Abstract The present-day landmass of England and Wales offers a wealth of geological variety. Remarkably, all the geological systems are represented within this relatively small area ( Fig. 1.1 ), which encompasses strata ranging in age from Neoproterozoic (late ‘Precambrian’) to Holocene. This partly explains why so many early advances in geology were made here, both in mapping rocks and in developing a geological timescale. In the late 18th and early 19th centuries, William Smith recorded and mapped the sequence of Upper Palaeozoic and Mesozoic rocks in England, and made the first detailed geological map of England and Wales and part of Scotland, published in 1815 ( Fig. 1.2 ). This pioneering effort was aimed primarily at practical people such as mine owners and surveyors, and was an early and fundamental demonstration of the applicability of geology to the broader needs of mankind. But the work of Smith 1799 and others also indicated the need for a geological timescale against which the local sequences could be calibrated. It was within England and Wales that some of the first major subdivisions of the geological record were made. Conybeare & Phillips (1822) combined three established rock units, ‘The Mountain Limestone’, the ‘Millstone Grit’ and the ‘Coal Measures’ to form a new division – ‘The Carboniferous’ – the same year that d’Omalius d’Halloy proposed the Cretaceous System in France. In the following two decades, work on the complex geology of Wales and the Welsh Borderland

Abstract The late Proterozoic rocks of England and Wales comprise part of eastern Avalonia. Characterization of the basement rocks in southern Britain allows the recognition of five distinct terranes in this part of eastern Avalonia known as the Monian Composite Terrane, the Cymru Terrane, the Wrekin Terrane, the Charnwood Terrane and the Fenland Terrane (Gibbons & Horák 1996; Pharaoh & Carney 2000; Fig. 2.1 ). During the Neoproterozoic, eastern Avalonia was situated on the NE margin of Gondwana on the southern margin of the Ran Sea (Nance & Murphy 1996; Hartz & Torvik 2002; Fig. 2.2a–d ). The Ran Sea itself was formed as a result of rifting of the older Rodinian continental landmass ( Fig. 2.2 ). Avalonian tectonics during this late Proterozoic period were driven by subduction on the NE margin of Gondwana, resulting in associated magmatism and arc basin development. With progressive obliquity of subduction, arc magmatism was replaced by a regime dominated by large-scale transform faulting that progressively dissected and dispersed the arc. The switch from arc mag- matism to intra-continental wrench-related volcanism and magmatism was diachronous, and is first seen in western Avalonia (Murphy et al. 2000). Neoproterozoic sediments of the Avalon Terrane are almost exclusively siliciclastic or volcaniclastic and were deposited within numerous geographically restricted strike-slip basins (Pharaoh et al. 1987a; Nance et al. 1991; McΙlroy et al. 1998; Hartz & Torvik 2002; Fig. 2.3 ).

Abstract >The Early Palaeozoic history of England and Wales was substantially influenced by the separation of Avalonia from Gondwana and its subsequent migration towards Laurentia. At the start of the Early Palaeozoic, the vast palaeocontinent of Gondwana straddled the South Pole and extended northwards into low latitudes. On the margin that hosted North Africa and North and South America there were areas of crust that were later to become detached terranes. The largest of these was Avalonia, the remnants of which now extend from NE USA, through the Atlantic Provinces of Canada and through England and Wales to Belgium and North Germany ( Cocks 2000 ). Elsewhere, at lower latitudes on the Gondwana margin, there were crustal segments that were later to become the terranes of Armorica (Britanny, Normandy and the Massif Central regions of France), Perunica (much of central Europe, but mainly preserved in the Bohemian part of the Czech Republic) and Iberia (Spain). In addition there are some smaller continental fragments whose history is difficult to establish. The area of England and Wales lay within Eastern Avalonia, which consisted of an initial crustal fragment that separated from Gondwana ( Fig. 3.1a ) and then accreted smaller terranes as it moved towards Laurentia. The core Avalon Terrane was probably assembled by accretion of crustal fragments on the Gondwana margin in the Late Precambrian or early Cambrian. At about the same time, this terrane accreted both the basement of the Welsh Basin ( Woodcock & Gibbons 1988 ) and an amalgamation

