Category:16. Bristol and Gloucester district

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This account provides a broad perspective of the geology of the Bristol and Gloucester region, covering most of Somerset, Bristol, Bath, south Gloucestershire and the Forest of Dean. Figure 1 provides a geological sketch map and key of this region showing the rock types occurring in relation to the major towns and cities. The region is one of the most geologically varied parts of the country, with almost every geological time period represented. This account outlines the geology to a depth of at least a kilometre and summarises the current and historical use of the geological resources in the area.

It is perhaps no coincidence that William Smith, the ‘Father of English Geology’ produced the World’s first geological map in this region, based on the country around Bath. The region also hosts some well known geological sites including Cheddar Gorge, the Bath Hot Springs and the Avon Gorge. Exploitation for mineral resources including lead, zinc, iron, coal and limestone (for aggregate and building stone) has taken place since Roman times. Consequently, there is a long heritage of geological research. The surface geology is reasonably well known, particularly from surface outcrops and especially in coalfield areas where records from coal mines, deep boreholes and exploration surveys provide information on the geology up to 300 m below the surface. Although geophysical seismic surveys which provide information on the rocks by sending sound waves through the ground have provided some data, the lack of deep boreholes means much of the geological structure and details of the rocks themselves below this depth remains poorly understood.

Geologically recent surface deposits

The Bristol and Gloucester region lay just outside the extent of the ice-sheets that have dominated the evolution of the British landscape over the past 2-3 million years; so there are no extensive glacial sediments preserved within this region despite it experiencing prolonged periods of extreme cold. The dominant geological process during this time has been one of uplift of the land; this has led to the erosion of the landscape, with the main rivers cutting deep valleys and depositing sand and gravel deposits along their valley floors. Since the end of the last glacial event in Britain around 11,000 years ago, extensive deposits of clay and peat up to 10m thick have built up on the Somerset Levels and along the Severn Estuary.

Subcategories

This category has the following 3 subcategories, out of 3 total.
The number of included categories (C), pages (P) and files (F) is stated in brackets.