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

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.

Holocene hydroclimatic variability recorded in sediments from Maddox Lake (northern California Coast Range)

“…Mo has a limit of detection of <5 ppm and Ti <25 ppm. A handheld XRF method for determining elemental concentrations in lacustrine sediments is a commonly used, rapid method (e.g., Niederman et al, 2021; Wright et al, 2023). However, the data should be considered semi-quantitative due to inherent sediment heterogeneity and its variable clastic, organic, and chemical components (Weltje and Tjallingii, 2008).…”

Investigating possible links between Holocene environmental changes and cultural transitions across India

“…Further, an unstable trend of strengthening occurred until ~1.5 cal kyrs BP, followed by a weakening monsoon that intensified at 0.8 cal kyrs BP. Niederman et al (2021) also reported episodes of dry events at 4.8, 4.2, and 3.1 cal kyrs BP based on multi-proxy analysis of sediment core retrieved from Deoria Tal. Contradicting this, Bhushan et al (2018) reported periods of enhanced monsoon at 5–4.2, 3.5–2.4, and 1.8–1 cal kyrs BP, respectively with relatively cold and dry periods occurring at 5.8–3.7 and 2.1–0.69 cal kyrs BP.…”

“…Tso Moriri (Mishra et al, 2015); 14. Deoria Tal (Niederman et al, 2021); 15. Manasbal Lake (Babeesh et al, 2019); 16.…”

Pyramid building and collapse

“…Nile flow is a function of seasonal Indian Summer Monsoon (ISM) precipitation over the Ethiopian highlands that provides an average 80% of the Lake Tana sources of the Blue Nile and Tekeze-Atbara Rivers measured by air mass back trajectories, which then provide 90% of Nile flow ( 11 – 13 ). The proximate cause of the abrupt ~4.2 ka BP Nile flow reduction was the ISM megadroughts at 4.2 ka BP to 4.17 ka BP, 4.14 ka BP to 4.08 ka BP, and 4.06 ka BP to 3.97 ka BP, now measured to subdecadal and seasonal resolution in Indus speleothem, marine ( 14 , 15 ), and lake cores ( 16 ).…”