: ''This article describes the

geology Geology () is a branch of natural science concerned with Earth and other astronomical objects, the features or rocks of which it is composed, and the processes by which they change over time. Modern geology significantly overlaps all other Ear ...

of the

ceremonial county The counties and areas for the purposes of the lieutenancies, also referred to as the lieutenancy areas of England and informally known as ceremonial counties, are areas of England to which lords-lieutenant are appointed. Legally, the areas i ...

Durham Durham most commonly refers to: *Durham, England, a cathedral city and the county town of County Durham *County Durham, an English county *Durham County, North Carolina, a county in North Carolina, United States *Durham, North Carolina, a city in No ...

. It includes the

borough A borough is an administrative division in various English-speaking countries. In principle, the term ''borough'' designates a self-governing walled town, although in practice, official use of the term varies widely. History In the Middle Ag ...

s of

Darlington Darlington is a market town in the Borough of Darlington, County Durham, England. The River Skerne flows through the town; it is a tributary of the River Tees. The Tees itself flows south of the town. In the 19th century, Darlington underwen ...

Hartlepool Hartlepool () is a seaside and port town in County Durham, England. It is the largest settlement and administrative centre of the Borough of Hartlepool. With an estimated population of 90,123, it is the second-largest settlement in County ...

and

Stockton-on-Tees Stockton-on-Tees, often simply referred to as Stockton, is a market town in the Borough of Stockton-on-Tees in County Durham, England. It is on the northern banks of the River Tees, part of the Teesside built-up area. The town had an estimated ...

but not those former northeastern parts of the county which are now in the county of

Tyne and Wear Tyne and Wear () is a metropolitan county in North East England, situated around the mouths of the rivers Tyne and Wear. It was created in 1974, by the Local Government Act 1972, along with five metropolitan boroughs of Gateshead, Newcastl ...

.'' The geology of County Durham in northeast

England England is a country that is part of the United Kingdom. It shares land borders with Wales to its west and Scotland to its north. The Irish Sea lies northwest and the Celtic Sea to the southwest. It is separated from continental Europe b ...

consists of a

basement A basement or cellar is one or more floors of a building that are completely or partly below the ground floor. It generally is used as a utility space for a building, where such items as the furnace, water heater, breaker panel or fuse box, ...

of Lower

Palaeozoic The Paleozoic (or Palaeozoic) Era is the earliest of three geologic eras of the Phanerozoic Eon. The name ''Paleozoic'' ( ;) was coined by the British geologist Adam Sedgwick in 1838 by combining the Greek words ''palaiós'' (, "old") and '' ...

rocks overlain by a varying thickness of

Carboniferous The Carboniferous ( ) is a geologic period and system of the Paleozoic that spans 60 million years from the end of the Devonian Period million years ago ( Mya), to the beginning of the Permian Period, million years ago. The name ''Carbonifero ...

and Permo-

Triassic The Triassic ( ) is a geologic period and system which spans 50.6 million years from the end of the Permian Period 251.902 million years ago ( Mya), to the beginning of the Jurassic Period 201.36 Mya. The Triassic is the first and shortest period ...

sedimentary rock Sedimentary rocks are types of rock that are formed by the accumulation or deposition of mineral or organic particles at Earth's surface, followed by cementation. Sedimentation is the collective name for processes that cause these particles ...

s which dip generally eastwards towards the

North Sea The North Sea lies between Great Britain, Norway, Denmark, Germany, the Netherlands and Belgium. An epeiric sea on the European continental shelf, it connects to the Atlantic Ocean through the English Channel in the south and the Norwegian S ...

. These have been intruded by a

pluton In geology, an igneous intrusion (or intrusive body or simply intrusion) is a body of intrusive igneous rock that forms by crystallization of magma slowly cooling below the surface of the Earth. Intrusions have a wide variety of forms and com ...

, sills and dykes at various times from the

Devonian The Devonian ( ) is a geologic period and system of the Paleozoic era, spanning 60.3 million years from the end of the Silurian, million years ago (Mya), to the beginning of the Carboniferous, Mya. It is named after Devon, England, whe ...

Period to the

Palaeogene The Paleogene ( ; also spelled Palaeogene or Palæogene; informally Lower Tertiary or Early Tertiary) is a geologic period and system that spans 43 million years from the end of the Cretaceous Period million years ago ( Mya) to the beginning o ...

. The whole is overlain by a suite of unconsolidated deposits of

Quaternary The Quaternary ( ) is the current and most recent of the three periods of the Cenozoic Era in the geologic time scale of the International Commission on Stratigraphy (ICS). It follows the Neogene Period and spans from 2.58 million years ...

age arising from

glaciation A glacial period (alternatively glacial or glaciation) is an interval of time (thousands of years) within an ice age that is marked by colder temperatures and glacier advances. Interglacials, on the other hand, are periods of warmer climate betw ...

and from other processes operating during the post-glacial period to the present. The geological interest of the west of the county was recognised by the designation in 2003 of the

North Pennines The North Pennines is the northernmost section of the Pennine range of hills which runs north–south through northern England. It lies between Carlisle to the west and Darlington to the east. It is bounded to the north by the Tyne Valley and ...

