Erosional Uplift of Greenland’S Marginal Mountains: Implications for Offshore Geology
Ebbe H. Hartz1, Sergei Medvedev2, Alban Souche2, Bjørn Martinsen1, Yuri Y. Podladchikov2, Niels Hovius3, Dani W. Schmid2, and Jan Inge Faleide4
1Aker Exploration, Oslo, Norway.
2Physics of Geological Processes, Oslo, Norway.
3Cambridge University, Cambridge, United Kingdom.
4Department of Geoscience, Oslo, Norway.
Greenland is rimmed by a marginal mountain range, which in many localities contain hydrocarbon bearing Mesozoic marine rocks. This scenario is most dramatic in East Greenland, where high peaks (2.5 to 3.7 km elevation) reside above a relatively thin crust. Some of Mesozoic marine sediments of the area have been uplifted up to 1.2 km during mid- to late- Cenozoic tectonic quietness. This Cenozoic uplift has remained enigmatic, although some studies relate it to intense heating and underplating by the Iceland hotspot during the break away of the Jan Mayen microcontinent, or the 55 Ma break up of the North Atlantic. We present tests of such thermal scenarios and suggest erosional unloading as an alternative mechanism. The uplifted area is cut by some of the world’s biggest fjords. Scoresby Sund alone, cuts 400 km into the land, is up to 60 km wide, and cuts more than 4 km down from the peaks of the region. In our approach we model the glacial erosion backward in time, the fjords are filled back to the summit surface while same weights of sediments are removed from the shelf. The model estimates the isostatical response of the flexing lithosphere due to loading and unloading of bedrock, sediments, water and ice. Our calculations demonstrate that: 1) Rocks in the central Fjord Mountains is uplifted about 1.1 km due to the erosional unloading and flexural isostatic effects, thereby being the main cause of post-Mid Cretaceous uplift; 2) The peripheral bulging effect due to the load of the Greenland ice sheet is insignificant (a few meters) and cannot explain alone the uplifted margins of Greenland; 3) That one can estimate the timing of the landscape formation by a mass balance of the eroded landscape, the dated deposits on the shelf, and paleosurfaces mapped out on land; 4) That basin models applied in hydrocarbon exploration (maturation, porosity etc), should include the dramatic effect of “erosional uplift”, rather “thermal uplift” or “footwall uplift”. 5) and that implication of the erosion-deposition driven vertical movements facilitates improved fits of basin geometries from the Greenland margin, across Iceland-Jan Mayen, and the Norwegian shelf. Much of the Arctic landmasses are rimmed by deeply carved mountain chains, suggesting that our model may be regionally applicable.
AAPG Search and Discover Article #90096©2009 AAPG 3-P Arctic Conference and Exhibition, Moscow, Russia