FACIES VARIATION IN THE CORALLIAN GROUP (U. JURASSIC) OF THE FARINGDON-SHELLINGFORD AREA (OXFORDSHIRE) AND THE ROCKGROUND BASE TO THE FARINGDON SPONGE GRAVELS (L. CRETACEOUS)

We describe the sedimentology of four cores which passed down from the Aptian Faringdon Sponge Gravels into several formations of the Oxford ian Corallian Group. The facies of the Corallian Group in the cores di ffer somewhat from those seen at outcrop at Shellingford and Stanford Quarries: biosparite lenses are absent from the Coral Rao, no unit of the Urchin Marls is present though the Osmington Oolite is noticably m uddier. as also is the Highworth Grit. At outcrop, the lower division (Shellingford Member) of the Highworth Grit is interpreted as deltaic distributary, point bar deposits which are truncated by an intraformat ional wedge of oolitic sands and clays floored by Diplocraterion. Intr a-Corallian Group faulting is suggested between deposition of the Osmi ngton Oolite and Coral Rag, with reactivation prior to cutting of the unconformity surface.