Area of Outstanding Natural Beauty An Area of Outstanding Natural Beauty (AONB; , AHNE) is an area of countryside in England, Wales, and Northern Ireland, that has been designated for conservation due to its significant landscape value. Areas are designated in recognition of thei ...

as a

European Geopark The European Geoparks Network (EGN) functions as the regional organization of the Global Geoparks Network (GGN) and the UNESCO International Geosciences and Geoparks Programme (UNESCO-IGGP). Its main objective is to ensure cooperation between geop ...

. The word 'geology' may be traced back to a coinage of

Richard de Bury Richard de Bury (24 January 1287 – 14 April 1345), also known as Richard Aungerville or Aungervyle, was an English priest, teacher, bishop, writer, and bibliophile. He was a patron of learning and one of the first English collectors of books. ...

who was a

Bishop of Durham The Bishop of Durham is the Anglican bishop responsible for the Diocese of Durham in the Province of York. The diocese is one of the oldest in England and its bishop is a member of the House of Lords. Paul Butler has been the Bishop of Durham ...

in the 14th century. He introduced the term ''geologia'' in his work ''

The Philobiblon ''The Philobiblon'' is a collection of essays concerning the acquisition, preservation, and organization of books written by the mediaeval bibliophile Richard de Bury shortly before his death in 1345. The purposes of the ''Philobiblion'' were "to ...

'' which he explained as 'the earthly science'.

Ordovician

The oldest rocks at or near the surface within County Durham are

Ordovician The Ordovician ( ) is a geologic period and System (geology), system, the second of six periods of the Paleozoic Era (geology), Era. The Ordovician spans 41.6 million years from the end of the Cambrian Period million years ago (Mya) to the start ...

age (485 - 443 Ma)

Skiddaw Group ''For the Skiddaw group of hills, see Skiddaw Group'' The Skiddaw Group is a group of sedimentary rock formations named after the mountain Skiddaw in the English Lake District. The rocks are almost wholly Ordovician in age ( Tremadoc through Are ...

rocks found in a small

inlier An inlier is an area of older rock (geology), rocks surrounded by younger rocks. Inliers are typically formed by the erosion of overlying younger rocks to reveal a limited outcrop, exposure of the older underlying rocks. Fault (geology), Faulting o ...

near Cronkley Fell in upper

Teesdale Teesdale is a dale, or valley, in Northern England. The dale is in the River Tees’s drainage basin, most water flows stem from or converge into said river, including the Skerne and Leven. Upper Teesdale, more commonly just Teesdale, falls ...

. They are recorded as the

Skiddaw Slate Skiddaw slate is an early Ordovician metamorphosed sedimentary rock, as first identified on the slopes of Skiddaw in the English Lake District. The base of this series is unknown. The thickness could, therefore, amount to several thousand feet of ...

s, better known from the

Lake District The Lake District, also known as the Lakes or Lakeland, is a mountainous region in North West England. A popular holiday destination, it is famous for its lakes, forests, and mountains (or ''fells''), and its associations with William Wordswor ...

50 km to the west. A small quarry in these

phyllite Phyllite ( ) is a type of foliated metamorphic rock created from slate that is further metamorphosed so that very fine grained white mica achieves a preferred orientation.Stephen Marshak ''Essentials of Geology'', 3rd ed. It is primarily compo ...

s was worked at one time to make slate pencils. Overlying these are

pyroclastic Pyroclastic rocks (derived from the el, πῦρ, links=no, meaning fire; and , meaning broken) are clastic rocks composed of rock fragments produced and ejected by explosive volcanic eruptions. The individual rock fragments are known as pyroc ...

rocks thought to belong to the

Borrowdale Volcanic Group The Borrowdale Volcanic Group is a group of igneous rock formations named after the Borrowdale area of the Lake District, in England. They are Caradocian (late Ordovician) in age (roughly 450 million years old). It is thought that they represent t ...

. No rocks from the succeeding

Silurian The Silurian ( ) is a geologic period and system spanning 24.6 million years from the end of the Ordovician Period, at million years ago ( Mya), to the beginning of the Devonian Period, Mya. The Silurian is the shortest period of the Paleozo ...

Period (443 - 419 Ma) are seen at outcrop in the county.

Devonian

No rocks of

age (419 - 359 Ma) are seen at outcrop in the county though a

, the

Weardale Granite The North Pennine Batholith, also known as the Weardale Granite is a granitic batholith lying under northeast England, emplaced around 400 million years ago in the early Devonian.Kimbell, G.S., B. Young, D. Millward and Q. G. Crowley (2010). 'Th ...

forming the North Pennine Batholith was intruded into Lower

rocks around 410 million years ago during the Devonian Period. It forms a part of the larger 'North of England Plutonic Suite', whose members (which include the

granite Granite () is a coarse-grained (phaneritic) intrusive igneous rock composed mostly of quartz, alkali feldspar, and plagioclase. It forms from magma with a high content of silica and alkali metal oxides that slowly cools and solidifies undergro ...

s at Shap and Skiddaw) were emplaced during the

Caledonian Orogeny The Caledonian orogeny was a mountain-building era recorded in the northern parts of the British Isles, the Scandinavian Mountains, Svalbard, eastern Greenland and parts of north-central Europe. The Caledonian orogeny encompasses events that occ ...

