Changes in the provenance of pebbly detritus in southern Britain and northern France associated with basin rifting

Abstract: Stratigraphical nd geographical variations in the composition of pebble suites in Upper Jurassic and Lower Cretaceous rocks in southern Britain and northern France provide a means for studying both local and regional changes in tectonic conditions associated with basin development. Local variations in pebble suites provide evidence of major fault-associated uplift and erosion of intrabasinal and basin-margin highs during earliest Cretaceous times, and the subsequent post-faulting subsidence and marine onlap in mid-Cretaceous times. Regional provenance studies have demonstrated that the Upper Jurassic and Lower Cretaceous pebble suites of southern Britain and Normandy are separable into six assemblages. Assemblage 1 is dominated by Carboniferous shelf chert, and is typical of Upper Jurassic pebble suites in Oxfordshire and Wiltshire, and Cretaceous pebble suites reworked from these older pebble beds. This detritus was probably derived from the western margin of the Anglo-Brabant Massif. Assemblage 2 which is quartz dominated, includes Carboniferous basinal chert an