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In this study, soil loss by water in the Chambal river basin (CHB) has been estimated using Google Earth Engine and Geographic Information System platforms employing the Revised Universal Soil Loss Equation (RUSLE). Google Earth Engine, a cloud-based platform, has been used for generating land use/land cover map from the voluminous satellite remote sensing data. The observed mean rate of soil erosion in the CHB is 1.17 t/ha/yr. The study reveals that very severe type of soil erosion in the Chambal river basin is found in the gullies/ravines and barren lands with the highest mean rate of soil erosion in the gully areas at 13.44 t/ha/yr. Catchment-wise soil loss estimates suggest that the four catchments namely Kali Sindh, Lower Chambal, Upper Chambal and Parbati are experiencing much higher soil loss in comparison to others; hence these catchments are prioritised for soil conservation efforts. Sensitivity analysis of individual factors and their interaction effect indicates that LS factor is the most influential factor in the study area followed by C factor. Research highlights: Estimates soil loss by water for the first time at basin scale in the Chambal river basin (mean rate 1.17 t/ha/yr) by integrating Google Earth Engine and GIS employing RUSLE. Provides insight into the spatial pattern and status of soil erosion in the study area. Reveals very severe type of soil erosion in the areas of gullies/ravines with the highest mean rate 13.44 t/ha/yr and 5.92 t/ha/yr, respectively. LS factor is the most influential factor in the study area, followed by C factor. Prioritises Kali Sindh, Lower Chambal, Upper Chambal and Parbati catchments for soil conservation efforts based on much higher soil loss. [ABSTRACT FROM AUTHOR]

The consideration of events of marine invasion within the continental Gondwanaland in the Indian subcontinent during the Permian is often doubted due to lack of appropriate fossil record. The Permian Barren Measures Formation within the Lower Gondwana Supergroup in eastern India is considered as deposited in a fluvio-marine estuarine setting, interpreted mostly based on sedimentological signatures in terms of marine tide and wave imprints within the so-called continental fluvial deposits. Fossilized shells of marine Gastropoda genus Baylea DeKoninck, 1883, are reported here from the siltstone beds of the prodeltaic sediments of the Barren Measures Formation, West Bokaro Basin. The in-situ preservation of the marine invertebrate fossils Baylea sp. provides definite proof of marine link of the West Bokaro Basin during the Barren Measures sedimentation. The present fossil record, when combined with sedimentological attributes, clearly signifies a marine inland encroachment event during the Permian time. [ABSTRACT FROM AUTHOR]

The interrelationship between the land use and land cover (LULC) pattern, land surface temperature (LST), carbon stock, and sequestration has been assessed using satellite data and Geographical Information System (GIS) tools in Imphal-West district, Manipur, India (North Eastern region of India). LST for the past 10 years (2011–2021) was calculated using three retrieval methods such as Mono Window Algorithm (MWA), Radiative Transfer Equation (RTE) and Single Channel Algorithm (SCA). The calculated LST (temperature varies in the range of 10°–40°C) was compared with atmospheric temperature values obtained from MODIS (Moderate Resolution Imaging Spectroradiometer) data as well as field (ground station) data collected. From the comparison, it was observed that the SCA method obtained a minimum mean temperature difference (minimum error) as compared to MODIS data, while the MWA method obtained a minimum mean temperature difference as compared to field data. The calculated (generated) results were again compared and validated using measured soil temperature data and observed similar trend showing MWA and SCA slightly efficient than RTE method. In order to understand the LULC change pattern in the study area as well as to estimate the aboveground biomass, LULC for the years 2011, 2016, 2021, and 2030 were also generated. Then, carbon stock for the years 2011, 2021, and 2030 and sequestration for the year 2030 were calculated using the InVEST (Integrated Valuation of Ecosystem Services and Tradeoffs) model. It is concluded that the study area has witnessed a gradual increase in urbanisation (built-up area increases by up to 2.9% in 10 years, i.e., between 2011 and 2021, but significantly decreases in barren land, 9.9%), but not an abrupt change in LST and carbon storage. However, the significant spatial change distribution of LST and carbon stock with the change in LULC pattern was observed. [ABSTRACT FROM AUTHOR]

Alaskan-type of plutonic complexes represent arc magma chambers and they occur throughout the earth's history from Archean to Phanerozoic periods around the globe. The ultramafic rocks from these complexes commonly contain spinels of varied chemistry, especially rich in Cr, Fe, and Ti coupled with low-Al contents when compared to the spinels from oceanic or continental rift domains. An attempt is made here to study Thenmudiyanur Mafic–Ultramafic Complex (TMUC) from the Belur Shear Zone (BLSZ) in the northeastern margin of Southern Granulite Terrane, located about 20 km SW of Tiruvannamalai Town. The important lithologies of TMUC include dunites, peridotites and pyroxenites surrounded by metagabbros and amphibolites. The dunites and peridotites are highly serpentinized with well-preserved cumulate olivines along with magnesite, chrome spinel and clinopyroxenes. The mineral chemistry of olivines represents higher forsterite (Fo88–90) and Mg# 87–90 [100×Mg/(Mg+Fe2+)] contents. The gradational contact within the rock types, compositional variations and cumulate nature of mineralogical characteristics suggest fractional crystallization of magma from a single parental source. The chrome spinels from these lithologies represent higher Cr# [100×Cr/(Cr+Al)] that ranges from 65 to 86 along with lower MgO (1.06–4.57 wt%) and MnO (<1 wt%) contents. The presence of chrome spinels together with olivine in dunites as well as peridotites and clinopyroxene mineral chemistry from pyroxenites reveal arc signatures for the evolution of TMUC, which seems to be similar to that of the Alaskan-type. Considering the tectonic setting and the age relationships of adjacent lithologies, it is opined that the TMUC might have evolved during the Neoproterozoic period. [ABSTRACT FROM AUTHOR]

The Debari Formation plays a vital role in constructing the stratigraphy of the Aravalli Supergroup. However, the Debari Formation occupies different positions in the stratigraphic schemes proposed by various workers, which created a continuing controversy. This problem might be linked to a lack of knowledge on detailed field relationships, underutilisation of the well-preserved sedimentary attributes and available detrital zircon ages of the polymictic conglomerate–sandstone–mudstone association that constitute the Debari Formation. Moreover, the same association has given different names in different sections. The present outcrop scale observations on the field relationships reveal that these sediments overlie the syn-rift volcanic associated fluvio-deltaic Delwara Formation and stromatolitic (phosphatic) carbonate-bearing platformal Jhamarkotra Formation (~1.7 Ga) across a basin-wide top-rift unconformity. The detrital zircon geochronology of the sediments lying below and above the unconformity suggests a nearly 20–50 Ma time lapse. Facies attributes of the polymictic conglomerate–sandstone–mudstone association (~1.6 Ga) point to deposition under ephemeral channels in steeper braid plain to storm-induced tidal flat environments. These sediments represent the initiation of a post-rift passive margin basin, which ultimately evolved into quickly subsiding deep half-grabens in between basement highs during rapid collapse at the rift to drift transition. These deep basins received turbidite sediments (~1.5 Ga) of the Udaipur Formation. However, equivalent sediments are named differently as Tidi Formation and Jharol Formation, exposed in other sections of the Aravalli basin. On the strength of the field studies, in-depth sedimentary facies analysis and available detrital zircon geochronology, a two-fold stratigraphy and a tentative basin evolution model have been proposed for the Aravalli Supergroup. [ABSTRACT FROM AUTHOR]

Assessment of land suitability for rain-fed cultivation in undulating terrains of red and lateritic zones (RLZ) is essential to enhancing agricultural productivity, given the recurrent droughts that are taking place due to the ongoing climate change. In this study, a GIS-based multi-criterion decision-making approach characterized the agricultural land suitability in Kashipur and Chhatna blocks (RLZs) of West Bengal, India. The land suitability analysis included multiple factors like slope, land use/cover, soil moisture, erosion, depth, texture, pH, geology, the proximity of the surface, and groundwater. The analytic hierarchical process assigned the weights of multiple criteria. The relative importance of agricultural potentiality decided the ranks of the subcriteria. This study mapped the spatial distribution of four potential land types, viz., unsuitable (8.52%), marginally suitable (41.58%), moderately suitable (38.22%), and highly suitable (11.69%). An error matrix generated an accuracy of 85% (on comparing the agricultural land suitability map with the ground data), and the kappa coefficient was 0.8. The findings indicated that the present methodology using AHP with supplemented parameterization provided more persuasive consequences to assess agricultural land use. The present study would optimize the yield by conserving soil and water in different agricultural land to reduce drought risk in RLZs. Highlights: Agricultural land suitability has been evaluated using GIS and AHP-based multi-criteria decision-making process in existing agricultural land for enhancing production in a sustainable way. Results have been validated by rigorous field surveys. The superior accuracy of field verification recommended that the present methodology will perform as an important tool for small land holding farmers in drought-prone undulating RLZ of India. Systematic cropping practices and water harvest management based on agricultural land suitability were discussed, which can help reduce soil erosion and drought impact. [ABSTRACT FROM AUTHOR]

