Paleoenvironmental changes in the northern South China Sea over the past 28,000 years: A study of TEX86-derived sea surface temperatures and terrestrial biomarkers

We have generated a record of TEX86 (TEX86H)-derived sea surface temperatures (SSTs) over the last 28 ka for core MD97-2146 from the northern South China Sea (SCS). The TEX86H-derived temperature of a core-top sample corresponds to the SSTs in warmer seasons. The SST record shows a drop during the Oldest Dryas period, an abrupt rise at the onset of the Bolling-Allered period, a plateau across the Younger Dryas period, and an abrupt rise at the beginning of the Holocene. The glacial-interglacial contrast in TEX86H-derived temperature is almost the same as that in foraminiferal Mg/Ca ratio-derived temperature, but it is larger than those in U-37(K') and transfer function-derived temperatures. Possible interpretations are: (1) the seasonal shift of glycerol dialkyl glycerol tetraether (GDGT) production, (2) the overestimation of temperature change by TEX86H, and (3) the underestimation of temperature change by U-37(K'), and transfer function approaches. The similar variation in TEX86H-derived temperature at the study site and Chinese stalagmite 8180 during the last deglaciation suggests that changes in TEX86H-derived temperature in this period reflected atmospheric and oceanic reorganization on a millennial timescale. The long-chain n-alkanes are mainly of higher plant origin before similar to 14 ka and a mixture of higher plant and lithic origins after 14 ka; the abundance ratio of long-chain to short-chain n-fatty acids decreases at similar to 15 ka, suggesting a drastic change in sediment sources at similar to 14-15 ka. We attribute the higher content of fresh higher plant n-alkanes and long-chain n-fatty acids before similar to 14-15 ka to enhanced aeolian transportation and/or arid environments. Increased precipitation likely due to intensified summer monsoon after similar to 14-15 ka enhanced the erosion of sedimentary rocks and increased the contribution of lithic n-alkanes. (C) 2010 Elsevier Ltd. All rights reserved.