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In the present study, grain size analysis has been undertaken to deduce the palaeo-depositional environment of Chandrabhaga beach sediments in the east coast of India. The sediments are medium- to fine-grained sand, moderate to moderately well sorted, near symmetrical to very coarse skewed, and platy to leptokurtic in nature. The predominance of medium- to fine-grained sand suggests relatively high- to moderate-energy of depositional conditions. A fluctuating trend of sorting corroborates the impact of the river and monsoonal variations along the coast and also indicates a good sorting of unimodal sediments or an association of two bimodal sediments in equal proportions. Linear discriminant functions unveil the beach setting and shallow marine depositional environment with minimal (6.33%) influence of the aeolian process, while multigroup discrimination suggests 2:1 ratio of beach and aeolian setting. C-M plot of Chandrabhaga beach sediments surmises that the transportation was mainly by rolling and bottom suspension conditions in a beach sub-environment. The tractive current plot indicates association of samples with the beach in the tractive current field signifying dominance of wave action. The quartz microtexture study by SEM unravels the physicochemical changes during sedimentation in contemporary coastline. [ABSTRACT FROM AUTHOR]

Previous geophysical investigations of the western continental margin of India (WCMI) confirm the two-phase breakup history of the margin with the first breakup taking place between India and Madagascar that created the Mascarene Basin in the Late Cretaceous and the second breakup event in Early Paleocene with Seychelles separating from India. Despite numerous geoscientific studies along the WCMI, the opening of the Laccadive basin, situated along the southern part of the margin, remains poorly constrained. In this study, we evaluate the multi-channel seismic reflection and gravity anomalies at the margin to identify the early rift signatures in conjunction with the magnetic anomaly identifications in the Mascarene Basin. The analysis led to the identification of two trends of extensional structures, a NNW–SSE-oriented structure over the Laccadive Ridge north of Tellicherry Arch, interpreted to result from ENE–WSW extension, and a SSW–NNE-oriented structure in the Laccadive basin region towards the south, interpreted to result from NW–SE extension. Previous plate reconstruction models of the Mascarene Basin using marine magnetic lineations suggest that the ENE–WSW extension observed over the Laccadive Ridge could be related to the India–Madagascar separation. We associate the pattern of sediment deposition and the presence of a Paleocene trap volcanics, linked with the NW–SE grabens observed in the Laccadive basin region, to the extension between the Laccadive Ridge and the western coast of India after the separation of Madagascar from India. We further propose that the anticlockwise rotation of India and the passage of the Réunion plume have facilitated the opening of the Laccadive basin. [ABSTRACT FROM AUTHOR]

Diatom analysis, despite its existence in archaeological science for over seven decades, remains an underutilized technique. While diatoms are often employed in site-based palaeoenvironmental reconstructions, their application in pottery sourcing and typology is relatively limited. This study focuses on diatom analysis of pottery sherds collected from six Iron Age sites in the lower Kaveri River Basin, Tamil Nadu, India. Scanning Electron Microscopy was utilized to examine the diatoms in 78 samples from 26 pottery sherds across these sites. The analysis revealed the presence of aquatic diatoms, predominantly from freshwater environments, along with desiccation-tolerant taxa belonging to the genera Nitzschia, Hantzschia, Luticola, Stauroneis and Tryblionella. Notably, the dominant genera were Nitzschia (70.73%), Hantzschia (21.95%) and Luticola (4.87%). These findings confirm the presence of a lacustrine environment with mesotrophic to eutrophic conditions and suggest that the clay used in pottery originated from a freshwater source. Moreover, this study highlights the potential of diatom analysis in reconstructing local environments and shedding light on the palaeoenvironmental conditions underlying archaeological sediment deposition in a tropical context. [ABSTRACT FROM AUTHOR]

Pristine depositions of beach sediments containing heavy minerals (HM) along the shorelines of Mangalore, south–west coast of India is reported in the study. Primordial radionuclide concentrations in the beach sediments collected were determined by high purity germanium (HPGe) gamma spectrometry method. The mineral identification and counting were performed using polarizing microscope. Geometric mean values (GM) [Geometric Standard Deviation (GSD)] of concentrations of 40K, 232Th and 226Ra are obtained to be 139 (2), 482 (5) and 110 (4) Bq kg−1 respectively and total heavy mineral weight percentage (TM%) of Monazite, Zircon, Ilmenite and Lithic fragments are obtained to be 0.17 (3.5), 0.51 (2.9), 5.3 (3.2) and 2.3 (2.5)% respectively. Seasonal variation studies and statistical analysis of the data are also performed to examine correlations between the origins of the radionuclides and elevated percentage of HM in these sediment depositions. [ABSTRACT FROM AUTHOR]

The influence of mangrove systems in advancing the process of sedimentation is very well studied over the years. However, understanding the actual mechanism of accretion at a specific point within a mangrove forest is difficult, due to the stochasticity of sediment distribution and deposition. Factors that influence the rate of sediment accretion within the mangrove forest such as plant litter accumulation and bioturbation were investigated in Pichavaram mangrove forest, India. The annual rate of vertical accretion was recorded as 1.5 ± 0.9 cm year-1 for the site at elevation 0.4 m, and 0.9 ± 0.04 and 0.9 ± 0.05 cm year-1 for the other two sites which are at -0.8 and -1.2 m respectively. Results show that the sites were accreting sediments but at varying rates, inter-site variability was low but the factors influencing the processes were different. Plant litter contributed significantly to the accretion, and organic matter estimates also supported this observation. A higher rate of organic matter accumulation was observed in one of the sites, which is not regularly inundated by tides. On the contrary, in sites which were regularly washed by tides, accretion was seen in both allochthonous and autochthonous inputs and the annual rate of vertical accretion was almost the same. [ABSTRACT FROM AUTHOR]

Previous geophysical investigations of theWestern Continental Margin of India (WCMI) confirm the double breakup history of the margin with the first breakup taking place between India and Madagascar in Late Cretaceous and the second breakup event in early Paleocene with Seychelles separation from India. Despite numerous geoscientific studies along the WCMI, the southern part of the margin, which is known to be the conjugate segment of the Madagascar, has been least studied. In this study, we evaluate the multi-channel seismic reflection and gravity anomalies at the margin to identify the early rift signatures in conjunction with the magnetic anomaly identifications in the Mascarene Basin. The analysis led to the identification of two extensional directions, a ENE-WSW oriented extension over the Laccadive Ridge north of Tellicherry Arch, and the NW-SE extension in the Laccadive Basin region towards south. Plate reconstruction models of the Mascarene Basin suggest the ENE-WSW extension observed over the Laccadive Ridge could be related to the India-Madagascar separation. However, the sediment deposition pattern and the presence of Paleocene trap associated with the NW-SE extensional grabens observed in the Laccadive Basin region has been attributed to the post-breakup extension between the Laccadive Ridge and the West coast of India. We further propose that the anti-clockwise rotation of India and the passage of the Reunion plume have facilitated the opening of the Laccadive Basin. [ABSTRACT FROM AUTHOR]

