Hydroclimate change in the Garhwal Himalaya, India at 4200\xa0yr BP coincident with the contraction of the Indus civilization

E A Niederman,B S Kotlia,D F Porinchu

doi:10.1038/s41598-021-02496-5

Abstract

High-resolution analysis of a 3.80 m sediment core recovered from Deoria Tal, a mid-elevation lake located at 2393 m a.s.l. in the Garhwal Himalaya, documents long-term and abrupt hydroclimate fluctuations in northern India during the mid- to late Holocene. The sediment chronology, based on ten 14C dates, indicates the core spans 5200 years. Non-destructive, radiological imaging approaches (X-ray fluorescence (XRF), X-ray imaging, and CT scans) were used to assess the response of the lake system to changing hydroclimatic conditions. Variations in elemental concentrations and sediment density evidenced notable hydroclimate change episodes centered at 4850, 4200, and 3100 cal yr BP. Elevated detrital input, greater sediment density, decreased lake ventilation, and lower autochthonous productivity reflects lake deepening between 4350 and 4200 cal yr BP. An abrupt shift in elemental concentrations and sediment density indicated the onset of lake drawdown at 4200 cal yr BP and a negative hydroclimate anomaly between 4200 and 4050 cal yr BP. Lower detrital flux, decreased sediment density, increased oxygenation, and higher autochthonous productivity, reflects a reduction in lake volume between 3200 and 3100 cal yr BP. The potential link between abrupt climate change at 4200 cal yr BP and the contraction of the Indus civilization is explored.

Highlights

The 4200 cal yr Before Present (BP) megadrought, which extended from 4200 to 3900 cal yr BP, was characterized by a reduction in the global monsoon and associated circulation systems, leading to droughts and seasonal precipitation failures worldwide[1]
Modeling and paleoenvironmental studies suggest that the rapid, step-wise, and sustained decline in population that characterized the Indus civilization, beginning at ~ 4200 cal yr BP, can be attributed to increasing water scarcity associated with a weakening of the Indian Summer Monsoon (ISM) and changes in regional hydroclimate[23,24,29]
We utilize non-destructive, radiological approaches, e.g. X-ray fluorescence (XRF) and Computerized Tomography (CT) scans of a well-dated lake sediment core recovered from Deoria Tal, a small, closed basin lake located in the Garhwal Himalaya to: (1) characterize regional hydroclimate variability during the mid- to late Holocene; (2) determine if evidence of an abrupt, short-lived climate event at 4200 cal yr BP is present at this

Summary

Introduction

The 4200 cal yr Before Present (BP) megadrought, which extended from 4200 to 3900 cal yr BP, was characterized by a reduction in the global monsoon and associated circulation systems, leading to droughts and seasonal precipitation failures worldwide[1]. Given that the EASM and the ISM are the main sources of precipitation for their respective regions, climate scientists and archaeologists have postulated that a dramatic reduction in the strength of the Asian summer monsoon at 4200 cal yr BP would have impacted the complex societies present in India and China during the mid- to late Holocene[7,8]. We utilize non-destructive, radiological approaches, e.g. X-ray fluorescence (XRF) and Computerized Tomography (CT) scans of a well-dated lake sediment core recovered from Deoria Tal, a small, closed basin lake located in the Garhwal Himalaya to: (1) characterize regional hydroclimate variability during the mid- to late Holocene; (2) determine if evidence of an abrupt, short-lived climate event at 4200 cal yr BP is present at this

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Discussion

Conclusion