--> Abstract: Episodic Uplift and Exhumation along Passive Margins in the North Atlantic Domain: Implications for Hydrocarbon Prospectivity, by Peter Japsen, Paul Green, Johan M. Bonow, Erik S. Rasmussen, James A. Chalmers, and Tomas Kjennerud; #90130 (2011)

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Episodic Uplift and Exhumation along Passive Margins in the North Atlantic Domain: Implications for Hydrocarbon Prospectivity

Peter Japsen1, Paul Green2, Johan M. Bonow1, Erik S. Rasmussen1, James A. Chalmers1, and Tomas Kjennerud3
1GEUS, Copenhagen, Denmark.
2Geotrack International, Melburne, VIC, Australia.
3Exploro Geoservices, Trondheim, Norway.

We present observations that demonstrate that the elevated passive margins (EPCMs) around the North Atlantic were formed by episodic, post-rift uplift movements that are manifest in the high-lying peneplains that characterise the coastal mountains, in the unconformities in the adjacent sedimentary basins and in accelerated subsidence in the basin centres. Results from West Greenland show that subsidence took place for c. 25 Myr after rifting and breakup in the Paleocene, as predicted by classical rift theory, but that this development was reversed by a series of uplift movements (starting at c. 35, 10 and 5 Ma).

East Greenland, Scandinavia and the Barents Sea seem to have had a similar evolution of post-rift subsidence followed by uplift starting at c. 35 Ma. There was no major fall in sea level at this time, so the subsiding basins must have been inverted by tectonic forces. We speculate that the forces causing this phase were related to the plate boundary reorganisation in the North Atlantic around Chron 13 time. The Cenozoic uplift history of the east Canadian EPCM is poorly known, but the east-west symmetry between Baffin Island and West Greenland and the similarity of landscapes on both sides of Baffin Bay suggest that the Canadian EPCM was also uplifted long after rifting and breakup. The presence of Eocene marine sediments, several hundred metres above sea level on the Canadian margin supports this conjecture.

One feature that these areas have in common is that uplift took place along the edges of cratons where the thickness of the crust and lithosphere changes substantially over a short distance. It may be that the lateral contrasts in the properties of the stretched and unstretched lithosphere make the margins of the cratons unstable long after rifting. These vertical movements have profound influence on hydrocarbon systems and confront us with questions like: How much section has been removed? When did maximum burial occur? How have migration paths been affected? Has a significant amount of hydrocarbon charge been lost from a breached reservoir during uplift? Such questions become very important, not only in frontier areas such as Baffin Bay where Mesozoic basins are deeply truncated and exposed onshore, but also for the understanding of hydrocarbon systems in more mature areas such as the Barents Sea where low-angular unconformities represent episodes of deposition and removal of significant sedimentary sections.

 

AAPG Search and Discovery Article #90130©2011 3P Arctic, The Polar Petroleum Potential Conference & Exhibition, Halifax, Nova Scotia, Canada, 30 August-2 September, 2011.

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