Subaerial rise of Earth's first continents took place 3.3–3.2 Ga years ago. This had significant influence on the ocean, atmosphere, and biosphere. Two important sedimentological consequences of continental emersion were (1) development of terrestrial (alluvial fan–fluvial–aeolian) depositional systems and (2) formation of shallow-marine sedimentary basins near the continental margin. Late Paleoarchean–Neoarchean terrestrial deposits, including development of an extensive paleosol around 3.2 Ga, and Meso–Neoarchean shallow-marine deposits have been reported from the Singhbhum Craton, eastern India from several localities. However, lateral and vertical changes in sedimentary facies associations and stratigraphic correlation between these terrestrial to shallow-marine sedimentary deposits have not yet been investigated. In this paper, we have reviewed the sedimentological characteristics of Late Paleoarchean to Neoarchean (3.2–2.8 Ga) stratigraphic successions of the Singhbhum Craton and have discussed sea level change and mode of stratigraphic sequence building. Our analysis shows that Singhbhum granitoid complex was emplaced around 3.3 Ga in an intracontinental setting, resulting in high continental freeboard conditions that triggered terrestrial (alluvial fan–braided fluvial) sedimentation (Dhosrapahar Formation). Continental sedimentation continued until ca. 3.0 Ga. In the eastern (Simlipal Group), western (Birtola Formation), and southwestern (the Mankarchua, Mahagiri, and Keonjhar formations) parts, shallow-marine sedimentation occurred after 3.0 Ga as a result of transgression. However, in the northern part (Dhanjori Formation), continental sedimentation prevailed throughout the Archean. These Late Paleoarchean to Neoarchean terrestrial and near-coastal successions of Singhbhum Craton should be the prime targets for intense geobiological research. [ABSTRACT FROM AUTHOR]

Pookode, the freshwater lake in the Western Ghats, is a well-known tourist place in southern India, and human interference has turned the otherwise serene environment into a polluted one. This paper discusses the geochemical and textural characteristics of the Pookode lake and by determining the sedimentation rate, an attempt is made to predict the useful life of the lake. The predominance of mud fraction and high organic matter content in sediments favour the accumulation of heavy metals as indicated by the different indices. The sedimentation rate was determined using 137Cs dating method and the maximum lifespan of the lake maintaining its hydrological and ecological functions is estimated as ∼700 years. [ABSTRACT FROM AUTHOR]

Among the vast swathes of Gondwanan sedimentary rocks in India, exposures of the Lower Permian Talchir Formation at Manendragarh in India are exceptional for their cold marine faunal assemblage and muddy conglomerates of possible glacial origin. They may represent a record of the late Palaeozoic glaciation that affected Gondwana in the Permo-Carboniferous. Although the fossil record is relatively well documented, the sedimentology of this area is not well understood. This paper intends to fill the gap in knowledge regarding palaeogeography and the palaeoenvironmental changes within the basin through space and time. We distinguish conglomerates that are formed by glacial and mass flow processes. The lateral variation in facies associations along a NNE-SSW transect in the study area identifies the depositional basin as an interior sea that formed when the sea spilled over a steep basement ridge during a transgression. The benthic organisms remained confined to the seaward basin margin where they only flourished in the initial stage of basin filling. Locally derived, bioclastic storm beds are limited to the seaward flank of the basin. Alternating phases of glaciation and interglaciation resulted in an interbedded succession of grey shales and interglacial density flow deposits. The channels that fed these density flows are preserved closest to the landward margin of the basin. Co-existence of glacial diamictites and interglacial density flow deposits highlights the climatic changes in this part of Gondwana during the Late Palaeozoic. [ABSTRACT FROM AUTHOR]

Diversity of Plant Functional Types (PFTs) along a sediment core drilled in Lonar Crater Lake, Central India, is analysed, based on previously published pollen data for a total of 115 depth levels and covering the past 9.2 kyr. Our results support concepts of a dominantly humid period persisting until ca. 5 ka, succeeded by a significantly drier phase with weaker monsoon, including various prominent drying pulses. Throughout the Holocene, plant diversity at Lonar was composed of a variable proportion of herbaceous PFTs (ca. 40–60%) and mainly angiosperm woody PFTs. Changes in herbaceous diversity account for a considerable part of the observed PFT data variability. PCA analysis reveals a total of four partly alternating diversity associations (DAs) interpretable in terms of vegetation spanning from drier Savanna and dry deciduous forest to (semi-) evergreen woody vegetation, mainly recorded in older strata. It is shown that the succession of the DAs is largely triggered by climate change inferred from other proxies. Correlation analysis with geochemical data testifies that the diversity signal obtained is largely unaffected by sedimentary processes and detrital inflow, highlighting the potential of this archive to reflect 'true' diversity signals, rather than artefacts of sedimentary processes. While warm and humid conditions promoted diversity, drying and weak monsoon tended to cause diversity loss. In contrast, the relative diversity of dry herbs increased during drier periods. Short-term variability in our data is evident in varying diversity percentages of single PFTs and their ratios. Changing ratios of dry on mesic herbs, the relation of shrub and tree diversity, tropical on temperate PFTs, and total plant diversity are likely related to solar cycles. Evidence for recurrent cooling episodes through solar forcing comes from the observed coincidence of Grand Solar Minima and minima in the tropical/temperate PFT ratio. [ABSTRACT FROM AUTHOR]

How the Neotethyan Ocean evolved and extended southwards into Southeast Asia remains controversial. The paleographical correlation between India and the SE Asian blocks and/or terranes before the opening of the Neotethys and the initial opening time of the Neotethys is still unknown. The lack of this knowledge hampers our further understanding of the tectonic evolution of global Neotethys. Here we present a combined study on Triassic magmatism in the Tengchong Block and Triassic sedimentation in the Myitkyina area, located on the two sides of the Tagaung-Myitkyina Ophiolite Belt of northern Myanmar. Our results coupled with previous data demonstrate that a Triassic continental magmatic arc developed in the Tengchong Block and that the Triassic Myitkyina sedimentary sequence was part of the Tethyan Himalayan Langjiexue Group in northern India. Moreover, the Tengchong Triassic magmatic arc provided important detrital inputs to the whole Langjiexue Group of northern India. Such a provenance is the best explanation for the Permian--Triassic detrital zircons of the Langjuexue Group. Together, we propose that the Tagaung-Myitkyina Ophiolites in northern Myanmar are the relics of the Neotethyan Ocean rather than the Mesotethyan Ocean (Bangong-Nujiang Ocean) in SE Asia, and that the initial opening time of the Neotethys was the Early Jurassic of 200-190 Ma. Then, the earliest (185-165 Ma) intra-oceanic arc akin to the Izu-Bonin-Mariana arc in the West Pacific, developed soon after the Late Triassic opening of the Neotethys. [ABSTRACT FROM AUTHOR]