. The buoyancy of this

batholith A batholith () is a large mass of intrusive igneous rock (also called plutonic rock), larger than in area, that forms from cooled magma deep in Earth's crust. Batholiths are almost always made mostly of felsic or intermediate rock types, such ...

(it is less dense than the rock into which it was intruded) is considered to be responsible for the existence of the

Alston Block The Alston Block is a term used by geologists to describe the geological structure of the North Pennines of northern England and which forms a part of the Pennine Block & Basin Province which originated during the Carboniferous period. It is defin ...

which coincides with the

and which is essentially an eastward dipping horst bounded to the west (outside of County Durham) by the Pennine Fault System, to the north by the Stublick and Ninety Fathom faults (in Northumberland) and by the Butterknowle Fault and Stainmore Trough to the south.

Carboniferous

There is a thick succession of rocks in County Durham which originated during the

Period (359 - 299 Ma). The detail of the rock succession varies from one part of the county to another and in no one location is the entire sequence detailed below in place. The sequence over the Alston Block is generally thinner than elsewhere. The western half of the county forms a part of the Pennine range of hills which are formed largely by the

sandstone Sandstone is a clastic sedimentary rock composed mainly of sand-sized (0.0625 to 2 mm) silicate grains. Sandstones comprise about 20–25% of all sedimentary rocks. Most sandstone is composed of quartz or feldspar (both silicates) ...

s and

limestone Limestone ( calcium carbonate ) is a type of carbonate sedimentary rock which is the main source of the material lime. It is composed mostly of the minerals calcite and aragonite, which are different crystal forms of . Limestone forms whe ...

s of the

Great Scar Limestone The Great Scar Limestone Group is a lithostratigraphy, lithostratigraphical group (stratigraphy), term referring to a succession of generally fossiliferous rock stratum, strata which occur in the Pennines in northern England and in the Isle of Ma ...

and overlying

Yoredale Wensleydale is the dale or upper valley of the River Ure on the east side of the Pennines, one of the Yorkshire Dales in North Yorkshire, England. It is one of only a few Yorkshire Dales not currently named after its principal river, but t ...

groups. Further east it is the younger Coal Measures rocks which are found at the surface. Further east again the Carboniferous succession is overlain by younger rocks but they are present at increasing depth to the North Sea coast and beyond. Note that the subdivision of the British Carboniferous rock sequence has undergone considerable revision in recent years and many traditional sequence names are now obsolete in formal use, though of course they remain widespread in the literature. What is now referred to as the Pennine Coal Measures Group would once have been referred to simply as the 'Productive Coal Measures' and the Yoredale Group was the 'Yoredale Series'. The 'Millstone Grit' of County Durham (minus the 'Great Limestone Member') has been renamed as the 'Stainmore Formation', having also been referred to somewhat confusingly as the Stainmore Group at one time. A feature of much of the Carboniferous succession in northern England is its cyclicity which has involved regular changes between marine deposition and sedimentation from rivers. The phenomenon is manifest as

cyclothem In geology, cyclothems are alternating stratigraphy, stratigraphic sequences of Marine (ocean), marine and non-marine sediments, sometimes interbedded with coal seams. Historically, the term was defined by the European coal geologists who worked ...

s and is especially prominent in the Yoredale Group sequence.

Great Scar Limestone Group

A part of the Carboniferous Limestone Supergroup, the

Great Scar Limestone Group The Great Scar Limestone Group is a lithostratigraphical term referring to a succession of generally fossiliferous rock strata which occur in the Pennines in northern England and in the Isle of Man within the Tournaisian and Visean stages of th ...

consists of a number of different formations except over the Alston Block where a 107m thickness of largely Asbian age limestones and sandstones occurs and is known as the Melmerby Scar Limestone Formation. *Great Scar Limestone Group **Knipe Scar Limestone Formation **Potts Beck Formation **Ashfell Limestone Formation **Ashfell Sandstone Formation **Breakyneck Scar Limestone Formation **Brownber Formation **Scandal Beck Limestone Formation **Coldbeck Limestone Formation Limestone was widely quarried for the production of lime for agriculture and

lime mortar Lime mortar or torching is composed of lime and an aggregate such as sand, mixed with water. The ancient Egyptians were the first to use lime mortars, which they used to plaster their temples. In addition, the Egyptians also incorporated various ...

for building. Industrial scale quarrying accompanied the growth of the iron and steel industries but has since declined. The Frosterley Marble, a

bituminous Asphalt, also known as bitumen (, ), is a sticky, black, highly viscous liquid or semi-solid form of petroleum. It may be found in natural deposits or may be a refined product, and is classed as a pitch. Before the 20th century, the term a ...

