The crustal and sedimentary structure of the Irish Atlantic margin
Abstract
Wide-angle seismic reflection/refraction profiles have been acquired in the Porcupine, Rockall and Hatton basins, and the Hatton margin areas of the Irish Atlantic continental margin. The wide-angle data have been integrated with normal-incidence reflection lines, gravity and magnetic data to reveal a clear picture of the regional crustal and upper mantle structure, and of the large-scale sedimentary geometry of the Late Palaeozoic-Cenozoic basins in the area. The region contains a series of large sedimentary basins resting upon thinned continental crust. The crust beneath the basin-bounding structural highs is typically ∼ 25 km thick, with the crust beneath the basins being as thin as 6 km. The crustal structure suggests that attenuation was achieved primarily by differential crustal stretching. The Moho beneath the Rockall Basin shows a clear asymmetry, with a steeper gradient along the eastern margin of the basin. Variations in lower crustal and upper mantle velocities are interpreted as serpentinised mantle beneath the Rockall Basin and as underplating to west of the Hatton High. Differences in the nature of the continental/oceanic boundary are modelled between the boundary south of the Rockall Basin and the boundary west of the Hatton High. Up to eight seismically distinct layers were identified above the basement in the Rockall Basin, with P-wave velocities of 1.8 - 5.3 kms-1. A smaller number of layers are identified in the other basins. A number of high-velocity layers are present locally within the Rockall Basin and are interpreted as either igneous bodies or as cemented sediments. The upper sedimentary layers modelled from the wide-angle seismic data correlate very closely with sequences identified on coincident normal-incidence seismic reflection profiles. However, the deeper wide-angle layers cannot be resolved on the reflection profiles due to the effects of Tertiary igneous sheet-like bodies. A significant variability in thickness of the various sedimentary layers is seen on the wide-angle data. Modelling of the wide-angle data, together with migration of the data, reveal hitherto unseen marked topographic irregularity at the base of the sedimentary succession. This is interpreted as the result of extensive multi-phase Mesozoic rifting.
- Publication:
-
EGS - AGU - EUG Joint Assembly
- Pub Date:
- April 2003
- Bibcode:
- 2003EAEJA....10715M