Ham Hill, Somerset
Ham Hill is a geological Site of Special Scientific Interest, Scheduled Ancient Monument, Iron Age hill fort, Roman site, Local Nature Reserve and country park, to the west of Yeovil in Somerset, England. The hill has given its name to the distinctive quarried hamstone and to two nearby villages: Stoke-sub-Hamdon and Norton Sub Hamdon, whose names mean "under-Ham-hill"; the Mendip Hills, Blackdown Hills, Quantock Hills and Dorset Downs are all visible from Ham Hill from its war memorial. It is popular for picnicking and mountain biking in the grassy hollows of the old quarry workings; the geology supports a wide range of fauna including mammals, invertebrates and amphibians living on lichens, fungi and flowering plants. The hill is part of ridge of sandy limestone rock, elevated above the lower lying clay vales and nearby Somerset Levels; the sedimentary rocks were laid down in the part of the early Jurassic known as the Toarcian Stage. They are given their colour by the weathering of the iron content of the stone and contain fossils such as the ammonite Dumortieria moorei.
The hamstone is a distinctive honey-coloured building stone, used in many local villages and for buildings such as Montacute House and Sherborne Abbey. Extensive old quarry workings have changed the landscape into a warren of stony ridges and grassy hollows. Quarrying has unearthed many important historical artefacts, but destroyed much of the archaeological context; the hill is an 11.1 ha geological Site of Special Scientific Interest, notified in 1971, due of its particular importance to geologists because of the assemblages of fossils which it contains, the sedimentary features which it displays and the way it relates to other rocks of equivalent age in the close vicinity. Ham Hill is managed as a Local Nature Reserve, under Section 21 of the National Parks and Access to the Countryside Act 1949, because of the rare calcareous grassland which supports a wide variety of plant and animal species and its wild flower meadows and wide open grassland areas such as Witcombe Valley. Fauna include mammals, invertebrates and amphibians while the flora include lichens, fungi and flowering plants.
The name may come from the Old English ham and hyll giving a meaning of "the settlement hill", however its original name was Hamdon, meaning "the hill among the water meadows". There is evidence of occupation from the neolithic periods. Ham Hill is the site of a large Bronze Age and Iron Age hill fort of the Durotriges tribe, from the 1st century BC; the 3 miles ramparts enclose an area of 210 acres. Most of the perimeter is ditch. There is a major entrance to the south-east, on the line of the modern road and another to the north-east, following a track from the Church of St Mary the Virgin at East Stoke in Stoke-sub-Hamdon. Archaeological finds include bronzework, chariot parts, iron currency bars and silver coins and burials; the hill was captured around AD 45 by the Roman Second Legion, led by the future emperor Vespasian, who had captured Maiden Castle and other hill forts to the south. Many Roman military artefacts have been found and it is quite that the Second Legion made a temporary camp on the hill, as at Hod Hill.
After the initial campaigns, a more permanent Roman camp was established at nearby Ilchester and the Fosse Way military road was constructed within 1 mile of Ham Hill, on its way to Axminster and the garrison at Exeter. The area was prosperous in the Roman period and several major villas have been found nearby, including one on the eastern part of the hill in the field known as "Warren", with extensive mosaic. Other villas have been found at Stoke-sub-Hamdon, Odcombe and West Coker. Just to the east of the main plateau is the isolated St. Michael's Hill, the "pointed hill" that gives its name to the village of Montacute and, turned into a motte-and-bailey castle by the Normans. South of the main hill are strip lynchets, or low terraces created by ancient ploughing and cultivation and the deserted medieval village of Witcombe, abandoned in the 17th century. In the 1800s there were 24 small quarries operating on the hill employing some 200 men; this continued into the Victorian era with over 200 small family run quarries and masonry businesses.