coral Corals are marine invertebrates within the class Anthozoa of the phylum Cnidaria. They typically form compact colonies of many identical individual polyps. Coral species include the important reef builders that inhabit tropical oceans and sec ...

iferous limestone once worked at Harehope Quarry in Weardale is used as a decorative stone and can be found in many churches in the region. Concentrations of such corals as '' Dibunophyllum bipartitum'' and of

brachiopod Brachiopods (), phylum Brachiopoda, are a phylum of trochozoan animals that have hard "valves" (shells) on the upper and lower surfaces, unlike the left and right arrangement in bivalve molluscs. Brachiopod valves are hinged at the rear end, w ...

remains contribute to its attractiveness when sections are polished.

Yoredale Group

Rocks assigned to the

Yoredale Group Wensleydale is the dale or upper valley of the River Ure on the east side of the Pennines, one of the Yorkshire Dales in North Yorkshire, England. It is one of only a few Yorkshire Dales not currently named after its principal river, but t ...

overlie the Carboniferous Limestone succession. The Group is subdivided into a lower/older Alston Formation and a higher/younger Stainmore Formation. The former is largely of Brigantian age whilst the latter is of Asbian/Brigantian to Yeadonian age. The latter is broadly equivalent to the Millstone Grit of the central and southern Pennines. Note that in northeast England some hard rock units are traditionally described as 'sills', a local term for a hard band of rock of whatever origin. Nowadays geologists reserve the term for flat-lying igneous intrusions such as the Whin Sill which is described below. *Yoredale Group **Stainmore Formation (formerly ''Millstone Grit'') ***''various un-named sandstones and mudstones'' ***Grindstone Sandstone (formerly ''Grindstone Sill'') ***''various un-named sandstones and mudstones'' ***Firestone Sandstone (formerly ''Firestone Sill'') ***''various sandstones and mudstones'' **Alston Formation (formerly ''Alston Group'') ***Great Limestone Member (formerly part of ''Stainmore Group'' of ''Millstone Grit'' - Pendleian) ***Four Fathom Limestone Member ***''various sandstones and limestones'' ***Three Yard Limestone Member ***''various sandstones and limestones'' ***Five Yard Limestone Member ***''various sandstones and limestones'' ***Scar Limestone Member ***''various sandstones and limestones'' ***Tynebottom Limestone Member ***''various sandstones and limestones''

Coal Measures

Overlying the Yoredale Group rocks is a thick sequence of Coal Measures across which the

Durham Coalfield The Durham Coalfield is a coalfield in north-east England. It is continuous with the Northumberland Coalfield to its north. It extends from Bishop Auckland in the south to the boundary with the county of Northumberland along the River Tyne in the ...

developed. The sequence in County Durham is divided into Lower, Middle and Upper formations. Each of the three are dominated by mudstones but contain abundant sandstones and

coal seam Coal mining is the process of extracting coal from the ground. Coal is valued for its energy content and since the 1880s has been widely used to generate electricity. Steel and cement industries use coal as a fuel for extraction of iron from ...

Ironstone Ironstone is a sedimentary rock, either deposited directly as a ferruginous sediment or created by chemical replacement, that contains a substantial proportion of an iron ore compound from which iron (Fe) can be smelted commercially. Not to be con ...

bands occur in the lower part of the sequence. At least eleven marine bands (shelly mudstones in general) occur within the Coal Measures. Of these, the 'Quarterburn' marine band defines the base of the Lower Coal Measures Formation, the 'Harvey' marine band defines its junction with the overlying Middle Coal Measures Formation and the 'Down Hill' marine band defines the latter's junction with the Upper Coal Measures Formation. The Quarterburn, Harvey and Down Hill marine bands correlate with the standard ''Subcrenatum'', ''Vanderbeckei'' and ''Cambriense'' marine bands of elsewhere. The top of the entire Coal Measures sequence is an erosion surface. *

Pennine Coal Measures Group The Pennine Coal Measures Group is a lithostratigraphical term referring to the coal-bearing succession of rock strata which occur in the United Kingdom within the Westphalian Stage of the Carboniferous Period. In formal use, the term replaces ...

