Early Cretaceous synrift uplift and tectonic inversion in the Loppa High area, southwestern Barents Sea, Norwegian shelf

Tectonic inversion of rift basins is most commonly reported in the literature to occur after rifting has ceased. In contrast, we present evidence for synrift, localized tectonic inversion from the Loppa High area, southwestern Barents Sea and present a model for the formation of inversion structures as a result of differential uplift. The structures are of early Barremian to mid-Albian age (c. 131 - 105 Ma) and are focused in or near pre-existing extensional boundary faults along the margins of the Loppa High. Inversion is interpreted to be the result of uplift of the high along its inclined boundary faults, leading to space accommodation problems as uplift was not properly compensated by extension in the region. The model constrains the initiation of uplift of the Loppa High to the early Barremian and shows that the asymmetric margin configuration of the high may have led to a bulk clockwise rotation of the high around a vertical axis during uplift. The cause of uplift is not fully understood, but is suggested to be linked to contemporaneous extreme lithospheric thinning in neighbouring basins to the west. Processes involved may include isostatic flexure, thermal heating, lithological phase changes and/or far-field stresses, although these aspects need to be further tested.