A study describes the use of natural (210Pb) and anthropogenic (137Cs) radiometric dating techniques to determine sedimentation rates and age of Kodaikanal Lake. The core sediment from 46 cm was collected and analyzed for 210Pb and 137Cs using an Alpha spectrometer 7200-04 and a Gamma-ray spectrometer GC-3520. Bathymetry studies aided in selecting a representative sample location and measuring the lake's underwater depth, with maximum and mean depths of 11 and 3.38 m, respectively. The maximum and minimum dry bulk density ranged from 0.57 to 1.05 g/cm3 (mean of 0.73 g/cm3), and the weight percentage of porosity collected sediment sample ranged from 60.33 to 78.63 wt.% (mean of 72.32 wt.%). This study determined the sediment grain size and the percentages of sand, silt, and clay. The findings indicate that the core sediment samples contain 56.05 to 69.62 wt.% (mean of 63.21 wt.%) sand, 28.03 to 41.71 wt.% (mean of 34.55 wt.%) silt, and 1.81 to 3.98 wt.% (mean of 2.34 wt.%) clay. The 210Pb technique was used to assess a model of time changes in the deposit for geochronology studies in core sediments. The sedimentation rate depended on the consistent rate supply (CRS) of the 210Pb model. The 210Pb model was confirmed using 137Cs radioactivity released into the global fallout after nuclear testing (1963) and the Chernobyl accident (1986). The depth concentration of 210Pb ranged from 3.89 ± 0.1 to 15.4 ± 1.6 Bq/kg, with a mean of 210Pb concentration is 7.23 ± 0.86 Bq/ kg. The 137Cs radioactivity varied from the upper and lower peaks that appeared clearly at depths of 16 and 29 cm, respectively, with successive phases of 18.68 ± 1.36 and 22.04 ± 1.4 Bq/kg. According to the CRS model, the mean sedimentation rate was 0.51 ± 0.14 cm/year, and the core age was 86 years. The 137Cs have likely been the mean sedimentation rate of 0.535 ± 0.07 cm/year and 83 years. The evaluated life of Kodaikanal Lake as an average of 210Pb and 137Cs sedimentation rate since 1933 is about 650 ± 24 years and 582.75 ± 19 years. [ABSTRACT FROM AUTHOR]

The Jara dome in the western part of the Kachchh basin is the distal-most exposure of the Callovian to Aptian age sediments of the Kachchh stratigraphy. These outcrops are represented by three formations, namely, the Jumara, Jhuran, and Bhuj formations. The central part of this dome is represented by the entire succession of the Jumara Formation (Member-I to IV). This paper aims to document ichnofabric changes in the distal part of the basin during a basinal-scale transgression. The Jumara succession at the Jara dome is represented by finer sediments compared with the other coeval sediments across the basin. Ichnofabric analysis of the Jumara Formation at the Jara dome implies 21 ichnospecies from 12 ichnogenera with the reconstruction of ichnofabric constituent analysis for all four members. Member-I implies low diversity-low density trace fossils with a simple tiering profile. Member II is two thick bands of marls rich with high diversity and density occurrence of Zoophycos. Ichnofabric analysis suggests slow sedimentation in the shelf environment below the Storm wave base under dysoxic conditions. Ichnofabric analysis of overlying Member III suggests deposition below the fairweather wave base with well-oxygenated, shifting substrate-type environments. Ichnological analysis of Member IV (Dhosa oolite Member) suggests that a transgression event was inferred at Jumara Dome. Thus, the ichnofabric analysis of the Jumara Formation suggests an increase in ichnodiversity steadily from member-I to III and then a decline. A comparison of the Jara dome ichnology data with other coeval sediments of the Kachchh basin suggests high diversity in the Jara dome area. [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]

Confluence of river channels plays a significant role in channel avulsion, flood plain evolution and dynamics of the fluvial system. The principal objectives of the present study are (i) to analyze the direction and degree of confluence shifting through the recent past (1955–2020) by applying geospatial techniques and (ii) to find out the probable causes of confluence dynamics of the Raidak river system within quaternary geological sites of a Himalayan foreland basin in West Bengal, India, applying fluvio-geomorphological and sedimentary bank facies. Modified Normalized Difference Water Index method is also used. The result shows that the Raidak-Sankosh confluence (RSC) shifted by 9.94 km of the total distance between 1955 and 2020, whereas Raidak-I-Torsa confluence (RTC) has shifted 4.29 km overall distance during the same period. Both confluences were shifted toward the south and south-east directions. Total erosion and accretion area at the proximity of RSC and RTC has been registered as 40.1 sq km and 47.57 sq km and 39.67 sq km and 37.99 sq km, respectively, for the 65-year period. The key factors of confluence dynamics are regular flood events and channel avulsion, non-cohesive bank materials and huge channel bed sedimentation with multiple bars. [ABSTRACT FROM AUTHOR]

Natural radiation measurements for 232Th and 238U were undertaken for the first time in the subsurface area, at the eastern coastal part of India. The primary objective of the present study was to study the dependence of specific grain sizes exhibiting higher abundance of radioactivity, irrespective of their depths. This would enable to optimize the fraction with specific grain size for effective mining in view of the resource potential. The relationship between the radioactivity counts of 232Th and 238U with grain size has been established in this article for the first time. The site of coring has been chosen based on handheld Gamma survey meter. The sand size range between 125 and 180 µm contains more 232Th and 238U counts as compared to the more extensive size range. The average activity concentrations of radioactive elements such as 232Th and 238U were obtained using a HPGe detector and found to be 371.42 ppm, 211.17 ppm, and 405.66 ppm for 232Th and 13.05 ppm, 10.77 ppm and 19.16 ppm for 238U, respectively, for Core-1, 2 and 3. Core-1, being close to the Rushikulya river, the deposition of sediments is affected by fluvial and allied marine processes. The upper part of Core-3 is more affected by various processes, but the deeper part is less affected and deposition as well as sedimentation played a crucial role in subsurface enrichment. The enhanced Th/U ratio in the entire study area, irrespective of grain size and depth provides an opportunity for Th exploration for recent advance in technological application and defence system. The major providers for the enhanced level of 232Th and 238U are monazite and zircons, the SEM analysis also confirmed the presence of monazite and zircons. [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]

Lowland rivers across the world are characterized by accumulation of sediment due to a decrease in the channel slope. Despite the antiquity of the topography, the lowland part of the west‐flowing rivers of Western Ghat, India is characterized by poorly developed floodplains except for the southern part of the Ghat. This poses a question of the sediment transportation and deposition capacity in these lowland rivers, which in turn governs geomorphic characteristics. In this study, we adapted a novel method to integrate hydrological model‐derived discharge estimates, channel slope estimates from digital elevation models, bankfull channel width estimates from high‐resolution Google Earth satellite images and field observations. We modelled the downstream distribution of total stream power (Ω), specific stream power (ω) and shear stress (τb) for four west‐flowing river systems from different lithological and climatic settings. The 75th percentile discharge from monthly time series data was used in modelling to assess channel processes. The peak values of Ω are distributed all along the longitudinal profile, whereas the peak values of ω and τb are consistently higher in the escarpment. Scaling relationships between hydrogeomorphic parameters were also established to understand the inherent controls on the distribution of these driving parameters. We inferred that ω is sufficient to transport large grain sizes even in the low‐gradient lowland stretches. Hence sediments are mostly absent in the channel, and floodplains are not well developed. Despite having a low gradient, the lowland coastal rivers can efficiently evacuate most of the eroded sediments to the offshore region. Finally, the lithological control is manifested by the variability of channel width regulating the sediment transport in the coastal rivers of the Western Ghat. [ABSTRACT FROM AUTHOR]