Many of these small quarries had ceased working by 1910. Today hamstone is only quarried in two areas at the top of Ham Hill; the North quarry, near the modern stone circle and war memorial, is the longest running hamstone quarry in existence. The southern, Norton Quarry extracts its stone from some 20–30 metres below the surface and is quarried by Harvey Stone; this quarry was reopened around 15 years ago, having been the last quarry abandoned in the 1930s due to there being, according to the masons working the hill "no good quality stone left". Both quarries are owned by the Duchy of Cornwall; the northern end of the plateau is crowned by a war memorial to the dead of the nearby village of Stoke-sub-Hamdon killed during the two World Wars and subsequent conflicts. It was designed in 1920 and unveiled in 1923 with four steps which lead to a square plinth and a tapering four-sided obelisk with a flat top; the memorial is visible from the surrounding countryside, including the A303 trunk road which now follows the course of the Fosse Way near the base of the hill.
Just below the Monument is a bench dedicated to the memory of local student Alan Kneebone, murdered in 2001 while at Wakefield College. The hill and the country park around it provide a venue for a variety of leisure and recreational uses, including walking, horse ri
Beds are the layers of sedimentary rocks that are distinctly different from overlying and underlying subsequent beds of different sedimentary rocks. Layers of beds are called strata, they are formed from sedimentary rocks being deposited on the Earth's solid surface over a long periods of time. The stratigraphy are layered in the same order that they were deposited, allowing a differentiation of which beds are younger and which ones are older; the structure of a bed is determined by its bedding plane. Beds can be differentiated including rock or mineral type and particle size; the term is applied to sedimentary strata, but may be used for volcanic flows or ash layers. In a quarry, bedding is a term used for a structure occurring in granite and similar massive rocks that allows them to split in well-defined planes horizontally or parallel to the land surface. Other kinds of beds are graded beds. Cross beds are not layered horizontally and are formed by a combination of local deposition on the inclined surfaces of ripples or dunes, local erosion.
Graded beds shows a gradual change in clast sizes from one side of the bed to the other. A normal grading is when there are bigger grain sizes on the older side while an inverse grading is when there are smaller grain sizes on the older side. By knowing the type of beds, geologists can determine the relative ages of the rocks. A bed is the smallest lithostratigraphic unit ranging in thickness from a centimeter to several meters and distinguishable from beds above and below it; the thickness of the bed is determined by the time period involving the deposition of the rocks. Thick Bed - 100cm Thick Bed - 30cm Medium Bed - 10cm Thin Bed - 3cm Very Thin Bed - 1cm Thinner than 1cm is called a Lamina In geotechnical engineering a bedding plane forms a discontinuity that may have a large influence on the mechanical behaviour of soil and rock masses in, for example, foundation, or slope construction. There are geologic principles that the beds follow. Though there can be cases where the principles do not apply due to faults, they are true for most cases.
Law of Superposition is the law that states that the oldest rocks are deposited first and has the younger layers deposited last, as long as the beds have not been overturned through tectonic activities. This is used to date their relative ages. Law of Original Horizontality states that if the beds are not horizontal the layers were caused to either fold or tilt through tectonic activities, they were all deposited horizontally due to gravity. Law of Lateral Continuity states; this means that if two places separated by erosional features have similar rocks, it could mean that they were continuous. Cross-Cutting Relationship states, it helps with dating the rocks. Geological unit Lamination Stratigraphy Stratum Lamina, Laminaset and Bedset. Campbell, Charles V. Sedimentology, vol. 8, issue 1, pp. 7-26
Somerset is a county in South West England which borders Gloucestershire and Bristol to the north, Wiltshire to the east, Dorset to the south-east and Devon to the south-west. It is bounded to the north and west by the Severn Estuary and the Bristol Channel, its coastline facing southeastern Wales, its traditional border with Gloucestershire is the River Avon. Somerset's county town is Taunton. Somerset is a rural county of rolling hills, the Blackdown Hills, Mendip Hills, Quantock Hills and Exmoor National Park, large flat expanses of land including the Somerset Levels. There is evidence of human occupation from Paleolithic times, of subsequent settlement by the Celts and Anglo-Saxons; the county played a significant part in Alfred the Great's rise to power, the English Civil War and the Monmouth Rebellion. The city of Bath is a UNESCO World Heritage Site. Somerset's name derives from Old English Sumorsǣte, short for Sumortūnsǣte, meaning "the people living at or dependent on Sumortūn"; the first known use of Somersæte is in the law code of King Ine, the Saxon King of Wessex from 688 to 726, making Somerset along with Hampshire and Dorset one of the oldest extant units of local government in the world.
