Snowdon Hill Quarry

Also within

Somerset County

Condition (Natural England)

Geology & landscape

Mining / Industrial: Quarry · Geological Period: Cretaceous · Rock Type: Chalk, Chert, Flint, Greensand, Limestone

Description

Area, 0.6 ha. 1.6 ac. Description Snowdon Hill Quarry is of great importance because of the rock exposures which it provides, through the units known as the Upper Greensand and the Chalk. In particular, the fossils which occur within both of these units are of great significance to geological study since they are both unique and exceptionally well preserved; the site is therefore a key locality for the study of palaeontology in Britain. During the Cretaceous part of geological time, some 100 million years ago, southern England lay beneath an extensive sea in which a series of marine sandstones and limestones, containing beds of chert a form of flint were laid down; these rocks are known as the Upper Greensand. Snowdon Hill Quarry provides the best section in the westernmost basin of sedimentation of the Upper Greensand and of the Chalk which lies above it. The sandy limestones and cherts of the Upper Greensand are notable not only for the regular layering of chert bands which occurs but also because of the assemblage of fossil crustaceans which they contain and which have been found nowhere else in Britain. The Upper Greensand is overlain by the basal part of the Chalk with, at its base, a richly fossiliferous band of sandy limestone known as the Lower Chalk basement bed. This band contains a very rich and diverse assemblage of fossils, preserved as the mineral calcium phosphate, which is of great importance in palaeontological studies. The unit has been dated to the subdivision of the Chalk known as the Turrilites a cutus Zone, named after one of the characteristic fossils which occurs