The widespread Early Holocene sea-level rise observed along the global coastal realms reinvigorated the need to decipher sea-level variability on a local and regional scale, yet limited attempts were made on simultaneously addressing sea-level and climate variability. The southwest coast of India is endowed with several geomorphic features providing cues on the paleosea-level and climate variability engrossed with its sedimentary sequence in the lowlands. In view of this, the present study aims to decipher the Holocene sea-level and climate variability based on geochemical and palynological proxies supported by 10 AMS radiocarbon ages on a 32 m long sediment core (L7) raised from Upper Kuttanad Kole wetlands (Kuttoor), Kerala, Southwest India. The study demonstrated high sea-level along with warm and wet climate due to Indian summer monsoon (ISM) intensification during 9.69–7.56 ka corroborating with the Holocene Climate Optimum (HCO). However, a break in the sediment deposition is observed between 7.56 and 3.51 ka, the reason for which is yet to be fully understood. During 3.51–2.55 ka, the gradual weakening of ISM has been invoked with an intermittent monsoon spell during 3.20–3.40 ka. After 2.55 ka the sediment core records occurrence of coarser clastics indicating sediment deposition by the migrating distributary channel of the Pamba-Manimala rivers. The high sea level during HCO attests that the core location plausibly represented the southward extension of the Vembanad lagoon which transformed into part of the terrestrial system due to the gradual sea regression during the mid-late Holocene period followed by deposition of alluvial sediments from the hinterland rivers. [ABSTRACT FROM AUTHOR]

New and published apatite fission‐track data provides evidence for differential exhumation between the eastern and western passive margins of southern India. The eastern margin records significant Late Jurassic to Early Cretaceous rifting‐triggered exhumation in response to Gondwana break‐up and minor Cenozoic cooling. In contrast, Meso–Cenozoic rifting and posterior tectonic events did not deeply exhume the basement of the western margin. The anomalous thick crust of the Western Dharwar Craton might explain why Mesozoic deformation in this area was subdued. In addition, the Cenozoic eastward tilting of the Indian plate and the onset of Bengal Fan sedimentation ca. 23 Ma allowed the accumulation of thick sedimentary sequences in the eastern coastal basins, probably inducing a flexural response of fault reactivation on the eastern margin. More generally, we demonstrate the influence of lithospheric strength and post‐rifting sedimentation to the exhumation history of passive margins. [ABSTRACT FROM AUTHOR]

In this study, sedimentary deposits around the confluence of the Narmada River and its tributary, Orsang River, western India, were studied to understand the confluence dynamics. The results indicate that the sediment sequences exposed at three sites represent the contribution from the Narmada River, the Orsang River and the Heran River at various stages. During the Late Pleistocene, the sedimentation occurred as channel beds and bars in the wider than present and bedload dominant Narmada River. The channel aggradation, shifting and realignment, guided the Orsang River to change its course to flow through the lower course of the Heran River and join the Narmada in response to the early Holocene tectonic activity. High flood flows deposited fine sediments in the channel widening due to tributary confluence and within backflooded Orsang (tributary) valley during mid-late Holocene. The lateral migration of Narmada due to successive high flows during the mid-late Holocene probably led to the downstream movement of the Narmada–Orsang confluence. [ABSTRACT FROM AUTHOR]

A palynological analysis of borehole RB-1, Raniganj Coalfield, Damodar Basin, has been presented here. Based on the quantitative analysis of the spores and pollen grains of the productive samples, three palynoassemblages have been identified: Palynoassemblage-I demarcated at a depth between 335.00 and 284.00 m is distinguished by the dominance of nonstriate bisaccate pollen Scheuringipollenites and subdominance of striate bisaccate pollen Faunipollenites suggestive of an early Permian (Artinskian) age; Palynoassemblage-II identified at a depth between 278.00 and 32.00 m shows the prominence of striate bisaccate mainly Faunipollenites, Striatopodocarpites and subdominance of Scheuringipollenites signifies late early Permian (Kungurian) age, and the youngest Palynoassemblage-III marked at a depth between 30.00 and 03.00 m contains dominance of striate disaccates pollen, viz., Striatopodocarpites, Crescentipollenites, and monosaccate pollen Densipollenites spp. (D. invisus, D. densus, D. magnicorpus) corroborate with the latest Permian Raniganj (Lopingian) age. The rare occurrence of Densoisporites contactus and Lundbladispora warti in the assemblage, define the upper limit of the Raniganj Formation. The assemblages have been correlated with the Indian as well as other Gondwanian continents. The dominance of gymnosperms pollen glossopteridales, conifers, and cordaites, lesser quantitative spores of lycopsids, sphenopsids, filiciopsids algal elements indicate that the palaeoclimatic condition was warm and high humid, during the deposition of these sediments in the study area of the Raniganj Coalfield. Research Highlights: Palynological study has been carried out for the subsurface coal deposits from the borehole RB-1, drilled at Raniganj Coalfield to attempt to establish chronology of the sediments. The palynological investigation reveals three palynoassemblage zones and dated as early to latest Permian (Artinskian to Lopingian) age and this assemblage reveals the dominance of gymnosperms plant group such as Glossopteridales followed by conifers and cordaitales. The FADs (First appearance of Datum) of Densoisporites contactus, Lundbladispora warti and Lunatisporites pellucidus in the assemblage III indicate the end of Permian period. The overall palynological composition suggests that a warm to very hot with medium to low humidity climatic condition were prevailing in the study area. [ABSTRACT FROM AUTHOR]

The Brahmaputra River in Assam exhibits a typical braided pattern and is characterized by a sediment load comprising of sand and mud. The river contains channel-bars of varied types and dimensions and embraces the world's largest river island — Majuli, which at present is under the effect of severe bank-erosion along its southern margin. The objective of this study is to examine the characteristics of fluvial sedimentation prevailing along the southern margin of the Majuli landmass. Both channel as well as bank sediments were analyzed to understand the mechanism of transportation, depositional process and hydrodynamic behavior. Both channel and bank sediments consist of very fine to medium sand with subordinate amount of silt and mud. Majority of the sediments exhibit well to very well sorting and positive skewness. The Probability curves of grain size distribution indicate transportation of sediments dominantly by saltation mode with minor amount by suspension and surface-creep mode. CM plot suggest transportation by graded suspension (saltation) with subordinate rolling and uniform suspension process by means of tractive current. The internal stratifications are dominated by planar cross stratifications followed by horizontal stratifications, trough cross stratifications, ripple laminated layers and massive sand. The bank sediments in few locations exhibit a general fining upward sequence which ends up with the deposition of a mud layer. The lithofacies sequences of the study area show prevalence of both lower as well as upper flow regime energy conditions indicating fluctuations of energy conditions during their respective sedimentation. [ABSTRACT FROM AUTHOR]

Palynofloral study along with palynofacies analysis has been undertaken in Nandira colliery, Talcher basin, Odisha, India. Recovered palynoassemblage is characterized by the dominance of monosaccate pollen grains viz., Parasaccites spp. (25%), Plicatipollenites spp. (5%), Potonieisporites sp. (1%) and Diavarisaccus lelei (1%) along with nonstriate bisaccate Scheuringipollenites maximus (35%). The recovered palynoflora shows its affinity towards the Upper Karharbari palynoflora of the early Artinskian age. The organic matter studied from the palynofacies investigation includes palynomorphs (SP), structured phytoclasts/translucent phytoclasts (ST), opaque phytoclasts/charcoal (CH), degraded organic matter (DOM), and amorphous organic matter (AOM). The carbonaceous shale (Sample Na) is dominated by SP (34.67%) and sub-dominated by ST (22%) along with CH (13.34%), DOM (19%), and AOM (11%). Coal samples (Nb to Ne) are completely devoid of palynomorphs. They are mainly dominated by CH (24.87–62.34%) and ST (20.20–73.38%) with presence of DOM (0.7–8.7%) and AOM (0.4–8.7%). Deposition of the sediments in a lower carbonaceous shale bed (Na) might have occurred in a dysoxic forest swamp in low-energy settings. The coal beds (Nb to Ne) have been deposited in the oxidized swamps in the proximal setting. The predominant occurrence of the opaque phytoclasts associated with the coal sediments may indicate a regular occurrence of palaeofires during the Artinskian. [ABSTRACT FROM AUTHOR]

