Mesozoic–Cenozoic Exhumation Events in the Eastern North Sea Basin:

Paul Green¹, Peter Japsen², Erik Rasmussen², Lars Nielsen³, and Torbjen Bidstrup^2
1Geotrack International, Melbourne, Australia
²Geological Survey of Denmark and Greenland (GEUS), Copenhagen, Denmark
³Geological Institute, University of Copenhagen, Copenhagen, Denmark

Combined apatite fission track analysis, vitrinite reflectance and sonic velocity data from eight wells in Denmark has revealed four Mesozoic–Cenozoic cooling episodes, each interpreted as reflecting km-scale exhumation. Integration of these results with regional geological information provides further insight into the nature of these events. Middle Jurassic exhumation due to regional doming of the North Sea area was broadly contemporaneous with deep exhumation in Scandinavia. Mid-Cretaceous exhumation contemporaneous with the onset of deposition of a thick, impure chalk interval in the late Turonian reflects inversion of the Sorgenfrei-Tornquist Zone, contemporaneous with inversion identified in a parallel study of the Sole Pit axis (southern North Sea). Mid-Cenozoic exhumation correlates with a late Oligocene unconformity (c. 24 Ma) in the eastern North Sea, and the prior deeper burial is interpreted as reflecting progradation of lower Oligocene wedges southwards from Norway and westwards from southern Sweden as a result of Scandinavian uplift initiated in the early Oligocene (c. 33 Ma). Late Neogene exhumation affected the eastern (and western) North Sea Basin including Scandinavia. Another cooling episode reflects climate change during the Eocene. These exhumation episodes correlate with regional unconformities recognised over a wide area, suggesting they represent a plate-scale response to forces transmitted from plate boundaries. Such unconformities are often interpreted as representing periods of non-deposition, but experience shows that significant amounts of burial and subsequent exhumation can occur during these intervals, and can exert a critical control on regional patterns of hydrocarbon prospectivity.

AAPG Search and Discovery Article #90072 © 2007 AAPG and AAPG European Region Conference, Athens, Greece