A recent petrological study on the lesser-known Sholayar alkaline syenite complex (10°17′59.9′′N: 076°47′26.3′′E) accommodated in the high-grade rocks of the Southern Granulite Terrane reveals the presence of three distinct petrographic types namely leuco syenite, melanofelsic syenite and mela syenite. The syenites, in general, have the following constituent minerals, namely alkali feldspar (Or76.8Ab23.2–Or93.4Ab6.6), plagioclase (An4.1–An17.3), calcic amphibole (edenitic hornblende/ferropargasitic hornblende), quad pyroxene (diopside–hedenbergite), biotite and opaque minerals (magnetite and ilmenite). Mode-based statistical studies indicate that a highly significant correlation exists among certain mineralogical parameters including quartz%, total feldspar%, colour index, alteration index and hydration index. Isopleth plots of these parameters strongly suggest maintenance of a magmatic regime throughout, with increasing water content towards the end stage of crystallization. Several geothermobarometric methods point to shallow to moderate level emplacement (~9–23 km) of the alkaline/sub-alkaline syenite magma which was facilitated by a 'hydration event'. The steep change in water gradients (in localized pockets) of the syenite intrusives has been corroborated by textural evidences. Research highlights: First systematic petro-mineralogical report of Sholayar alkaline syenite complex from SGT. Involvement of single magmatic lineage with variable water content. Geothermobarometry suggests a moderate to shallow level of syenite emplacement. [ABSTRACT FROM AUTHOR]

Drifting buoys (DBs) are widely deployed to observe near-surface ocean currents and sea surface temperature. The National Institute of Ocean Technology (NIOT), Chennai, India, had indigenised the DB with the Indian satellite (INSAT) in 2012. This paper describes the results of various studies conducted by NIOT using the indigenised DBs and also describes unique features attempted in indigenised DBs to measure the near-surface ocean current with 24 position acquisitions per day to capture small-scale surface eddies and the use of real-time geostationary satellite communication every hour. Additionally, the surface currents observed with indigenous DB are compared with DBs available in the market, Marlin-Yug (coefficient of determination R2 > 0.88) and forecast using the ocean surface current analyses real-time (coefficient of determination R2 > 0.90). Our results show that the DBs in the Bay of Bengal are carried with the East India Coastal Current in the March–May periods and the in-situ observations by the DB provide accurate surface current observations than satellite-based data. Furthermore, the new observations near the world's largest tidal mangrove and delta system, the Sundarbans and Bengal Delta, will help in further enhancing our understanding of the spatiotemporal variability in the region in terms of coastal currents and its influence on marine environments. [ABSTRACT FROM AUTHOR]

The summer monsoon rainfall affects most of the population of the Indian subcontinent. A slight variation of strength and spatial distribution in monsoon rains has huge societal impacts. So understanding the significance of its variability and the factors that control this variability is an imperative task. The Indian monsoon (also regarded as a global phenomenon) varies with the global climatic components like geopotential height, sea surface temperature, outgoing long-wave radiation and mean sea level pressure. The paper presents a statistical analysis of rainfall (over India) and climatic components (over the Arabian Peninsula) and the relationship between them. The period (1979–2013) shows a decrease in monsoon rainfall over the country. During this period, there was an increase in the tropospheric temperature over the Arabian Peninsula. Rainfall showed a direct relationship with the tropospheric temperature and thickness that gets stronger during the period (1979–2013). Except for the northeastern region of India, the rest showed a strong positive correlation with the middle and upper tropospheric temperature over the Arabian Peninsula while the lower tropospheric temperature showed a weak relationship. However, this correlation gets weakened during the El Nino and La Nina years. The findings will be helpful to enhance the Indian rainfall variation and the climatic factors responsible for this variation. [ABSTRACT FROM AUTHOR]

Neoproterozoic Ambaji granulite, in the South Delhi terrane (SDT) of the Aravalli–Delhi mobile belt (ADMB), is multiply deformed at different stages of its exhumation from the middle–lower crust. It was intruded by four phases of granites, G 0 - 3 , of which the G 3 was syntectonic with brittle shearing. The orientation of the G 3 granite veins was used, in this paper, to measure the palaeostress and magma pressure during its intrusion. The G 3 granite has a porphyritic texture with quartz, microcline and biotite minerals and contains magmatic foliation; biotites are aligned oblique to such foliation, suggesting the syntectonic intrusion of the granite with normal faulting. Stereoplot of the poles of the granite veins shows concentration in the NW and SW quadrants and lack data over an elliptical area at the centre, indicating a girdle pattern. This implies that the magma pressure P m > σ 2 , compression σ 1 was vertical and extension σ 3 was NW–SE horizontal. Values of θ 2 = 16 ∘ and θ 3 = 40 ∘ were obtained from the stereoplot, used to calculate stress ratio Φ = 0.81 , driving pressure R ′ = 0.92 and the construction of the 3D Mohr plot for P m and principal stresses. Result suggests that the G 3 granite intruded under extensional tectonics that probably contributed to the exhumation of the Ambaji granulite. [ABSTRACT FROM AUTHOR]

Eastward-moving upper air troughs in the subtropical westerlies, commonly known as the western disturbances (WDs) in the Asian subcontinent, are primary sources of precipitation over the north-west Himalayan (NWH) region and the northern plains of India during winter. Many simulation case studies with the help of numerical weather prediction models and a few observational case studies have been conducted to understand the spatial structure, dynamics, energy and weather associated with the WDs over the NWH in the past. However, studies using in situ observations on the impacts of the approaching WDs on various surface meteorological variables at a local scale in the high-altitude mountainous regions of the NWH are lacking. The objectives of this study are to examine the impacts of the approaching WDs on various surface meteorological variables for 11 stations in the NWH and the associated precipitation amount in a 24-hr time interval. Changes (departures) in the values of various meteorological variables are examined on the first precipitation day of the occurrence of active WDs to study the impacts of the approaching WDs and the associated precipitation amount in the 24-hr time interval which are found to depend on the altitude and geographic location of a station. The mean drop in the maximum and ambient air temperatures are found to be 2.0 ∘ and 0.7 ∘ C , respectively, while the mean rise in the minimum air temperature was found to be 0.8 ∘ C . A mean drop in the surface atmospheric pressure and a mean increase in the relative humidity are found to be 0.9 hPa and 19.5%, respectively, in a 24-hr time interval. The mean precipitation amount and mean maximum precipitation amount associated with the active WDs in the 24-hr time interval are found to be 8.9 and 68.8 mm, respectively. The results are briefly discussed in the paper. The findings of this study can be useful for operational weather forecasting and a selection of precursor variables for developing a real-time local scale weather forecast model(s) for remote areas of the NWH for the winter season. [ABSTRACT FROM AUTHOR]

This paper describes a new method based on the particle swarm optimisation (PSO) technique for interpreting the second moving average (SMA) residual gravity anomalies. The SMA anomalies are deduced from the measured gravity data to eradicate the regional anomaly by utilising filters of consecutive window lengths (s-value). The buried structural parameters are the amplitude factor (A), depth (z), location (d) and shape (q) that are estimated from the PSO method. The discrepancy between the measured and the predictable gravity anomaly is estimated by the root mean square error. The PSO method is applied to two different theoretical and three real data sets from Cuba, Canada and India. The model parameters inferred from the method developed here are compared with the available geological and geophysical information. [ABSTRACT FROM AUTHOR]

Globally, climate change has caused changes in frequency and intensity of climate extremes such as heat waves, droughts, floods and tropical cyclones. There is a need to understand the pattern of regional climate extremes to develop crucial adaptation strategies for the farming community. This paper focuses on developing the Expert Team on Climate Risk and Sector-specific Indices for rainfall, relevant for the agriculture and food security sector. The indices have been developed for Lower Vellar River sub-basin, a coastal basin in Tamil Nadu, India. Trend analysis has been done for the climatic and cropping seasons in the sub-basin. Overall, there has not been any trend in the annual rainfall index values. The monthly trend values for the different indices have mostly exhibited insignificant trends throughout the study period (1978–2015) except for a few indices. Overall, the southwest monsoon season has shown a significantly decreasing trend in the indices. The northeast monsoon season has shown insignificant trends with positive slopes for most indices. There were insignificant or no trends in the indices for the summer season. The findings from the study can be used as a guiding tool for developing adaptation strategies, for the farming community. [ABSTRACT FROM AUTHOR]

