Review of Oxfordian (Upper Jurassic) sequence stratigraphy of England (Yorkshire to Dorset) and a comparison with the North Sea Basin

A critical investigation is made of the unconformities reportedly present in Oxford Clay Formation and Corallian Group (Jurassic, Oxfordian) strata in central and southern England. A revised cross-section through strata belonging to the coeval Coralline Oolite Group and Upper Calcareous Grit and Ampthill Clay formations of the Tabular Hills, North Yorkshire is used to show the lateral extent of unconformities within these strata. There is definite correlation of only two of these unconformities present in Yorkshire with similar erosive episodes in the equivalent strata in southern England. The extent to which the sequences of strata delimited by these unconformities can be correlated with sequences defined in the North Sea Basin is discussed. The tectonic nature of the unconformities is evident, as there was not a simple drop in relative sea-level causing erosion. Erosion occurred down to deeper levels in certain areas, this being caused by differential uplift. The reasons for this phenomenon are still to be determined.