Gamma-ray log correlation and interpretation of Fitton’s and Casey’s stratigraphy with offshore borehole 99/16-1

Abstract

The Chale Bay type section of the Lower Greensand Group (LGS) Atherfield Clay, Ferruginous Sands and Sandrock formations is characterised by members, bounded by hiatuses, formerly recognised (if not named as such) by Fitton as his ‘groups’ and Casey in defining ammonite zone and sub-zone boundaries. Subsequent work has shown that some of the formations of the LGS are recognised elsewhere on the Isle of Wight, in southern England and in northern France. Likewise, some members of the Atherfield Clay and Ferruginous Sands formations can be recognised beyond the Chale Bay type section. In this work, we have measured outcrop gamma-ray emission from the type section: gamma-ray peaks recognised on all datasets are used to attempt a correlation of the Lower Greensand Group between the Isle of Wight and an offshore borehole (99/16-1). This is partially successful, showing that Fitton and Casey’s stratigraphy maybe recognised basin-wide.