This paper documents three phases of folding within the Meso-Proterozoic Champaner Fold Belt (CFB) located at the eastern part of Gujarat, western India. The first phase ( F 1) displays WNW plunging F 1 fold of moderately inclined nature in the schists of the Khandia Formation. The second phase ( F 2) refolded F 1 along a similar trend to produce folds of tight isoclinal nature in the Khandia and Narukot quartzites. Additionally, these F 1 folds depict second-order tight, and F 2 folds as first-order open type in the younger sequences of the CFB with varying amplitude vs. wavelength ratio. The ratio for F 1 folds ranges from 2:1 to 3:1, obtained along 3–4 m length across 3–6 m 2 area, whereas for F 2 folds the ratio ranges from 1:4 to 1:5 and is obtained along 1–2.5 km length across 0.5–1.5 km 2 area. The fold interference pattern developed on account of F 1 and F 2 folds has resulted into Type-III or hook-shaped geometry regionally. The last phase of folding is characterised by N–S trending F 3 folds of open type over kilometre long limbs of F 1 and F 2 folds. The superposition of F 1 - 3 folds developed map scale Type-I or Dome and Basin geometry over Type-III superposed folds. The overall compressional direction for F 1 and F 2 folds ranges from N–S to NNE–SSW and for F 3 ranges from E–W to ESE–WNW. [ABSTRACT FROM AUTHOR]

The forecast of snow avalanches in the Himalayan region has critical importance due to repetitive hazard scenarios and huge loss of property and lives. In recent years, avalanche forecast models have been developed using meteorological data collected from surface observatories (SO) at Defence Geoinformatics Research Establishment (erstwhile Snow and Avalanche Study Establishment (SASE) and now DGRE), India. For operational forecasting, outputs of a Weather Research Forecasting (WRF) model are used in real-time. The objective of this study is to determine a suitable bias correction approach for three key variables: mean temperature (T), relative humidity (RH), and wind speed (WS) which can be implemented in the operational forecast services at four observatory stations in Himachal Pradesh, India. We consider data of seven cold seasons (November–April) from 2011 to 2018 obtained from SO and WRF model output. Three quantile-based bias-correction approaches: Quantile Mapping (QM), Quantile–Quantile Mapping (QQ), and Quantile–Delta Mapping (QD), have been applied. In applying the QD method, two types of delta terms: multiplicative and additive, have been experimented according to the density distribution of the data. For evaluation, a leave-one-season-out-cross-validation approach is used. The results indicate that the QM and QD methods significantly reduced the bias associated with the mean temperature, relative humidity, and wind speed, whereas the performance of QQ method has limitations for all the variables. Furthermore, to meet the objective of generating bias-corrected data for operational forecasting services, uniform parameter set is generated for each variable associated with all the observatory stations. This approach is effective only for temperature, and for other variables, the improvements were not significant, mainly because of the high topographical variability in the Himalayan terrain. [ABSTRACT FROM AUTHOR]

The Mahanadi Shear Zone (MSZ) in the Eastern Ghats Mobile Belt (EGMB) separates the southern segment of EGMB with dominant NE–SW structural trend from its northern segment with dominant E–W trend. The MSZ is a high-temperature ductile shear zone in which mylonite–ultramylonite occurs intimately associated with pseudotachylite. The association of two components of contrasting origins (ductile and brittle deformations) is possibly attributed to contemporaneous evolution or multiple stages of evolution. Therefore, field and petrographic studies including clast-size analysis of three samples from different localities across the MSZ have been carried out. Field observations suggest that pseudotachylite veins often cut across the mylonitic fabric. In addition, there is variation in orientation of gneissic and mylonitic fabrics in the clasts within the pseudotachylite zones. The pseudotachylites occasionally exhibit crude flow structures and rims around clasts. These features clearly indicate that the mylonitic fabric in the MSZ predates brittle deformation, and the pseudotachylites have not suffered any subsequent deformation after their formation. Clast-size analysis in all three cases follows the Power Law and demonstrates linear distribution. Lower value for fractal dimension (D = 0.51–0.69) and involvement of large range of size distribution of clasts in the studied pseudotachylite samples are attributed to brittle deformation at high strain rate, independent of the ductile deformation event. The present study suggests evolution of the MSZ in two stages, i.e., early development of mylonite–ultramylonite by ductile deformation at deeper level followed by pseudotachylite development at later stage by brittle deformation at a shallower level, thereby overprinting of brittle deformation over the ductile deformation. Research highlights: The Manuscript describes the coexistence of pseudotachylite, mylonite and ultramylonites in the MSZ. Clast size analysis of pseudotachylite suggests a single brittle deformation event. We have highlighted the deformation evolution of the MSZ in the EGMB. [ABSTRACT FROM AUTHOR]

In western Manipur, India, a ~765 m thick dominantly fine-grained succession of the Late Eocene–Early Oligocene Laisong Formation, constituted of siltstone-silty-shale heterolithic units at its lower part and thickly bedded sandstones in the upper part, allowed documentation of subaqueous part of a tidal delta. The abundant incidence of features including lenticular, wavy bedding, starved ripple trains, syn-sedimentary deformation, reactivation and erosional surfaces, double-mud drapes, tangential bottom set contact, rip-up mud clasts bear tell-tale evidence in favour of tidal modulations. Furthermore, a prominent thickening- and coarsening-up progradational facies stacking motif is correlated as signature for tide-dominated delta. From process-based facies and facies succession analysis, five different sub-aqueous environments of delta were delineated which include prodelta, terminal distributary channel, distal delta front, proximal delta front sheet and proximal delta front lobe in order of stratigraphic superposition. The river-fed sediments were extensively reworked by accentuated tidal currents in an embayed coastline, developed along a narrow, elongated ocean basin bordered by the Indian plate on its west and Burmese micro-plate in the east. A local-scale subsidence and sea-level rise is inferred as trigger for the Laisong tidal delta development in the backdrop of its Late Eocene–Early Oligocene time frame that otherwise witnessed large-scale growth of east Antarctic ice sheet and regional scale fall in sea-level. [ABSTRACT FROM AUTHOR]

The flora of Early Permian Talchir Formation is very significant as it holds evidence for the appearance of altogether new flora, the 'Glossopteris flora'. This study contributes to our current understanding of Talchir flora. It also reveals a poor diversity of macrofloral assemblage recorded from the Lower Permian sediments of non-coaliferous Talchir Formation from Singrauli coalfield, Son–Mahanadi valley basin. Recovered plant assemblage is characterised by the occurrence of mostly leaf forms namely, Cordaitales (Euryphyllum), Glossopteridales (Gangamopteris, Palaeovittaria and Cordaicarpus) and Coniferales (Paranocladus) along with stem casts/impressions. Flora is marked with the abundance of the genus Gangamopteris with five species, followed by genus Euryphyllum with four species. The present macroflora is broadly similar to other known contemporaneous floral records of India and other Gondwanan continents but the lack of the genus Noeggerathiopsis in the present assemblage makes it distinct. Genera Euryphyllum (E. elongatum, E. obovatum and E. whittianum) and Palaeovittaria (P. kurtzii) along with taxon Gangamopteris rajaensis, are being reported for the first time from the Talchir Formation of India. Based on the present macrofloral records, the studied sediments have been corroborated to be of Early Permian (Sakmarian) age when the climate was still cold. Research highlights: Euryphyllum, Palaeovittaria and taxon Gangamopteris rajaensis are reported for the first time from Talchir Formation of India. Insightful interpretation of Early Permian (Sakmarian) megaflora of Talchir Formation from Singrauli basin and its distribution in other Gondwana basins of India. The flora is co-relatable with the 'middle floristic zone' of Talchir flora when the climate was still cold, though not harsh. Represents correlation of Talchir flora of India with contemporaneous flora of other Gondwana continents. [ABSTRACT FROM AUTHOR]

This study reports electron probe micro-analysis of relict clinopyroxenes in Neoarchean Kotima basalt of the Dongargarh Supergroup, Central India and their petrogenetic significance. Kotima clinopyroxenes plot in the field of augite and show an overall limited sub-alkaline fractionation trend. Inter-elemental variation diagrams reveal an overall magmatic trend and preservation of magmatic chemistry, whereas their euhedral to subhedral form indicates near equilibrium conditions of crystallisation. Besides wollastonite, enstatite and ferrosilite major components, 'other components' comprises Ca–Al tschermak, esseneite, CaTiAl2O6 (Tp), kosmochlor, aegirine, jadeite and johannsenite. Single clinopyroxene geothermobarometers indicate magmatic temperatures (1180–1050°C) and shallow depths (2–3 kb pressure) of crystallisation of Kotima clinopyroxenes. The clinopyroxene chemistry and chondrite-normalised whole-rock rare-earth element plots imply the derivation of Kotima basalt from a relatively primitive parent magma, in which pH2O and fO2 decreased with fractionation, a hallmark of arc-related volcanics. The overall low-Ti (and Al) contents of the Kotima clinopyroxenes imply their formation from a subduction-related sub-alkaline magma, whereas discriminant plots of Si vs. Al, Na vs. Ti, Al vs. Ti and Ti vs. Alz reveal their formation in a mixed rifting (non-orogenic) continental arc tectonic setting in response to ridge subduction. [ABSTRACT FROM AUTHOR]

