Abstract
SUMMARY: Analysis of a late Ryazanian to early Barremian Speeton Clay section in a cored North Sea borehole has revealed a pattern of changing mineral composition that is believed to represent changes in sea-level, climate and palaeogeographical configuration. The lithological sequence can be broadly matched with that of the onshore Speeton Clay section, with precise onshore-offshore correlations being provided by sporadic bentonite layers. Because the factors controlling changes in the mineral assemblages are likely to have been of regional effect, the mineral stratigraphy established for the borehole sequence may prove to be of use not only in correlating within the North Sea marine realm, but also in relating the marine sequences to the paralic to non-marine Wealden sequences of southern England.