The Erris and eastern Rockall Troughs: structural and sedimentological development

Abstract

Abstract Wide-angle seismic reflection profiles across the western Irish shelf region have resolved the deep crustal structure of the shelf transition into the Rockall Trough. A three-layered sedimentary succession up to 5 km thick is determined within the Rockall Trough. The lowermost layer probably comprises a thin early Mesozoic syn-rift sediment package, while the upper two layers represent Cretaceous to Recent, mostly post-rift, sediments. The seismic response of the crust changes beneath the Erris Trough into the eastern Rockall Trough, as the crust thins from c. 30 km onshore in Ireland to between 5 and 6 km in the deep water region of the Rockall Trough. However, the thinning of seismic layers in response to stretching is not uniform. Differential stretching of the crust can explain seismic observations of both crustal and upper mantle structure. Low upper mantle velocities may be due to partial serpentinization of the upper mantle lithosphere, facilitated by rheological hardening during lithospheric stretching. The model predicts the occurrence of starved deep marine sediments during the late Mesozoic and Cenozoic.