File Name: the geology of england and wales .zip
The geology of Great Britain is renowned for its diversity. As a result of its eventful geological history, Great Britain shows a rich variety of landscapes across the constituent countries of England , Wales and Scotland.
This article is an abstract from a collection of papers originating from a meeting held in on the history of hydrogeology in Britain.
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Britain's first geological map
The geological structure of Great Britain is complex, resulting as it does from a long and varied geological history spanning more than two billion years. This piece of the Earth's crust has experienced several episodes of mountain building or ' orogenies ', each of which has added further complexity to the picture.
A wide range of geological structures occur across Britain and include examples at a variety of scales of:. Our understanding of Britain's large-scale structure has been gained over many decades by simple geological field survey together with an increasing range of technological methods including gravity surveys , seismic surveys , aeromagnetic surveys and other forms of remote sensing.
A useful approach to considering Britain's geological structure is to examine the various terranes from which it is composed. These are essentially continental fragments whose boundaries are generally defined by faults. Individual terranes typically contain suites of structures, the histories and form of which differ from those of neighbouring terranes. Each of these terranes form a part of the former continent of Laurentia whose southeastern margin is defined by the Iapetus Suture Zone, which runs parallel to the English-Scottish border, though some miles to its south.
Central to this composite terrane is the triangular-shaped Midlands Microcraton ; within it, the north-south aligned Malvern Line or 'Malvern Lineament' divides the Wrekin Terrane in the west from the Charnwood Terrane in the east. The Isle of Anglesey and parts of the Lleyn peninsula are deemed to be composed of numerous micro-terranes, known collectively as the Rosslare - Monian Terranes.
Northern England is characterised by a series of fault-bound blocks separated by sedimentary basins whose origin can be traced back to the Carboniferous period. It is separated from the Askrigg Block to the south by the Stainmore Trough. This latter block, coincident with the Yorkshire Dales , is defined to the west by the Dent Fault and to the south by the Craven Fault System. The Northumberland and Gainsborough Troughs lie to the north and south of these two blocks.
Another approach to the study of the geological structure of the area is through consideration of the variety of structures resulting from each of several orogenies or 'mountain-building' episodes which have taken place over geological history. Structures originating in one event may play a part in subsequent orogenic events and be modified by them.
Thus lines of crustal weakness commonly associated with, for example, the Caledonian Orogeny will often predate this particular mountain-building period, much as some of those created during this phase were reactivated during later events. The Caledonian Orogeny took place between about and million years ago as the former micro-continent of Avalonia collided obliquely with the former continent of Laurentia along a line approximating to the modern English-Scottish border.
This long drawn-out, multi-phase event resulted in innumerable geological structures, many of which have persisted to the present day and help to shape the landscapes of much of Britain, from South Wales northwards to the Shetland Islands. Key structures include:. Each of these structures is aligned northeast - southwest, albeit with the more northerly of them trending closer to NNE - SSW. A map or satellite photo readily reveals these major trends. There are hundreds of other lesser faults and folds which follow a similar alignment - a trend known as the Caledonoid trend.
The Variscan Orogeny was a complex affair whereby the former micro-continent of Armorica collided with Laurussia otherwise known as Euramerica or the Old Red Continent , followed by a further collision between Gondwana and the enlarged Laurussia. In Britain it resulted in a variety of geological structures across the southwest from Pembrokeshire and South Glamorgan in Wales to Devon and Cornwall.
Structures include:. The Alpine Orogeny began million years ago and continues to the present day. It comprises a series of collisions involving various micro-continents between northern Europe and Africa. Its effects are most evident in the Alps , Pyrenees , Carpathians and other mountain ranges of southern Europe , but the northernmost 'ripples' of this event have affected the structure of southern England.
Structures include;. From Wikipedia, the free encyclopedia. A wide range of geological structures occur across Britain and include examples at a variety of scales of: faults thrust faults folds sedimentary basins grabens and horsts unconformities Our understanding of Britain's large-scale structure has been gained over many decades by simple geological field survey together with an increasing range of technological methods including gravity surveys , seismic surveys , aeromagnetic surveys and other forms of remote sensing.
Main article: Caledonian orogeny. Main article: Variscan orogeny. Main article: Alpine orogeny. The Geological Society, London. Namespaces Article Talk. Views Read Edit View history. Help Learn to edit Community portal Recent changes Upload file. Download as PDF Printable version. Add links.
Geology of Great Britain
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By the end of , seven sheets were completed and, after consultation, the Treasury funded the Ordnance Geological Survey, then part of the Ordnance Survey. In , William Edmond Logan created and published the horizontal and vertical sections. The horizontal sections were meticulously surveyed on a scale of six inches to a mile while the vertical ones were usually at a scale of one inch to forty feet. By , nearly the whole of Somerset, the western half of Gloucestershire, the counties of Monmouth, Glamorgan, Carmarthen and Pembroke, and nearly the whole of Brecknock and Herefordshire together with part of Worcestershire had been mapped and published and by the whole of Wales had been completed. Mapping was still undertaken on the scale of one inch to one mile but, following the example in Ireland, the new mapping of the northern counties was done on six-inch to the mile scale field sheets.
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