The Upper Jurassic sequence at Rid's Hill, Brill, Buckinghamshire, and the age of the Brill Serpulite Bed

Abstract

Geological mapping in the Thame district (Oxfordshire and Buckinghamshire) has led to a reassessment of the stratigraphy of beds formerly exposed in the brickpit at Rid's Hill near Brill, best known for the elusive presence of the Brill Serpulite Bed. The brickpit showed Ampthill Clay (Upper Oxfordian) and Kimmeridge Clay (mainly Lower Kimmeridgian); the contact between the two formations is now believed to be faulted. The Brill Serpulite Bed is in the Regulare Zone (Upper Oxfordian). Rid's Hill is capped by sands of the Pectinatus Zone (Upper Kimmeridgian) but the remainder of the succession is of normal clay facies and is correlatable with sequences elsewhere in southern and central England. Sections recorded during the construction of the nearby Great Western Railway showed Ampthill Clay underlain by Oakley Member and West Walton Formation. Stratigraphic overlap of the brickpit and railway sections is demonstrated.