British regional geology: Bristol and Gloucester region

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The British regional geology: Bristol and Gloucester region has been converted to a series of articles for this wiki. The book is available for purchase at the BGS Online Shop Its full reference is:

Green, G W. 1992. British regional geology: Bristol and Gloucester region (Third edition). (London: HMSO for the British Geological Survey.)

British Regional Geology: Central England. Cover image. P894510.

Contents

Introduction

Physiography
Scenery
Early geological works

Cambrian

Breadstone Shales
Micklewood Beds

Silurian

Tortworth
Sharpness
Newnham
Wickwar
Mendips
Batsford (Lower Lemington) Borehole

Old Red Sandstone (Silurian–Carboniferous)

Stratigraphy
Lower Old Red Sandstone
Upper Old Red Sandstone
West of River Severn
Sharpness–Thornbury
Bristol
Bath
Mendip Hills

Lower Carboniferous (Dinantian)

Classification
Sedimentation
Stratigraphy
Lower Limestone Shale
Black Rock Limestone
Clifton Down Group and Hotwells Group
Arenaceous facies in the Clifton Down Group and Hotwells Group
Cannington Park
Igneous rocks

Upper Carboniferous (Namurian)

Bristol area
Southern areas
Western areas

Upper Carboniferous (Westphalian and Stephanian)

Classification
Conditions of formation of the Coal Measures
Plants of the Coal Measures
Fauna of the Coal Measures
The coal basins
Other Coal Measures occurrences

Intra-Palaeozoic earth movements

The Malvern 'Axis'
Pre-Carboniferous movements
Intra-Carboniferous movements
Permo-Carboniferous movements

Permo-Triassic

Classification
Conditions of deposition
Permo-Triassic Sandstones
Mercia Mudstone Group
Penarth Group

Lower Jurassic

Classification
Lower Lias
Middle Lias
Upper Lias

Middle Jurassic (Inferior Oolite Group)

Classification
Depositional pattern
Lower and Middle Inferior Oolite
Upper Inferior Oolite

Middle Jurassic (Great Oolite Group)

Classification
Depositional pattern
Stratigraphy
Dorset—Somerset Province
Bath—Cotswolds Province
Tormarton—Nailsworth
Minchinhampton
Cirencester—North Cotswolds
Cornbrash

Middle/Upper Jurassic (Kellaways Beds and Oxford Clay)

Cretaceous

Post-Variscan structure and sedimentation

Main structural elements
Post-Bathonian structural history

Quaternary

Events in the Lower Severn and Avon valleys
Glacial deposits
Terrace gravels
Head, including Fan Gravel
Alluvium
Raised beach deposits
Cave and fissure deposits

Economic geology

Coal
Roadstone, aggregate and lime
Iron
Lead and zinc ores
Manganese
Brick, tile and pottery clays
Oil shales
Water supply
Bath–Bristol hot springs

Foreword to the third edition

The second edition of the Bristol and Gloucester regional guide was produced in 1948, but since that time much new information has been collected and there was a need to produce this third edition to incorporate the information derived from mapping carried out by the British Geological Survey and exploration undertaken by the coal, petroleum and water industries.

The Bristol and Gloucester district is one of the geologically most varied parts of Britain. This in turn provides the scenic variety for which the area is renowned, including the deep gorges of Cheddar Gorge and the Wye Valley, prominent escarpments such as those of the Cotswolds and the Forest of Dean, and the wide valleys flanking the Thames and the Severn. The area is also famous for its caves, such as Wookey Hole. It is the combination of a congenial environment and mineral resources which has attracted people to the Bristol and Gloucester district since the days of early man.

The geology of the district, as outlined in this volume, provides a fascinating insight into the history and evolution of the area, extending back more than 500 million years. The region contains some of the oldest rocks exposed in southern England whilst at the other end of the geological timescale, because the region was located near the edge of the massive ice sheets which at times covered much of Britain, it provides us with a dramatic picture of changing environments over the last two million years.

Elucidating the geological history is essential if we are to understand the controls on the distribution of mineral resources in the region. These resources include lime and aggregate, which are extracted in large quantities, and resources which are not presently mined, such as coal, evaporites, ironstone, clay, lead, (worked from Roman times), zinc and oil shales. Groundwater is one of the most important and widely used resources in the regionthe geological investigations undertaken by the BGS in the region will help to conserve this important resource for present and future generations. Bath and other thermal waters have been the subject of recent investigations which have shown that their composition (and temperature) are closely related to their underlying geology.

The first two editions of this regional guide were very popular and I am confident that the third edition will be equally popular with geologists, planners, environmentalists, explorers, tourists and all those interested in the geological development of this beautiful area and its conservation.

British Geological Survey
Keyworth
Nottingham NG12 5GG
1 March 1992
Peter J Cook, DSc
Director


Acknowledgements

The author wishes to acknowledge the great help he has received from numerous colleagues on the Survey in writing this account in particular to Dr P M Allen and Mr B J Williams for editing the text, and to members of the palaeontological and petrographical departments for evaluating appropriate sections. Special mention must also be made of Mr R J Wyatt, not only for checking the entire work and seeing it through the press but also for supplying valuable help with Chapter 12 (Great Oolite Group). The figures were prepared by Mr J W Arbon. Thanks are due to the Council of the Geological Society of London for permission to use and adapt Figure 15 (from the Journal of the Geological Society, 1983), and to Messrs Blackie for Figures 32 and 33.