Glacial-interglacial climatic variations at the Schirmacher Oasis, East Antarctica: The first report from environmental magnetism

We discuss in this paper the first detailed environmental magnetic record of glacial-interglacial climatic variations in the Schirmacher Oasis, East Antarctica. We determined environmental magnetic properties and inter-parametric ratios (χ_lf, χ_fd %, χ_ARM, SIRM, χ_ARM/SIRM, χ_ARM/χ_lf, χ_ARM/χ_fd, SIRM/χ_lf, S-ratio and HIRM) for sediment samples of a core from the Sandy Lake. Accelerator mass spectrometer (AMS) ¹⁴C dates were obtained on the organic matter from bulk sediment samples. The sediment core spans the past ~42.5cal. ka B.P. The magnetic minerals are mainly detrital and catchment-derived, as there is no evidence for the presence of authigenic greigite, bacterial magnetite or diagenetic dissolution. The last glacial period is characterized by a high concentration of ferrimagnetic minerals such as titanomagnetite (high values of χ_lf, SIRM etc.) and coarse magnetic grain size (low χ_ARM/SIRM and χ_ARM/χ_lf values and high S-ratio values). Deglaciation in the Schirmacher Oasis began around 21cal. ka B.P. as suggested by the low magnetic mineral concentration. The Holocene period is characterized by relatively warm climatic events as seen in the low values of magnetic susceptibility which is primarily contributed by fine-grained titanomagnetite resulting from pedogenesis (high χ_fd % values). Several of the relatively warm and cold events that we deciphered from the environmental magnetic data are correlatable with lake sediments from the Schirmacher Oasis and other ice-free areas in East Antarctica and from ice-core records on the Antarctic Plateau.