The Old Red Group (Devonian) – Rotliegend Group (Permian) Unconformity in the Inner Moray Firth

Abstract

AbstractA major stratigraphical problem in the offshore Paleozoic of the Inner Moray Firth is the identification of the top of the Devonian Old Red Sandstone Group beneath the lithologically similar Permian Rotliegend Group. Wireline log criteria for a revised Old Red Group to Permian boundary are given for the Inner Moray Firth. Section lines drawn using these criteria and flattened on the overlying Triassic Smith Bank or Permian Kupferschiefer formations show a relatively thin development of Rotliegend with two depocentres. The underlying Devonian when flattened on the Eday Marl shows a systematic subcrop pattern. There is currently no exposed onshore Old Red to Rotliegend boundary, but the possibility remains that a Permian section is present in the ‘Upper Old Red Sandstone’ of Tarbat in Easter Ross. An exposed Permian–Devonian boundary is present in East Greenland and provides an analogue for the Inner Moray Firth.