Tectonic (in)stability of terrains is of major concern in financial investment for hydrocarbon exploration from such terrains. Morphometric studies of a river can explain neotectonics of the terrain. This study presents the southeast (SE) frontier of the Brahmaputra river valley of the upper part of the state of Assam, northeast India, where geomorphic changes are observed through remote sensing studies. Two primary geomorphic observations of the study are: (1) formation of palaeostream at the valley due to cut-off of headwater discharge due to the activation of frontal thrust (Naga thrust) along the SE boundary of the valley and the Naga Hills (Assam–Arakan fold-thrust belt), and (2) shifting of confluence points Lohit river (tributary of the Brahmaputra river) causing avulsion and formation of a river island (Dibru Saikhowa). The first event is related to the recent tectonic activities, i.e., uplift of a fault-propagation fold (Digboi anticline). The later event of migration of the Lohit river might be associated with tilting of the SE side of the basin due to activities along the blind thrust systems of the Himalayan foot-hills and the basement high over the last 25 years. This gradually elongated its drainage basins. The southern propagation of the frontal thrust systems of Arunachal Himalaya and Mishmi hills has already shifted the course of the Lohit river towards the south leading to significant changes in geomorphology over the last few decades. N–S-oriented compressional stress axis apparently indicates possible movements along the fault systems bounding the inter-drainage basin facilitating the fluvio-morphometric changes. [ABSTRACT FROM AUTHOR]

Using the integrated approach of sedimentology, petrography and geochemistry, we tried to understand the provenance, palaeo-weathering and depositional pattern of Carboniferous Fenestella Shale Formation (consisting of shales and sandstones) exposed in the Kashmir Valley, north-west Tethys Himalaya. Five lithofacies are identified from base to top of the studied succession, viz., quartz-arenite facies, pebbly sandstone facies, sandstone-siltstone facies, silty-shale facies and shale facies collectively suggest a shallow and deep-water depositional environment. The dominance of small-scale bi-directional cross-stratification relative to large-scale planar cross-bedding in the quartz-arenite facies intercalated with shale facies reflects deposition in a shelf to shore setting during regressive to transgressive phases. The discrimination diagrams also suggest the passive margin depositional setting of these rocks. The chemical index of alteration (ranging from 53 to 77) and weathering index of Parker (ranging from 37 to 57) reflect that the source rocks underwent a low-to-moderate degree of chemical weathering. The presence of plutonic (granitic) rock fragments and dominance of heavy mineral grains, e.g., zircon, rutile and tourmaline in the Fenestella sandstones suggest plutonic rocks as pristine source rocks. Based on coupled sedimentological and geochemical characteristics and available geochronological data sets, it is suggested that the Neoproterozoic Pan-African granites situated south of the Tethys Himalaya could be the possible source rocks for Fenestella Shale Formation. [ABSTRACT FROM AUTHOR]

We present evidence for frictional–viscous flow (or steady creep) behaviour of the blind detachment below the Indo-Burmese wedge (IBW), as characterised by the fault gouge exposed along the Churachandpur–Mao Fault, which is one of the splay faults to the blind detachment. The petrography of the exhumed phyllonitic gouge material (considered the wedge material from the detachment and representative of the detachment) indicates evidence of pressure solution and viscous flow. We use a microphysical model involving frictional–viscous flow, and together with microstructural observations from the exhumed gouge we interpret low shear strength (<20 MPa) within the frictional–viscous transition zone. The results of the model also suggest that the geodetically estimated strain rate in this region lies in the domain of steady creep or velocity strengthening frictional behaviour. We suggest that the presence of phyllosilicate-rich rocks may significantly weaken mature fault cores along the detachment beneath the IBW and facilitate frictional–viscous flow at shallow depth. This new evidence suggests a significantly reduced seismic hazard across the megathrust. Research Highlights: Frictional–viscous flow along the blind detachment beneath the Indo-Burmese Arc. Exhumed fault gouge indicates evidence of pressure solution and viscous flow. Phyllosilicate rich rocks significantly weaken mature fault cores along this detachment. Microphysical model imply low shear strength of the blind detachment. [ABSTRACT FROM AUTHOR]

The heavy mineral suite of Quaternary succession of Central Narmada reflects their mixed derivation from Deccan Trap basalts and dykes, Vindhyan Supergroup, Gondwana Supergroup, Mahakoshal Group, Precambrian granites and gneisses. Based on variations in frequency percentages of heavy minerals, provenance sensitive indices (PSI), coupled with paleocurrent information; five provenance events are recognised: (i) Pilikarar Formation showing polycyclic nature, highest ZTR (zircon + tourmaline + rutile), low PSI; derived from Vindhyan Supergroup exposed in north, Mahakoshal Group and Deccan Trap basalts in northeast, (ii) decrease in ZTR index and garnet; with progressive increase in augite, GZi (garnet/garnet + zircon) and GtZRT (garnet/ZRT) from Dhansi, Surajkund and Baneta Formation derived from Mahakoshal Group, Gondwana Supergroup and Deccan Trap basalts present in southeast and east, (iii) slight increase in ZTR index, appreciable quantity of garnet and hornblende; higher GZi, GtZRT, SZi (staurolite/staurolite + zircon) in coarser clastics of Hirdepur Formation derived from Mahakoshal Group and Gondwana Supergroup exposed in south and southeast, (iv) increased augite and ZTR index in finer clastics of Hirdepur Formation, higher augite and appreciable garnet content, higher GZi, GtZRT, RZi (rutile/rutile + zircon) in succeeding Bauras Formation derived from Deccan Trap basalt and Mahakoshal Group exposed in east and southeast and (v) higher augite, garnet and hornblende contents, higher GZi, GtZRT, AmZRT (amphiboles/ZRT) in Ramnagar Formation suggest derivation from Mahakoshal Group, Gondwana Supergroup and Deccan Trap basalt from south and southeast. These events provide important evidences about tectonic, depositional and diagenetic conditions prevailing in Central Narmada basin during the Quaternary period. [ABSTRACT FROM AUTHOR]

The Deccan Volcanic Province (DVP), which is one of the largest flood basalt regions in the world, together with Dharwar Craton constitutes a large portion of the Precambrian South Indian shield. To understand the evolutionary nature of the DVP, we determine the lithosphere structure across the DVP–Eastern Dharwar Craton (EDC), using seismological waveforms recorded at 18 seismological stations. We use joint modelling of teleseismic receiver functions and surface wave dispersion data as well as teleseismic relative residuals. The calculated thickness of the lithosphere shows a significant difference between the DVP and EDC; it is ~50–60 km thinner in the DVP compared to that in the EDC. Through interrelation of these results with available data, we find that the DVP may have an intimate relationship with the break-up of the Gondwanaland. [ABSTRACT FROM AUTHOR]

The earthquakes have the most dominating societal and economic impact on the built environment. The earthquakes in an intraplate region are infrequent but often damaging. The uncontrolled urban growth in cities due to population explosion and migration makes it necessary to assess seismic hazards in an active region. It provides parameters for seismic safety and helps in disaster mitigation. The Kachchh Rift Basin (KRB) of western India is a seismically active intraplate region where many damaging earthquakes have occurred in the past (Mw 7.8 in 1819, Mw 7.6 in 2001). The KRB hosts many economic corridors and ports. Though the region has been put in a category with highest seismic hazard, the entire region is not prone to high hazards. The primary objective of the study is to integrate major attributes that influence seismic hazard on a GIS platform and prepare a multi-criteria-based hazard map by multi-criteria decision process named as analytical hierarchy process (AHP) developed by Saaty. In this study, the information about some of the attributes like peak ground acceleration (PGA), geology and geomorphology, and tsunami hazard is taken from published literature, whereas shear wave velocity to 30 m depth (Vs)30 and amplification factor were obtained through empirical relationships. The integration of these different attributes was performed, and weights were assigned depending on their contribution to the seismic hazard. The multi-criteria approach reveals that the southwestern part comprising of Kachchh mainland has a low hazard as compared to central and northern parts and almost 1 million people and around 0.18 million houses are exposed to moderate to high hazard. Large swaths of land are prone to liquefaction hazard. The corridor comprising of Bhuj, Bhachau and Rapar needs seismic microzonation. This macro level hazard map will be beneficial for the urban planners and government authorities to decide the areas, where seismic microzonation or site-specific studies are required that would help in mitigating earthquake disasters in the future. [ABSTRACT FROM AUTHOR]