Abstract The evolution of Silurian geology in Britain was strongly influenced by the final stages of the closure of the lapetus Ocean ( Fig. 4.1 ). Avalonia united with Baltica at around the time of the Ordovician-Silurian boundary (443ma) and impacted with the Laurentian margin ( Fig. 4.1 ), between 440 Ma and 420 Ma, probably during the Llandovery or Wenlock ( Soper & Woodcock 1990 ; Cocks & Torsvik 2002 ). The Avalonian margin apparently remained tectonically active throughout the final stages of convergence as indicated by sporadic volcanicity and evidence of early to mid Silurian crustal extension within the Welsh Basin ( Fig. 4.2 ). The initial effects of the collision of Laurentia and Avalonia particularly affected the development of the Lakesman Basin (see section on Lakesman Basin), but later, as Laurentia and Avalonia were driven more tightly together, crustal shortening ended the regime of extensional subsidence in the Welsh Basin. An influx of sediment from the uplifted land to the north and from the land area (Pretannia) to the south caused the basin to become progressively filled in the Late Silurian (Woodcock in Aldridge et al. 2000 ) as the basin underwent thermal subsidence prior to the onset of compression. However, this was punctuated by an interval of southeasterly migrating crustal flexure and increased subsidence, as Laurentia or the advancing accretionary prism overrode Avalonia from the north (King 1994).

Abstract The Lake District, Isle of Man and Leinster basins lie within the Leinster–Lakesman Terrane, which is situated between the Monian Terrane and the Iapetus Suture ( Fig. 5.2 ). It is sometimes convenient to refer to the Isle of Man and Lake District pre-Caradoc basins together as the Lakesman Basin because they have a similar early Ordovician history characterized by a thick accumulation of mudrocks and turbidites, although the basins may have been separate entities. Following the early phase of basin evolution there was an extensive development of volcanism in the Lake District. The mildly alkali tholeitic composition of the volcanic rocks of the Eycott Group might reflect an immature volcanic arc built on a thin outer edge of the continent. The Borrowdale Volcanic Group records the climactic phase of arc volcanism. After the end of most, but not all, volcanic activity the Lake District Basin subsided, accommodating a thick sequence of clastic sediments in what is interpreted as a foreland basin, which filled and shallowed in its final stages. The Lakesman terrane was subsequently deformed during the Acadian Orogeny (Chapter 4).

Abstract Deformation of the Early Palaeozoic rocks of England and Wales has traditionally been ascribed to a late phase of the Caledonian Orogeny that occurred in end-Silurian time. More recently, it has been recognized that this deformation took place towards the end of the Early Devonian and forms part of the Acadian orogenic belt, which extends from the NE Appalachians through western Europe to Poland ( McKerrow 1988 ) ( Fig. 6.1 ). The Caledonian mountains, as originally defined by Suess in the early 20th century, extended between Scotland and Norway and were thought to result from the deformation of an Early Palaeozoic geosyncline. It was soon recognized that the Caledonian orogen continues into the Appalachians and East Greenland, flanked to the west by a faunally distinctive foreland sequence of Cambro-Ordovician platform deposits, which includes the Durness succession of NW Scotland. In a seminal pre-plate tectonic interpretation Wilson (1966) saw the Caledonides as the result of closure of a ‘Proto-Atlantic’ ocean that existed in late Precambrian and Early Palaeozoic time, subsequently named the Iapetus Ocean by Harland & Gayer (1972). In the first plate tectonic model to interpret Caledonian orogenesis in terms of lithospheric convergence driven by ocean spreading and subduction, Dewey (1969a) envisaged closure between two major continental plates, North America–Greenland and Europe, which produced the N–S-striking North Atlantic Caledonides and NE–SW Appalachians. The British Caledonides, located at the intersection of the two margins,

