The Geikie igneous centre, west of Lewis: its structure and influence on Tertiary geology

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Abstract
Synopsis: The Geikie igneous centre is identified from a large positive gravity anomaly to the west of Lewis. The anomaly is satisfied by a simple two cylinder model with a maximum diameter of 26 km. The centre is covered by Palaeocene basalts which are domed and radially disposed around it. The centre occurs near the apex of a topographic bulge on the slope west of Scotland which overlies thinned crust. The intrusion has had a marked influence on the Tertiary development of the area, principally because it deflected faulting/flexuring associated with Eocene subsidence of the Rockall Trough to a zone seaward of the intrusion. Subsequent subsidence of the basalt and overlying Tertiary sediment wedge has been hinged at the transition between normal and thinned crust to the east of the centre. The curved bathymetric Geikie Escarpment is not faulted, but is an eroded feature cut into Oligocene sediments on this subsiding wedge.