Cenozoic palaeogeography and isochores predating the Neogene exhumation of the eastern North Sea Basin

This study emphasises that the tectonic development of a region cannot be reconstructed solely on evidence from the sedimentary record. Such reconstructions need also to be based on the record of physical indicators of palaeothermal and palaeoburial phases related to the former presence of geological units now removed. We have found evidence for three tectonic phases that have affected southern Scandinavia during the Cenozoic: (1) A phase that began at the Eocene-Oligocene transition at c. 33 Ma as indicated by the onset of progradation of clastic wedges away from southern Norway and inferred progradation away from southern Sweden. (2) A phase that began at the Oligocene-Miocene transition at c. 24 Ma, as indicated by early Neogene exhumation of the areas adjacent to the presently exposed basement areas and by early Miocene coarse-grained braided fluvial systems south of Scandinavia. (3) A phase that began in the early Pliocene at c. 4 Ma, as indicated by the widespread, late Neogene exhumation, the intra-Pliocene unconformity and subsequent tilting of the Neogene succession in the eastern North Sea. These phases are consistent with the stratigraphy in the north-east Atlantic Ocean (Stoker et al. 2005) and around southern Norway (e.g. Michelsen et al. 1998; Faleide et al. 2002; Rasmussen 2004). The observations thus suggest that southern Norway, with peaks higher than 2 km above sea level, emerged during several phases since Eocene times, when a deep ocean covered much of the region.