Iapetus Ocean serpentinites and Mesozoic intra-platform basins revealed by gravity and magnetic modelling across the Greater East Shetland Platform (Northern North Sea, UK)

The Greater East Shetland Platform and its intra-platform basins (i.e. the Dutch Bank Basin and East Orkney Basin) are examples of poorly explored areas in the UK Continental Shelf (Northern North Sea), hosting a locally thick (1–8 km) Devonian-to-Tertiary sedimentary succession that unconformably overlies the Caledonian crystalline basement. Starting from a grid of seismic reflection lines, six recently acquired profiles were selected, interpreted and depth-converted. The resulting geological cross sections were integrated with forward modelling of the observed Bouguer gravity and magnetic anomalies, and constrained by the available wellbore-derived petrophysical parameters. Our seismic interpretation and modelling suggest that the first-order contributors to the observed Bouguer gravity anomalies are related to the scattered distribution of the Mesozoic sedimentary sequences in the intra-platform basins. Furthermore, the main sources of the modelled magnetic anomalies are related to high-susceptibility (≤0.05 SI units) bodies in the crustal basement that locally correspond to zones of high reflectivity imaged in the seismic profiles. Such deep sources are interpreted as paleo-domains inherited from the pre-Devonian tectonic evolution of the study area and assembled during the Caledonian Orogeny. This may be relatable to the offshore extension of first-order pre-Devonian tectonic lineaments exposed in the Scottish Highlands and Orkney-Shetland islands.