Editing Derbyshire (section)

===Geology===
Derbyshire's solid geology can be split into two very different halves. The oldest rocks occur in the northern, more upland half of the county, and are mostly of [[Carboniferous]] age, comprising [[limestone]]s, [[gritstone]]s, [[sandstone]]s and [[shale]]s. In its north-east corner to the east of [[Bolsover]], there are also [[Magnesian Limestone]] rocks of Permian age. In contrast, the southern and more lowland half of Derbyshire contains much softer rocks, mainly [[mudstone]]s and sandstones of Permo-Triassic age, which create gentler, more rolling landscapes with few rock outcrops. Across both regions can be found drift deposits of [[Quaternary]] age – mainly terrace and river gravel deposits and boulder clays. Landslip features are found on unstable layers of sandstones and shales, with [[Mam Tor]] and [[Alport Castles]] being the best-known. Cemented screes and [[tufa]] deposits occur very rarely in the limestone dales and rivers, whilst cave systems have been created naturally in the limestone since Pleistocene times. A recently discovered cave chamber near [[Castleton, Derbyshire|Castleton]], named [[Titan (cave)|Titan]], is the deepest shaft and biggest chamber of any cave in Britain.<ref name="bbc">{{Cite news |work=BBC News |title=Cave boasts UK's biggest chamber |url=http://news.bbc.co.uk/2/hi/uk_news/england/leicestershire/6122884.stm |access-date=18 August 2015 |date=8 November 2006 |archive-url=https://web.archive.org/web/20160306165041/http://news.bbc.co.uk/2/hi/uk_news/england/leicestershire/6122884.stm |archive-date=6 March 2016 |url-status=live |df=dmy-all}}</ref>

The oldest rocks are Lower Carboniferous limestones of [[Dinantian]] age, which form the core of the White Peak within the Peak District National Park. Because northern Derbyshire is effectively an uplifted dome of rock layers that have subsequently eroded to expose older rocks in the centre of the [[Derbyshire Dome]], these are encircled by progressively younger limestone rocks, until they in turn give way on three sides to Upper Carboniferous shales, gritstones and sandstones of [[Namurian]] age.

[[File:Peak District Cross Section.gif|400px|thumb|center|A cross-section of northern Derbyshire, from west to east, showing the approximate structure of an eroded dome, with younger Coal Measure rocks to the east, and older limestone exposed in the centre]]
Younger still are the sandstones, shales and coal deposits found on the eastern flank of Derbyshire, forming the coal measures, which are of [[Westphalian (stage)|Westphalian]] age. All these rock layers disappear south of a line drawn between Ashbourne and Derby under layers of clays and sandstones ([[Mercia Mudstone Group]] and [[Sherwood Sandstone Group|Sherwood Sandstones]]) of Permo-Triassic age. Small amounts of carboniferous limestones, gritstones and coal measures reappear in the far south of Derbyshire from [[Ticknall]] (limestone) to [[Swadlincote]] (coal measures).<ref>[http://www.bgs.ac.uk/downloads/start.cfm?id=1615 "A Building Stone Atlas of Derbyshire & The Peak National Park"]. ''English Heritage''. September 2011. Retrieved 17 August 2015.</ref>

Some areas of the White Peak exhibit contemporaneous basalt flows (e.g. Ravens Tor at Millers Dale), as well as subsequent dolerite sill intrusion at a much later stage (e.g. near Tideswell Dale),<ref>[http://peaklandheritage.org.uk/index.asp?peakkey=00103521 "Rocks and Fossils"]. {{Webarchive |url=https://web.archive.org/web/20151002112716/http://peaklandheritage.org.uk/index.asp?peakkey=00103521 |date=2 October 2015}}. ''Peakland Heritage website''. Retrieved 20 August 2015.</ref> whilst mineralisation of the carboniferous limestone in a subsequent period created extensive lead and fluorite deposits which have formed a significant part of Derbyshire's economy, as did coal mining. Lead mining has been important here since Roman Times.<ref name="Geology">{{Cite web |url=http://www.peakdistrictinformation.com/features/geology.php |title=The Peak District is a very interesting area geologically |work=Peak District Information |publisher=Cressbrook Multimedia |year=2008 |access-date=17 August 2015 |archive-url=https://web.archive.org/web/20150905184536/http://www.peakdistrictinformation.com/features/geology.php |archive-date=5 September 2015 |url-status=live |df=dmy-all}}</ref> The more recent river gravels of the Trent valley remain a significant extractive industry today in south Derbyshire, as does the mining of limestone rock in central and northern parts of the county.<ref>[https://www.derbyshire.gov.uk/images/DD%20MLP%20Part%201_tcm44-189489.pdf "Derby and Derbyshire Minerals Local Plan"]. {{Webarchive |url=https://web.archive.org/web/20160304042104/https://www.derbyshire.gov.uk/images/DD%20MLP%20Part%201_tcm44-189489.pdf |date=4 March 2016}}. ''Derbyshire County Council and Derby City Council''. Adopted April 2000 (revised 2002, currently under review in 2015). Retrieved 17 August 2015.</ref> Coarse sandstones were once extensively quarried both for local building materials and for the production of gritstone grinding wheels for use in mills, and both former industries have left their mark on the Derbyshire landscape.