Holocene morphodynamics in the Ugii Nuur basin, Mongolia - insights from a sediment profile and 1D electrical resistivity tomography

摘要

Sediment profile analysis and electrical resistivity tomography were applied in the Ugii Nuur basin, central Mongolia, in order to gain insight into the sedimentary architecture of valley fillings. It is shown that important constituents in the near surface ground are aeolian fines. Coarse grainsizes were predominantly deposited during the Late Pleistocene and the beginning of the Holocene indicating local dune activity and arid conditions. Since the Early to Mid Holocene a larger proportion of silt suggests an increase in mineral dust deposition. In combination with soil formation this points at dust trapping by a denser vegetation cover that reflects more humid conditions in the Ugii Nuur basin. Yet, 1D electrical resistivity tomography (VES) shows that Holocene deposits represent only a minor part of the thick valley fillings. Hence, it is assumed that their main extent has been established during the Pleistocene.