The Quaternary period is considered one of the most eventful periods of all geologic periods. The present study intends to understand the paleo-environmental conditions that prevailed in the southern part of the Kerala State, India, during the Late Quaternary period. The present study aims to understand the climatic variability of the Holocene epoch in the Chirakkara region, the easternmost part of Polachira wetland, Kollam district, South Kerala, by using granulometric data and geochemical proxies. A core of 2.5 m in length has been collected from the study area, and both textural and TOC/TN analyses were carried out. The variation in grain size is attributed to the variations in the energy level of the transporting medium and turn to the climatic conditions, especially rainfall. The sediments encountered in the core are dominated by sand-sized particles indicating dynamic high energy conditions and high precipitation events. The ternary plot of the sediment samples also suggests violent environmental conditions during the deposition of the sediments. The predominance of low values of TOC/TN ratio found at both ends of the core indicates an autochthonous source for organic carbon, possibly due to the aggravated aquatic phytoplankton activity, and increased lake bioproduction, and/or decline in the delivery of organic matter from the terrestrial environment. High values of the TOC/TN ratio noted at the middle portion of the core at depths from 120 cm to 210 cm indicate the allochthonous source for the organic carbon. Among allochthonous sources, the C3-type plant is dominant, indicating a cool and wet climate. At the same time, the extremely high TOC/TN values at 170 cm core depth indicate a short period of hot and sunny climatic conditions. The analysis of the granulometric data and organic matter proxies suggest that the study area has experienced wet climatic conditions with occasional dry spells during the Late Quaternary Period. [ABSTRACT FROM AUTHOR]

This review study has focused on existing sedimentological information of Late Jurassic transgressive deposits of Tendaguru Formation (110 m thick), Mandawa basin, Tanzania exposed around Tendaguru hill and Kanthkot Formation (150 m thick), Kachchh basin, India exposed near Wagad hill. Based on comparison between the two coeval deposits shows variable transgressive characteristics. Studies have revealed that during transgression there existed a storm-dominated sedimentary facies in Kanthkot Formation and tidally influenced facies type in Tendaguru Formation. Both represent similar cyclic sedimentation patterns and high-energy transgressive deposits into different depositional regimes. Lithofacies review reveals that Kachchh basin (Wagad region) was an open marine and relatively deeper and steeper shelf environment in late Jurassic time. However, Mandawa basin (Tendaguru region) was a restricted marginal marine with an estuarine setting. Faunal affinities in both formations indicate a shallow marine environment of deposition with variable depth. The close similarity of transgressive episodes and upward stacking pattern of facies successions in both basins indicates overall shallowing of the sea that correlates with the global trend of relative sea-level fall during late Jurassic time. [ABSTRACT FROM AUTHOR]

Major element compositional spectrum, formation in diverse magmatic and metamorphic rocks, and relative stability during sediment transport, burial, and diagenesis make garnet an important indicator of sedimentary provenances. However, a fundamental question yet to be answered is whether the low-grossular–high-pyrope detrital garnets reflect source characteristics or record sedimentary processes. To address this problem, we have analysed garnets from the beach sands of the East Coast of India and in the source lithologies of the catchment area within the Eastern Ghats Mobile Belt. Investigated garnets show a broad compositional spectrum; most garnets are dominated by almandine 49 – 86% with variable contents of pyrope 9 – 47% , minor grossular 0.8 – 15% , and low spessartine 0.5 – 4%. Using multiple proxies, including a state-of-the-art machine-learning-based garnet discrimination scheme, we found that 96 % of analysed beach sand garnets are of metamorphic origin and 4 % igneous. Amongst the metamorphic garnets, 85 % were derived from granulite facies, 5 % from eclogite/ultrahigh-pressure facies, 5 % from amphibolite facies, and 1 % from blueschist/greenschist facies rocks. Concerning host-rock bulk composition, 93 % of garnets belong to intermediate–felsic/meta-sedimentary class and 7 % belong to the mafic category. The chemistries of the beach sand detrital garnets of the East Coast of India are readily coupled with the compositions of the garnets from source rock lithologies of the Eastern Ghats Mobile Belt. Very low-grossular garnets are derived from meta-pelitic rocks (khondalites) and mafic granulites, whereas slightly grossular-rich garnets are derived from charnockites. The present study indicates that the low-grossular–high-pyrope detrital garnets are vital signposts of sedimentary provenances. We advocate that the high P-T granulite facies mobile belts are distinctive sources for the low-grossular–high-pyrope detrital garnets. • High P-T granulite facies mobile belts are distinctive sources for the low-grossular–high-pyrope detrital garnets. • Alm-Prp garnets are derived from meta-pelites, migmatites, and mafic granulites; Alm-Prp-Grs garnets are from charnockites. • The source for the Bengal Fan low-grossular–high-pyrope garnets possibly lies in the Eastern Ghats Belt. • Sedimentary basins with high proportions of low-grossular–high-pyrope garnets can be linked to (palaeo-) orogenic belts. [ABSTRACT FROM AUTHOR]

Deciphering the crustal architecture of the Cretaceous Barmer-Sanchore Basin (BSB) and Neoproterozoic provinces in the NW Indian Shield presents significant challenges due to extensive sediment deposition and widespread felsic igneous rocks. To address such intricacies, we employ a transdimensional Bayesian joint inversion of teleseismic P-wave polarizations and receiver functions to resolve the detailed structure of the upper 10 km of the crust beneath 29 seismic stations deployed in the study area. The new data is analyzed separately within each of the three different backazimuthal groups to identify any strong variations in the shallow subsurface structure and derive a more robust, averaged model for every station site. The resulting 1-D models reveal heterogeneous sediment cover in BSB and Marwar Basin, with respective thicknesses ranging from ∼1.3–5.5 km and 1–1.5 km. Remarkably low shear-wave velocities (Vs < 1.0 km/s) of sediments with increased Vp/Vs (>2.3) are observed in BSB and adjacent areas, which are related to highly unconsolidated Quaternary-Tertiary deposits. The Marwar Basin is imaged to have 0.3–0.5 km of uncompacted sediments that overlie 0.5–1 km thick Marwar Supergroup sequence. The Erinpura Granites (EG) and Malani Igneous Province (MIP) are characterized by a variably thick sediment blanket, typically ranging within 1 km in thickness. The Vs of the sediments in these regions exceeds 2.4 km/s that possibly corresponds to Mesozoic and older sediments. The basement beneath EG exhibits Vs faster than 3.4 km/s, consistent with moderately metamorphosed granites. In MIP, the basement is characterized by non-uniform shear velocities, suggesting the influence of intrusions linked to magmatic episodes in NW India. • P-wave polarization and receiver function unveiled NW India's top 10 km structure. • The Barmer-Sanchore Basin contains 1–5.5 km thick sediments, mostly uncompacted. • Malani Igneous Province and Erinpura Granites exhibit thin (< 1 km) sediment cover. • Shear velocities offer insights into sedimentation and rock formation in NW India. [ABSTRACT FROM AUTHOR]

