ИСТИНА

Geological crossection of quaternary deposits 15 m depth in Larsemann Hills oasis was studied with the use of drilling rig and complex laboratory analyses of cores. Lower stratigraphic unit was interpreted as lacustrine-marine sediments 37820-17860 years BP meaning that relative sea level during MIS3-MIS2 period was at least 30 meters higher than present sea level allowing lagoon-type deposition. Upper stratigraphic unit was interprerated as end morain which marks the position of last glaciation which moved so far to the north during pre-Antarctic Cold Reversal glaciation 14 Ka BP or some minor Holocene surges. Two different types of ground ice were observed in these deposits. The upper layer of ground ice is allocated on the contact between morain and lacustrine-marine deposits or in the upper meters of lacustrine-marine sediments. It is mostly clean transparent ice, sometimes with admixture of gravel and sand. The lower layer of ice lays into lacustrine-marine strata quite close to the aquiclude, which is presented by rock foundation; it is composed by laminated icy sediments with narrow-meshed inclined ice schliers 1-2 cm thick. Both ice layers were found in boreholes near the margin of Lake Reid at the quite close depths interval – 33-37 m a.s.l. for upper layer and 24-26 m for the lower layer. We present results of complex analysis of the ice core including detailed characterization of ice structure, texture and contacts with host sediments, as far as isotopic composition of ice. This data allow us to make a choice between several theoretical possibilities of ground ice origin including sea or lake ice, glacier, firn snow, injection or segregation ice. The work has been supported by RFBR, projects No 12-05-31442 mol_a and 12-05-31125 mol_a.