The purpose of this paper is to provide a general overview of the geology and geophysics of western Iberia, and in particular of the western Portuguese Margin, in order to help the reader to integrate the other papers in this volume into a more general geological, tectonic, and magmatic framework. Thus, we review the geoscientific literature that describes both the onshore and offshore history and development of the margin. No attempt is made here to address the issue of the conjugate margin off the Grand Banks of Canada, the history of which, until continental breakup occurred, must have been very similar to what is described here. The nature of the Grand Banks shelf and margin has been extensively described elsewhere (e.g., Keen and de Voogd, 1988; Tankard and Welsink, 1989; Welsink et al., 1989; Tucholke et al., 1989; Srivastava et al., 1990a; Srivastava and Verhoef, 1992), particularly in view of the very extensive exploration for hydrocarbons on the Grand Banks shelf.
We lay particular emphasis on bringing together the onshore and offshore geology and geophysics, an aspect of this margin that in the past has not received as much attention as it deserves. In spite of the different nature and density of the information available from observations on land and at sea, a coherent and consistent picture emerges of the history of this margin, which is perhaps unique among nonvolcanic margins in the degree to which both the onshore and offshore geology and geophysics are now understood.