Estimation of sediment sources and budget at Lake Onego watershed after the last glaciation with GIS modeling and sediment geochemistry

Abstract

GIS modeling was performed to assess sediment budget of Lake Onego in the Late Glacial time. For this purpose, the procedure of river valley recognition was conducted using Digital Elevation Model and Topographic Position Index for the watershed of Lake Onego. The lake lost its connection with a glacier ca.12 ka BP. This time silty clays began to accumulate in the lake, thus this period was selected as a starting point for our calculation. The Lake Onego watershed was at least twice larger as compared with the modern one and extended more than 300 km southward out of the modern watershed border. The calculated sediment budget was varied from 13.4 to 49.4 km³. Our estimates also demonstrate that the share of sediments eroded from the Russian Platform was on several times higher, than from the Baltic Crystalline Shield. This was also evidenced by vertical geochemical structure of Lake Onego sediments. A gradual increase was observed in the share of the Russian Platform clays sedimentary rocks from north to south direction achieving their full prevalence in sediments of the southern part of Lake Onego.