The Kachchh province of India has witnessed several major earthquakes in the past 100 years. These earthquakes have reactivated major faults of the region and modified the landscape. Morphometric analysis of the Wagad Highland was carried out to assess the vulnerability of regional fracture patterns for neotectonic activities. The analysis of regional fractures (using hypsometric curves and rose diagrams) of the first order drainage brought out the presence of three major orientations, i.e., N005°, N025° and N075°. Five quantitative parameters, viz., mountain front sinuosity (Smf), asymmetry factor (AF), hypsometric integral (HI), the ratio of valley floor width to valley height (Vf), and sinuosity parameter (Sp) were combined to a common parameter, the index for relative active tectonics (IRAT), having four classes (very high, high, moderate and low). The intensity of the neotectonic activity decreases from Class 1 to Class 4. About 62% (~151 km2) of the total area (~244 km2) is under Class 1 and Class 2, out of which ~50% (~122 km2) is in the western part of the study area. Based on these IRAT classes, a major NE–SW lineament, passing through the center of the study area, was identified to be neotectonically more active. Research Highlights: Drainage basin morphometry of the Wagad Highlands (Rapar), India was analysed. Index for relative active tectonics (IRAT) supports very high neotectonic activity. IRAT map provides demarcation of neotectonically active zones. Seismicity in the Kachchh region is related to high strain along regional faults. [ABSTRACT FROM AUTHOR]

In the northeastern states of India, an in-cave expedition to Krem (cave) Mawmluh in Meghalaya has been carried out to document and study the stalagmite sample KM-24. The architectural structure is well preserved with alternating lamina/band of mixed calcite (C) and/or aragonite (A) possibly due to their polymorphic relationship as CaCO3 primarily precipitated as aragonite and later transformed into calcite due to neomorphism through time. Evidence in support of neomorphic processes have been deciphered through mineralogical fabrics (unstable polymorph to stable polymorph), intercrystalline voids in coalescence aragonite needle-like fabrics, sparite crystallite calcite in voids, fine micrite (M) within fabrics and growth breach (time gap). The variation in laminae thickness (BMLP) and major oxides (CaO and MgO wt.%) along the growth laminae may be associated with CaCO3 deposition, reflecting surface precipitation and disequilibrium conditions. Preserved biogenic remains (pink–red colour, filament or thread like-structures) within mineralogical fabrics, intercrystalline voids and outer laminae (A) may depict biogenic activity which might have facilitated precipitation of CaCO3. Research highlights: Architectural structure of KM-24 consists of alternation lamina/band of mixed calcite /or aragonite possibly due to their polymorphic relationship as CaCO3. Digenetic modification and neomorphism transformation are observed through primary features (mineralogical fabrics, intercrystalline voids, laminae thickness, etc.) The BMLP and major oxides (CaO and MgO wt.%) along the growth laminae may be associated with CaCO3 deposition, reflecting surface precipitation and disequilibrium conditions. Preserved biogenic remains associated with primary features may depict biogenic activity. [ABSTRACT FROM AUTHOR]

Research highlights: Delineated groundwater potential zones by a weighted overlay analysis based on conventional method with 110 electrical resistivity surveys and 40 lithological data. MODFLOW was used to calibrate and validate the flow pattern and characteristics of groundwater. Groundwater potential map was validated with specific capacity and MODFLOW results were validated with pumping test results. The groundwater volume during the calibration and validation period was found to be 7.12 and 7.52 Mm3, respectively. The groundwater mass balance assessment performed in this study can be useful in the planning and management of groundwater resources. The assessment of groundwater potential zones is crucial for estimating and managing available groundwater resources. In the proposed study, quantification of groundwater availability is performed using the information collected from the hydrogeological and geophysical (electrical resistivity) investigation of the aquifer. We delineate groundwater potential zones using a weighted overlay analysis based on the conventional method with 110 electrical resistivity surveys and 40 lithological data. MODFLOW is used to calibrate and validate the flow pattern and groundwater characteristics. The study area comprises a complex geological formation. The groundwater potential map is prepared using the observed groundwater level instead of rainfall data as the study area lacks rainfall stations. The final potential map is validated with the specific capacity obtained from the pumping test. This map is divided into 13 zones and each zone is considered as boundaries for the MODFLOW simulation. The thickness of each zone is assessed using the electrical resistivity method. The calibration and validation of the groundwater model are performed for one year and 1.5 years, respectively, between November 2012 and March 2015. We consider two layers, namely topsoil and unconfined/semi-confined aquifers in the groundwater model. During the calibration and validation periods, the groundwater volume is found to be 7.12 and 7.51 Mm3, respectively. The groundwater mass balance assessment performed in this study will be helpful in the planning and management of groundwater resources in the area. [ABSTRACT FROM AUTHOR]

The vast unexplored lateritic terrain of Kabirdham District, Chhattisgarh has received attention due to the presence of localized bauxite mines. In the present study, the ASTER images are processed to demarcate the ore, based on the spectral features of boehmite, gibbsite, and goethite in the VNIR–SWIR electromagnetic domain. This approach delineates the target and helps us to pinpoint the potential areas of bauxite deposits more easily from laterite. The bauxite ore is mainly enriched in Al2O3 (37.30–59.90%), TiO2 (4.30–13.40%), and Fe2O3 (1.75–29.07%), with low amounts of SiO2 (0.69–9.83%) of metallurgical grade. Boehmite is the predominant mineral in the study area followed by gibbsite. The band ratio, relative band depth images from ASTER data and the sub-pixel classifications of bauxite are mapped by using Adaptive Coherence Estimator (ACE), Matched Filtering (MF) and Linear Spectral Unmixing (LSU) methods. The bauxite-rich pixels derived from density-sliced images are overlaid on the digital elevation model (DEM) to interpret the relationship between the high-level bauxite distributions and the topographical slope/altitude. The results are validated by conducting substantial fieldwork. An integrated approach of spectral analysis with the petrological and colorimetric studies at Bamhantara block has supported the evidence of bauxite deposits and aided to find out the similar type of deposits at another lateritic province. [ABSTRACT FROM AUTHOR]

Harvesting of water by tunnelling in the Western Ghats lateritic terrains of India known as surangam (tunnel well) is practiced since ages. It is common even today in the northern parts of Kerala state in India. Surangams are featured by horizontal tunnel wells, dug manually within the laterite, where the tunnel wall collects the seepage water, flows out under gravity and get accumulated in open tanks or dug wells for further use. The tunnels are laid horizontally or slightly inclined, placed just over the lithomarge clay so that maximum seepage can be accumulated through the porous laterites (generally of 3.95–30.20 m thick). A study is done on surangams from the Kasaragod district of Kerala, where it is still popularly used. They represent different designs; single tunnel, criss-cross tunnels and diversion tunnels, depending upon the terrain conditions, the permeability of the laterites and thickness of the saturated zones within laterites, demand of water and location of delivery points, etc. Surangam system may start from a dug well, end in a dug well and there can be an open shaft or dug well in between. Total 32 surangams are inventoried in Bedadka Panchayath, of which 24 are investigated in detail. The discharge varies from 0.078 to 13.29 m3/day during pre-monsoon while it remains between 172.80 and 691.20 m3/day during monsoon period in 2019. In 2019 summer, 12 inventoried surangams remained dry. The hydrochemical facies of water from the surangams generally varies from Ca–HCO3 type to Ca–Mg–Cl type indicating rock–water interaction. Because of lack of proper maintenance caving of walls occur during the rainy season. Lack of maintenance renders the priceless traditional groundwater abstraction structures disappearing fast. Surangams with good discharge are to be protected with proper concrete reinforcing of the outlet of the tunnel and proper storage options and arrangement of delivery systems up to the user point. Besides, water harvesting measures in the catchment of surangams are required for round the year sustainability of yield. A plan has been proposed for the revival of the surangams along with design specifications. [ABSTRACT FROM AUTHOR]

Two linear NE–SW trending belts of platformal orthoquartzite-carbonate sequence, namely, the East Jahazpur Belt (EJB) and the West Jahazpur Belt (WJB), within a vast tract of slate–argillite–metagreywacke and subordinate metavolcanics of Hindoli Group (HG) together occur sandwiched between Vindhyan sediments to the east and Banded Gneissic Complex-II (BGC-II) to the west, at the eastern boundary of Aravalli Craton, Rajasthan, India. A NE–SW trending crustal-scale transpressive shear separates this low-grade supracrustal sequence from the gneisses of older Mangalwar Complex (BGC-II) to the west and the Great Boundary Fault (GBF) restricts it in the east against the Vindhyan rocks. A lensoid body of strongly deformed and mylonitised Jahazpur Granite (JG), is the basement for the supracrustal rocks and occupies the core of a SE verging D1-antiformal nappe defined by the EJB (Jahazpur Group-I) rocks. This large scale D1 thrust nappe structure in the EJB is manifested by stacking of early recumbent folds in the carbonate and quartzite units and a prominent zone of brecciation and ferruginisation all along the eastern margin of EJB. In the WJB (Jahazpur Group-II), D1 is represented by large scale isoclinal reclined fold geometry, likely to be influenced by the major transpressive shear and refolding at its western margin. D2 deformation phase, variably superposed over the D1 structures, together controls the NE–SW disposition of Hindoli and Jahazpur rocks. Based on the structural patterns and lithostratigraphic characters, we propose a revised stratigraphy of the Hindoli–Jahazpur rocks. Whole rock Rb–Sr dating of the strongly deformed and mylonitised Jahazpur Granite constrained the age of the tectono-metamorphic event that affected these rocks. Two suites of mylonitised Jahazpur Granite from two different localities yielded ages of 1423 ± 52 and 1393 ± 33 Ma, using Sector 54 TIMS. The tectonism that resulted in folding, thrust nappe, shearing and mylonitisation involving basement JG of Neoarchean age and the overlying Paleoproterozoic Jahazpur–Hindoli supracrustal sequences, therefore, represents a Mesoproterozoic (~1.4 Ga) orogeny that is correlatable with the breaking-up of Columbian Supercontinent along the eastern margin of the Aravalli craton. [ABSTRACT FROM AUTHOR]

