Saprolites on- and offshore Norway; new constraints on formation processes and age
Saprolites on- and offshore Norway; new constraints on formation processes and age (in Goldschmidt abstracts 2013, Anonymous)
Mineralogical Magazine (2013) 77 (5): 1108
The origin of landscapes in Scandinavia has been debated for more than a century and the discussion is as vigorous as ever today. In short, one school proposes that most of the geomorphology can be explained by glacial and periglacial processes, while others argue that the landscape partly is inherited from earlier etching, stripping and exhumation episodes, and has been preserved through cover of sedimentary rocks and selective glacial erosion. One key argument used by the latter proponents is the relatively widespread occurrences of saprolite in Scandinavia. Here we attempt to characterize and date these saprolites both on- and offshore Norway. One key locality is the Utsira high, which is an offshore crystalline basement horst in the Norwegian North Sea partly overlain by Paleozoic and Mesozoic strata. The area has received significant attention recently due to large petroleum finds, specifically the Edvard Grieg (16/1-8, 2007), the Johan Sverdrup (16/2-6, 2010) and the Luno 2 (16/4-6 S 2013) discoveries done by Lundin Norway. Significant areas of the Utsira high basement appear to be deeply weathered and saprolite is found in exploration wells. We utilize K-Ar dating of illite diagenesis and geochemical analysis of the saprolite to characterize weathering age and processes. The data suggest deep weathering of a granitic landscape during late Triassic, followed by a transgression and deposition of sedimentary strata. The K-Ar data thus agrees with the stratigragraphic position of Utsira high saprolite below Jurassic sediments. Our hypothesis is that the similar landscape and saprolite onshore Scandinavia is of similar origin and age as the offshore equivalent. Preliminary onshore data are inconclusive but more testing will be made.