LATE QUATERNARY ICE HISTORY ALONG THE SOYA COAST, LUTZOW-HOLM BAY, ANTARCTICA

The paleoenvironment during the late Quaternary along the northern Soya Coast, Lutzow-Holm Bay, can be estimated on the basis of the raised beach stratigraphy, AMS ¹⁴C ages and oxygen isotopic ratios of the fossil shells. The AMS ¹⁴C dating revealed that the ¹⁴C ages of in situ fossil shells are clearly classified into two groups: the younger group is 3,000-8,000 yrs BP, in the Holocene, and the older is 30,000-46,000 yrs BP, in the late Pleistocene, probably the last interstadial, without the reservoir corrections. The locality containing the late Pleistocene in situ fossils is confined to the northernmost part of the Soya Coast region. This fact indicates that marine transgression occurred twice during the late Quaternary in that region. In the northernmost part of the Soya Coast region, extremely fragile shells of Laternula elliptica, dated in the last interstadial, retain their living form in situ in the raised beach sediments without removal or shattering by the ice sheet. This fact indicates that the East Antarctic Ice Sheet had retreated at least from the Ongul Islands and the northern part of Langhovde by the last interstadial, and did not advance over the Ongul Islands and the northern part of Langhovde again, even during the LGM. It is not clear whether the southern part of Soya Coast was free from the East Antarctic Ice Sheet during the interstadial or not. However, most ice-free rocks on the southern part of the Soya Coast had become free from the East Antarctic Ice Sheet by the middle of the Holocene. The values of ¹⁸O (PDB) for the Holocene and last interstadial shells of Ongul Islands range from about 3.9 to 4.6 ñ; on the other hand the values for the last interstadial shells of Langhovde range from about 2.9 to 3.8 ñ. The difference of oxygen isotopic ratio is considered to mostly depend on ¹⁸O-depleted melt water from the Antarctic ice sheet. This also suggests that the ice margin of the East Antarctic Ice Sheet had been located at the northern part of Langhovde during the last interstadial.