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 intraplatform basins. Furthermore, the main sources of the modelled magnetic anomalies are related to highsusceptibility (≤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 preDevonian 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.