New Insights into Basin Evolution and Development of Continental Margin in SW Barents Sea

Po Wan Wong

Deep basins in SW Barents Sea developed in 3 major phases: (1) the Late Jurassic to Early Cretaceous rifting that centered on the Tromsø and Bjørnøya basins, but also involved the Harstad and Sørvestanaget basins, (2) Late Cretaceous to Early Paleocene rift-shear that further deepened the Sørvestsnaget and Harstad basins and (3) Early Eocene continental break-up and related margin uplift that shaped the southern Sørvestsnaget basin into a major depository for Mid-/late-Eocene sediments. Structural studies of the Tromsø and Bjørnøya Basins show two important observations – general absence of typical syn-rift wedges, and rapid differential subsidence centered on the NE-SW trending basin axes. Together, these imply sagging was the major mechanism of sediment accommodation. Although cooling of mantle/ crustal dome is a common causes of sag basin formation, salt movement controlled by structural inheritance would be a more reasonable hypothesis given the presence of salt diapirs in the vicinity and the scale and shape of these sag basins, . In addition, our new structural map demonstrates strong along-strike variation of the Eocene continental margin (the Senja Fracture Zone; SFZ). From 71°20’ to the north, the amount of uplift and width of eroded zone of the marginal high (MH) gradually increases with decrease of latitude. Its southern counterpart maintains a relative uniform geometry but much stronger folding of pre–Eocene strata. From 70°38’ southward, the margin shows a more landward position until it fades away around 69°51’. Also revealed are series of strong but rough reflectors that appear mainly as continuous lines with slight curvature but occasionally as typical bell shape curves. These reflectors cover area between 0.25 to 1.8 degrees west of the MH – an area traditionally regarded as pure oceanic crust. Since, this area does not show clear magnetic anomalies which characterize the Norwegian-Greenland Sea, it is likely that the reflectors represent lava flows overlying transitional crust. Anyhow, our observations are not in accord with the image of SFZ being a typical strike-slip fault. We suggest that other tectonic events like change of relative plate motion at C21 and removal of continental sliver (formation of the Greenland Ridge) are required to explain such complexity. Overall, our new insights present alternative perspectives on both basin evolution modelling and plate reconstruction along the SW Barents Sea margin.

AAPG Search and Discovery Article #90177©3P Arctic, Polar Petroleum Potential Conference & Exhibition, Stavanger, Norway, October 15-18, 2013