** Pennine Upper Coal Measures Formation ** Pennine Middle Coal Measures Formation (Duckmantian) ** Pennine Lower Coal Measures Formation (Langsettian) Over the

the middle and upper Coal Measures are missing. Similarly in the

Stainmore Trough Stainmore is a remote geographic area in the Pennines on the border of Cumbria, County Durham and North Yorkshire. The name is used for a civil parish in the Eden District of Cumbria, England, including the villages of North Stainmore and South ...

on the

Yorkshire Yorkshire ( ; abbreviated Yorks), formally known as the County of York, is a Historic counties of England, historic county in northern England and by far the largest in the United Kingdom. Because of its large area in comparison with other Eng ...

border, both the upper part of the Middle and the entire Upper Coal Measures are absent. The

rank Rank is the relative position, value, worth, complexity, power, importance, authority, level, etc. of a person or object within a ranking, such as: Level or position in a hierarchical organization * Academic rank * Diplomatic rank * Hierarchy * H ...

of coal increases in the west, a result of the heating of these strata by the Weardale Granite. Some such seams are semi-

anthracite Anthracite, also known as hard coal, and black coal, is a hard, compact variety of coal that has a submetallic luster. It has the highest carbon content, the fewest impurities, and the highest energy density of all types of coal and is the hig ...

s. Workings for coal date back centuries though the height of the industry was the nineteenth century. There are no deep pits remaining in the county though opencasting continues. Various of the county's Coal Measures sandstones have been quarried for building stone, for example the Low Main Post sandstone in

which was used in the construction of the city's cathedral.

Late Carboniferous intrusive rocks

The 'Hett Subswarm' of

tholeiitic The tholeiitic magma series is one of two main magma series in subalkaline igneous rocks, the other being the calc-alkaline series. A magma series is a chemically distinct range of magma compositions that describes the evolution of a mafic magma i ...

quartz-dolerite dykes run WSW-ENE across country to the south of

. The subswarm includes the

Hett Heavy Equipment Transporter System (HETS) is the name of a U.S. Army logistics vehicle transport system, the primary purpose of which is to transport the M1 Abrams tank. It is also used to transport, deploy, and evacuate armored personnel carriers ...

Dyke and Ludworth Dyke amongst others which cut Coal Measures rocks in a WSW-ENE alignment but do not pass into the overlying Permian succession.

Permian and Triassic

As with the Carboniferous sequence, the subdivision of the British

Permian The Permian ( ) is a geologic period and stratigraphic system which spans 47 million years from the end of the Carboniferous Period million years ago (Mya), to the beginning of the Triassic Period 251.9 Mya. It is the last period of the Paleoz ...

(299 - 252 Ma) and

(252 - 201 Ma) has been considerably revised in recent years. Traditional sequence names have been replaced in formal use by new names, though the older names are frequently encountered in books and on maps. The full sequence of Permian and Triassic rocks forming the New Red Sandstone Supergroup locally is this (uppermost/youngest first): *

Mercia Mudstone Group The Mercia Mudstone Group is an early Triassic lithostratigraphic group (a sequence of rock strata) which is widespread in Britain, especially in the English Midlands – the name is derived from the ancient kingdom of Mercia which corresponds to t ...

(formerly ''Keuper Marl'') (Triassic) *

Sherwood Sandstone Group The Sherwood Sandstone Group is a Triassic lithostratigraphic group (a sequence of rock strata) which is widespread in Britain, especially in the English Midlands. The name is derived from Sherwood Forest in Nottinghamshire which is underlain by r ...

(formerly ''Bunter Sandstone'') (Triassic) *

Zechstein Group The Zechstein (German either from ''mine stone'' or ''tough stone'') is a unit of sedimentary rock layers of Middle to Late Permian (Guadalupian to Lopingian) age located in the European Permian Basin which stretches from the east coast of Englan ...

(Permian) **Roxby Formation (calcareous mudstone, formerly ''Upper Anyhdrite and Marl'') **Sherburn Anhydrite Formation (in Stockton area only) **Rotten Marl Formation (formerly ''Rotten or Carnallitic Marl'') **Boulby Halite Formation (formerly ''Middle Halite'' in Durham area) **Seaham Formation (formerly ''Upper Magnesian Limestone'' - calcareous mudstone) **Seaham Residue & Fordon Evaporite Formation (Edlington Formation in Stockton area (formerly ''Permian Middle Marls'')) **Roker Formation (formerly ''Hartlepool Anydrite & Roker Dolomite'') **Ford Formation (formerly ''Middle Magnesian Limestone'') **Raisby Formation (formerly ''Lower Magnesian Limestone'') **Marl Slate Formation (formerly ''Marl Slate'') * Rotliegendes Group (Permian) **Yellow Sands Formation (formerly ''Basal Permian (Sands &) Breccia'') The Yellow Sands Formation comprises aeolian dune-bedded sandstones. The Yellow Sands Formation continues to be worked for building sand. These are overlain by the thin bituminous limestones of the 'Marl Slate' representing the start of a series of inundations of the area by rising sea levels. It contains abundant fish remains. The sequence from the Marl Slate up to and including the Seaham Formation was formerly known as the

Magnesian Limestone The Magnesian Limestone is a suite of carbonate rocks in north-east England dating from the Permian period. The outcrop stretches from Nottingham northwards through Yorkshire and into County Durham where it is exposed along the coast between Ha ...

. The 'Zechstein Group' replaced the former Don, Aislaby, Teesside, Staintondale and Eskdale groups. Several of these units have proved economically valuable.

