Late Devonian transpressional tectonics in Spitsbergen, Svalbard, and implications for basement uplift of the Sørkapp–Hornsund High

Abstract: The Late Devonian Svalbardian event relates to the final activity in the Caledonian Orogen, and affected Devonian strata in Spitsbergen by major folding, oblique thrusting and basement uplift. In southern Spitsbergen, the Devonian deformation and the complementary, presumed Mid-Carboniferous Adriabukta event deformation caused uplift of the Sørkapp–Hornsund basement high or horst. This high is fault-bounded by Devonian sandstones and a questionably aged Early or Mid-Carboniferous mudstone unit (Adriabukta Formation). The Adriabukta Formation at Hornsund occurs in the core of a major syncline, with underlying Devonian strata in the west limb, all truncated in the footwall by a steep, east-side-up oblique-reverse fault. Mid- to Late Carboniferous rifting reversed the motion and produced rift-fill deposits, and these strata overlie the deformed Devonian rocks and the Adriabukta Formation with an angular unconformity. A similar basin architecture and major syncline bounded by a reverse fault with lateral movement characterize the Svalbardian deformation in the Mimerdalen–Pyramiden area at Billefjorden farther north. Similarity also exists between a Late Devonian unit (Plantekløfta Formation) at Mimerdalen and the Adriabukta Formation at Hornsund, and we question the previous interpretation of the Adriabukta Formation as Carboniferous. Rather, we suggest that the Adriabukta and Svalbardian deformation events may have been part of the same event.