View source for Central England area - Geology

==Recent surface deposits==
At the surface there are widespread recent deposits of relatively recent origin, formed during the last million years and spanning the Ice Ages and Interglacial periods. These are known as superficial deposits and include sands, gravels, clays and peat laid down by former ice-sheets and rivers. These superficial deposits are less than 100 m in thickness. Examples include the glacial boulder clays, the sands and gravels deposited along the rivers and the peat deposits of the Fenlands. Most of the superficial deposits are soft and easily eroded, as they have not been deeply buried and consolidated to form strong rocks.

==Geology at depth==
Below the superficial deposits, or with just a cover of soil where such deposits are absent, are older rocks which geologists broadly split into two distinct types:

* The sedimentary bedrock geology is composed of quite hard rocks formed from 415 to 160 million years ago as layers of sediments which were deposited in shallow seas, deserts and vast river systems in times when Britain lay closer to the Equator and the climate and landscape were very different from those of today.
* The basement geology, which underlies the bedrock, is over 415 million years old and mainly comprises harder and denser rocks which have been strongly consolidated and folded. They include both rocks originally deposited as sediments and others that are products of volcanic activity or formed from the solidification of molten rock below ancient volcanoes.

[[Image:P902248.jpg|thumb|300px|right|Schematic cross-section of the geology of the Central England region from west to east. The alignment of the section and key are shown in '''Figure P902247'''. P902248.]][[Image:P902249.jpg|thumb|300px|left|Schematic cross-section of the geology of the Central England region from north to south. The alignment of the section and key are shown in '''Figure P902247'''. P902249.]]
In the course of the past 415 million years there have been periods when the area of the UK formed a landmass and was being eroded, and other periods when it was sinking and new layers of sediment were being deposited. The history of erosion and deposition has not been the same in all parts of the UK. In the Central region the oldest sedimentary bedrocks are similar to rocks occurring at the surface in parts of northern England, and include limestones, sandstones, shales and coal beds. These rocks were buried and deformed by the forces of continental plates moving against each other, and are referred to here as the older sedimentary bedrock. Subsequently, a younger sequence of sedimentary rocks, including limestones, sandstones and clays, was laid down and are known as the younger sedimentary bedrock. These include Jurassic rocks, comparable to those seen along the coast of Dorset and north Yorkshire. In the time between the end of deposition of the older sedimentary bedrock and the start of the deposition of the younger sedimentary bedrock, uplift and erosion took place. As a result, when deposition restarted the younger sediments were laid down on a variety of different older sediments. This situation where younger rocks rest directly on rocks of different older ages because of uplift and erosion is referred to by geologists as an unconformity.

In the central and western parts of the region, the bedrock geology is complex, with distinct areas separated by geological faults, where the rocks on each side of a fracture have moved relative to one another. In the east, younger rocks are tilted very gently towards the south-east and are more continuous. Over much of the region the sedimentary bedrock layers have a total thickness of around 1000 m, but this varies from about 200 m to nearly 5000 m. Throughout the region the sedimentary bedrock rests on a foundation of the older and harder basement rocks.''' Figures P902248 and P902249''' provide vertical sections through the geology to illustrate the patterns of variation across the area; these are referred to as geological cross-sections.


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