A multi-proxy lake sediment record of Indian summer monsoon variability during the Holocene in southern India

Abstract

We present here a 11,000-year palaeomonsoonal record from a sediment core (SS-1) from Shantisagara (SS) Lake in Peninsular India, which is the longest published so far from the region. This is also a region with limited palaeoclimate records. Environmental magnetic, organic geochemical, sedimentological and carbon isotopic studies were carried out on the SS-1 sediments to reconstruct the Indian summer monsoon (ISM) variability during the Holocene. The chronology of the sediments is constrained by three AMS 14 C dates. Environmental magnetic data reveal that there is no contribution from bacterial magnetite, greigite and anthropogenic magnetite/lithogenic grains and that the magnetic signal is contributed mainly by the pedogenic component. The environmental magnetic data also depict variations in pedogenic magnetite production in the catchment and detrital influx to the lake, which in turn is related to monsoonal rainfall amount. The sedimentological data reveal variations in sediment size related to monsoon. The C org /N ratio and δ 13 C indicate palaeovegetational variations in the SS catchment. Periods of strong monsoon are characterised by high values of concentration-dependent magnetic parameters like χ lf , χ fd , χ ARM and SIRM, high sand content, low C org /N ratio (fully aquatic-deep water conditions), relatively depleted δ 13 C values (more C 3 but less C 4 land plants) and vice versa. The prominent palaeomonsoon events documented in this study are: (i) 11,100-10,700 cal yr BP with a weak ISM, (ii) 10,700 to 8600 cal yr BP characterized by intensified ISM, corresponding to the Early Holocene Optimum, (iii) 8600 to 4500 cal yr BP with a weakened ISM (iv) 4500 to 3300 cal yr BP characterized by fluctuating monsoonal conditions, (v) 3300 cal yr BP to the Present with a slight increasing trend in ISM. A similar pattern is also documented in many palaeomonsoon records from the region, which indicate that Shantisagara sediments were able to record regional climatic variations as well.

Paleoenvironmental shifts spanning the last ~6000 years and recent anthropogenic controls inferred from a high-altitude temperate lake: Anchar Lake, NW Himalaya

“…Sedimentary basins such as lakes are closely connected with their surrounding environments especially the catchment areas, making them as sensitive recorders of perturbations within their catchment watersheds (O'Beirne et al, 2015). Lake sediments provide direct evidence of the past environmental changes on the local and/or regional scale, with a relatively high, millennial to centennial resolution (Mills et al, 2014;Plater et al, 2006;Sandeep et al, 2017). Elemental geochemistry of lake core sediments provides a principal tool for reconstructing the paleoenvironmental and paleoclimate changes that have occurred during the Holocene period (Jiang et al, 2007;Li et al, 2016Li et al, , 2017Lone et al, 2018c;Sadori et al, 2016).…”

Holocene climate variability and cultural dynamics in the Indian subcontinent

“…The first global cooling event recorded during the Holocene epoch is marked by fluctuation in the North Atlantic deepwater circulation and northward movement of heat due to the mixing of meltwater from Laurentide ice sheets (Hong et al, 2003;Walker et al, 2012;Marzin et al, 2013;Menzel et al, 2014). Considering dating uncertainty, this event has been reported in several terrestrial (Anoop et al, 2013b;Walker et al, 2012;Dixit et al, 2014;Rawat et al, 2015;Sandeep et al, 2017) as well as marine archives (Gupta et al, 2003;Govil and Naidu, 2011;Rashid et al, 2011). However, no major focused studies have yet been done in India to explicitly link 8.2 ka event with specific cultural adaptations/changes, though this is a time when the Neolithic lifestyle is well-established in some regions and just beginning to appear in other regions of the subcontinent (Figure 1).…”

“…Riwasa paleolake (Dixit et al, 2014); 15. Shantisagara Lake (Sandeep et al, 2017); 16. Ziro basin (Ghosh et al, 2014); 17.…”

“…The lacustrine records from the central (Lonar Lake) and southern India (Shantisagara Lake) indicate early Holocene climate intensification with initiation of a wet phase at ca. 11 kyr BP Sandeep et al, 2017) (Figure 2). The paleorecord from the Lahuradewa Lake in the Gangetic plain also shows intensified monsoon condition during 9.2 to 5.3 kyr BP with maximum intensity around 7 kyr BP (Saxena et al, 2013) (Figure 2).…”

“…The majority of paleo-records in the Indian subcontinent is characterized by decreasing monsoonal precipitation during the mid-Holocene with termination at around 4200 yr BP (also termed as 4.2 ka event) (Staubwasser and Weiss, 2006;Berkelhammer et al, 2012;Walker et al, 2012;Sinha et al, 2015;Kathayat et al, 2017;Sandeep et al, 2017) (Figure 2). The paleoclimate record from the continental Oman (Fleitmann et al, 2007), Arabian Sea (Gupta et al, 2005), Bay of Bengal (Ponton et al, 2012;Contreras-Rosales et al, 2014) and southern India (Sandeep et al, 2017) demonstrated progressively decreasing monsoon intensity during the mid-Holocene in response to solar variability. However, the pollen-based records from the Gangetic plains and paleo-records from NW India show fluctuating precipitation condition, probably due to a variable moisture source and proxy sensitivities (Prasad and Enzel, 2006;Saxena et al, 2013Saxena et al, , 2015Saxena and Trivedi, 2017) (Figure 2).…”