Clay Mineralogical Characteristics of Sediments Deposited during the Late Quaternary in the Larsen Ice Shelf B Embayment, Antarctica

Abstract

Variations in grain size, clay mineral composition, and stable isotopes (delta C-13 and delta N-15) are closely linked to the sedimentary facies that reflect mineralogical and geochemical modification during the retreat and advance of the Larsen ice shelf. A whole round core of marine sediment (EAP13-GC17, 236 cm below the sea floor) was collected on the northwestern Larsen B embayment of the Antarctic Peninsula during a marine geological expedition (the ARA13 Cruise Expedition by the Korea Polar Research Institute, 2013). Four sedimentary facies (U1-U4) were clearly distinguishable: bioturbated sandy mud (open marine, U1), laminated sandy mud (sub-floating ice shelf, U2), sandy clay aggregates (deglacial, U3), and muddy diamictons (sub-glacial, U4), as well as interbedded silty. Clay minerals, including smectite, chlorite, illite, and kaolinite, were detected throughout the core. An increase in the clay mineral ratio of smectite/(illite + chlorite) was clearly observed in the open marine condition, which was strongly indicated by both a heavier isotopic composition of delta C-13 and delta N-15 (-24.4 parts per thousand and 4.3 parts per thousand, respectively), and an abrupt increase in Be-10 concentration (similar to 30 times). An increase in the average values of the crystal packet thickness of illite (similar to 1.5 times) in U1 also indicated sediments transported in open marine conditions. Based on the clay mineral composition in U1, the sediments are likely to have been transported from the Weddell Sea. The clay mineralogical assessments conducted in this region have significant implications for our understanding of paleodepositional environments.