On the western part of the eastern Indian shield, Archaean basement (Bonai granite) is overlain by radioactive conglomerate. The conglomerate contains well-rounded, fractured Mg-poor (<0.18 wt.% MgO), Al-rich (up to 21.14 wt.% Al2O3) Zn-rich chromite (>35.0 wt.% Cr2O3) containing up to 15.5 wt.% ZnO. This is the first reported occurrence of detrital zinc-rich chromite having such unusually high ZnO from India, and to our knowledge, the third reported occurrence in radioactive quartz-pebble conglomerate after Witwatersrand, South Africa and Tarkwa, Ghana. Zinc-rich chromite grains are either clean or contain exsolution blebs/lamella of rutile. The conglomerates show evidence for post-depositional hydrothermal fluid influx and fluid-induced mineral alteration. The strong negative correlation between Zn and Fe2+, Al and Cr, and Al and Fe3+, and strong positive correlation between Zn and Al suggest secondary incorporation of Zn and Al by substitution of Fe2+ and Cr (and Fe3+), respectively, leading to partial transformation of (Fe)(Cr,Al,Fe3+)2O4 towards ZnAl2O4 composition. The chromite grains were possibly derived from komatiite. The timing of Zn enrichment, either at the provenance prior to sedimentation, or at the depositional site post-dating sedimentation, remains unresolved. [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]

Accumulated Sediment layer thickness is an important parameter to assess the capacity lost in any reservoir. The study focuses on assessing the quantity and depth of sediment layers at various points of Wellington reservoir using geophysical survey method. This electrical resistivity survey was done in fifteen locations in Wellington reservoir using ABEM Terrameter SAS 1000 with Schlumberger electrode arrangement. The data interpretation was carried out using IX1D v2 software. The results revealed that the resistivity of deposited sediments carried by inflow water ranges from, 0.8 Ωm to 58 Ωm and Sampling of sediments was done in those vertical electrical sounding points to validate the results and to characterize the type of soil. The thickness of sediments is around 4m near embankments and around 0.5 m thickness in the far ends of the reservoir. This study also revealed the native bed level of the reservoir and also the total volume of sediments of about 30.51 × 106 m3 which is responsible for the capacity loss of reservoir. Reservoir management practices against sedimentation like dredging needs information about the depth and distribution of sediment deposition. This method can only be adopted when the reservoir is dry and will give optimum results of sediment deposition by giving their depths. [ABSTRACT FROM AUTHOR]

A new bonebed recovered from the Late Triassic of India contains various macro- and microfossils, unionid bivalves and coprolites. The macrofossils include more than 700 identifiable skeletal specimens of 27 metoposaurid, four phytosaur and two rhynchosaur individuals whereas the microfossils comprise about 500 isolated teeth of varied chondrichthyans, dipnoans, actinopterygians, archosauriforms, and several non-mammalian cynodonts. The bonebed is a monodominant, multitaxic, parautochthonous, time-averaged, attritional assemblage. The Tiki floodplain was populated by highly diverse animal communities occupying terrestrial, semi-aquatic and aquatic realms, where scavenging and/or predation were common. Two distinct biostratinomic modes deduced are – (i), natural death, decomposition, and differential pre-burial modifications of the large terrestrial and semi-aquatic animals, and (ii) breaching of banks during flooding events, mass death, and high energy deposition of sediment load including various aquatic fishes and unionids. Similar REE patterns of a representative sample set of bone specimens and their encasing matrices suggest same diagenetic condition and a single burial event. The MREE enrichment, cerium and uranium content indicate reducing burial microenvironment for the studied fossil specimens. The Late Triassic scenario comprised highly dynamic animal communities that had different mortality dynamics and fossilisation pathways depending on the habitats and palaeobehaviour of the animals. [ABSTRACT FROM AUTHOR]

The Cretaceous chaetetid sponge Acanthochaetetes huauclillensis Sánchez-Beristain and García-Barrera is reported for the first time from the Aptian–Cenomanian Khalsi Formation, Ladakh Himalaya, India. Its low- to high-domical growth form could suggest an adaptation to either an environment with constant sedimentation rates, or to an irregular substrate. However, these growth forms also may indicate an absence of important environmental/sedimentological changes during the lifespan of the sponges. In addition, the growth form of this species suggests a calm, non-turbulent, reef-like microenvironment. Along with the other faunal assemblages, such as the rudists, corals, and the gastropod Nerinea, A. huauclillensis indicates a tropical to subtropical shallow marine carbonate platform setting. This new finding extends its stratigraphic range from the upper Hauterivian to the Aptian–Cenomanian interval in the eastern Tethyan realm. [ABSTRACT FROM AUTHOR]

As of mid-2021, four hydroelectric dams are operational on the main channel of the Teesta River in the mountainous and tectonically active Sikkim-Darjeeling-Kalimpong region of India. Riparian ecological and fluvial morphological changes after damming have not been documented. This paper describes an early study of a section of the middle Teesta River, at two of the dam-created reservoirs, just before the river enters the plains. High-resolution, multi-beam, geo-located sonar was used to map the bathymetry of the reservoirs. This resulted in the creation of 30cm-resolution bathymetric maps of the two reservoirs showing valley bottom morphology within them. The bathymetric maps were compared with pre-dam digital elevation models of the valley to create topographic change-maps. The change-maps indicate significant differences in valley morphology due to erosion and deposition processes. Land cover changes due to inundation were quantified from analysis of satellite imagery time series data of the reservoir riparian zones. Land cover change analysis showed a loss of ~ 74,000 trees in ~ 225 ha of flooded riparian corridors due to long-term inundation. The study shows that the dams have caused 7.4% of the river length to become quasi-lentic, and drastically altered sediment dynamics and hydrologic flow. Sediment deposition calculations indicate the reservoirs losing almost three-quarters of their surface areas to sediment deposition features within 15 years. This study will serve as an important baseline for future studies, and influence design and policy regarding riparian and fluvial ecosystem management, monitoring, and evaluation in the Teesta and similar mountainous river basins in the Eastern Himalaya. [ABSTRACT FROM AUTHOR]

Sediment characteristics and distribution analysis along the Chandipur Coast in Odisha, India was performed using a variety of techniques that include sedimentary characteristics including variation in grain size, shape and character of quartz grain surfaces (determined in light microscope and electron microscope scanning). Samples were taken from various locations representing high-tide areas and low-tide areas for analysis of the grain size, intended to determine physical properties and textural parameters such as mean, sorting, skewness and kurtosis. Grain size distribution research was conducted to characterize sedimentary transportation behaviours. CM diagram defines the rolling, saltation and graded suspension process for sediment deposition at the beach. Linear Discriminant Function (LDF) indicates the superiority of marine environment with lower deposition areas. Scanning Electron Microscope (SEM) was used to examine the quartz grains to determine the origin of the sediments and to establish the physical and chemical processes that occurred during their period of deposition in recent coastal sediments. [ABSTRACT FROM AUTHOR]

Soil erosion causes significant damage to humans by reducing soil productivity and filling reservoirs from sediment deposition in Narmada Basin, India; hence, it is important to recognize soil erosion prone areas for preventive steps in this basin. In this research, prioritization of sub-watersheds of Narmada Basin has been done using game theory-based approaches such as Condorcet and Fallback bargaining. For this purpose, Digital Elevation Model (DEM) generated by Shuttle Radar Topography Mission (SRTM) was used to extract and analyze 12 morphometric parameters including linear, aerial, and relief parameters. Based on the Condorcet and Fallback bargaining methods, the Mohgaon watershed came at the first priority ranking, that means it's the most vulnerable watershed from the point of soil erosion (SE). Game theory was successfully implemented for prioritizing watersheds in term of SE. The findings showed that morphometric parameters and game theory approach have a high efficiency in recognizing areas that are vulnerable to erosion. [ABSTRACT FROM AUTHOR]

