A Model For The Development Of The Porcupine Basin West Of Ireland: Evidence For Regional Syn-rift Tectonic Linkages?
Abstract
The Porcupine Basin developed during the Mesozoic Era and is sited between the highly stretched crust of the Rockall Basin (where beta = 5 to 6) and the Protero- zoic crust of the Irish mainland, where the crust thickens to 30 km. Marine gravity sur- veys around Ireland together with satellite gravity data from the deeper ocean are used to investigate the larger-scale crustal structure of these two basins. Crustal structure derived from wide-angle and vertical incidence seismic data controls the interpretation and modeling of gravity data. An axial NE-trending gravity low caused by seismically defined crustal thickening towards the centre of the Rockall Basin is also present in the South Porcupine Basin where the crust has been extended by similar amounts. In contrast the amount of extension is less across the narrower North Porcupine Basin, where a N-trending axial gravity high is present due to poorly understood anoma- lous density variations in the crust/upper mantle. The change in crustal geometry and gravity properties occurs across a distinctive set of NW trending gravity lineaments. These are interpreted as a set of cross-basin syn-rift faults which control large-scale segmentation of extensional deformation at mid to upper crustal levels. Lithospheric stretching in the South Porcupine Basin involved a large anticlockwise rotation of the South Porcupine High, while to the north the stretching involved a smaller antipathetic clockwise rotation of the North Porcupine High. Restoration of the pre-rift crustal ge- ometry requires that a large amount (10's of km) of cumulative sinistral motion on NW-trending cross-basin faults accompanied these rotations, causing the southward broadening of the Rockall Basin. A tectonic linkage between the syn-rift development of the two basins and the smaller more numerous inboard basins in the Celtic area to the east is also required in this model. The NW-trending fault systems may have been important in focusing fluid flow in the lithosphere causing rheologically controlled serpentinisation of the mantle, inferred from earlier wide-angle seismic studies in the Rockall Basin. Similar linked rheological and fluid flow processes may perhaps also have occurred locally in the Porcupine Basin.
- Publication:
-
EGS General Assembly Conference Abstracts
- Pub Date:
- 2002
- Bibcode:
- 2002EGSGA..27.4866O