Holocene climate variability from the lake sediment core in Schirmacher Oasis region, East Antarctica: Multiproxy approach

A 1.62 m sediment core was retrieved from one of the landlocked freshwater lakes (L-6) in the Schirmacher Oasis (SO), East Antarctica during the 24th Indian Antarctic Expedition (2004-2006). The sediment core samples were analyzed for Total Organic Carbon (TOC), Biogenic Silica (BSi), grain size and elemental concentration ratios (Mg/Ca and Mn/Fe). The sediment core represents the time period of last ∼11.6 cal ka BP as ascertained by AMS 14C radiocarbon dates. The sedimentation accumulation rate variation of ∼13.6 cm/ka from ∼11.6 to ∼10 cal ka BP reveals a warm phase followed by a low sedimentation accumulation rate of ∼2.9 cm/ka from ∼10 ka BP to ∼3.1 ka BP, indicating a cold period in the region. The sedimentation accumulation rate again increased from ∼3.1 cal ka BP to recent with a maximum of ∼88 cm/ka which reveals the initiation of glacier retreat or ice-free conditions in the study area. The Total Organic Carbon (TOC) is <2% from ∼10 to ∼3.1 cal ka BP indicating a prolonged colder phase in the study area. However, elevated TOC, BSi and Mg/Ca ratio since ∼3.1 cal ka BP to recent points indicates towards ice-free conditions (continental ice sheet retreat) and subsequently high productivity in the region. Moreover, the productivity was higher at the Pleistocene-Holocene boundary as evidenced by the Mg/CA, Mn/Fe ratio and Biogenic Silica (BSi). The present study identified a colder phase (or re-advancement of continental ice sheet) during the early to mid-Holocene and initiation of ice-free or continental ice-sheet retreat during the late Holocene and their implications on the productivity changes.