Ham Hill

Also within

Somerset County

Condition (Natural England)

Geology & landscape

Geological Period: Jurassic · Rock Type: Limestone

Description

Area, 11.1 ha. 27.6 ac. Description Ham Hill is important because of the exposures of the sandy limestone known as Ham Hill Stone which occur here. The stone is restricted to a small area in the Ham Hill district and is particularly important to geologists because of the assemblages of fossils which it contains, the sedimentary features which it displays and the way it relates to other rocks of equivalent age in the close vicinity. During early Jurassic times, some 180 million years ago, southern England lay beneath a shallow sea in which a series of marine sediments accumulated. The rocks seen at Ham Hill were laid down in the part of the early Jurassic known as the Toarcian Stage and are an unusual local development of massive limestones which occur in a restricted area around Ham Hill. When the rocks are followed away from Ham Hill they can be seen to change laterally into a thick series of rocks known as the Yeovil and Bridport Sands, which were laid down at the same time as the Ham Hill Stone but under different environmental conditions. This observation, together with detailed study of the fossil ammonites and brachiopods which occur within the Ham Hill Stone and also with study of the sedimentary features of the stone, enable geologists to build up a detailed understanding of the evolution of southern England during early Jurassic times.