Holocene Paleoenvironment Changes Near Lake Funazoko-Ike, East Antarctica, Based on Analyses of Sediments and Microfossils

Abstract

Lake Funazoko-Ike was formed by a relative sea level fall due to crustal uplift after the melting of the ice sheet. Today, the lake surface lies approximately 25 m below the present sea level. Evidence of these processes is recorded in sediments deposited from the sill to the lake surface around Lake Funazoko-Ike during the middle to late Holocene. A total of 123 sediment samples were collected from outcrops of the Holocene-raised beach around Lake Funazoko-Ike in Skarvsnes, Antarctica, during geomorphological surveys by the 38th and 46th Japanese Antarctic Research Expeditions (JARE38 and JARE46). The samples were analyzed for grain size, carbon, nitrogen, and sulfur (CNS) contents, as well as microfossil assemblages, including arenaceous foraminifera and siliceous microfossils. Radiocarbon dating of marine fossils yielded ages ranging from approximately 4100 to 800 cal. yr. BP. From six samples, we identified at least 54 species belonging to 29 genera of siliceous microfossils. Arenaceous foraminifera were identified in one additional sample. Three sea-ice indicator diatom taxa were dominant in all six samples. These results suggest that Lake Funazoko-Ike was in an open marine environment from approximately 4100 to 1200 cal. yr. BP. The lake became isolated from the sea sometime between 800 and 1200 cal. yr. BP. This timing aligns with the isolation of the coastal margin in northwest Skarvsnes, providing evidence to understand spatial and temporal variations in ice sheet dynamics during the Holocene.