ИСТИНА

The covering and surrounding of relatively small, low and flat Schirmacher Oasis (East Antarctica) by glaciers during the last glaciation caused development here the lakeland since the beginning of Holocene warming. Three main stages of this development were recognized during our field work in summer season 2007-2008: I (early middle Holocene). The highest marks of past lakes water level, composed of poorly preserved stony to gravely terraces, evidence glacial and/or proglacial lakes dammed among glaciers and moraines. A uniform altitude of the marks in the territory suggests that system of connected water bodies could occupy significant part of the oasis. II (middle late Holocene). The middle marks of past lakes water level reflect conditions, when lakes are still supported by melt-water streams, and volumes of lakes are strongly controlled by altitudes of outflow from their catchments. III (late Holocene recent). Many lake basins in the oasis north were abandoned by glaciers: lakes are situated in closed catchments, have no more regular supply by melt-water and exhibit the tendency to drying. The sequences of lake sediments follow from inorganic glacial clastics, than often through laminated clayey silt with detritus rich layers, to the homogenous microbial mats. All recent lakes at different development stages are characterized by more or less clayey microbial mats at the bottom.