Topography of the Top Chalk surface on- and offshore Denmark

Abstract

A time-structure map of the top of the Upper Cretaceous–Danian Chalk Group (the Top Chalk surface) in the entire Danish sector is presented. The present topography of the Top Chalk surface is a result of various erosional and tectonic events taking place during the Cenozoic. The analysis shows that the Cenozoic is characterised by significant reactivation of the Mesozoic structural elements of which the Central Graben, the Ringkøbing–Fyn High and the Sorgenfrei–Tornquist Zone are the most important. A tectonically controlled relief caused the generation of widespread sheet like erosion on the Ringkøbing–Fyn High and incisions along the margins of Ringkøbing–Fyn High during the mid Paleocene. Incisions in the northern part of the Danish sector formed valleys, which probably transported sediment towards the west. The present topography of Top Chalk in the eastern part of the Danish Sector is highly influenced by the late Cenozoic erosion of the uplifted eastern margin of the North Sea Basin. The topography of Top Chalk also reflects the distribution of mobile Zechstein salt as collapse structures follow the pitch-out line of mobile salt onto the Ringkøbing–Fyn High, and numerous salt structures deformed the Top Chalk surface.