Research highlights: The frequency-dependent shear-wave quality factor and site amplification are computed simultaneously for the Garhwal region, NW Himalaya. A regional quality factor relationship of form, Qβ(f) = (102 ± 3.9)f(1.0±0.1) is established for the Garhwal Himalaya. The acceleration records corrected from the obtained site effect are used to develop attenuation relations at each recording station. The close resemblance of obtained Qβ(f) relations and the geology has been observed for the study region. The frequency-dependent shear-wave quality factor (Qβ(f)) and site amplification are computed for the seismically and tectonically active Garhwal Himalaya. The inversion technique of strong motion data is applied to obtain Qβ(f) and site effect at each recording station. The strong motion data of 82 earthquakes recorded in the Garhwal region is used for the present inversion algorithm. The comparison of site effects obtained by the present inversion scheme and well developed H/V technique (H/V is the ratio of Fourier spectra horizontal to vertical components) shows that site effects computed through the inversion technique have close resemblance with these estimates from the H/V technique. Both horizontal components are used to establish the frequency-dependent Qβ(f) relations at each station. The values of 'Qo' and 'n' at different stations vary from 92 to 112 and 0.9 to 1.1, respectively. The close resemblance of obtained Qβ(f) relations at different stations suggest, the presence of almost similar type of lithology, i.e., hard rock at these stations. A regional quality factor relationship of form, Qβ(f) = (102 ± 3.9)f(1.0±0.1) is established for the Garhwal Himalaya based on modelled Qβ values of each station. This relationship reveals low Qo value (<200) and high n value (>0.8) for the Garhwal Himalaya, which correspond to tectonically and seismically active region. [ABSTRACT FROM AUTHOR]

We describe the variability of the West India Coastal Current (WICC) during 2009–2017 using data from acoustic Doppler current profilers (ADCPs) attached to moorings deployed on the outer shelf at a water-column depth of 100–200 m at three locations: off Kollam (9°N), Bhatkal (13.9°N), and Goa (15°N). Our study shows that the characteristics of the WICC on the outer shelf are similar to those observed on the slope except for the occasional decorrelation observed between them. Both shelf and slope WICC have a weak mean flow and a strong annual cycle. As seen on the slope, the depth of the undercurrent on the shelf changes with season because of the strong upward phase propagation associated with the annual cycle. Though the currents at all three shelf locations exhibit a strong seasonal cycle, there are prominent differences between the currents off the southwest coast of India (Kollam) and the central west coast of India (Bhatkal and Goa). The seasonal cycle off Kollam is often punctuated by strong intraseasonal bursts, which cause the shelf WICC off Kollam to be highly unpredictable; this unpredictability implies that on a given day of the year, one cannot expect a poleward (equatorward) current during the winter (summer) monsoon. On the central west coast, the poleward (equatorward) direction during the winter monsoon (summer monsoon) is prominent. Comparison with the available datasets shows that the WICC is occasionally coherent along and across the shelf, and the coherence is stronger for the seasonal cycle. Research highlights: Characteristics of the WICC on the outer shelf are similar to those observed on the slope. Shelf WICC has a weak mean flow and a strong annual cycle. Differences observed between currents off central west coast and southwest coast of India. Seasonal cycle off Kollam is often punctuated by strong intraseasonal bursts. [ABSTRACT FROM AUTHOR]

Prediction of heavy/extreme rains is still a challenge, even for the most advanced state-of-the-art high-resolution Numerical Weather Prediction (NWP) modelling systems. Hydrological models use the rainfall forecasts from the NWP models as input. This study evaluates the performance of the UK Met Office Unified Model (UM) in predicting the rainfall exceeding 80th and 90th percentiles. Such high rainfall amounts occur over the Western Ghats (WGs) and North East (NE) India mainly due to the forced ascent of air parcels. Apart from the significant upgrades in the UM's dynamical core, the model features an increased horizontal grid (40–10 km) and vertical resolution (50–70 levels). The prediction skill of heavy rainfall events improves with an increased horizontal resolution of the model. The probability of detection (POD), false alarm ratio (FAR), and critical success index (CSI) are the verification metrics used. As per these metrics, model rainfall forecasts have improved during 2007–2018 (increase in CSI from 0.29 to 0.38, POD from 0.45 to 0.55, and decrease in FAR from 0.55 to 0.45). Additionally, to verify extreme and rare events, the symmetric extremal dependence index (SEDI) is also used. SEDI also shows an increase from 0.47 to 0.62 and 0.16 to 0.41 over WGs and NE India during the study period, suggesting an improved skill of predicting heavy rains over the mountains. The improved forecast performance is consistent and relatively higher over WGs than over NE states. [ABSTRACT FROM AUTHOR]

Thunderstorms, associated with lightning and heavy rain, are a weather hazard causing human deaths, urban floods and damage to crops. Current work attempted to study the thunderstorms over Andhra Pradesh, coastal state in southeast India, using multiple satellite datasets, gridded rainfall, Doppler Radar Images and Advanced Research Weather Research and Forecasting (ARW) model simulations during the pre-monsoon seasons of 2017 and 2018. Thermodynamic stability indices computed using INSAT-3D/3DR satellite data were used to identify precursors and lead time of prediction. India Meteorological Department (IMD) daily gridded rainfall data were used to identify the thunderstorm occurrence days, and Doppler Radar Images and INSAT imagery were conjointly used to fix the location. Eight severe thunderstorm cases were analyzed to assess the precursors and the predictability. Further, ARW model predictions for two thunderstorm cases were performed and stability indices computed using model output were compared with satellite-based indices for evaluation. Statistical metrics had shown good agreement of ARW model-based stability indices with satellite-based stability indices. Model had simulated rainfall and cloud properties associated with thunderstorm activity. The results illustrated the predictability of the location and intensity of thunderstorms with 3–4 hrs lead time, which would find usefulness in the real-time prediction of thunderstorms. Research Highlights: Occurrence of thunderstorms using satellite and radar imagery. Identification of thunderstorm occurrences using daily rainfall data. Emphasizing the use of thermodynamic stability indices in the prediction of thunderstorms. Numerical model predictability of thunderstorms. Predictability of thunderstorms collocating satellite and model experiments. [ABSTRACT FROM AUTHOR]

The National Capital Region of India (NCR Delhi) receives around 26 rainy days with majority of short duration high intensity rainfall events. Yet, the city faces severe waterlogging during south-west monsoon, and shortage of water in other seasons due to rapid urbanization and changing hydrological flow patterns. In an uncertain scenario, where spatiotemporal variability of rainfall at local scale is not very well understood, a location-specific robust model applicable for the megacity through interpretation of parameter estimates will improve understanding of extreme rainfall pattern with duration. Identification of the best-fit statistical model for prediction of short duration extreme events is done and parameters of the model are evaluated for different durations. The study finds that the 2-parameter gamma distribution and 3-parameter generalized extreme value (GEV) predict similar return levels of extreme intensity for short durations and short return periods. The shape parameter in GEV and shape and scale parameters in gamma explain the extreme quantile in the distribution responsible for prediction of high magnitude events. The more generic gamma model is robust and applicable at local scale, with pronounced shape parameter variations across durations (1–11.534, 2–8.264, 3–6.609 h). It is concluded that the knowledge of hourly variation in extreme rainfall events will help in informed decision making in this acutely water-stressed region of the world. Highlights: Short duration extreme rainfall events are frequent in semi-arid urban regions and characterization of these storms is important. The extreme rainfall pattern characteristics is defined through the parameter estimates of shape and scale of gamma distribution. Within 1 h duration rainfall events pattern, the higher shape factor identifies storms in a more wet regime (α-14.05) than the mean (α-11.534), while the lower shape factor identifies dry regime (α-9.018). The 4 h and 6 h events have the lowest shape factor and high scale factor, implying variation, and unpredictability. Short duration storms have the potential to cause flash floods, the hydrological insights provided by this study will be useful in similar geographical regions. [ABSTRACT FROM AUTHOR]