An alternative suggestion is the name derives from Seo-mere-saetan meaning "settlers by the sea lakes". The Old English name is used in the motto of the county, Sumorsǣte ealle, meaning "all the people of Somerset". Adopted as the motto in 1911, the phrase is taken from the Anglo-Saxon Chronicle. Somerset was a part of the Anglo-Saxon kingdom of Wessex, the phrase refers to the wholehearted support the people of Somerset gave to King Alfred in his struggle to save Wessex from Viking invaders. Somerset settlement names are Anglo-Saxon in origin, but numerous place names include Brittonic Celtic elements, such as the rivers Frome and Avon, names of hills. For example, an Anglo-Saxon charter of 682 refers to Creechborough Hill as "the hill the British call Cructan and the Anglo-Saxons call Crychbeorh"; some modern names are Brythonic in origin, such as Tarnock, while others have both Saxon and Brythonic elements, such as Pen Hill. The caves of the Mendip Hills were settled during the Palaeolithic period, contain extensive archaeological sites such as those at Cheddar Gorge.
Bones from Gough's Cave have been dated to 12,000 BC, a complete skeleton, known as Cheddar Man, dates from 7150 BC. Examples of cave art have been found in Aveline's Hole; some caves continued to be occupied until modern times, including Wookey Hole. The Somerset Levels—specifically dry points at Glastonbury and Brent Knoll— have a long history of settlement, are known to have been settled by Mesolithic hunters. Travel in the area was facilitated by the construction of one of the world's oldest known engineered roadways, the Sweet Track, which dates from 3807 BC or 3806 BC; the exact age of the henge monument at Stanton Drew stone circles is unknown, but it is believed to be Neolithic. There are numerous Iron Age hill forts, some of which, like Cadbury Castle and Ham Hill, were reoccupied in the Early Middle Ages. On the authority of the future emperor Vespasian, as part of the ongoing expansion of the Roman presence in Britain, the Second Legion Augusta invaded Somerset from the south-east in AD 47.
The county remained part of the Roman Empire until around AD 409, when the Roman occupation of Britain came to an end. A variety of Roman remains have been found, including Pagans Hill Roman temple in Chew Stoke,Low Ham Roman Villa and the Roman Baths that gave their name to the city of Bath. After the Romans left, Britain was invaded by Anglo-Saxon peoples. By AD 600 they had established control over much of what is now England, but Somerset was still in native British hands; the British held back Saxon advance into the south-west for some time longer, but by the early eighth century King Ine of Wessex had pushed the boundaries of the West Saxon kingdom far enough west to include Somerset. The Saxon royal palace in Cheddar was used several times in the 10th century to host the Witenagemot. After the Norman Conquest, the county was divided into 700 fiefs, large areas were owned by the crown, with fortifications such as Dunster Castle used for control and defence. Somerset contains HM Prison Shepton Mallet, England's oldest prison still in use prior to its closure in 2013, having opened in 1610.
In the English Civil War Somerset was Parliamentarian, with key engagements being the Sieges of Taunton and the Battle of Langport. In 1685 the Monmouth Rebellion was played out in neighbouring Dorset; the rebels landed at Lyme Regis and travelled north, hoping to capture Bristol and Bath, but they were defeated in the Battle of Sedgemoor at Westonzoyland, the last pitched battle fought in England. Arthur Wellesley took Duke of Wellington from the town of Wellington; the Industrial Revolution in the Midlands and Northern England spelled the end for most of Somerset's cottage industries. Farming continued to flourish and the Bath and West of England Society for the Encouragement of Agriculture, Arts and Commerce was founded in 1777 to improve farming methods. Despite this, 20 years John Billingsley conducted a survey of the county's agriculture in 1795 and found that agricultural methods could still be improved. Coal mining was an important industry in north Somerset during the 18th and 19th centuries, by 1800 it was prominent in Radstock.
