Mineralogical proxy to determine the depositional condition in the Larsen Ice Shelf B, Antarctic Peninsula

Variations in grain size, clay mineral compositions, stable isotopes (δ¹³C and δ¹⁵N) and illite crystallinity (IC) reflect the unique sedimentary facies for the retreat and advance of Larsen ice shelf B (LIS-B). A marine geological expedition (ARA13 Cruise Expedition by the Korea Polar Research Institute) was conducted in the Larsen ice shelf embayments of Weddell Sea in 2013. A whole round core (236 cm below the sea floor) of marine sediment (EAP13-GC16B) was collected on the northwestern part of LIS-B embayment. The clay assemblage showed that major clay minerals were smectite, chlorite, illite and kaolinite consistent through the depths. In the interglacial period, increase in the relative proportion of smectite is dominant compared to the glacial period. The recent sediment deposited under LIS-B has been oxygenated as the ice shelf has retreated and IC abruptly decreased in the oxygenated sediment unit of bioturbated/non-laminated facies. These results indicate that illite crystal structure responding in IC has been modified through a various redox conditions associated with the oxygenation.