Gravity Variations in the Rockall and Porcupine Basins West of Ireland: Evidence for a Linked Structural Development
Abstract
The crustal structure of the large Mesozoic Rockall and Porcupine basins west of Ireland determines the broader scale behaviour of the free air gravity field in the region. Marine gravity surveys in the shallow shelf seas around Ireland together with satellite gravity data from the deeper ocean to the west are used to investigate the larger-scale crustal structure of these major basins. Crustal structure derived from wide-angle and vertical incidence seismic data is used to control the interpretation and modeling of gravity data. The Porcupine Basin is situated between the highly stretched crust of the Rockall Basin (where β = 5 to 6) and the thicker Proterozoic crust of the Irish mainland and shelf area, where the crust approaches 30 km in thickness. The crust of the south Porcupine Basin has undergone similar amounts of bulk stretching to that of the southern Rockall Basin and has very similar gravity patterns. The crust of the northern Porcupine Basin is less severely stretched and an axial gravity high is present due to anomalous density variations in the crust or upper mantle. The change in crustal geometry and gravity properties occurs across a distinctive set of NW-trending gravity lineaments, which may correlate with cross-basin crustal faults, controlling large-scale basin segmentation. Lithospheric stretching south of these gravity lineaments involved a large anticlockwise rotation of the southern part of the Porcupine High, while to the north the stretching involved a smaller antipathetic clockwise rotation of the northern Porcupine High. This pattern of tectonic block rotation controls the southward broadening of the Rockall Basin and suggests a strong structural linkage between these two large basins.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2001
- Bibcode:
- 2001AGUFM.T52C0954R
- Keywords:
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- 1219 Local gravity anomalies and crustal structure;
- 3010 Gravity;
- 8105 Continental margins and sedimentary basins;
- 8109 Continental tectonics: extensional (0905);
- 9325 Atlantic Ocean