The Somerset Coalfield reached its peak production by the 1920s, but all the pits have now been closed, the last in 1973. Most of the surface
Limestone is a carbonate sedimentary rock, composed of the skeletal fragments of marine organisms such as coral and molluscs. Its major materials are the minerals calcite and aragonite, which are different crystal forms of calcium carbonate. A related rock is dolostone, which contains a high percentage of the mineral dolomite, CaMg2. In fact, in old USGS publications, dolostone was referred to as magnesian limestone, a term now reserved for magnesium-deficient dolostones or magnesium-rich limestones. About 10% of sedimentary rocks are limestones; the solubility of limestone in water and weak acid solutions leads to karst landscapes, in which water erodes the limestone over thousands to millions of years. Most cave systems are through limestone bedrock. Limestone has numerous uses: as a building material, an essential component of concrete, as aggregate for the base of roads, as white pigment or filler in products such as toothpaste or paints, as a chemical feedstock for the production of lime, as a soil conditioner, or as a popular decorative addition to rock gardens.
Like most other sedimentary rocks, most limestone is composed of grains. Most grains in limestone are skeletal fragments of marine organisms such as foraminifera; these organisms secrete shells made of aragonite or calcite, leave these shells behind when they die. Other carbonate grains composing limestones are ooids, peloids and extraclasts. Limestone contains variable amounts of silica in the form of chert or siliceous skeletal fragment, varying amounts of clay and sand carried in by rivers; some limestones do not consist of grains, are formed by the chemical precipitation of calcite or aragonite, i.e. travertine. Secondary calcite may be deposited by supersaturated meteoric waters; this produces speleothems, such as stalactites. Another form taken by calcite is oolitic limestone, which can be recognized by its granular appearance; the primary source of the calcite in limestone is most marine organisms. Some of these organisms can construct mounds of rock building upon past generations. Below about 3,000 meters, water pressure and temperature conditions cause the dissolution of calcite to increase nonlinearly, so limestone does not form in deeper waters.
Limestones may form in lacustrine and evaporite depositional environments. Calcite can be dissolved or precipitated by groundwater, depending on several factors, including the water temperature, pH, dissolved ion concentrations. Calcite exhibits an unusual characteristic called retrograde solubility, in which it becomes less soluble in water as the temperature increases. Impurities will cause limestones to exhibit different colors with weathered surfaces. Limestone may be crystalline, granular, or massive, depending on the method of formation. Crystals of calcite, dolomite or barite may line small cavities in the rock; when conditions are right for precipitation, calcite forms mineral coatings that cement the existing rock grains together, or it can fill fractures. Travertine is a banded, compact variety of limestone formed along streams where there are waterfalls and around hot or cold springs. Calcium carbonate is deposited where evaporation of the water leaves a solution supersaturated with the chemical constituents of calcite.
Tufa, a porous or cellular variety of travertine, is found near waterfalls. Coquina is a poorly consolidated limestone composed of pieces of coral or shells. During regional metamorphism that occurs during the mountain building process, limestone recrystallizes into marble. Limestone is a parent material of Mollisol soil group. Two major classification schemes, the Folk and the Dunham, are used for identifying the types of carbonate rocks collectively known as limestone. Robert L. Folk developed a classification system that places primary emphasis on the detailed composition of grains and interstitial material in carbonate rocks. Based on composition, there are three main components: allochems and cement; the Folk system uses two-part names. It is helpful to have a petrographic microscope when using the Folk scheme, because it is easier to determine the components present in each sample; the Dunham scheme focuses on depositional textures. Each name is based upon the texture of the grains. Robert J. Dunham published his system for limestone in 1962.
