Lithostratigraphic correlation of Upper Jurassic sandstones within the Norwegian Central Graben: sedimentological and tectonic implications

Abstract

Log correlations combined with sedimentological, chronostratigraphic and seismic data of more than 60 exploration wells suggest that at least five different sequences of marine sandstones exist in the Upper Jurassic strata of the Norwegian sector of the Central Graben. The sequences are distinguished by their regional and stratigraphic distributions and by their depositional environment. The marine transgression in ?Callovian to Oxfordian times deposits a basal sandy unit which consists of resedimented older sandy sediments and is especially thick, in the axial part of the graben. The Heno Formation Equivalent was deposited during a regressive phase in Late Oxfordian to Middle Kimmeridgian times, and is an often thin but regionally extensive sandstone sheet throughout most of the northeastern flank of the Central Graben. The Fulman Formation was developed on the western flank of the graben. Locally, in the Feda Graben area, the Eldfisk Formation was developed. It is situated between the two shale units of the Haugesund and the Farsund formations. The Ula Formation is restricted to the hanging wall of the Hidra Fault Zone. Its distribution is closely linked to activity of the fault and to rapid subsidence that took place during the Late Kimmeridgian to Early Portlandian. -Authors