Forest Marble Formation


The Forest Marble is a geological formation in England. Part of the Great Oolite Group, it dates to back to the late Bathonian stage of the Middle Jurassic.

Bradford Clay

Bradford Clay in geology, is a thin, rather inconstant bed of clay or marl situated in England at the base of the Forest Marble, the two together constituting the Bradfordian group in the Bathonian series of Jurassic rocks. The term "Bradford Clay" appears to have been first used by J. de. C. Sowerby in 1823 as an alternative for W. Smith's "Clay on Upper Oolite". The clay came into notice late in the 18th century on account of the local abundance of the crinoid Apiocrinus Parkinsoni. It takes its name from Bradford-on-Avon in Wiltshire, whence it is traceable southward to the Dorset coast and northward towards Cirencester.
It may be regarded as a local phase of the basement beds of the Forest Marble, from which it cannot be separated upon either stratigraphical or paleontological grounds. It is seldom more than 10 feet thick, and it contains, as a rule, a few irregular layers of limestone and calcareous sandstone. The lowest layer is often highly fossiliferous; some of the common forms being Arca minuta, Ostrea gregaria, Waldheimia digona, Terebratula coarctata and Cidaris bradfordensis.

Lithology

The primary lithology of the formation typically consists of greenish grey silicate mudstone, with lenticular cross bedded limestone units deposited in a marine setting.

Dinosaurian fauna

Ornithischians

Saurischians

Microvertebrate fauna

Despite the formation being nearly entirely marine, at several localities abundant remains of terrestrial microvertebrates are found, the primary locality being the Kirtlington Mammal Bed near Kirtlington, Oxfordshire. Another important locality is Watton Cliff in Dorset.

Amphibians

Turtles

Choristoderes

Lepidosauromorphs

Crocodyliformes

Mammaliamorphs

Footnotes