Clay mineral stratigraphy during the last 2.4 Ma at IODP Exp. 323 Site U1343 in the Bering Sea

• Stratigraphy of clay mineral compositions at the IODP Expedition 323 Site U1343 during the last 2.4 Ma
• Quaternary provenances of the clay minerals and their transport processes in terms of glacial–interglacial cycles
• Less variation of smectite/(illite + chlorite) [S/(I + C)] ratios between interglacial and glacial periods
• Unchanged main provenance (Aleutian Island Arc) of clay minerals to Site U1343 between interglacial and glacial periods
• Additional source of clay minerals to Site U1343 during glacial periods after Mid-Pleistocene Transition

The clay mineral composition at IODP Exp. 323 Site U1343 in the Bering Sea was analyzed so as to unravel their provenance over glacial–interglacial cycles for the last 2.4 Ma. Smectite was negatively correlated with the sum of illite and chlorite; therefore, their ratio [S/(I + C)] was used as an indicator of clay mineral composition changes. In general, the S/(I + C) ratio was rather similar for glacial and interglacial periods during most of the last 2.4 Ma. In addition, these results overlap with those of surface sediments in the modern East Aleutian Basin, which suggests that smectite-rich clay particles are delivered from the Aleutians by the northward Bering Slope Current (BSC) rather than from rivers in western Alaska. However, some clay mineral compositions of the glacial periods after the Mid-Pleistocene Transition (MPT: 1.25–0.7 Ma) were characterized by low illite and relatively high smectite. During this period, extensive ice-rafting might have transported the smectite-rich clay particles to Site U1343 from the glacial shelf off Alaska and/or from glacial rivers from that area.