Lithostratigraphy and paleoceanography in the Chukchi Rise of the western Arctic Ocean since the last glacial period

Abstract

Paleoceanographic multi-proxies were investigated from two piston cores PC01 and PC04, along with two pilot cores PL01 and PL04, collected from the Chukchi Rise in the western Arctic Ocean during the R/V Mirai Cruise MR09-03. Both cores were composed of three lithologic units (Unit I: the Holocene brownish sandy mud, Unit II: the deglacial IRD layer, and Unit III: the glacial and gray thick mud with intervened IRD layers). The age estimate of the core units were decided by AMS 14C dates and confirmed by the correlation of the geochemical properties and ice-rafted debris (IRD) pattern with the well-dated core (P2) in the study area. The geochemical, isotopic, and mineralogical properties indicate different paleoceanographic conditions of three lithologic units in the Chukchi Rise: low primary production during the glacial period (Unit III), high terrigenous contribution during the deglacial period (Unit II), and increase in diatom productivity during the late Holocene (Unit I). In particular, most IRDs were specified as detrital carbonates (calcites and dolomites) by SEM-EDS examination. The sediment source from the northern North America and the transport pathway by the Beaufort Gyre were confirmed by the isotopic signature of bulk IRDs and high kaolinite content of fine-grained particles.