A framework comprising of four interdependent modules has been developed to analyse demand–supply scenarios under future uncertainties of climate change in an irrigation command where any mismatch can affect sustainability and wellbeing of the rural population. In the absence of runoff records, the water balance module of framework computes daily runoff from catchment considering all inputs, outputs and losses from the system. The climatic parameters and rainfall were forecasted for three future projected periods using statistical downscaling for six different climate projections. The Soil and Water Analysis Tool (SWAT), a physically based spatially distributed hydrological model and SWAT-CUP, an application for calibration and uncertainty analysis of SWAT model have been used to calibrate and validate a model for the base period (BP:1981–2015) and further applied to generate multiple future runoff series to asses water availability. The module-IV was designed to compute evapotranspiration using ETo calculator (a software to compute evapotranspiration) and then irrigation demand for Tandula command in the Chhattisgarh state of India considering present overall efficiency of 51% for the base (1991–2015) and future assessment periods. The analysis of all projected scenarios suggested an increase of annual temperature from present 26.2°–27.1°, 27.3° and 27.8°C during near (FP-1: 2020–2035), mid (FP-2: 2046–2064) and far century (FP-3: 2081–2099) periods, respectively, may demand more water which could be adversely affected by reduced rainfall. The water requirement may vary in the range of 410.4–464 MCM and supply from 426.2 to 453.2 MCM based on future projection from GCMs. [ABSTRACT FROM AUTHOR]

Kohima Synclinorium is one of the most tectonically active corridors of Indian subcontinent and displays complex tectonics of the region. Mapping the basement structure beneath the Kohima Synform is, therefore, vital to provide deep insight into the understanding of the crucial thrust geometry of the region. The vertical gravity gradient anomalies and available geological evidences suggest that the underlying area is occupied by thrust geometry embedded with prominently known tectonic trends of Schuppen Belt (SB), Kohima–Patkai Synclinal (KS–PS) and adjoining Inner Fold Belts (IFB). By keeping in view the massive complex tectonic upheaval in the region, we carried out 2D Bouguer gravity data analysis using the radially averaged power spectral techniques and GMSYS modelling to map the basement depth more precisely. Our results suggest that there is a wide range of heterogeneity in the underlying undulating basement indicating an average sedimentary thickness of the order of 2.2–5.5 km. The gravity PDEPTH modelling results show that source depth varies from 2.5 to 6.5 km. There is an uplifted basement tending towards the southwestern part while gradual deepening of basement was observed towards the eastern part of the study area. The profile modelling results show the presence of basement in a depth range of 2.5–3.8, 3.8–4.0, and 3.8–4.2 km beneath Foreland Basin (FB), Kohima–Patkai Synclinal structures (KS–PS), and Inner Fold Belts (IFB), respectively. The underlying results of integrated profiles, PDEPTH and GMSYS modelling would be useful to understand the detailed basement structure and tectonic trends of Belt of Schuppen (BS), Kohima–Patkai Synclinal structures (KS–PS) and adjacent Inner Fold Belts (IFB) of north-eastern region of India. [ABSTRACT FROM AUTHOR]

A comprehensive geophysical and petrological study was carried out at Giddalur area in Prakasam district, Andhra Pradesh, which is geologically a highly deformed area and is difficult to delineate the aquifer zone(s). The task was to find out the exact rock type in which aquifer is concealed as well as to delineate the aquifer zone, which can yield sufficient quantity of water. The resistivity models derived from geophysical dataset were interpreted in terms of hydrogeology and the results revealed substantial resistivity contrast of the geological formations within the study area. We have delineated two major groundwater potential zones based on this study. These zones were tapped at different depths in diverse rock types. Drilled hand specimens (rock cuttings) were not adequate, so these specimens were petrographically studied to reveal the exact contact zones of the rock type. On integration of the geophysical and the petrographic results, it was illustrated that two aquifer zones were struck at a depth of 92 and 122 m between shale-phyllite and phyllite-quartzite, respectively. These findings were correlated, which matched with the lithology of the drilled borehole. This integrated approach will be helpful in strategy for groundwater assessment as well as prospecting groundwater resources in different geological terrain. [ABSTRACT FROM AUTHOR]

Landslides induced due to monsoon rainfall and earthquakes are very common phenomena in Uttarakhand Himalayas of India. For example, many such landslides got induced and reactivated by the 1999 Chamoli earthquake. In view of above, authors have made an attempt to prepare pre- and post-earthquake landslide susceptibility zonation (LSZ) maps for a part of Chamoli district, Uttarakhand, India. The novelty of this work lies in producing an LSZ map considering peak ground acceleration (PGA) as one of the controlling factors for earthquake-induced landslide occurrences and validating the LSZ map with the post-earthquake landslide inventory. For this purpose, a spatial database of seven controlling factors, i.e., slope angle, slope aspect, slope curvature, geology, distance to drainage, normalized difference vegetation index (NDVI) and peak ground acceleration (PGA) was prepared in Geographic Information System (GIS). Then, relative frequency ratio (RFR) method was adopted for the LSZ maps. The landslide inventory of 276 landslides (220 pre-earthquake and 56 post-earthquake landslides) was prepared for the study area. Firstly, an LSZ map was generated using six controlling factors excluding PGA and the pre-earthquake landslide inventory (Case I). In another attempt, the LSZ map is prepared using seven controlling factors including PGA and pre-earthquake landslide inventory to examine the influence of seismic parameter (PGA) in landslide susceptibility assessment (Case II). Subsequently, pre- and post-earthquake landslide inventory along with seven controlling factors were used to construct another LSZ map (Case III). Finally, these three LSZ maps were validated and compared with the training and testing data. In this study, a spatial predictive model for earthquake-induced landslide is developed. [ABSTRACT FROM AUTHOR]

The present study is undertaken in the eastern coast of India, along the coastal tract of Bay of Bengal (BoB), to delineate the submarine groundwater discharge (SGD)-borne nutrient flux at temporal scale and their impact to coastal ecology and biogeochemical processes. Solutes chemistry, seepage meter study, stable-isotopic signature, and geophysical techniques were used to identify the surface water–groundwater interaction zone, SGD rate and nutrient flux. The estimated rate of major annual discharge of nutrient fluxes were 240 and 224 mM m−2 day−1 for NO3− and Fetot. The variation of solute and nutrient fluxes was depending on the load of terrestrial water masses, which is triggered by the local monsoonal meteoric recharge. The ecohydrological response to this solute flux results in spatio-temporal patterns of N and P-sensitive algal blooms in the intertidal zones. Most algae were identified as dinoflagellates and some haptophytes, with greenish and brownish hue that provides a distinct look to the coastal landscape. The algal blooms were found to be substantially influenced by the seasonal-nutrients flux and discharge location. Our study is expected to increase the understanding of a rarely reported eco-hydrological response to terrestrial–marine water interactions and their implications in the tropical ocean adjoining the Indian Subcontinent. [ABSTRACT FROM AUTHOR]

Three drifters were deployed in the northeastern Arabian Sea at (69.18 ∘ E, 19.77 ∘ N). They were released almost at the same time on 29 November 2016. The three drifters, initially moved poleward along the direction of the west India coastal current. The distance between any two drifters is less than 5 km for initial 8 days. The drifters veered apart when they moved along the edge of an anti-cyclonic or cyclonic circulating loop, thereby increasing the distance between them. Within a period of six months, the three drifters were in different directions and the distance between them was more than 600 km. [ABSTRACT FROM AUTHOR]

Moderately preserved shallow-marine extinct, fossil benthic community has been recovered from a sub-surface Late Palaeocene limestone cave section near Lumshnong in the Jaintia Hills, Meghalaya, NE India. The present contribution focuses on the ecostratigraphic implications of the carbonate microbiofacies based on the evaluated facies gradients. Precise field assessments and microscopic observations led to the identification of three microbiofacies: benthic foraminiferal–algal grainstone, coralline algal framestone and oolitic grainstone–packstone. The microbiofacies distinguished in the study suggest a general shallowing-upward trend from an inner shelf setting to a lagoonal–shoal environment depicting the distinct changes in the benthic community. Presence of coralline alga Distichoplax biserialis and benthic foraminifera Idalina sinjarica, Daviesina khatiyahi, Miscellanea primitiva, Rotalia trochidiformis and Vania anatolica assign the studied carbonates to Early Thanetian (SBZ 3) corresponding to the lower part of the Lakadong Limestone. In this study, ecostratigraphy has facilitated the classification of a single carbonate section corresponding to a solitary shallow benthic zone into multiple microbiofacies attributed to variable environmental depositional conditions. This clearly demonstrates its potential in improving the applicability of biostratigraphy worldwide. [ABSTRACT FROM AUTHOR]