Abstract Intrusive igneous rocks contributed very significantly to crustal growth in northern England and the English Midlands during Ordovician and Devonian times, and the buoyancy effect of these mainly granitic rocks beneath the Lake District, Cheviot Hills and the Askrigg and Alston areas of the north Pennines was to have a profound effect on the later development of Carboniferous and Permo-Triassic extensional basins in the region. During late Ordovician times voluminous subduction- related intrusive rocks were emplaced at the margin of Eastern Avalonia in a zone extending at least from Ireland, through the Lake District and the Midlands, to Belgium as a result of closure of the Iapetus Ocean and Tornquist Sea. By contrast, Early Devonian granitic plutons in northern England and the Southern Uplands belong to suites that were emplaced across the Iapetus suture zone, before, during and after the Acadian Orogeny. A similar sequence may be present in the Isle of Man. In the Lake District, the main components of a large, subvolcanic, granitic batholith ( Fig. 7.1 ), along with a wide variety of minor intrusions, were emplaced contemporaneously with the Caradoc Eycott and Borrowdale volcanic groups (Millward 2002, 2004 and references therein). Some of the exposed intrusions are linked geochemically to the volcanic rocks, whereas others have distinctive geochemical signatures (e.g. O’Brien et al. 1985). To the SE, within the Askrigg Block and in central England, late Ordovician calc-alkaline intrusive and volcanic rocks comprise a relatively small number of exposures

Abstract Classically, the Old Red Sandstone (ORS) embraces the continental, predominantly siliciclastic deposits of Devonian age, being in part the terrestrial correlatives of the marine Devonian of SW England. Subsequent stratigraphical revision (e.g. House 1977 ) demonstrated that the base of the ORS is actually of Silurian age in many places. The ORS has long been of interest due to the presence of early vascular plants and vertebrate faunas. Studies of the ORS have spawned significant sedi-mentological advances, for example the now classic analysis of high-sinuosity fluvial channels ( Allen 1965a , 1970 ). Today, the ORS is a term applied to tectono-stratigraphic units of Upper Silurian–Carboniferous age bordering the North Atlantic Ocean ( Friend 1969 , Friend et al. 2000 ). It has long been seen as representing the syn- to post-orogenic depositional response (molasse) to the Caledonian Orogeny, being modified by synchronous tectonism and volcanicity. The influence of Variscan tectonics on basin formation and subsequent deformation has recently being highlighted ( Friend et al. 2000 ). Lithologically, it embraces a wide range of textural grades from mudrocks to conglomerates. Fluvial, lacustrine, aeolian, pedogenic and marginal marine deposits have been recognized. In England and Wales, the ORS crops out in four main areas ( Fig. 8.1 ): the Anglo-Welsh Basin, Anglesey, Edenside (Cumbria) and North Devon.

Abstract The structural evolution of England and Wales during the Carboniferous was primarily a consequence of an oblique (dextral) collision between Gondwana and Laurussia ( Warr 2000 ). Several phases can be recognized. The Rhenohercynian Ocean opened during Early–Mid Devonian regional bacK–Arc transtension between Avalonia and Armorica ( Fig. 9.1 ), possibly associated with northward-directed subduction along the southern margin of Armorica. A narrow seaway floored by oceanic crust developed, extending across southwest England, northern France and Germany. Cessation of the subduction, associated with the Ligerian orogenic phase of central Europe, resulted from the collision of the Iberian and Armorican microplates ( Fig. 9.1 ). During the Late Devonian, transpressive closure of this restricted ocean, associated with the Bretonian orogenic phase, may have occurred in response to short-lived southward-directed subduction of the Rhenohercynian oceanic plate beneath Armorica. A return to northward-directed subduction of the Theic oceanic plate along the southern margin of Iberia/Armorica ( Fig. 9.1 ) resulted in a Late Devonian–Early Carboniferous phase of bacK–Arc extension within the Avalonian part of the Laurussian plate ( Warr 2000 ). The resultant N–S rifting affected all of central and northern England and North Wales, initiating development of a series of graben and half-grabens,

