Monsoon variability and major climatic events between 25 and 0.05 ka BP using sedimentary parameters in the Gangotri Glacier region, Garhwal Himalaya, India

Abstract

Gangotri Glacier has attracted international attention for its rapid rate of retreat. It is one of the best studied Himalayan glaciers, however there are no unanimous views about the history of climate change for the Gangotri Glacier. We prepared the lithologs/textural logs by making two trenches in the kame terraces and analysed it in detail for sediment grain parameters and 14C AMS dates to infer the depositional sedimentary environments, monsoon variability and major climatic events in the Gangotri Glacier region.The sedimentary parameters and geomorphic analysis revealed that the sediments of the kame terraces are consolidated to semi-consolidated, stratified, very coarse to fine grained layers of sand, silt and clay with few gravels and sedimentary structures. The sediment size indicating energy of the depositional environment varies from medium to fine sand (1.02–2.26 Φ). The standard deviation is poorly sorted (0.89–1.46 Φ) which describes that the energy of the depositional environment is continuously fluctuating. The positive skewness (0.32–0.98 Φ) indicates the excess of finer sediments and dominance of low energy whereas, very leptokurtic kurtosis (2.28–4.47 Φ) describes the fluctuating energy conditions.The present study explains the glacial stages and weak Indian Summer Monsoon (ISM) around 19.5, 14.5, 13.1, 10.1, 8.6, 7.5, 2.2, 0.54, 0.08 ka BP and warm and intense ISM during 23.9, 22.7, 19.4, 1.15, 0.05 ka BP. The higher percentage of clay in both the trenches around 0.65–0.2 ka BP (1300–1750 AD) and higher percentage of silt and low clay content around 1.15–0.55 ka BP (800–1400 AD) validates the Little Ice Age (LIA) and Medieval Warm Period (MWP) respectively.