Anhydrite Anhydrite, or anhydrous calcium sulfate, is a mineral with the chemical formula CaSO4. It is in the orthorhombic crystal system, with three directions of perfect cleavage parallel to the three planes of symmetry. It is not isomorphous with the ...

was sourced beneath

and

gypsum Gypsum is a soft sulfate mineral composed of calcium sulfate dihydrate, with the chemical formula . It is widely mined and is used as a fertilizer and as the main constituent in many forms of plaster, blackboard or sidewalk chalk, and drywall. ...

near

. The Magnesian Limestone forms a broken west-facing scarp running from the western edge of

Sunderland Sunderland () is a port city in Tyne and Wear, England. It is the City of Sunderland's administrative centre and in the Historic counties of England, historic county of County of Durham, Durham. The city is from Newcastle-upon-Tyne and is on t ...

southwards through

Houghton-le-Spring Houghton-le-Spring ( ) is a town in the City of Sunderland, Tyne and Wear, North East England which has its recorded origins in Norman times. Historically in County Durham, it is now administered as part of the Tyne and Wear county. It is s ...

and

Hetton-le-Hole Hetton-le-Hole is a town situated in the City of Sunderland, Tyne and Wear, England. It is in the historic county of Durham. A182 runs through the town, between Houghton-le-Spring and Easington Lane (the latter borders the County Durham Distri ...

Coxhoe Coxhoe is a village in County Durham, England. It is situated about south of Durham City centre. The civil parish also includes nearby Quarrington Hill. The electoral ward of Coxhoe stretches beyond the boundaries of the parish and has a total ...

where its outcrop is offset to the west by the Butterknowle Fault.

English Nature English Nature was the United Kingdom government agency that promoted the conservation of wildlife, geology and wild places throughout England between 1990 and 2006. It was a non-departmental public body funded by the Department for Environmen ...

has defined this part of the county east of the scarp where the sequence is exposed at or near the surface, as the 'Durham Magnesian Limestone Plateau' in its assessment of ' character areas'. The occurrence of gypsum and anhydrite reflects the extreme nature of the evaporation of the shallow

Zechstein Sea The Zechstein (German either from ''mine stone'' or ''tough stone'') is a unit of sedimentary rock layers of Middle to Late Permian (Guadalupian to Lopingian) age located in the European Permian Basin which stretches from the east coast of Englan ...

on occasion though such

evaporites An evaporite () is a water-soluble sedimentary mineral deposit that results from concentration and crystallization by evaporation from an aqueous solution. There are two types of evaporite deposits: marine, which can also be described as ocean ...

are economically valuable. They also present constraints on development as ongoing subterranean solution of these deposits causes occasional catastrophic ground collapse. Similar solution in Palaeogene times has created 'collapse breccias' of overlying strata.

Dolomite Dolomite may refer to: *Dolomite (mineral), a carbonate mineral *Dolomite (rock), also known as dolostone, a sedimentary carbonate rock *Dolomite, Alabama, United States, an unincorporated community *Dolomite, California, United States, an unincor ...

from the Roker Formation has been quarried for building construction along the Durham coast. It has sometimes been referred to as 'Cannonball Rock' due to the appearance of calcitic concretions in certain beds. St Oswald's Church in Hartlepool is constructed from this stone.

Permian intrusive rocks

The Whin Sill and associated

igneous Igneous rock (derived from the Latin word ''ignis'' meaning fire), or magmatic rock, is one of the three main rock types, the others being sedimentary and metamorphic. Igneous rock is formed through the cooling and solidification of magma or ...

dykes were intruded into the existing sedimentary sequence during the

early Permian 01 or '01 may refer to: * The year 2001, or any year ending with 01 * The month of January * 1 (number) Music * '01 (Richard Müller album), 01'' (Richard Müller album), 2001 * 01 (Son of Dave album), ''01'' (Son of Dave album), 2000 * 01 (Urban ...

around 295 Ma. The thickness of the

quartz-dolerite Quartz dolerite or quartz diabase is an intrusive rock similar to dolerite (also called diabase), but with an excess of quartz. Dolerite is similar in composition to basalt, which is volcanic, and gabbro, which is plutonic. The differing crystal s ...

sill averages about 30m. The sill underlies the larger part of the county at depth and appears to extend beneath the North Sea to the east. Thermal metamorphism has altered the surrounding strata, the 'country rocks', to a distance of tens of metres or more. One such is the Sugar Limestone of upper Teesdale which weathers in characteristic fashion and hosts a rare assemblage of plants. Mudstones in contact with the sill have been altered into

hornfels Hornfels is the group name for a set of contact metamorphic rocks that have been baked and hardened by the heat of intrusive igneous masses and have been rendered massive, hard, splintery, and in some cases exceedingly tough and durable. These pro ...

