This study investigates the geothermal system of the Yumesamdong region in the eastern Himalayas through integrated geophysical, geological, and structural analyses. Apparent resistivity and vertical electrical profiling results reveal a prominent folded formation at approximately 50 meters depth, intersected by multiple steeply dipping, low-resistivity zones indicative of fluid-filled fractures. A dense cluster of these conductive features occurs between 40 to 60 meters, with several converging at the crest of the fold to form an extensive fracture conduit system facilitating the upward migration of geothermal fluids. Numerical factor analysis further aids in delineating the depth and extent of these fractures, supporting a conceptual model of dynamic mixing between shallow glacial meltwater and deep geothermal fluids. Although the geophysical and field-based observations support this model, the absence of isotopic and long-term hydrochemical data limits definitive validation. The findings indicate that meteoric water, circulating through tectonically controlled fractures, likely associated with the South Tibetan Detachment Zone, interacts with deep magmatic heat sources, producing elevated temperatures and distinctive geochemical markers, notably in sulfate and strontium concentrations. This work proposes a conceptual hydrogeological framework that connects surface recharge with deep thermal processes and underscores the geothermal potential of the structurally active eastern Himalayan region. The study provides a scientific foundation for sustainable geothermal energy exploration and resource management in similar high-altitude, tectonically dynamic environments.
Morphotaxonomical study on leaf impressions recovered from the Middle Siwalik sediments of a road cutting section in Sarkaghat area, Mandi District, Himachal Pradesh, India revealed presence of two new fossil leaves, Mappia siwalica n. sp. and Leea himachalensis n. sp. of the family Icacinaceae and Leeaceae respectively. The extant comparable taxa of these fossils reported here, are distributed chiefly in the tropical moist deciduous forests of South and North east and central India respectively which may suggest that a tropical forest under moist conditions was prevalent during the Upper Miocene times in this region in contrast to a mixed deciduous forest under the tropical humid climate having reduced precipitation at present. The fossil records of the genus Leea Royen ex. Linn. indicates that this is widely distributed from Late Cretaceous to Miocene. Its oldest record in India is from Late Cretaceous of central India which suggests that this genus is of Gondawanan origin.
This study presents the development of an updated and homogenized earthquake catalogue for the Reasi-Katra belt, a seismically active region within the northwestern Himalaya. Leveraging the robust General Orthogonal Regression (GOR1) technique, new empirical magnitude conversion relationships have been derived to support this effort. The selection of the Reasi-Katra belt is motivated by the presence of the active Reasi thrust, a notable increase in recent seismic activity, and previous geodetic studies (e.g., GPS measurements) that collectively underscore the region's tectonic sensitivity and the need for focused seismic assessment. The study has two principal objectives: (i) to develop regional empirical regression relationships between different magnitude scales and (ii) to construct a homogenized earthquake catalogue in the most recent and advanced magnitude scale, M-wg(Das Magnitude Scale). The dataset spans from 1555 to October 16, 2022, covering a geographical domain of 32 degrees-36 degrees N and 72 degrees-78 degrees E. The primary source of data is the International Seismological Centre (ISC) catalogue, supplemented by regional and historical records. The resulting M(wg )based homogenized catalogue is a significant advancement for this region, contributing improved accuracy and consistency over traditional magnitude scales such as Mw. Recent developments in seismological research support the superiority of the M(wg )in estimating seismic energy, particularly for intermediate and small-to-moderate earthquakes. Previous studies lackthe implementation of the GOR1 technique for homogenizing earthquake data in this region using the M(wg )hereby positioning the present work as the pioneering effort in this region. This catalogue compilation will serve as a critical input for future seismic hazard assessments and regional tectonic studies.
Tunnelling through the geologically active Lesser Himalayan region poses substantial engineering challenges, including instability caused by squeezing ground conditions, faulted and folded strata, high overburden, and groundwater ingress. Ensuring tunnel face stability and optimizing stand-up time necessitates careful selection of excavation techniques and construction sequences. This study evaluates various excavation approaches to improve face stability for a megatunnel, typically defined by diameters exceeding 10 m, using actual geological and geotechnical data from a representative site in the Lesser Himalaya. Finite Element Analysis (FEA) was employed to model and analyse vertical crown displacements at different excavation stages. A detailed parametric analysis was also carried out to assess the influence of water pressure on overall tunnel stability. Result indicate ring-cut excavation offers the most effective initial control, as it excavates the tunnel face sequentially in concentric rings from the periphery toward the centre, followed by the New Austrian Tunnelling Method (NATM), and eventually by mechanized excavation methods. For Tunnel Boring Machine (TBM) operations, precise prediction of machine parameters is critical to mitigate jamming risks. The presence of water was found to intensify face stability challenges and complicate pressure estimations. The findings contribute essential guidance for tunnel design and execution in the complex geology of the Lesser Himalayas.
This study examines the factors influencing the hydrogeochemical characteristics and stable isotope composition of groundwater in the study area. A systematic analysis of groundwater samples was carried out to evaluate both physical and chemical parameters, revealing the predominant ionic concentration order as Ca-2(+) > Na+ > Mg-2(+) > K+ > NH4+ > Li+ for cations and HCO3- > Cl- > SO42- > NO3- > F- > NO2- for anions. To interpret the hydrogeochemical processes governing groundwater composition, multiple analytical techniques were employed, including bivariate plots, Piper trilinear diagrams, and Principal Component Analysis (PCA). The Piper diagram highlights the dominance of the Ca-Mg-HCO3 water type, suggesting that chemical weathering of carbonate and silicate minerals significantly influences groundwater chemistry. The Chloro-Alkali Indices, which exhibit positive values, indicate reverse ion exchange reactions, where Na+ or K+ from groundwater are exchanged with Mg-2(+) or Ca-2(+) from the aquifer matrix. In contrast, samples with negative CAI values exhibit a direct ion exchange reaction. Saturation index calculations further suggest that groundwater hydrochemistry is primarily governed by geogenic factors, while PCA results reveal that contamination is influenced by geological weathering, ion exchange processes, and anthropogenic sources. Stable isotope analysis of delta D (ranging from -50.078 parts per thousand to -33.443 parts per thousand) and delta O-1(8) (ranging from -9.074 parts per thousand to -2.899 parts per thousand) indicates that groundwater recharge occurs predominantly after evaporation and precipitation, with evidence of paleo-water recharge in certain locations. Regarding agricultural suitability, the majority of groundwater samples fall within acceptable limits for irrigation purposes, affirming its usability for agricultural applications.