Abstract The upper Palaeozoic Orogenic Province of SW England is a part of a belt of Devonian and Carboniferous basins that extended from Devon and Cornwall through to Germany, some 800 km to the east. Their complex sequence of basin development and phases of deformation, described in this chapter cumulatively comprise the Variscan Orogeny in this region. Synchronously with the Devonian events within the Variscan Orogen, the mainly fluvial facies of the Old Red Sandstone filled basins in the Avalonian continent north of the Variscan front (Chapter 6). During the succeeding Carboniferous, basins within the continent were mainly extensional in origin, until a period in the late Carboniferous when many basement faults were inverted (Chapter 7) resulting in uplift of the basin fill, that initiated a new palaeogeography at the start of the Permian. The South Wales Basin represents a transitional zone between the mobile Variscan belt and the continent to the north. This transitional position is reflected in the Devonian by the interdigitationof the Old Red Sandstone facies and marine sediments at the northern margins of the Variscan basins (Chapter 6). Throughout the Dinantian and Namurian the succession within the South Wales basin had much in common with successions in basins within the continent to the north (Chapter 7). It was not until the Silesian that Variscan deformation affected basin development and caused its deformation (see this chapter).

Abstract The essentially E–W-trending structural grain of the Devonian and Carboniferous Variscan orogen of mainland SW England (see Chapter 10) is punctuated by five large granite plutons ( Fig. 11.1 ), which are now known to have been emplaced during very latest Carboniferous–Early Permian times. This chronological frame is after the final compressional stage of the Variscan orogeny, and it is now considered that the Cornubian granites were associated with crustal extension and orogenic collapse – this is discussed more fully later. From east to west the plutons are: Dartmoor (650 km 2 ), Bodmin Moor (220 km 2 ), St Austell (85 km 2 ), Carnmenellis (135 km 2 ) and Land’s End (190 km 2 ). Offshore, to the west of Land’s End, the Isles of Scilly pluton has a seabed crop of about 120 km 2 . Onshore, there are a number of smaller granite bodies, including Hemerdon Ball (south of Dartmoor), Hingston Down, Kit Hill and Gunnislake (between Dartmoor and Bodmin Moor), Belowda and Castle-an-Dinas (to the north of St Austell), Carn Brea, Carn Marth, St Agnes and Cligga Head (to the north of Carnmenellis), St Michael’s Mount and Tregonning–Godolphin (between Carnmenellis and Land’s End). The higher parts of the granite outcrops are characterized by moorland, with thin peaty soils from which arise sporadic tors and their associated boulder screes, ‘clitter’ in the local dialect.

Abstract The distribution of Permian rocks in England and Wales ( Fig. 12.1 ) is more complex than that of the overlying Mesozoic formations, which in the onshore area form a broad swathe displaying, as William Smith noted, an overall NE–SW-trending strike. Permian sediments, by contrast, are more patchily developed but rest in many locations on Carboniferous rocks, with a palaeotopography generated by Variscan mountain building and later erosion. Assessment of how the Permian landscape might have appeared is best achieved through consideration of the sedimentary evidence from both the Permian and the preceding Carboniferous strata. There are strong indications in the rock record of a changing tectonic and palaeoclimatic regime in NW Europe during this time, which reflected broader, even global, events. The general tectonic scene was one in which the southern supercontinent Gondwana moved north through Carboniferous time to collide with its northern counterpart Laurasia in the latest Carboniferous and earliest Permian. This continental collision was achieved as the Devonian–Carboniferous Rheic Ocean closed and Pangaea formed ( Fig. 12.2 ). Simultaneously, the Ural Mountains were forming as the Kazakstan microplate collided with Fennos- candia, the final coalescence of Pangaea. The sedimentary fill of the Rheic Ocean is now preserved as deformed and locally metamorphosed pre-Permian successions in Cornwall, Devon, northern France,Belgium and Germany.