, known locally as 'whetstone'. The presence of the Whin Sill gives rise to

High Force High Force is a waterfall on the River Tees, near Middleton-in-Teesdale, Teesdale, England. The waterfall is within the North Pennines Area of Outstanding Natural Beauty (AONB) and the European Geopark. The waterfall is part of the historic coun ...

where the

River Tees The River Tees (), in Northern England, rises on the eastern slope of Cross Fell in the North Pennines and flows eastwards for to reach the North Sea between Hartlepool and Redcar near Middlesbrough. The modern day history of the river has be ...

drops in spectacular fashion over this erosion-resistant rock. The Little Whin Sill is a thinner, more geographically restricted intrusion of

dolerite Diabase (), also called dolerite () or microgabbro, is a mafic, holocrystalline, subvolcanic rock equivalent to volcanic basalt or plutonic gabbro. Diabase dikes and sills are typically shallow intrusive bodies and often exhibit fine-grained ...

of similar age outcropping in upper

Weardale Weardale is a dale, or valley, on the east side of the Pennines in County Durham, England. Large parts of Weardale fall within the North Pennines Area of Outstanding Natural Beauty (AONB) – the second-largest AONB in England and Wales. T ...

. A quarry near

in upper Teesdale works the dolerite (or 'whinstone') of the Whin Sill for roadstone,

aggregate Aggregate or aggregates may refer to: Computing and mathematics * collection of objects that are bound together by a root entity, otherwise known as an aggregate root. The aggregate root guarantees the consistency of changes being made within the ...

and as larger blocks for coastal protection purposes.

Northern Pennine Orefield

The Northern Pennine Orefield comprises an extended network of veins and 'flats' developed within the Carboniferous sedimentary sequence and is considered one of the finest examples of Mississippi Valley type orefields. Epigenetic mineralisation (i.e. mineralisation at a shallow level) of veins and faults took place shortly after emplacement of the Whin Sill at the start of the Permian Period. Mining for

lead Lead is a chemical element with the symbol Pb (from the Latin ) and atomic number 82. It is a heavy metal that is denser than most common materials. Lead is soft and malleable, and also has a relatively low melting point. When freshly cu ...

copper Copper is a chemical element with the symbol Cu (from la, cuprum) and atomic number 29. It is a soft, malleable, and ductile metal with very high thermal and electrical conductivity. A freshly exposed surface of pure copper has a pinkis ...

and

zinc Zinc is a chemical element with the symbol Zn and atomic number 30. Zinc is a slightly brittle metal at room temperature and has a shiny-greyish appearance when oxidation is removed. It is the first element in group 12 (IIB) of the periodi ...

has taken place over several centuries across these uplands.

Palaeogene

Volcanism Volcanism, vulcanism or volcanicity is the phenomenon of eruption of molten rock (magma) onto the surface of the Earth or a solid-surface planet or moon, where lava, pyroclastics, and volcanic gases erupt through a break in the surface called ...

centred on western

Scotland Scotland (, ) is a country that is part of the United Kingdom. Covering the northern third of the island of Great Britain, mainland Scotland has a border with England to the southeast and is otherwise surrounded by the Atlantic Ocean to the ...

took place during the

Period and resulted in the intrusion of innumerable dykes, one of which is the Cleveland Dyke which extends from

Galloway Galloway ( ; sco, Gallowa; la, Gallovidia) is a region in southwestern Scotland comprising the historic counties of Wigtownshire and Kirkcudbrightshire. It is administered as part of the council area of Dumfries and Galloway. A native or i ...

through County Durham to the

North York Moors The North York Moors is an upland area in north-eastern Yorkshire, England. It contains one of the largest expanses of Calluna, heather moorland in the United Kingdom. The area was designated as a national parks of England and Wales, National P ...

. This intrusion of

basaltic andesite Basaltic andesite is a volcanic rock that is intermediate in composition between basalt and andesite. It is composed predominantly of augite and plagioclase. Basaltic andesite can be found in volcanoes around the world, including in Central Ameri ...

which is up to 30m wide in places has been dated to 55.8+/- 0.9Ma

Structure

The broad structure of the Alston Block has been described in the Devonian section above. The block is itself cut north to south a by a complex structure known as the 'Burtreeford Disturbance' which comprises both faults and folds. To the east of the block the cover of late Palaeozoic and early Mesozoic rocks dip into the

North Sea Basin The North Sea lies between Great Britain, Norway, Denmark, Germany, the Netherlands and Belgium. An epeiric sea on the European continental shelf, it connects to the Atlantic Ocean through the English Channel in the south and the Norwegian S ...

Quaternary

Glacial legacy

Much of the county is mantled with a layer of

glacial till image:Geschiebemergel.JPG, Closeup of glacial till. Note that the larger grains (pebbles and gravel) in the till are completely surrounded by the matrix of finer material (silt and sand), and this characteristic, known as ''matrix support'', is d ...

though this is thinner on the higher ground in the west. There are also spreads of glacially derived sand and gravel, especially across part of the lower ground in the east.

Alluvium Alluvium (from Latin ''alluvius'', from ''alluere'' 'to wash against') is loose clay, silt, sand, or gravel that has been deposited by running water in a stream bed, on a floodplain, in an alluvial fan or beach, or in similar settings. Alluv ...

deposited by rivers occupies the floors of valleys such as that of the

Wear Wear is the damaging, gradual removal or deformation of material at solid surfaces. Causes of wear can be mechanical (e.g., erosion) or chemical (e.g., corrosion). The study of wear and related processes is referred to as tribology. Wear in m ...

whilst river terraces are frequent in the Tees valley.

