U-series constraints on granite weathering across climatic gradient in the Garhwal Himalaya and metagenomic insights on microbial mediation in weathering

Illustration showing the development of weathering profile, LWP with time and microbial mediated weathering processes in different zones of this weathering profile. • Weathering rate and timescales are established in Himalaya using U-series isotopes. • Weathering in humid Lesser Himalaya is ∼3.5 times faster than the Higher Himalaya. • Element flux in the Lesser Himalaya is ≥2 times higher due to humid climate. • Glacial retreat in Higher Himalaya controls rock exposure and weathering timescales. • Microbes aids CO 2 capture and drive weathering based on nutrient availability. Weathering is a key exogenic process that supplies sediments to rivers and drives global biogeochemical cycles. This study quantifies the impact of water availability on rock weathering using U-series isotopes from two granite weathering profiles in the climatically distinct Himalayan regions: the humid Lesser Himalaya and the semi-arid Higher Himalaya. The humid conditions in the Lesser Himalaya have accelerated weathering rates by up to 3.5 times compared to the semi-arid Higher Himalaya, with at least a twofold increase in element flux. The ∼60 ka weathering record in the Higher Himalaya corresponds to the deglaciation period, and due to low residence time, the profile here is thinner and weathering intensity is less than that of the Lesser Himalayan weathering profile. The metagenomics-based study on the Lesser Himalayan weathering profile provides further insights into biogenic mediation in weathering. Microbes disintegrate primary minerals in fresh rock to utilize mineral-bound nutrients and reprecipitate secondary carbonate in the soil. In contrast, in the nutrient-depleted, highly weathered zone, microbes rely on carbon sources, produce organic acids, and disintegrate K-feldspar to release potassium for plant uptake. Additionally, they capture soil CO 2 and convert it into bicarbonates, highlighting the importance of quantifying biological carbon capture. The datasets produced in this study represent granite weathering fluxes across the climate gradient in the Himalaya. Further, by providing the first in-situ U-series-based weathering timescales, the research bridges a critical gap in understanding weathering dynamics in one of the world’s most tectonically active mountain belts.