Sedimentary environment evolution and biogenic silica records over 33,000 years in the Liaohe delta, China

The burial efficiency of biogenic silica (BSi) in deltaic sediments is associated both with the nutrient balance in estuarine ecosystems and with the carbon cycle and climate change. To explore these relationships, foraminifera data, physical and chemical parameters, and ages determined by accelerator mass spectrometry C-14 and optically stimulated luminescence from a core drilled at the southwestern edge of the Lower Liaohe Plain in May 2012 were presented. The sedimentary environments since 33,000 cal yr BP were divided into four depositional units, namely, a fluvial deposit (U1), lacustrine deposit (U2), marine-related deposit (U3), and upper delta plain deposit (U4). Environmentally mediated differences in apparent mass accumulation rates (AMARs) of BSi and organic carbon (C-org) were significant. The BSi-AMAR in the later parts of U1 and U2 occurred mainly in the Pleistocene and averaged 11.34 +/- 0.22 and 16.69 +/- 0.91 g m(-2) y(-1), which is lower than the analogues for U3 (23.59 +/- 2.89-41.74 +/- 6.37 g m(-2) yr(-1)) and U4 (37.25 +/- 9.96 g m(-2) y(-1)) that occurred during the Holocene. The BSi record responded more coherently and was more sensitive than Corg to Northern Hemisphere paleoclimatic variations on a long timescale and to abrupt/periodic winter monsoon winds or warming forcings on a short timescale. There was a negative correlation between the concentration of bioavailable Fe2O3 and the ratio of BSi/Corg, the implication being that Fe availability may have modulated silicic acid uptake on a very short timescale and in turn impacted the dynamics of carbon burial.