Lacustrine A lake is an area filled with water, localized in a basin, surrounded by land, and distinct from any river or other outlet that serves to feed or drain the lake. Lakes lie on land and are not part of the ocean, although, like the much larger ...

clay Clay is a type of fine-grained natural soil material containing clay minerals (hydrous aluminium phyllosilicates, e.g. kaolin, Al2 Si2 O5( OH)4). Clays develop plasticity when wet, due to a molecular film of water surrounding the clay par ...

s and

silt Silt is granular material of a size between sand and clay and composed mostly of broken grains of quartz. Silt may occur as a soil (often mixed with sand or clay) or as sediment mixed in suspension with water. Silt usually has a floury feel when ...

s occur in parts of the east where for example, towards the end of the last ice age, Glacial Lake Wear and Glacial Lake Edderacres formed as drainage eastwards was blocked by an icesheet occupying the North Sea.

Post-glacial

Peat has developed extensively across the higher ground of the North Pennines. A variety of coastal deposits are found around the Tees estuary and up the coast to

and beyond.

Geoconservation and Geotourism

Some locations in County Durham are afforded statutory legal protection against adverse developments through being designated as one or more of the following:

Local geological sites

geodiversity Geodiversity is the variety of earth materials, forms and processes that constitute and shape the Earth, either the whole or a specific part of it.Zwolinski, Zb. 2004. ''Geodiversity'', in: ''Encyclopedia of Geomorphology'', A.Goudie (ed.), Routle ...

audit of County Durham produced many locations which are now afforded recognition as 'Local geological sites' (formerly referred to as ' Regionally Important Geodiversity Sites' or simply 'RIGS'.

Local nature reserves

LNRs may be designated for their biological or geological interest. In any case, more often than not, the biological interest is dependent upon the geological interest as at Wingate Quarry LNR north of

Trimdon Grange Trimdon Grange is a village in County Durham, in England. It is situated ten miles to the west of Hartlepool, and a short distance to the north of Trimdon. Colliery disaster At 14:40 on 16 February 1882 the Trimdon Grange colliery suffered a maj ...

village where 'Magnesian Limestone grassland' may be found

Sites of Special Scientific Interest

Numerous SSSIs include citations referring to their geological interest. The extensive

Moorhouse and Cross Fell Moorhouse and Cross Fell is a Site of Special Scientific Interest covering an extensive area of moorland in the Wear Valley district of west County Durham and the Eden district of Cumbria, England. It is contiguous with Upper Teesdale SSSI to ...

SSSI (shared with

Cumbria Cumbria ( ) is a ceremonial and non-metropolitan county in North West England, bordering Scotland. The county and Cumbria County Council, its local government, came into existence in 1974 after the passage of the Local Government Act 1972. Cumb ...

) is one of the most important for a range of subjects.

Natural England Natural England is a non-departmental public body in the United Kingdom sponsored by the Department for Environment, Food and Rural Affairs. It is responsible for ensuring that England's natural environment, including its land, flora and fauna, ...

and other conservation bodies own and manage these locations. The

Durham Coast The Durham Coast is a Site of Special Scientific Interest in County Durham, England. Starting just south of Crimdon Dene, north of Hartlepool, it extends, with a few interruptions, northward to the mouth of the River Tyne at South Shields. Notab ...

is one such which is designated in part for its coastal

geomorphology Geomorphology (from Ancient Greek: , ', "earth"; , ', "form"; and , ', "study") is the scientific study of the origin and evolution of topographic and bathymetric features created by physical, chemical or biological processes operating at or n ...

. Bodies such as the North Pennines AONB Partnership and

Durham County Council Durham County Council is a local authority administering all significant local government functions in the unitary authority area of County Durham in North East England. The council area covers part of the ceremonial county of County Durham, e ...

have published local geodiversity action plans (or 'LGAPs') which summarise an area's geological interests and propose various measures to

conserve Conserve may refer to: * Conserve (condiment), a preserve made from a mixture of fruits or vegetables * Conserve (NGO), an Indian environmental organization * Conserve (publisher), a Dutch publisher * Conserved sequence, a protein or nucleic aci ...

what is perceived to be valuable.

North Pennines AONB and Geopark

The North Pennines AONB was designated as Britain's first

in 2003 partly in acknowledgement of its geological and geomorphological interest. The AONB and Geopark extend beyond the boundaries of County Durham to include parts of

Northumberland Northumberland () is a county in Northern England, one of two counties in England which border with Scotland. Notable landmarks in the county include Alnwick Castle, Bamburgh Castle, Hadrian's Wall and Hexham Abbey. It is bordered by land on ...

and

.http://www.northpennines.org.uk/Pages/Europeanandglobalgeopark.aspx Geopark website

References

{{Geology of England , state=expanded Geography of County Durham