Correlation of the Lower Greensand Group (Woburn Sands and Carstone) of the Bedfordshire Province, England

Abstract

The late Aptian-early Albian Lower Greensand Group of the Bedfordshire Province is a series of sands with minor sandstone, silt, clay and ironstone. The sequence includes shallow, nearshore, strongly tidally-influenced sands, sandwaves and localized estuarine sands (channel and sandbar). A detailed correlation of the deposit across southern England from Buckinghamshire to Norfolk has shown two distinct depositional areas, the Bedford and Norfolk Basins. Detailed study has also made the recognition of a more refined subdivision possible, which comprises four units. Correlation techniques were varied and include assessing the gamma-ray signature of the subdivisions of the Lower Greensand. New palynological evidence, together with the sedimentological study, further refines the environment of deposition of the sands in the south Bedfordshire area to be that of an estuary mouth. The estuarine and the marine environment alternate in dominance in different parts of the succession. This interpretation goes some way in explaining the different character of the Lower Greensand in Bedfordshire compared to the rest of southern England. A new interpretation of the controls on sedimentation in this area during the late Aptian-early Albian is possible using the new refined stratigraphic subdivision. This shows that in addition to environmental factors there is a relationship between basement structure and the sedimentary character of the Lower Greensand.