The stratigraphy of the Kimmeridge Clay Formation (Upper Jurassic) in the RGGE Project boreholes at Swanworth Quarry and Metherhills, south Dorset

Abstract

Three continuously cored boreholes were drilled in the Kimmeridge Clay Formation in south Dorset to provide unweathered samples for a multidisciplinary study of late Jurassic rhythmic sedimentation and its possible causes. Taken together, the borehole cores provide the first complete sequence through the Kimmeridge Clay and the Kimmeridgian Stage in their type area. The cores have been correlated in detail with the succession exposed in the nearby Kimmeridge cliffs and other sections in south Dorset, as well as with those proved in borehole sections elsewhere in southern and eastern England. The cores have enabled the current chronostratigraphical classification of the Kimmeridge Clay to be extended to the top of the formation, covering strata that are poorly exposed at outcrop. Four types of small-scale rhythm are present within the formation, each of which can be related to the sequence stratigraphy. Only one of these is organic rich and of importance as an oil-source rock