Abstract The Guyana Basin formed during the Jurassic opening of the North Atlantic. The basin margins vary in tectonic origin and include the passive extensional volcanic margin of the Demerara Plateau in Suriname, an oblique extensional margin inboard at the Guyana–Suriname border, a transform margin parallel to the shelf in NW Guyana, and an ocean–ocean margin to the NE, which morphed from transform to oblique extension. Plate reconstructions suggest rifting and early seafloor spreading began with NNW/SSE extension ( c. 190–160 Ma) but relative plate motion later changed to NW/SE. The fraction of magmatic basin floor decreases westwards and the transition from continental to oceanic crust narrows from 200 km in Suriname to less than 50 km in Guyana. The geometry and position of the onshore Takutu Graben suggest it formed a failed arm of a Jurassic triple junction that likely captured the Berbice river during post-rift subsidence and funneled sediment into the Guyana Basin. Berriasian to Aptian shortening caused crustal-scale folds and thrusts in the NE margin of the basin along with minor inversions of basin margin and basin-segmenting faults. Stratigraphically trapped Liza trend hydrocarbon discoveries are located outboard of inverted basement faults, suggesting a link between transform margin structure and their formation.

Abstract This paper presents a new interpretation of well-known outcrops on the south coast of the Bristol Channel at Watchet in southern England. It is prompted by our recent experience of high-quality three-dimensional seismic datasets from areas such as the Gulf of Mexico and Brazil which are dominated by salt tectonics. Previous structural interpretations of the Watchet outcrops were explained in terms of extension, inversion and strike-slip tectonics. We suggest that some of the structures in the area are not easily explained by any of these mechanisms, but that they are collapse structures associated with salt withdrawal and imply salt diapirism during the Late Triassic and Early Jurassic.