Meteorological drought during the southwest monsoon season and for the northeast monsoon season over five meteorological subdivisions of India for the period 1901-2015 has been examined using district and all India standardized precipitation index (SPI). Whenever all India southwest monsoon rainfall was less than −10% or below normal, for those years all India SPI was found as −1 or less. Composite analysis of SPI for the below normal years, viz., less than −15% and −20% of normal rainfall years indicate that during those years more than 30% of country's area was under drought condition, whenever all India southwest monsoon rainfall was -15% or less than normal. Trend analysis of monthly SPI for the monsoon months identified the districts experiencing significant increase in drought occurrences. Significant positive correlation has been found with the meteorological drought over most of the districts of central, northern and peninsular India, while negative correlation was seen over the districts of eastern India with NINO 3.4 SST. For the first time, meteorological drought analysis over districts and its association with equatorial pacific SST and probability analysis has been done for the northeast monsoon over the affected regions of south peninsular India. Temporal correlation of all India southwest monsoon SPI and south peninsular India northeast monsoon SPI has been done with the global SST to identify the teleconnection of drought in India with global parameters. [ABSTRACT FROM AUTHOR]

Unprecedented precipitation along with heavy falls occurred over many parts of India from 28th February to 2nd March 2015. Many of the stations of northwest and central India received an all time high 24 hr cumulative precipitation of March during this period. Even the national capital, New Delhi, broke all the previous historical 24 hr rainfall records of the last 100 years to the rainfall record in March 2015. Due to this event, huge loss to agricultural and horticultural crops occurred in several parts of India. In the present study, an attempt is made to understand the various meteorological features associated with this unprecedented precipitation event over India. It occurred due to the presence of an intense western disturbance (WD) over Afghanistan and neighbouring areas in the form of north-south oriented deep trough in westerlies in middle and upper tropospheric levels with its southern end deep in the Arabian Sea, which pumped huge moisture feed over Indian region. Also, there was a jet stream with core wind speed up to 160 knots that generated high positive divergence at upper tropospheric level over Indian region; along with this there was high magnitude of negative vertical velocity and velocity convergence were there at middle tropospheric level. It caused intense upward motion and forced lower levels air to rise and strengthen the lower levels cyclonic circulations (CCs)/Lows. Moreover, the induced CCs/Lows at lower tropospheric levels associated with WD were more towards south of its normal position. Additionally, there was wind confluence over central parts of India due to westerlies in association with WD and easterlies from anticyclone over north Bay of Bengal. Thus, intense WD along with wind confluence between westerlies and easterlies caused unprecedented precipitation over India during the 1st week of March 2015. [ABSTRACT FROM AUTHOR]

Stable isotope composition of precipitation from Pamba River basin, Kerala, India, is evaluated to understand the role of spatial and temporal variations on rainwater isotope characteristics. Physiographically different locations in the basin showed strong spatial and temporal variations. δ O varied from −7.63 to −1.75 ‰ in the lowlands; from −9.32 to −1.94 ‰ in the midlands and from −11.6 to −4.00 ‰ in the highlands. Local Meteoric Water Lines (LMWL) for the three regions were determined separately and an overall LMWL for the whole of the basin was found to be δ H = 6.6 (±0.4) δ O+10.4 (±2.0). Altitude effect was evident for the basin (0.1 ‰ for δ O and 0.8 ‰ for δ H per 100 m elevation), while the amount effect was weak. The precipitation formed from the marine moisture supplied at a steady rate, without much isotopic evolution in this period may have masked the possible depletion of heavier isotopes with increasing rainfall. Consistently high d-excess values showed the influence of recycled vapour, despite the prevailing high relative humidity. The oceanic and continental vapour source origins for the south-west and north-east monsoons were clearly noted in the precipitation in the basin. Rayleigh distillation model showed about 30% rainout of the monsoon vapour mass in the basin. [ABSTRACT FROM AUTHOR]

Dryland rivers, dominated by short-lived, localised and highly variable flow due to discrete precipitation events, have characteristic preservation potential, which serves as suitable archives towards understanding the climate-tectonic coupling. In the present study, we have investigated the fluvial records of a major, southerly-draining river - the Rukmawati River in the dryland terrain of southern Kachchh, in western India. The sediment records along the bedrock rivers of Kachchh register imprints of the Indian summer monsoon (ISM), which is the major source of moisture to the fluvial system in western India. The Rukmawati River originates from the Katrol Hill Range in the north and flows towards the south, into the Gulf of Kachchh. The field stratigraphy, sedimentology, along with the optical chronology suggests that a braided-meandering system existed during 37 ka period due to an overall strengthened monsoon. A gradual decline in the monsoon strength with fluctuation facilitated the development of a braided channel system between 20 and 15 ka. A renewed phase of strengthened monsoon with seasonality after around 15 ka which persisted until around 11 ka, is implicated in the development of floodplain sequences. Two zones of relatively high bedrock uplift are identified based on the geomorphometry and morphology of the fluvial landform. These zones are located in the vicinity of the North Katrol Hill Fault (NKHF) and South Katrol Hill Fault (SKHF). Geomorphic expression of high bedrock uplift is manifested by the development of beveled bedrock prior to or around 20 ka during weak monsoon. The study suggests that the terrain in the vicinity of NKHF and SKHF is uplifting at around 0.8 and >0.3 mm/a, respectively. Simultaneously, the incision in the Rukmawati River basin, post 11 ka, is ascribed to have occurred due to lowered sea level during the LGM and early Holocene period. [ABSTRACT FROM AUTHOR]

Fossil leaflet impression described here as a new species Rourea miocaudata sp. nov., showing close resemblance with the modern leaflets of Rourea caudata Planch. (Connaraceae R. Br.), has been recorded from the lower part of the Siwalik sediments (Dafla Formation, middle-upper Miocene) exposed at the road-cutting section of Pinjoli area in West Kameng district, Arunachal Pradesh. The important morphological characters of the fossil are its narrow elliptic leaflet, cuneate base, long caudate apex, entire margin, eucamptodromous to brochidodromous secondary veins, presence of intersecondary veins, percurrent and reticulate tertiary veins and orthogonally reticulate quaternary veins. This is the first authentic record of the occurrence of leaflet comparable to R. caudata of Connaraceae from the Cenozoic sediments of India and abroad. At present R. caudata does not grow in India and is restricted only in southeast Asia especially in China and Myanmar. This taxon probably migrated to these southeast Asian regions after lower Siwalik sedimentation (middle-upper Miocene) due to climatic change caused by post-Miocene orogenic movement of the Himalaya. The recovery of this species and other earlier-described evergreen taxa from the same formation, suggests the existence of a tropical, warm and humid climatic conditions during the depositional period. [ABSTRACT FROM AUTHOR]

Surface level soil moisture from two gridded datasets over India are evaluated in this study. The first one is the UK Met Office (UKMO) soil moisture analysis produced by a land data assimilation system based on Extended Kalman Filter method (EKF), which make use of satellite observation of Advanced Scatterometer (ASCAT) soil wetness index as well as the screen level meteorological observations. Second dataset is a satellite soil moisture product, produced by National Remote Sensing Centre (NRSC) using passive microwave Advanced Microwave Scanning Radiometer 2 measurements. In-situ observations of soil moisture from India Meteorological Department (IMD) are used for the validation of the gridded soil moisture products. The difference between these datasets over India is minimum in the non-monsoon months and over agricultural regions. It is seen that the NRSC data is slightly drier (0.05%) and UKMO soil moisture analysis is relatively wet during southwest monsoon season. Standard AMSR-2 satellite soil moisture product is used to compare the NRSC and UKMO products. The standard AMSR-2 and UKMO values are closer in monsoon season and AMSR-2 soil moisture is higher than UKMO in all seasons. NRSC and AMSR-2 showed a correlation of 0.83 (significant at 0.01 level). The probability distribution of IMD soil moisture observation peaks at 0.25 m/m, NRSC at 0.15 m/m, AMSR-2 at 0.25 m/m and UKMO at 0.35 m/m during June-September period. Validation results show UKMO analysis has better correlation with in-situ observations compared to the NRSC and AMSR-2 datasets. The seasonal variation in soil moisture is better represented in UKMO analysis. Underestimation of soil moisture during monsoon season over India in NRSC data suggests the necessity of incorporating the actual vegetation for a better soil moisture retrieval using passive microwave sensors. Both products have good agreement over bare soil, shrubs and grassland compared to needle leaf tree, broad leaf tree and urban land cover types. [ABSTRACT FROM AUTHOR]

The direct impact of high resolution land surface initialization on the forecast bias in a regional climate model in recent years over Indian summer monsoon region is investigated. Two sets of regional climate model simulations are performed, one with a coarse resolution land surface initial conditions and second one used a high resolution land surface data for initial condition. The results show that all monsoon years respond differently to the high resolution land surface initialization. The drought monsoon year 2009 and extended break periods were more sensitive to the high resolution land surface initialization. These results suggest that the drought monsoon year predictions can be improved with high resolution land surface initialization. Result also shows that there are differences in the response to the land surface initialization within the monsoon season. Case studies of heat wave and a monsoon depression simulation show that, the model biases were also improved with high resolution land surface initialization. These results show the need for a better land surface initialization strategy in high resolution regional models for monsoon forecasting. [ABSTRACT FROM AUTHOR]