Hydrochemistry and sediment characteristics of polar periglacial lacustrine environments on Fisher Island and Broknes Peninsula, East Antarctica

摘要

Fisher Island and Broknes Peninsula in the Larsemann Hills constitute part of a polar lowland periglacial environment between marine and glacial ecosystems.The landscape is characterized by gently rolling hills and broad valleys interspersed with lakes formed in glacially scoured basins.We analyzed the physicochemical parameters and the ionic constituents of water samples from 10 lakes in each of these two locations.Our results showed considerable differences between the two regions and demonstrated the influence of lithology and processes including weathering,evaporation,and atmospheric precipitation.All major cations and anions in the lake waters showed positive correlations indicating balanced ionic concentrations.Unconsolidated sediments were sparsely distributed and scattered over glacial deposits,valley fills,and occasional moraine ridges.The type and rate of sedimentation was mainly controlled by surface run-off and aeolian influx.The sediment samples from lake beds and the catchment area on Fisher Island were immature and poorly to very poorly sorted,consisting of gravelly sand with negligible silt and finer fractions.Sediments had a polymodal grain size distribution with the two major populations lying between-2 and-1 phi and between 0 and 1.5 phi.The sediments were lithic arenite to arkosic in composition and the microtextures imprinted over quartz grains were dominated by mechanical textures resulting from several stages of glacial crushing and grinding.The presence of deep dissolution cavities,cryptocrystalline precipitation,and euhedral crystal growth signified the effect of chemical activity after the deposition of grains in the lacustrine environment.