Microtremor measurements are used for preliminary site effect of the Quaternary sediments of Varanasi in Indo-Gangatic plain, which is being planned as a Smart City of India. We evaluated site effects using single and arrays Microtremor measurements at various sites in the Varanasi City, Uttar Pradesh, India. At City, H/V spectral ratios using microtremor measurements indicate fundamental frequency range 0.37–0.63 Hz, corresponds amplification 5 to 14 times. This indicates that the deep thickness of the upper soft soil at about several hundreds of meters. Such huge amount of sediments deposition sources could be associated with fluvial rivers system in the area and sediment drain from Himalaya. The average peak frequency (~0.5) may reflect the Quaternary-Tertiary boundary. Microtremor array measurements at two sites were taken using circular arrays (30 and 60 m) which consists of three recording stations on the circumference of circle and one in the centre of circle. The Phase velocity dispersion of Rayleigh wave is calculated from array using SPAC method, and a 1-D shear wave velocity structure is determined by means of inversion processes. The top layers up to 50 m show shear velocities between 280 and 320 m/s and the velocities of underneath layer vary between 1500 and 1600 m/s till 100 m of depth. These results from the present study would be useful for future planning purposes as well as risk management and to reduce severity of earthquake effects in the study area. [ABSTRACT FROM AUTHOR]

The rare earth elements (REE) in the clay fraction of sediments in 15 rivers and their estuaries along the east coast of India were analysed in this study. The total REE content (∑REE) varied from 130.98 to 289.85 μg/g and from 70.89 to 352.61 μg/g in rivers and estuaries respectively. The ∑REEs of estuarine clays (except the Brahmani and Baitarani) was lower than in rivers. The Post-Archean average Australian Shale-normalized REE patterns in rivers and estuaries were similar and categorized into three types. The REE patterns reflect the composition of dominant geological formations in river basins and extent of sediment mixing from different sources during transport. Hydrodynamic conditions controlled the abundance and fractionation of REE in the estuaries. The Sm/Nd ratios of clays were largely controlled by mineral composition and Y/Ho ratios were affected by sedimentary processes in the estuaries. [ABSTRACT FROM AUTHOR]

Sedimentation in lakes occurs from the time of its formation and continues till the final deposition. The rate of sedimentation varies depending upon climate, geology, soil cover and relief. In the present study, an attempt has been made to investigate the distribution and variation of sedimentation rate in Indian lakes. For this purpose, Indian lakes are classified into three zones viz., North Indian lakes (NIL), Central Indian lakes (CIL), South Indian lakes (SIL) and 27 sampling points distributed throughout India has been considered among all three zones. Correlation of rate of sedimentation data with catchment area, surface area and lithology is done in order to understand the controlling factors, rainfall and temperature data are also taken into consideration to know the effect on the sedimentation rate. In all three zones, the highest precipitation observed 2488, 1800 and 4000 mm/yr in the Nainital lake, Chilika lake and Pookot lake, respectively and temperature fluctuations in the northern region of India is higher than the central and southern region. The results showed that the NIL have relatively higher sedimentation rate compared to the CIL and SIL due to slopy terrain, higher precipitation, temperature and lithological inconsistency in northern Indian region whereas all these factors are less effective in other two zones with a minor contribution from other independent factors. NIL have ~0.634-0.804 cm/yr and ~0.636-1.117 cm/yr more sedimentation rate than CIL and SIL, respectively. [ABSTRACT FROM AUTHOR]

In the present study from the late Pliocene ofNeillWest Coast Formation, Neil Island, serpulid tubes assignable toDitrupa gracillima Grube have been identified with the help of tube morphological (light microscopy) and ultrastructural (SEM) studies. This is the first record of the species from the late Pliocene of India. The outer layer ofD. gracillima is entirely different from other invertebrates, and the presence of Ridged Prismatic Structure (RRP) exclusively characterises this particular species. The mineralogical analysis (Raman spectroscopy and EDS) reveals a Mg-Ca skeletal for D. gracillima. Isotopic analysis indicates that there is a narrow range of variation in the 18Ovalues ofD. gracillima The 13CofD. gracillima shows significant variation and displays themost 13Cdepleted values. Based on isotopic analysis it has been inferred that the deposition of sediments took place in a shallow marine environment and D. gracillima thrived in the proximity of hydrocarbon seepages. The present day distributional pattern of D. gracillima indicates that they are mainly confined in the Indo-Pacific region. [ABSTRACT FROM AUTHOR]

The assessment of chronological evolution of the channel functional units is an imperative aspect to understand the channel avulsion nature and planform change. In this study, the channel functional units (channel, aggradational and abandoned) and their distinct micro-morphologies have been assessed through the landuse and landcover classification, terrain analysis, lithostratigraphic records and fluctuating flow regimes in the ancient delta fan of the Subarnarekha basin. The distinct micro-morphological features of the functional units have been formed and evolved under the dominance of fluvial environment coupled with the fluctuating strength of Indian summer monsoon (ISM) and regression phase of sea-level since 6000 years before present (YBP). However, the borehole lithostratigraphic records reveal that the ancient delta fan was formed under the different fluvio-marine depositional environments of the marine transgression, regression and stillstand phases since 32,200 YBP. The riverbed of the recent course is ascended than the palaeo-courses due to declining trends of water discharge and sediment load in the last four decades as well as during the late Holocene mega-drought event. The channel unit and abandoned unit have been transformed into the aggradational unit with micro-morphologies of point bar, fill-terrace, and natural levee under the influence of channel avulsion and bulk of sediment deposition related to the fluctuating flow regime and base level of erosion. The micro-morphological features (marshes, oxbow lakes and meander neck-cuts) of the abandoned unit have been modified from the channel unit after diversion of the recent course from the palaeo-course owing to extreme discharge and valley drowning during lowstand. [ABSTRACT FROM AUTHOR]

Quaternary sediments are preserved in disconnected patches along the middle and lower reaches of major river valleys like Damanganga, Par, Ratakhadi and Dongarkhadi in the Dadra and Nagar Haveli region of Konkan coastal belt, Western India. These deposits mainly consist of stratified sand, silt, clay and gravel beds. The study area has been earlier affected by moderate earthquakes. The identified soft-sediment deformation structures (SSDS) are mainly developed in the sand silt, sand gravel and clay beds; and includes intrusive sedimentary bodies (dykes and sills), slump structures, suspended clast blocks and convolute structures. The nature, shape and dimension of SSDS suggest that the trigger mechanism and driving forces for the origin of these structures were seismic shock waves. Sediment loading and storm events as a trigger for the SSDS are less likely the reason and the proximity of these structures to the faults support the inference that it may be of seismic origin. Deformation in the Quaternary sediments of Dadra and Nagar Haveli imply the presence of neotectonic activity and points to an earthquake of magnitude >5.5 that struck the study area after sediment deposition. [ABSTRACT FROM AUTHOR]

