Mid- to late Holocene climate response from the Triloknath palaeolake, Lahaul Himalaya based on multiproxy data

Abstract

A 2.13-m-thick palaeolake sequence deposited between the right lateral moraine and the valley wall of Triloknath glacier, has been studied at high resolution to understand the past climatic changes in Lahaul Himalaya. The OSL and AMS14C chronology suggests that the lake building activity was initiated post-cooling phase since ~6484cal.YBP. The combination of sedimentological, geochemical, and environmental magnetic parameters helped to infer five first-order climatic zones. The influx of magnetic minerals along with a notable increase in antiferromagnetic mineralogy (appearance of hematite) and higher chemical index of alteration (CIA) values during ~5925cal.YBP to 5676cal.YBP suggests warm and wet conditions owing to enhanced Indian Summer Monsoon (ISM) precipitation corresponding to the mid-Holocene warming. Further, reduction in the magnetic mineral concentration with few peaks of antiferromagnetic mineralogy and higher CIA values suggests warmer episodes within an overall cold climate, and the finer ferrimagnetic grain size suggests intermittent low energy and ponding conditions during ~3904cal.YBP to 2365cal.YBP. This was followed by fluctuating cold arid conditions in response to reduced ISM precipitation during ~2365cal.YBP and 1758cal.YBP. Further, between 1758cal.YBP to the present, episodic warming, pedogenic enhancement, and increased monsoon precipitation have been recorded. A major warm episode (Medieval warm period) as depicted from enhanced antiferromagnetic mineralogy and higher CIA values has been recorded between ~742cal.yrs. BP and 593cal.YBP. The sudden drop in the magnetic mineral concentration as well as the CIA value, around ~300cal.YBP (1650 CE) is likely because of colder conditions prevailing during the Little Ice Age (LIA). The study illustrates high sensitivity of the lake sediment sequence to witness the climatic episodes experienced in the glaciated regime of the Triloknath glacier.