Structure and evolution of the Galicia Interior Basin (Atlantic western Iberian continental margin)

Abstract

An industrial multichannel seismic reflection data set is presented on the Galicia Interior Basin (G.I.B.), a sedimentary basin that has been poorly studied until now. Seismic stratigraphic units defined in other areas of the western Iberian continental margin as well as some deeper reflections can also be identified within this basin, although they show some particular characteristics. The G.I.B. is bounded to the east by a major fault identified beneath the continental shelf and to the west by an alignment of highs (“Western Banks”). The structural framework of the area consists of NNW-SSE-trending normal faults cross-cut by NE-SW transfer faults. The inception of the G.I.B. probably ocurred during Triassic times. Within the Late Jurassic-Early Cretaceous rifting phase it probably experienced several extensional episodes, the most intense one being during Valanginian times. Evidence for compressional tectonic activity in this basin during Cenozoic times has also been found. When comparing the G.I.B. with the adjacent “deep Galicia margin” a gap in the timing of the main extensional events as well as some differences in the structural styles have been found. In a wider regional context, an integration of data about the timing of the processes of continental rifting and oceanic spreading along the whole western Iberian margin is consistent with a northward propagating rift for the Late Jurassic-Early Cretaceous phase.