Clay mineral provenance and its response to paleochimate in the central Okinawa Trough since the last Deglaciation (19 ka)

In this paper, the authors discussed the clay mineral provenances and their environmental significance since the last Deglaciation on the basis of clay minerals and AMS14C dating analysis carried out for Core CS2, which was located in the central Okinawa Trough. The results show that Core CS2 mainly consists of illite and lesser amounts of chlorite, with associated kaolinite and smectite. Downcore variability of clay mineral content allows Core CS2 to be divided into three units. The sediments were primarily derived from Changjiang with lesser amounts from Huanghe and Taiwan in unit 1 (19-12 ka BP) and unit 2 (12-8 ka BP), which was mainly controlled by sea level change. In unit 3 (8- 0 ka BP), the sediments were primarily derived from Changjiang and Taiwan, with lesser amounts from Huanghe, which was mainly controlled by Kuroshio evolution. The ratios of (smectite+ kaolinite)/(illite+chlorite) at CS2 were adopted as proxies for East Asian monsoon evolution. The consistent variation of this clay proxy with those from Sanbao Cave δ¹⁸O and GISP2 δ¹⁸O shows that two profound shifts of the East Asian winter monsoon intensity and the intensity of winter monsoon relative to summer monsoon occurred at 16.4-14.8 ka BP and12.8-11.6 ka BP.