Cornbrash Formation

Geological formation in England / From Wikipedia, the free encyclopedia

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The Cornbrash Formation is a Middle Jurassic geological formation in England. It ranges in age from Bathonian to Callovian, the uppermost part of the Middle Jurassic.[1] Dinosaur remains are among the fossils that have been recovered from the formation, although none have yet been referred to a specific genus.[2] The name Cornbrash is an old English agricultural name applied in Wiltshire to a variety of loose rubble or brash which, in that part of the country, forms a good soil for growing corn. The name was adopted by William Smith for a thin band of shelly limestone which, in the south of England, breaks up in the manner indicated. Although only a thin group of rocks (10–25 feet c. 3–7 m), it is remarkably persistent; it may be traced from Weymouth to the Yorkshire coast, but in north Lincolnshire it is very thin, and probably dies out in the neighborhood of the Humber. It appears again, however, as a thin bed in Gristhorpe Bay, Cayton Bay, Wheatcroft, Newton Dale and Langdale. In the inland exposures in Yorkshire it is difficult to follow on account of its thinness, and the fact that it passes up into dark shales in many places the so-called clays of the Cornbrash, with Avicula echinata. The Cornbrash is of little value for building or road-making, although it is used locally; in the south of England it is not oolitic, but in Yorkshire it is a rubbly, marly, frequently ironshot oolitic limestone. In Bedfordshire it has been termed the Bedford limestone.[3]

Quick facts: Cornbrash Formation, Type, Unit of, Underlies...
Cornbrash Formation
Stratigraphic range: Bathonian-Callovian 168–164 Ma
Cornbrash Formation at Shorncote Quarry in Gloucestershire
TypeGeological formation
Unit ofGreat Oolite Group
UnderliesKellaways Formation, Cayton Clay Formation
OverliesForest Marble Formation, Blisworth Clay Formation, Scalby Formation
Thickness0-10.5 m
CountryFlag_of_the_United_Kingdom.svg UK
ExtentDorset coast to Yorkshire coast