Variation of calcium carbonate content and Dansgaard-Oeschger events in the continental slope of the central Bering Sea during the last 65 kyr

Abstract

A piston core (MR06-04 PC23A) collected from the northern continental slope in the central Bering Sea has recorded the high-resolution millennial-scale variation of calcium carbonate (CaCO3) content during the last 65 kyr. An estimation of the age of the core sediments was carried out by using the lithologic correlation of the deglacial laminated layers with a neighboring core (HLY02023JPC), complementing the last appearance datum of both Lychnocanoma nipponica sakaii (54 kyr) and Amphimelissa setosa (85 kyr). The probable age of core MR06-04 PC23A was approximately younger than 65 kyr. Two distinct events of a significant increase of CaCO3 in the deglacial laminated sediments clearly correspond to MWP1A and MWP1B in the Bering Sea (Gorbarenko et al. 2005) and to T1ANP and T1BNP in the North Pacific (Gorbarenko 1996). These pronounced peaks of CaCO3 contents result from the elevated carbonate production in the surface water and the subsequent weakened dilution due to terrestrial input, along with an enhanced oxygen minimum zone. The CaCO3 contents are low (∼2%) during the last glacial period mainly because of a low carbonate production caused by an expanded sea-ice cover and an increased dilution by terrigenous particles due to their closer distance to the continent during the sea-level low stand. The occurrence of seven distinct CaCO3 peaks in core MR06-04 PC23A is remarkable during MIS 3 and MIS 4, and they most likely correlate to the short-term millennial Dansgaard-Oeschger events.