Oxford clay. The boundary between the Callovian and Oxfordian Stages is well exposed on the coast at Ham Cliff and is well-known for its ammonite faunas and contribution to Oxfordian biostratigraphy. Important individual features include the well-preserved aragonitic ammonites and nodule beds. In particular the Red Nodule Bed exposed at Furzy Cliff is associated with a beautifully preserved three dimensional ammonites and bivalves. The Dorset Oxfordian sections have contributed to significant publications and ongoing work in many fields. The Oxford Clay (Callovian) is hydrocarbon-rich and has produced fine faunas of marine invertebrates and reptiles. Callovian: upper Macrocephalus to Lamberti Zones.
The Kellaways Formation and Lower Oxford Clay are poorly exposed along the Fleet shore from East Fleet to near Tidmoor Point. They represent the initiation of the fourth major sedimentary rhythm (J4), which ends with the carbonates of the Corallian Beds (upper Oxfordian).
The Cornbrash is exposed at Shipmoor Point, Berry Knap and near East Fleet. This thin limestone comprises a shallow-water facies with abundant brachiopods, bivalves and other fauna. The faunas show a major change within the Cornbrash at which the Bathonian/Callovian boundary is drawn. Lower Cornbrash (Barry Member), Bajocian: Discus Zone: Upper Cornbrash (Fleet member), Callovian: Macrocephalus Zone.
Forest Marble.Discontinuously exposed just west of West Bay, between Burton Bradstock and Abbotsbury Castle, and along the shores of the Fleet. The overlying sequence from the mudstones of the Fuller’s Earth through mudstones and calcareous sands of the Forest Marble to the limestones of the Cornbrash represent the third major sedimentary cycle (J3) of the Jurassic and the Bathonian Stage.
The Frome Clay Limestone forms the uppermost reservoir in the Wytch Farm Oilfield. It includes richly fossiliferous horizons and fossil oyster beds. Bathonian: Zigzag Zone to lower Discus Zone.