Jurassic sandstone provenance and basement erosion in the Møre margin - Froan Basin area

Abstract

Upper Triassic, Jurassic and Lower Cretaceous sandstones and conglomerates from different settings around the Møre-Trøndelag Fault Complex have been studied for interpretation of sediment provenance and basement erosion history. Mineralogical and petrographic data provide evidence of eriosion of local sources in different geological provinces, probably connected to tectonic activity at various times. The continental and paralic Triassic and Lower Jurassic sediments off Møre were sourced from erosion of retrograde, high-grade metamorphic, eclogite-bearing rocks from the Western Gneiss Region, and the sedimentation in the northwestern part of Slørebotn Subbasin was sourced from outboard structural high of lower grade, metamorphic igneous rocks. Middle Jurassic shallow-marine sandstones have mixed compositions of local basement provenance and longer transported metamorphic components. Middle Jurrasic sandstones from Frohavet (Froøyene erratics) were sourced from medium- and low-grade, metamorphic pelitic and mafic rocks, most likely from the Trondheim Nappe Complex. Upper Jurassic and Lower Cretaceous marine mass-flow deposits in the Froan Basin are dominantly sourced from felsic plutonic rocks which may represent outboard extensions or analogues to the Hitra-Frøya igneous complex. The main provenance development with time in the study area is from a local provenance of varied metamorphic and igneous rocks in the Triassic - Lower Jurassic sediments to a mixed provenance in the Middle Jurassic and an increasing contribution from erosion of Palaeozoic plutonic rocks in Upper Jurassic and Lower Cretaceous, mass-flow sediments. The main diagenetic influences on sandstone porosity in the studied areas include carbonate cementation inthe shallow-buried locations, and feldspar dissolution, clay mineral growth and quartz cementation in the deeper welles in the Slørebotn Su