Tectonic control on the formation of Roskilde Fjord, central Sjælland, Denmark

Abstract

Roskilde Fjord is a characteristic N–S-trending geomorphological element in north-east Sjælland (Fig. 1). The eastern coastline of the fjord forms a nearly straight, SSE– NNW-trending lineament from the town of Roskilde to the coastal areas at Kattegat. Due to the records from wells, it has long been known that a fault zone has to be present along this lineament (Bondesen 1979). The fault is named after the fjord: the Roskilde Fjord Fault (Fig. 2). However, a detailed analysis of the well data in the Roskilde area has shown that a number of minor faults are present, superposed by various landscape elements. These are the inner fjord and valley distributary at Roskilde, the Kornerup Å valley, the inlet of Lejre Vig and its contributory, and the peninsula of Bognæs (Figs 1, 2). In this paper we propose a lithostratigraphic division of the Cenozoic deposits and their dynamic development in the Roskilde area. A distribution of the faults with estimated maximum displacements is presented, and their relations to the geomorphological features are outlined. The description is based on several years’ studies of the Roskilde Fjord fault complex and presented here due to the recent interest in neotectonics in Denmark and environmental considerations focused on Roskilde Fjord (Gravesen & Pedersen 2005).