pedogenic activity, and provenance of Shantisagara lake sediments in southern India for the past 11,000 years reconstructed using geochemical and magnetic susceptibility data. The results showed that K/Al, Fe/Al, Ti/Al, and Zn/Al ratios exhibited significant down‐core variations, whereas P/Al, Pb/Al, Na/Al, Cu/Al, and Ba/Al display steady values. The sediments have resulted from moderate to intense degree of chemical weathering and show high compositional maturity. The discrimination function diagrams, Al2O3/TiO2 and K2O/Na2O values, point towards a change from an intermediate source during the Early‐ and Mid‐Holocene to a felsic one during the Late Holocene. The similar LREE‐enriched chondrite‐normalized REE patterns indicate no significant change. The Early Holocene phase was characterized by a moderate influx of fine detrital fraction with a peak around 10,500 cal. Years B.P. The pedogenesis was strong in the catchment area during this period, with oxic conditions prevailing in the lake. The catchment area experienced moderate to high rainfall during this period. A fluctuating trend of terrigenous influx and chemical weathering is documented during ~8,000–4,000 cal. Years B.P. period in response to variable rainfall. Decreasing rainfall trends are observed during 4,000–2,000 cal. Years B.P., with a slight increase from 2,000 cal. Years B.P. to the Present. Anoxic conditions were present in the lake during the Middle‐ and Late Holocene with low pedogenic activity in the catchment. [ABSTRACT FROM AUTHOR]

Detrital mineralogy, major oxides, trace, and rare earth elements (REE) were examined in the Middle Jurassic Fort Member Sandstone (FMS) of the Jaisalmer Formation in Western India to understand palaeoweathering, provenance of sediments, and to decipher the tectonic setting. The sandstones are classified as arkose to sub‐litharenite types according to their relative percentages of quartz, feldspar, and lithic fragments, and major elemental ratios. The values of Chemical Index of Alteration (67–85), Plagioclase Index of Alteration (78–97) and Chemical Index of Weathering (83–97) along with A‐CN‐K diagram suggest moderate to intense chemical weathering in the source region. Presence of fresh feldspars and dominance of monocrystalline quartz, showing both parallel and undulose extinction, indicate plutonic and volcanic felsic igneous provenance. Contribution from metamorphic orogen sources is indicated by the lithic fragment population. Various geochemical parameters such as Th/Sc, Cr/Th, Ti/Zr, and Eu/Eu* support a dominant felsic provenance. Higher Zr/Sc ratios relative to the magmatic Zr/Sc‐Th/Sc trend, higher Zr and Hf concentrations in the FMS indicate some extent of sedimentary recycling and zircon sorting. LREE enrichment, flat HREE pattern, negative Eu anomaly and trace element ratios, in conjunction with palaeocurrent data, indicate a likely sediment contribution from basement source terrains including Erinpura‐Mount Abu‐Sirohi granites, Malani Igneous Suite, and Aravalli‐Delhi orogens. The major and trace element tectonic setting discrimination diagrams for the FMS indicate a passive margin setting. [ABSTRACT FROM AUTHOR]

The unconventional reserves are vital future energy resources and globally augmented interest endeavours the discovery of gas and oil‐rich shales. The Kommugudem Formation, Krishna Godavari Basin was evaluated based on sample laboratory and well log studies from six wells deciphering mineralogical and organic geochemical parameters to provide an understanding of hydrocarbon potential and brittleness. Kommugudem Formation constitutes Type III kerogen dominantly with high total organic carbon (TOC) and Tmax indicating the presence of high organic matter. The mean vitrinite reflectance indicates mature to post‐mature shale majorly in the gas generation window. Fourier transform infrared spectroscopy functional group investigation revealed the presence of aromatics and aliphatics with a higher degree of abundance owing to higher TOC content. The basic well logs recorded in the studied region are used to estimate the continuous TOC and porosity of the formation and corroborate with laboratory core data. Petrographic, X‐ray diffraction, and field emission scanning electron microscopy studies revealed the presence of dominantly siliceous mineral matter with relatively lower clay and carbonates. Organic mudstone classification indicates formation is dominantly silica‐dominated lithotype and clay‐rich siliceous mudstone. Microfractures and micropores are observed in mineral and organic matter that may act as storage sites for hydrocarbons. Kommugudem Formation on the basis of mineralogy indicates compositional analogy with brittle zones of Barnett Shale Formation. The high mineralogical brittleness index of the Kommugudem Formation indicates good conditions for hydraulic fracturing. The present investigation demonstrates excellent hydrocarbon generation potential and good brittleness in wells A and B while C, D, E, and F have relatively lower potential and may have low gas and oil sources. [ABSTRACT FROM AUTHOR]

Clast morphometry and sedimentary facies analysis of polymictic conglomerate of the Hiriyur Formation in the Gadag greenstone Belt, Western Dharwar Craton, India, was conducted to constrain the palaeohydraulic condition, depositional environment, and type of sedimentary basin. The conglomerate grades from clast‐supported to matrix‐supported with siltstone‐sandstone intercalations. Eight lithofacies along with five major lithofacies associations are recognized in the Majjur and Attikatti Domains of the Gadag greenstone Belt. The lithofacies architecture suggests sedimentation commenced with rapid deposition of slope‐derived debris in a proximal high‐energy alluvial fan setting followed by a braided river environment. Clast morphometry and palaeohydraulic data indicate a low palaeoslope (0.000024 m/m), and stream discharge value (1.913 m3/s) calculated from the channel fill conglomerates. Greywacke overlying the conglomerate has been interpreted as turbidites from a continental slope. The accompanying 40‐m‐thick banded iron formation and carbonate rocks also support a marine context. The lack of transitional deposits between river and deep marine settings suggests that the greywacke turbidites sequence is separated from the conglomerate deposits by substantial unconformities. This change in depositional setting could be due to a change in basin subsidence rate, tectonic rejuvenation, or major sea‐level changes. [ABSTRACT FROM AUTHOR]

