Revision of the stratigraphy of the Inferior Oolite at Frogden Quarry, Oborne, Dorset, UK

摘要

The stratigraphy of part of the Inferior Oolite Formation at Frogden Quarry, Dorset, U.K. is revised based on new ammonite evidence. In the Lower Inferior Oolite Formation the Oborne Ironshot Member is erected to include beds 4 to 5 of the section (Sauzei and Humphriesianum zones). Oborne is designated as the type locality. For part of the Upper Inferior Oolite Formation of the Inferior Oolite Group in the Sherborne area of Dorset a new formal lithostratigraphical scheme is proposed, with the Sherborne Limestone Member at the base (including the basal Acanthothyris Beds, Sherborne Building Stone Beds and Redhole Lane Beds) followed by the Combe Limestone Member. The Sherborne Limestone Member is shown to belong to one ammonite faunal horizon, Bj-24a Garantiana dichotoma, of the Garantiana Zone. In the Combe Limestone Member a new ammonite faunal horizon Bj-24b Garantiana subgaranti is described for the first time in England. Faunal horizons Bj-25 Garantiana tetragona and Bj-26 Parkinsonia rarecostata are confirmed in the Sherborne area. A mechanism is suggested for the deposition of the Sherborne Limestone Member.