Dunham divides the rocks into four main groups based on relative proportions of coarser clastic particles. Dunham names are for rock families, his efforts deal with the question of whether or not the grains were in mutual contact, therefore self-supporting, or whether the rock is characterized by the presence of frame builders and algal mats. Unlike the Folk scheme, Dunham deals with the original porosity of the rock; the Dunham scheme is more useful for hand samples because it is based on texture, not the grains in the sample. A revised classification was proposed by Wright, it adds some diagenetic patterns and can be summarized as follows: See: Carbonate platform About 10% of all sedimentary rocks are limestones. Limestone is soluble in acid, therefore forms many erosional landforms; these include limestone pavements, pot holes, cenotes and gorges. Such erosion landscapes are known
St Mary's Church, Chedzoy
The Anglican Church of St Mary in Chedzoy, England dates from the 13th century and has been designated as a grade I listed building. There is evidence of a Church in Chedzoy in 1166 when it was given along with the parent church in North Petherton to Buckland Priory; the tower dates from the early 16th century when the porch, the arch into the north transept, the windows in the north aisle were added. Much of the current building is from the 17th century, although the Norman chancel, chancel arch and doorway remain, it was extensively remodelled by William Butterfield in 1861. A late medieval screen and rood loft were removed around 1841; the font has survived since the 13th century. The pulpit is from the 16th century. Amongst the memorials is a brass believed to commemorate Richard Sydenham who died in 1499. Local tradition says that the church still bears marks form the forces of the Duke of Monmouth during the Monmouth Rebellion who sharpened their swords before battle, however this is unlikely to be the true source of the marks.
The parish is part of the benefice of Westonzoyland with Chedzoy within the Sedgemoor deanery. List of Grade I listed buildings in Sedgemoor List of towers in Somerset List of ecclesiastical parishes in the Diocese of Bath and Wells St. Mary's Church, Chedzoy website Chedzoy Parish Council website
Sir Simon David Jenkins is a British author and a newspaper columnist and editor. He was editor of the Evening Standard from 1976 to 1978 and of The Times from 1990 to 1992. Jenkins chaired the National Trust for Places of Historic Interest or Natural Beauty from 2008 to 2014, he writes columns for both The Guardian and the Evening Standard. Jenkins was born 10 June 1943, in England, his father is United Reformed Church minister Daniel Thomas Jenkins. He was educated at Mill Hill School and St John's College, where he read Philosophy and Economics. After graduating from University of Oxford, Jenkins worked at Country Life magazine, before joining the Times Educational Supplement, he was features editor and columnist on the Evening Standard before editing the Insight pages of The Sunday Times. From 1976 to 1978 he was editor of the Evening Standard, before moving to become political editor of The Economist, he edited The Times from 1990 to 1992, but since has worked as a columnist. In 1998 he received the What the Papers Say Journalist of the Year award.
On 28 January 2005, he announced he was ending his 15-year association with The Times to write a book before joining The Guardian as a columnist. He was a contributing blogger at The Huffington Post, he gave up both on becoming chairman of the National Trust in 2008, when he resumed an occasional column for the London Evening Standard. On 14 April 2009, The Guardian newspaper withdrew one of his articles from its website after former African National Congress leader and South African President Jacob Zuma sued the paper for defamation. In February 2010, in favour of the Falklands War, argued in a Guardian article that the Falkland Islands are an example of anachronistic British colonialism and should be handed over to Argentinian control, he said that they could be leased back under the auspices of the UN. He remarked that the 2,500 or so British islanders should not have an "unqualified veto on British government policy". In March 2012, he stated on Question Time that Britain should begin negotiating the handover of the Falkland Islands to the Argentine government.
Only his fellow panellist. In 2010 Jenkins spoke disparagingly on the Radio 4 Today programme about the Shard, a skyscraper in south London. Jenkins has expressed varying opinions on the subject of national defence. In a piece in The Guardian in 2010 he wrote that the government should "cut, all £45 billion of it... With the end of the Cold War in the 1990s that threat vanished." However, he wrote in the same paper in 2016 in support of NATO membership, saying: "It is a real deterrent, its plausibility rests on the assurance of collective response."Jenkins voted for the UK to Remain within the European Union in the United Kingdom European Union membership referendum, 2016 arguing that leaving would provide Germany with dominance over the remainder of the union: "It would leave Germany alone at the head of Europe, alternately hesitant and bullying". Jenkins has written several books on the politics and architecture of England, including England's Thousand Best Churches and England's Thousand Best Houses.
