Wadia Institute of Himalayan Geology

The geomorphological evolution of landscapes is primarily governed by the coupled influence of tectonics and climate, with their relative dominance varying through time and space. In the Ladakh Himalaya, where active deformation intersects pronounced Quaternary climatic fluctuations, this coupling produces a distinct geomorphic signature. The Muglib Valley, formerly the outlet of Pangong Tso, demonstrates a system in which tectonic forcing initiated hydrological reorganisation, subsequently amplified by climatic variability. The region lies along the Karakoram Fault system, where oblique right-lateral slip with a vertical component (3–5 mm yr⁻¹) has modified basin geometry, offset valley alignments, and generated localised blockages that facilitated lake formation. Detailed geomorphic and sedimentological analyses across seven field sections reveal marked spatial variability: stacked gravels and conglomerates represent sustained fluvial aggradation, while thick fan and lacustrine deposits reflect progressive sediment overloading and hydrological stagnation, respectively. Optically Stimulated Luminescence (OSL) ages indicate a steady flow of water from Pangong Tso between ~54 ± 4.3 ka and 21 ± 3 ka. Thereafter, the channel was cut and eventually abandoned at ~9 ± 1 ka. The latter coincides with intensified monsoonal precipitation during the Holocene Climate Optimum, which enhanced sediment flux and triggered fan progradation, ultimately blocking the Muglib outlet. This geomorphic transformation converted Pangong Tso from an open to a closed basin, isolating an upstream catchment of ~2000 km² and terminating water and sediment supply to the Tangste River. The findings demonstrate that slow but persistent tectonic activity along the Karakoram Fault primarily governed drainage reorganisation, while monsoon intensification acted as an additive trigger that accelerated fan aggradation and hydrological isolation. The Muglib system thus provides an example of coupled tectonic–climatic feedback that has reshaped the fluvial architecture and sediment connectivity in the Trans-Himalayan landscape.

Abstract We use continuous Global Navigation Satellite System (GNSS) measurements from >1600 sites on and around the Indian subcontinent, including 64 sites in the Indian plate interior, to estimate site motions and their seasonal variations. Stations in the Himalayan and Indo‐Burmese plate boundary zones exhibit rapid velocities (15–20 mm/year with respect to the Indian plate) and correspondingly higher strain rates (70–100 ηstrain/year). We find that the southern part of the plate interior is more stable, with residual motions <1 mm/year. Although the northern part of the plate interior appears more deformable (∼2 mm/year), there is no clear fragmentation of the Indian plate. The southern part exhibits a low shear strain of ∼1 ηstrain/year, while the northwestern India region, referred to as the Rajputana block lying west of the Aravalli Delhi Fold Belt (ADFB), consistently shows a higher shear strain rate of >2 ηstrain/year and higher southward motion with respect to the region to the east. Such a motion is consistent with sinistral shear along the ADFB and ∼north‐south contraction across the Kachchh failed rift in the south, explaining the higher earthquake productivity in Gujarat. Long‐term vertical rates on the Indian plate are low except in the northwestern region where Gravity Recovery and Climate Experiment (GRACE) measurements show negative equivalent water height changes and GNSS measurements record uplift, caused by the depletion of groundwater storage. Seasonal variations in the GNSS and GRACE data distinctly show the influence of hydrological loading on land movement. After the monsoon, the entire hydrological load seems to be centered in the Indo‐Gangetic plains and the central‐east India region.

The origin and association of high-silica granites (HSGs; SiO2 ≥ 71 wt%) and residual intermediate to felsic cumulates remain enigmatic due to their rare coexistence. These limitations complicate their characterization, parental source, and tectonic setting identification. This work presents a case study from the Mikir Hills, NE India, utilizing zircon U-Pb geochronology, mineral chemistry, and geochemical thermodynamic modeling constraints to understand the origin and relationship of ca. 508 Ma high-K monzogranites, granites, and HSGs. The monzogranites show accumulated plagioclase crystals and high Ba, Sr, and CaO, whereas the HSGs show depleted Ba, Sr, and CaO, representing fractionated melt. The redox calculations (ΔNNO −0.3 to −0.1) and thermometry results (∼880−902 °C) using amphibole chemistry show oxidized and high-temperature conditions for monzogranites. The monzogranites’ high K2O and large-ion lithophile elements suggest the role of a sediment-derived enriched mantle source in their origin. The rhyolite-MELTS and Magma Chamber Simulator modeling results suggest the monzogranites’ parental melt resulted from a silicic metasomatized phlogopite-stabilized lithospheric mantle wedge that underwent subsequent lower crust assimilation. The polybaric (∼6−4 kbar) crystallization of the generated assimilated melt formed the monzogranites with plagioclase and K-feldspar as the dominant crystallizing phase (>50%). Plagioclase-melt equilibrium tests yield slightly higher liquid-only saturation temperatures than plagioclase-liquid pairs, indicating progressive crystallization and melt extraction. The rhyolite-MELTS geobarometer suggests the highly felsic melts separated from the crystal mush between ∼3.8 kbar and 2.8 kbar and emplaced at subvolcanic levels as failed rhyolite eruptions. We suggest the HSGs represent extracted evolved melt, while monzogranites represent residual silicic cumulates formed in a syn- to postcollisional setting during Gondwana assembly.