Sequence of strata with consistent and monotonous repetition of two or more kind alternating lithologies are quite common in geological record through the ages and are interpreted as a product of cyclic sedimentation. Cyclic depositional pattern is extensively found in fluvial deposits. Here a brief model of regional depositional stacking pattern is proposed based on the observations from regional geophysical log correlation as well as core based interpretation from Karanpura field. Subsurface facies study from this marginal Gondwana basin enhanced the understanding of stacking pattern and depositional cyclicity preserved in middle Permian Barakar Formation. Four major fining upward depositional cycles have been established regionally, each consisting of low and high accommodation system tracts at bottom and top of individual cycle respectively. Findings have been correlated with basin evolution process and major geological time events. [ABSTRACT FROM AUTHOR]

The nature and stratigraphic position of the Beawar gneiss unit (BGU) within the central Aravalli orogen (NW India) remain unresolved. These rocks are currently assigned to the South Delhi Supergroup, assumed to be deposited at 1200–1000 Ma. This interpretation is challenged by new results of petrography, combined with U-Pb dating, Hf isotope analyses of zircon, and whole-rock geochemistry. These data reveal that the BGU consists of both ortho- and paragneisses and that the protoliths were formed and/or deposited at the boundary between the late Paleoproterozoic and early Mesoproterozoic at ca. 1600 Ma. U-Pb ages of detrital zircon grains from a paragneiss sample indicate a maximum deposition age of 1614 ± 14 Ma and major age peaks at 2528, 1916, 1840, 1725, and 1617 Ma. These ages, in combination with Hf isotope data, suggest that the source area consisted mainly of felsic magmatic rocks similar to those exposed within the Aravalli orogen and in the Bundelkhand Craton and/or in terranes within the Central Indian Tectonic Zone. A single detrital zircon with an Eoarchean crystallization age of ca. 3630 Ma and Hf model age of 4.05 Ga point to the existence of the Hadean crust. Magmatic zircon in an orthogneiss sample yields an upper-intercept age of 1581 ± 24 Ma, indicating granite emplacement during the early Mesoproterozoic. Combined geochemical and Hf isotope data suggest that the orthogneiss protolith was a strongly peraluminous S-type granite, formed by melting of surrounding country rocks perhaps within a convergent setting. U-Pb ages (980–960 Ma) of zircon overgrowths and monazite grains suggest that all the rocks were affected by a Grenvillian metamorphic overprint during the assembly of Rodinia. [ABSTRACT FROM AUTHOR]

The higher rate of sedimentation in reservoirs is one of the main concerns in sustainable reservoir management, which impairs the functional capacity of reservoirs that may lead to various environmental risks. Estimation of sedimentation rate and useful life of a reservoir using appropriate methods is imperative for sustainable management. This paper deals with the computation of sedimentation rate and useful life of Tehri reservoir of Bhagirathi river, in India, using hydrographic survey analysis, Hydrologic Engineering Center's River Analysis System (HEC-RAS) modelling, satellite remote sensing (SRS) technique, and trap efficiency based empirical curve methods. The rate of sedimentation was found as 5.33 million cubic metres (MCM)/year based on hydrographic survey analysis from the data obtained for the years 2005, 2008 and 2013. Likewise, the mean annual rate of sedimentation was estimated to be 5.07 MCM/year and 5.75 MCM/year based on the HEC-RAS model and SRS techniques respectively. Brune's method and Churchill's method of trap efficiency were found to be inconsistent with the hydrographic survey results. The reservoir can be classified as Type III reservoir with respect to the sediment vertical distribution analysis. Changes in bathymetry obtained in the simulation studies showed that the Bhagirathi river's 28-30 km reach would be most vulnerable to sedimentation problems. The estimated useful life of Tehri reservoir was found to be in the range of 160-180 years. The SRS technique and hydrodynamic model provided a better fit with the observed data. [ABSTRACT FROM AUTHOR]

A shoreline is dynamic in nature which makes the interface of land and water that offers socio-economic and cultural protection to its adjacent population. The purpose of this study was to understand long-term (1973-2015 and 2015-2057) shoreline transformation as well as the patterns of soil loss/sedimentation owing to physical and anthropogenic activities along the Andhra coast. Satellite imageries of LANDSAT from 1973 to 2015 were utilized to delineate the shoreline. Shoreline fluctuations were analyzed by Net Shoreline Movement (NSM) and End Point Rate (EPR) statistics using the Digital Shoreline Analysis System (DSAS) computer software of USGS. The highest and lowest EPR of about 67.63 m/y and -43.14 m/y were recorded in the Andhra coast. The high rate of deposition was recorded in the Godavari delta, whereas Krishna delta experienced low erosion. This study establishes the use of remote sensing data and statistical techniques such as EPR and NSM for shoreline monitoring are helpful for soil loss/accretion evaluation and future shoreline prediction. [ABSTRACT FROM AUTHOR]

Sandstones belonging to the Oligocene Barail Group and Miocene Surma Group of the Mizoram Foreland Basin have been studied geochemically to constrain their provenances, tectonic setting, and other sedimentary processes (weathering and mineral sorting etc.). Based on their mineralogical compositions, these sandstones are classified as quartzarenite and sublithic-arenite. The sandstones of Barail and Surma Groups have similar contents of most of the major elements except for SiO2 and Al2O3. The Barail sandstones are relatively more siliceous and less aluminous compared to the Surma sandstones. Barail and Surma sandstones were plotted in a singular array on different geochemical discrimination diagrams. The CIA and CIW values of the sandstones of Barail (69 and 77 respectively) and Surma Groups (68 and 77 respectively) suggest that the sandstones were derived from moderately weathered source rocks. In the A–CN–K diagram, the studied samples plotted along a roughly singular trend that originates from granodiorite as well as Trans-Himalayan granitoids and also confined within the field of Siwalik sediments. Chondrite-normalized REE patterns for the Surma and Barail sandstones are identical and are similar to upper continental crust, with moderate to high LREE enrichment and prominent negative Eu anomalies (Eu/Eu* for both Barail and Surma sandstone = 0.69), indicating their derivation from a felsic magmatic source. The values of Eu/Eu*, (LaN/LuN), La/Sc, La/Co, Th/Sc, Th/Co, and Cr/Th ratios of Surma and Barail sandstones are also not significantly different, and the values are similar to fine-fractions derived from the weathering of felsic rocks. In the K2O/Na2O versus SiO2, Th–Sc–Zr/10 and Ti/Zr versus La/Sc tectonic discrimination diagrams the studied samples of Barail and Surma sandstones plot within the fields of greywacke from continental island arcs and active continental margin. The geochemical characteristics of the studied sedimentary rocks and their similarity with the Siwalik foreland sediments thus suggest were sourced from different felsic magmatic lithounits of Himalaya and were deposited in an active continental margin. [ABSTRACT FROM AUTHOR]

Karanpura field is the western most member of the E-W trending Damodar Valley basin, belonging to Indian Gondwana sedimentation. This paper aims to provide a field-scale depositional model of Permian Barakar Formation from Karanpura field in order to enlarge the knowledge of stratigraphic and facies architecture. The study reviews the findings from extensively available cores. Four major facies were defined, which represented a fluvial depositional environment. Observations from core analyses were integrated with high resolution geophysical log data to understand the stacking pattern and depositional cyclicity of Barakar Formation. The lateral and vertical distributions of the facies associations were highlighted by well correlations, which established major fining upwards depositional cycles in the area. The depositional model has been interpreted on a regional scale. [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]