Abstract: Inter-Basinal Correlation of Lower Jurassic Stratigraphic Events in Western Europe

Neil Parkinson, Stephen Hesselbo

Stratigraphic interpretations of the western European Lower Jurassic have historically placed great upon the coastal sections of Dorset and Yorkshire, England. New spectral gamma-ray data from these sections enable us to monitor anoxia, clay supply and proximal-distal relationships and result in a unified sequence-stratigraphic correlation between the two sections involving cycles of some 8 Ma duration.

We interpret the Dorset Blue Lias (planorbis to bucklandi Zones) as a starved facies with maximum starvation in the angulata Zone. Sediment supply increases at a basal semicostatum Zone downlap surface in Dorset, with maximum regression in the late Sinemurian. Earliest Pliensbachian flooding re-establishes distal facies in Dorset and Yorkshire, though a regressive cycle of jamesoni to ibex Zone age is detected in these distal facies. Davoei-margaritatus Zone regression sees the introduction of the first sand to both basins and at least three higher-frequency sedimentary cycles may be recognized in the expanded Dorset succession at this time. Backstepping characterizes the latest margaritatus and the spinatum Zones of both basins, leading to earliest Toarcian flooding and falciferum Zo e peak transgression, after which, progradation sees the return of sand to both basins in the levesquei Zone.

The cyclicity identified in the English sections has been sought in contrasting sections from Western Scotland, Portugal, Southern Germany, the Western Alps and the Northern North Sea. Data from these areas suggest, particularly for the Pliensbachian-Toarcian, that the cycles are at least pan-European in extent.

AAPG Search and Discovery Article #90986©1994 AAPG Annual Convention, Denver, Colorado, June 12-15, 1994