Abstract The collision of Siberia and the Kazakstan microplate with the eastern side of the Fennoscandia continent in the Permian amalgamated the last major continental fragments to produce the supercontinent Pangaea, which persisted into the Jurassic ( Fig. 13.1 ). During the last phases of this collision, during the latest Permian–Early Triassic, extrusion of massive amounts of flood basalts occurred in Siberia, to the east of the Urals ( Otto & Bailey 1995 ). Some have proposed this event as one of the key processes controlling the largest extinction in Earth’s history at the Permian–Triassic boundary ( Wignall 2001 a ; Benton & Twitchett 2003 ). During the Triassic, England and Wales lay beyond the western termination of the Tethys Ocean, which was divided into a northern part, the Palaeotethys, and a southern part, the Neotethys ( Fig. 13.1 ). Between these oceans occurred the Cimmerian terrains; several now widely separated continental fragments which had rifted from the northern fringe of Gondwana in the Permian ( Stampfli & Borel 2002 ). The Triassic witnessed the northward drift of these Cimmerian terrains, and the northward subduction of the Palaeotethys, which was mostly completed by the Late Triassic.

Abstract >The Jurassic Period in NW Europe began with an interval of pulsed subsidence that may be linked to local extensional fault movements. This parallels movements farther south where the western end of the Tethys opened in the Early Jurassic with a period of discontinuous rifting that lasted some 40 Ma and that is referred to as the Ligurian cycle; this phase of extensional tectonism resulted in block-faulting and tilting and was followed by rapid subsidence and the development of regional erosional surfaces (De Graciansky et al. 1998). The Tethys Ocean had long been established as a large oceanic area contiguous with the great Panthalassa Ocean to the east, but in the Early Jurassic it was bounded by continental areas on all other sides, with little marine connection across these areas. Britain was situated in a seaway between the Laurentian margin and Scandinavia that allowed limited interchange of water northwards from the Tethys into the Arctic Sea; the latter extended from about 60°N to the pole. This seaway was interrupted by a series of islands of different sizes, including in the western European area the Spanish Meseta, the French Massif Central and Brittany, the Anglo-Brabant Massif, Cornubia, much of Ireland, the Scottish Highlands and Rockall. Interchange of waters between the Tethys and the Arctic sea was of fundamental importance in governing the faunas of the area; this movement was forced by differences in water-densities across the area, water flowing towards the areas of greater density. The Arctic sea received a considerable input of freshwater from high precipitation and continental run-off.

Abstract The Cretaceous was a particularly eventful period of geological time. It saw the continuing break-up of the former supercontinents of Laurasia and Gondwana, accompanied by major volcanic eruptions, experienced arguably the highest sea levels of Phanerozoic time, and endured an extraterrestrial bombardment. These aspects of Cretaceous history are reviewed briefly below, but for a comprehensive account the reader is referred to Skelton’s (2003) review of the Cretaceous world. The Cretaceous climate is often described as an equable, ‘greenhouse’ one, although this view is being challenged increasingly. Certainly the Cretaceous world was noticeably warmer than today’s, with temperatures apparently rising overall through Early Cretaceous times to reach a peak in the Late Cretaceous. At mid to low latitudes highest temperatures were reached during the Cenomanian–Turonian interval, while at high latitudes they persisted to the earliest Campanian ( Gale 2000 ) (see Figs 15.5 – 15.7 for Cretaceous stages/ages). At low to mid latitudes, Early Cretaceous climate fluctuated between arid and humid phases, but aridity dominated through most of Late Cretaceous times, although there was a humid belt further north in which coniferous forests thrived, at times extending up to at least 85° N (e.g. Spicer & Corfield 1992; Spicer 2000). There is no firm evidence of polar ice, although the possibility has been suggested (e.g. Kemper 1987; Frakes & Francis 1988),

