ABSTRACT Late Cenozoic growth of the Mount Diablo anticline in the eastern San Francisco Bay area, California, USA, has produced unique 3D exposures of stratigraphic relationships and normal faults that record Late Cretaceous uplift and early Tertiary extension in the ancestral California forearc basin. Several early Tertiary normal faults on the northeast flank of Mount Diablo have been correlated with structures that accommodated Paleogene subsidence of the now-buried Rio Vista basin north of Mount Diablo. Stepwise restoration of deformation at Mount Diablo reveals that the normal faults probably root into the “Mount Diablo fault,” a structure that juxtaposes blueschist-facies rocks of the Franciscan accretionary complex with attenuated remnants of the ophiolitic forearc basement and relatively unmetamorphosed marine forearc sediments. This structure is the local equivalent of the Coast Range fault, which is the regional contact between high-pressure Franciscan rocks and structurally overlying forearc basement in the northern Coast Ranges and Diablo Range, and it is folded about the axis of the Mount Diablo anticline. Apatite fission-track analyses indicate that the Franciscan rocks at Mount Diablo were exhumed and cooled from depths of 20+ km in the subduction zone between ca. 70−50 Ma. Angular unconformities and growth relations in the Cretaceous and Paleogene stratigraphic sections on the northeast side of Mount Diablo, and in the Rio Vista basin to the north, indicate that wholesale uplift, eastward tilting, and extension of the western forearc basin were coeval with blueschist exhumation. Previous workers have interpreted the structural relief associated with this uplift and tilting, as well as the appearance of Franciscan blueschist detritus in Late Cretaceous and early Tertiary forearc strata, as evidence for an “ancestral Mount Diablo high,” an emergent Franciscan highland bordering the forearc basin to the west. This outer-arc high is here interpreted to be the uplifted footwall of Coast Range fault. The stratigraphic and structural relations exposed at Mount Diablo support models for exposure of Franciscan blueschists primarily through syn-subduction extension and attenuation of the overlying forearc crust in the hanging wall of the Coast Range fault, accompanied by (local?) uplift and erosion of the exhumed accretionary prism in the footwall.

Abstract Widely distributed deep-water fan sandstones of early Tertiary age form the reservoir for one of the most successful and prolific plays in the North Sea and NE Atlantic margin. Stratigraphic interpretation of a large well database provides the basis for mapping sand distribution and depositional environments in these two hydrocarbon provinces. Sand thickness maps for five Paleocene–Lower Eocene plays illustrate the intimate relationship between pre-existing structural features and sand distribution and facies in the North Sea. Large-scale depositional environment mapping gives an insight into the similarities and differences between basin evolution and sand distribution in North Sea and NE Atlantic margin basins. Both provinces were affected by the same succession of pre-break-up and syn-break-up tectonic and magmatic events that led to early Eocene continental separation and the formation of the NE Atlantic. The impact of these events was muted within the North Sea, which was protected from Paleocene rifting on the NE Atlantic margin by the Scotland–Shetland hinterland and from Paleocene–early Eocene volcanism by its more distant location. However, it was the combination of tectonic and thermal uplift of this clastic source area that contributed the large volumes of sand that accumulated in both these provinces.