A 13,000 year record of environmental magnetic variations in the lake and peat deposits from the Chandra valley, Lahaul: Implications to Holocene monsoonal variability in the NW Himalaya Suman Rawat a, ⁎, Anil K. Gupta a,b , Priyeshu Srivastava c,1 , S.J. Sangode c , H.C. Nainwal d a Wadia Institute of Himalayan Geology, 33 GMS Road, Dehradun - 248 001, India b Department of Geology and Geophysics, Indian Institute of Technology, Kharagpur - 721302, India c Department of Geology, Savitribai Phule Pune University, Pune - 411 007, India d Department of Geology, H.N.B. Garhwal Central University, Srinagar - 246 174, India abstract article info Article history: Received 16 January 2015 Received in revised form 26 July 2015 Accepted 28 August 2015 Available online 6 September 2015 Keywords: Environmental magnetism Holocene Indian summer monsoon Medieval Warm Period Little Ice Age Himalaya An ~13,000 year old record of in situ peat bog and lacustrine sediments from a post glacial lake in the Chandra valley of the Lahaul Himalaya is studied to generate the record of environmental magnetic signatures in response to Indian summer monsoon (ISM) variability in the NW Himalaya. The chronology of studied Chandra Peat Trench (CPT) profile is based on 9 AMS 14 C calibrated dates (cal yr BP). The piece-wise linear regression anal- ysis of age-depth model indicates non-linear sedimentation with higher rates from ~4142 cal yr BP to the Present and lower accumulation during ~12,880–4142 cal yr BP. The mineral magnetism showed three dominant assem- blages of magnetic minerals with varying concentrations in peat-lake sediment sequence i.e. (1) mixed ferri- and antiferromagnetic minerals between ~12,880 and 11,019 cal yr BP, (2) dominant antiferromagnetic mineralogy from ~11,019 to 3172 cal yr BP, and (3) significantly increased concentrations of mixed ferri- and antiferromag- netic minerals from ~3172 cal yr BP to the Present with characteristically increased ferrimagnetic concentrations after ~2032 cal yr BP. The characteristic increase in antiferromagnetic mineral concentration accompanied by decreased ferrimagnetic concentration from ~ 10,398 to 5770 cal yr BP suggest possible oxidation of magnetite to hematite under warmer climate conditions and corresponds to increased ISM intensity during early to mid- Holocene warm-wet climate in the NW Himalaya. The distinctly increased concentration of antiferromagnetic min- erals from ~6732 to 5770 cal yr BP indicates mid-Holocene climate optimum (HCO) in the Lahaul Himalaya. The strengthening and weakening of ISM recorded in environmental magnetic signatures during ~1260–852 cal yr BP (~690–1098 AD) and between ~ 852 and 239 cal yr BP (~1098–1711 AD) corresponds to Medieval Warm Period (MWP) and Little Ice Age (LIA) events, respectively. © 2015 Elsevier B.V. All rights reserved. 1. Introduction The Indian summer monsoon (ISM) is one of the important climate systems in the world providing moisture source for agriculture and socio-economic development of the South Asian countries which constitute two-third of world population (Benn and Owen, 1998). At present, snow and glacier melts from the Himalaya contribute ~10–15% of total water resources and the rest is from seasonal precipi- tation of the ISM in the Indian subcontinent (Singhvi et al., 2010). The weakening of the summer monsoon led to changes in and adaptability of various civilizations such as that of Harappa or Indus (Staubwasser et al., 2003; Dixit et al., 2014; Leipe et al., 2014a), whereas extreme events in the ISM precipitation cause floods (Wasson et al., 2013) and landslides in the Himalaya (Dortch et al., 2009). Such events in the monsoon appear to have repeatedly occurred during the Holocene, allowing measures of adaptation and mitigation strategies by human civilizations as reported from the Indian subcontinent (Gupta et al., 2003, 2006). However, the intensity of ISM precipitation in different Indian basins was not uniform owing to variations in latitude, altitude, and distance from the sea (Kale et al., 2003; Prasad et al., 2007). Thus, there is an increasing demand to generate high resolution record of ISM variability from different geographic domains for better under- standing of the human–climate interactions (Prasad and Enzel, 2006; Leipe et al., 2014a, 2014b and references therein). The Holocene palaeomonsoon studies in the NW Himalaya has been significantly carried out from the Ladakh (Demske et al., 2009; Wünnemann et al., 2010; Leipe et al., 2014a, 2014b; Mishra et al., 2015). The late Pleistocene and Holocene tectonic and climatic studies Palaeogeography, Palaeoclimatology, Palaeoecology 440 (2015) 116–127 ⁎ Corresponding author at: Wadia Institute of Himalayan Geology, 33 GMS Road, Dehradun 248 001, India. Tel.: +91 1352525276; fax: +91 1352525200. E-mail address: rsuman26@gmail.com (S. Rawat). 1 Presently: School of Environmental Sciences, Jawaharlal Nehru University, New Delhi, 110 067, India. http://dx.doi.org/10.1016/j.palaeo.2015.08.044 0031-0182/© 2015 Elsevier B.V. All rights reserved. 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