In this study, we analysed a rich Miocene palynological assemblage from the Upper Bhuban Formation consisting of 21 genera and 25 species of fungal remains; spores and pollen grains, along with reworked Permian palynomorphs. The latter form a relatively high abundance throughout the studied section. The abundant Hammenisporis spp. with fungal remains and geochemical data of clay minerals in the section imply that a warm and humid freshwater with oxic to anoxic continental or near‐shore depositional environment and tropical–subtropical climatic conditions prevailed during the course of sedimentation of the Upper Bhuban Formation. Geochemical studies of four selected Bhuban shale samples have been analysed for major oxide, trace elements, and rare earth elements (REE) and infer a felsic igneous rock under an active continental margin setting, with a moderate chemical to an intense chemical degree of weathering. The Rock‐Eval pyrolysis results suggest that the organic matter composition is primarily type‐III kerogen, with mixed immature and mature hydrocarbon and gas potential. [ABSTRACT FROM AUTHOR]

The excellent exposures of plentiful Proterozoic granitic bodies in the north‐east Himalaya offer a chance to explore the evolution of continental crust in the Early Proterozoic period. The present comprehensive study from Bomdila area, western Arunachal Pradesh, NE India documents petrogenesis of Palaeoproterozoic Bomdila granite gneiss and metamorphic history of the region using the whole rock and mineral chemistry, and suitable mineral thermobarometry. The gneisses, with quartz, k‐feldspar, plagioclase, and mica mineralogy, are characterized by enrichment in rare earth elements (total REE up to 290 ppm), Rb, Ba, Th, and depletion in mafic elements (Ni, Cr, V, Sc). The gneisses are subalkaline and peraluminous with A/CNK (Al2O3/CaO + Na2O + K2O) > 1.1, indicating S‐type nature of the granites. The gneisses show fractionated REE patterns (LaN/YbN = up to 22) with LREE enrichment and HREE depletion. Geochemical characteristics such as enriched SiO2, Al2O3, alkalis, LREE, high incompatible element ratios (Rb/Sr and Ba/Sr), and depleted mafic contents with noticeable negative Eu anomalies (Eu/Eu* = 0.2 – 0.6) suggest an origin of gneisses through high‐temperature (>800°C) shallow crustal melting of a pelitic source similar to the metasedimentary enclaves within the gneisses. Mineral thermobarometric calculations suggest a tightly constrained P–T condition of 7.5–8.6 kbar and 560–590°C for the gneiss and schist from the study area. Almost identical P–T conditions of metamorphism from different lithologies attests that the Bomdila area may have attained an upper amphibolitic facies condition, possibly concomitant to the Himalayan Orogeny. Though rudimentary, temperature estimates from Ti‐in biotite thermometer suggest an increase in metamorphic grade towards the Main Central Thrust. [ABSTRACT FROM AUTHOR]

Mafic extrusive rocks (basalts) and intrusive rocks (gabbros) from the Nagaland–Manipur Ophiolite (NMO) of the Indo–Myanmar Orogenic Belt (IMOB), north‐east India, are investigated to understand their magmatic evolution in diverse tectonic environments. Basalts are distinguished into two types: basalt‐I and basalt‐II. Basalt‐I type shows the sub‐alkaline character with Nb/Y < 0.50, low Nb/Th (2.36–7.94), and low to moderate La/Sm (1.00–4.12) indicating derivation from a slightly enriched mantle source and also supported by their enriched LREE pattern with flat HREE. They are depleted in HFSEs (Nb and Ti) but enriched in U and Pb, which is indicative of a typical subduction origin derived from an MORB‐type mantle source. Investigated samples of basalt‐II and gabbros have an equal composition with alkaline characteristics. They have Nb/Y > 0.50, high Nb/Th (8.38–13.37), and highly enriched LREE (La/Sm = 4.41–6.35) pattern. They show typical Ocean Island Basalt (OIB) characters of a plume source. The two sets of basalts and gabbros found in this study have no sign of genetic relationship, and therefore, it strongly suggests that they were derived from two different mantle sources of a plume and a subduction zone mantle wedge. Our study supports the theory that the NMO has records of different magmatic episodes produced ranging from plume‐related magmatism, to divergent and convergent plate magmatism that were generated at diverse tectonic settings. [ABSTRACT FROM AUTHOR]

Landslides are a common and widespread phenomena in tectonically active mountains, impacting on landscape development, and lanslides pose a serious threat to the lives and properties when these interfere with humans and their associated infrastructure. However, the spatial distribution of these landslides is controlled by various geological and geomorphological parameters, including the neotectonic activity and the climatic pattern of the area. In the present study, various geomorphic parameters such as longitudinal and topographic swath profile, valley floor width to valley height ratio, channel steepness index, and stream length gradient index, along with the rainfall pattern of the Teesta river valley, Sikkim Himalaya, were correlated with the spatial distribution of landslides in the area. It has been concluded that landslides in the Higher Himalaya, north of the Main Central Thrust behind the orographic barrier, owe their origin mainly to the higher tectonic activity, and adjacent to the Main Central Thrust in the front of the orographic barrier to both tectonic activity and the higher rainfall. The distribution of landslides in the Lesser Himalaya is dominantly controlled by lithology and is mainly triggered by the rainfall. [ABSTRACT FROM AUTHOR]