Abstract. Global glacier mass loss is accelerating the formation and expansion of glacial lakes. These lakes store meltwater, contribute to enhanced glacier mass loss through positive feedback mechanisms, and in some cases can pose a risk to downstream populations, infrastructure, and ecosystems through glacial lake outburst floods (GLOFs). Although satellite-derived inventories of glacial lakes exist at both global and regional scales, they vary in spatial and temporal resolution. Critically, fully automated and systematic monitoring of lake area changes is lacking, yet such monitoring is essential for detecting anomalous changes, estimating water storage, and understanding lake-glacier feedbacks. Here, we present a foundational dataset to support lake monitoring for the Glacial Lake Observatory (GLO), with an initial focus on lakes in Nepal and transboundary catchments. We trained a deep learning model to extract water bodies from Sentinel-1 and Sentinel-2 image mosaics from 2017 to 2024, subsequently classifying them as glacier-fed or non-glacier-fed based on their hydrological connectivity. In total, 18,389 and 22,419 individual lake outlines (≥ 0.001 km2) were mapped respectively from Sentinel-1 and Sentinel-2 imagery (2017–2024), resulting in 2,966 and 4,150 uniquely identified lakes (respectively). The number and total area of lakes increased over the eight-year period, driven largely by sustained expansion in the Koshi basin, which hosts about 61% of all mapped lakes and nine out of ten of the fastest expanding. On average, glacial lakes covered an average annual area of 169 km², with growth concentrated in high-elevation, glacier-fed systems. Validation against existing inventories and manually digitised outlines demonstrated good accuracy of our deep learning datasets (F1 scores = 0.80–0.92), with Sentinel-2 most reliably capturing smaller lakes. Datasets, as well as deep learning models, are openly available (https://doi.org/10.5281/zenodo.17802334).

ABSTRACT The commencement of the Industrial Revolution has resulted in an unprecedented increase in the concentration of atmospheric CO2 (pCO2). It is, therefore, important to understand how plant communities respond to increased levels of CO2 levels in the environment. To this end, we examined the effects of spatial variation in pCO2 on plant physiology using carbon isotope ratios (δ13C values) and stomatal index (SI) in C3 plant leaves along a transect from the central Ganga Plain to the foothills of the Himalayas with industrial and non-industrial zones. Our study shows that the plants adjacent to the industrial areas have much lower δ13C values (avg. −31.8 ‰) and absorbed more fossil fuel-derived carbon (ca. 18 %) than those growing in non-industrial areas (−28.3 ‰). We also observed ca. 25 % lower SI values from the industrial area, suggesting that the increase in CO2 concentration (for a given water budget) led to high photosynthetic rates with low stomatal conductivity. Therefore, a long-term increase in pCO2 would lead to higher water-use efficiency in C3 plants, which would allow them to function better in low moisture conditions. We also suggest that the δ13C and SI values can be used for mapping carbon sequestration by plants growing in industrialized regions.

The study explores the Precambrian tectonic evolution and the growth of continental crust in the southern region of the North Odisha Singhbhum Craton (NOSC), delving into the potential petrogenetic processes and source characteristics. The Tikiba Granitic Complex (TGC) is in the contact area of the Eastern Ghat Mobile Belt (EGMB) and the NOSC. The present study involves the geochemical characteristics of TGC granitoids and their geochemical variations. Petrographically, the TGC is comprised of alkali feldspar granite, monzogranite to granodiorite. The major element geochemistry reveals calc-alkalic, ferroan to magnesian affinities, and a metaluminous, peraluminous and peralkaline character. It is enriched in LILE and HFSE like Yb, Sm, Zr and Y. The (La/Yb)N values range from 4.0–26.1 and exhibit distinct negative Eu anomalies (Eu/Eu*) (0.4-0.6). This granitic complex shows high ΣREE contents of 176-860ppm with variable enrichment in LREE. Both REE and other incompatible element compositions define an A-type affinity. Based on geochemical data, we conclude that these granitoids have probably derived from a predominant crustal source with variable mantle characteristics in a post-orogenic setting.