Meso-Cenozoic exhumation and relevant isostatic process: The Barents and Kara shelves

Abstract

Fennoscandia and Arctic shelves are known to have experienced several periods of Meso-Cenozoic uplift and erosion, but their magnitude and timing are still debated. The aim of our study is to estimate erosion volumes and distinguish between different erosional episodes, including glacial and pre-glacial ones. Our estimation approach is based on a combination of geological-geomorphological analysis, computer simulations of different erosion processes in time and space, mass-balance, burial control, and other methods Isostatic modelling is an obligatory component in the geomorphological reconstructions, since the erosion and subsequent isostatic uplift change the inclinations of various surfaces. Isostatic modelling is especially of significant importance in cases of poor or lacking age control.We find that the role of Neogene erosion might previously have been strongly exaggerated in some areas. Intensive Triassic-Jurassic deformations mark exhumation of positive structures (i.e. Novaya Zemlya, Pay-Khoy, Fedynsky). Novaya Zemlya − Pay-Khoy − Polar Ural belt was likely strongly exhumed during Neocomian (Berriasian). Upper Cretaceous erosion was noticeable in some structural zones, and strong Rupelian erosion is evident in Cenozoic. Changes of depositional provinces complicated the pattern, especially in Eocene.The role of climatic changes with global cooling could be discussed for Oligocene. Neogene erosion, with final glacial substages completed the erosional history, creating several prominent troughs and basins.We present a high-resolution model of Quaternary glacial and fluvioglacal erosion. Many landforms in the area were modified by glacial and periglacial processes, in particular by variable glacial erosion due to lithological, structural and topographic diversity. Glacial erosion of relative highs was often of minor importance, but other erosional agents could be active locally. We suggest a scenario of typical ice sheet development in the Barents Region, for the use in erosion computations. Radial glacial erosion pattern and significant basal ice velocities seem to be expected at the beginning of the early ice-age stage, resulting in widening of pre-glacial drainage elements. Pre-glacial lowlands and river pattern could provoke early stage onset of topographic ice-streams, especially in permafrost condition.Major ice streams were predefined by geological structures and tectonics.Different values of the elastic properties of the lithosphere dramatically impact isostatic movements and influence mass-balance computations, landscape features and delineation of watersheds.