Preglacial geomorphology of the northern Baltic Lowland and the Valdai Hills, north-western Russia

The aim of the ongoing investigation is to reconstruct the development history of preglacial (including deeply-incised) river network of the northwestern East European Platform during the Cenozoic. This paper describes the orography of the region. The results of studying the structure of modern and preglacial (pre-Quaternary) geomorphology are given. This synthesis is based on the geological information that has been acquired as a result ofsystematic state geological surveying and scientific investigations and also on the analysis of published materials for the study area.The hypsometric map of the pre-Quaternary surface is presented. Generalization of the above mentioned materials on a unified basis and at regional level allowed a new reconstruction of the preglacial river network in the Ilmen Lowland area, drainage from which to our opinion was to the west. Analysis of the preglacial and modern topography correlation shows that the latter, in general, is inherited. This leads to the conclusion on a quiet tectonic regime in the study area at least since the Mesozoic. Therefore, the question on the causes of deeply incised valleys requires further study.