Abstract The K/T (Cretaceous–Tertiary) boundary (more correctly the Cretaceous–Paleogene boundary) is defined by a mass extinction event, whose cause and characteristics is one of the most thoroughly investigated research topics of recent years. The extinction of almost all calcareous plankton produced lithological changes in open marine sediments which are also recognizable world-wide. In England and Wales and adjacent areas, a widespread sub-Paleogene unconformity has, however, removed any evidence of this event. In terms of geological processes the Early Paleogene is essentially a continuation of the Late Cretaceous, with similar high sea levels and warm climates to the Late Cretaceous ‘greenhouse world’. These are generally believed to be due to the absence of permanent polar ice sheets, although the existence of an Antarctic ice sheet in the Late Cretaceous (and presumably the early Paleogene) has been suggested recently (see Chapter 15). A very brief but intense warming episode at the Paleocene–Eocene boundary is believed to be due to the rapid release of large volumes of methane from sea-floor sediments. From the Mid Eocene a slow cooling set in, with a marked temperature drop at the Eocene–Oligocene boundary. These events mark the change to an ‘icehouse’ world, and are believed to reflect the first appearance and growth of a major permanent Antarctic icesheet. Oligocene and Neogene climates are characterized by fluctuating but overall lower temperatures, culminating in the Quatenary with the inception of extensive Pleistocene

Abstract The Quaternary, or final period of geological time, has been popularly equated for the last 150 years with the ‘ice age’, when glaciers invaded many high latitude and high altitude parts of the Earth’s surface not previously glaciated since at least the Permo-Carboniferous. Early in the 19th century a distinction was drawn between the ‘solid’ rock formations, which often show a regular stratigraphic order and uniform thickness because of deposition in extensive marine basins, and the thinner, unconsolidated and much more variable ‘drift’ or superficial formations now known to result from more recent deposition mainly in glacial and other non-marine environments. The terms solid and drift are still preserved in the legends of quite recently published British Geological Survey (BGS) maps, although since 2004 they have been replaced by ‘Bedrock’ and ‘Superficial Deposits’, respectively. Over most of England and Wales they correspond to pre-Quaternary and Quaternary deposits. The term drift (or diluvium) originally implied deposition by waters of the Biblical Flood, but with increasing exploration of polar regions in the 19th century it became popular to invoke floating ice as a depositional agent, accounting especially for the large blocks of identifiable rock types (erratics) displaced long distances from their nearest known outcrops. However, both flood and floating ice implied an unlikely submergence of great depth in order to deposit erratics and other drifts on mountains well above present sea level, for example on Moel Tryfan in North Wales, where Quaternary marine molluscs occur at 430 m OD.

Abstract Although geologists are used to looking backwards in time, to reconstruct past events and processes from the preserved rock record, one of the roles of the scientist is to use their evidence to predict the consequences of their observations. One of the most important lessons from the geological history of the British landmass is that the dynamic interaction of processes that operate at the Earth’s surface can produce highly differing but also predictable patterns of sedimentary sequences under varied environmental conditions. Moreover, the present, if it is indeed the key to the past in the true Huttonian sense, may also be seen as a key to predicting our geological future, albeit with the modifying effect of the interference of humans in the operation of natural processes. In this chapter an attempt is made to offer some insight into potential future geological and environmental developments. These ideas are based on a forward projection of processes operating today, or in the recent geological past, and give rise to what is hoped are interesting insights. For the sake of simplicity, three timescales are examined. First, the climate changes predicted to occur over the next two centuries are discussed, mainly focusing on the role of greenhouse-gas emissions on our modern climate and its implications. This is followed by a short review of the changes that might be expected over the next 130 ka, based on climate simulation modelling. Finally, a speculative review of long-timescale developments is presented.