More in his A Short History of England, he argues that the British Empire "was a remarkable institution that dismantled itself in good order." He wrote that England is "the most remarkable country in European history." Jenkins served on the boards of British Rail 1979–1990 and London Transport 1984–86. He was a member of the Millennium Commission from February 1994 to December 2000, has sat on the Board of Trustees of The Architecture Foundation. From 1985 to 1990, he was deputy chairman of English Heritage. In July 2008, it was announced. Although Jenkins had in the past been critical of some aspects of the Trust's work, he said he was "very pleased" by his appointment, that the Trust was "one of England's great institutions"; as chairman of the National Trust, a post he held until November 2014, Jenkins campaigned vociferously against the building of new houses, although according to housing minister Nick Boles he himself owned "at least two homes". Jenkins married the American actress Gayle Hunnicutt in 1978.
They have since divorced. He married Hannah Kaye in 2014. Jenkins was appointed a Knight Bachelor for services to journalism in the 2004 New Year honours. Simon Jenkins Education and Labour's Axe, Bow Publications, ISBN 0-900182-79-2 Simon Jenkins Here to Live: Study of Race Relations in an English Town Runnymede Trust, ISBN 0-902397-12-5 Simon Jenkins Landlords to London: Story of a Capital and Its Growth Constable, ISBN 0-09-460150-X Simon Jenkins Newspapers: The Power and the Money Faber, ISBN 0-571-11468-7 Simon Jenkins Newspapers Through the Looking-glass Manchester Statistical Society, ISBN 0-85336-058-8 Simon Jenkins and Andrew Graham-Yooll Imperial Skirmishes: War And Gunboat Diplomacy In Latin America Diane Publishing, ISBN 0-7567-7468-3 Sir Max Hastings and Simon Jenkins Battle for the Falklands M Joseph, ISBN 0-7181-2578-9 Simon Jenkins and Anne Sloman With Respect, Ambassador: Enquiry into the Foreign Office BBC, ISBN 0-563-20329-3 Simon Jenkins The Market for Glory: Fleet Street Ownership in the Twentieth Century Faber and Faber, ISBN 0-571-14627-9 Simon Jenkins and Robert Ilson "The Times" English Style and Usage Guide Times Books ISBN 0-7230-0396-3 Simon Jenkins The Selling of Mar
The Jurassic period was a geologic period and system that spanned 56 million years from the end of the Triassic Period 201.3 million years ago to the beginning of the Cretaceous Period 145 Mya. The Jurassic constitutes the middle period of the Mesozoic Era known as the Age of Reptiles; the start of the period was marked by the major Triassic–Jurassic extinction event. Two other extinction events occurred during the period: the Pliensbachian-Toarcian extinction in the Early Jurassic, the Tithonian event at the end; the Jurassic period is divided into three epochs: Early and Late. In stratigraphy, the Jurassic is divided into the Lower Jurassic, Middle Jurassic, Upper Jurassic series of rock formations; the Jurassic is named after the Jura Mountains within the European Alps, where limestone strata from the period were first identified. By the beginning of the Jurassic, the supercontinent Pangaea had begun rifting into two landmasses: Laurasia to the north, Gondwana to the south; this created more coastlines and shifted the continental climate from dry to humid, many of the arid deserts of the Triassic were replaced by lush rainforests.
On land, the fauna transitioned from the Triassic fauna, dominated by both dinosauromorph and crocodylomorph archosaurs, to one dominated by dinosaurs alone. The first birds appeared during the Jurassic, having evolved from a branch of theropod dinosaurs. Other major events include the appearance of the earliest lizards, the evolution of therian mammals, including primitive placentals. Crocodilians made the transition from a terrestrial to an aquatic mode of life; the oceans were inhabited by marine reptiles such as ichthyosaurs and plesiosaurs, while pterosaurs were the dominant flying vertebrates. The chronostratigraphic term "Jurassic" is directly linked to the Jura Mountains, a mountain range following the course of the France–Switzerland border. During a tour of the region in 1795, Alexander von Humboldt recognized the limestone dominated mountain range of the Jura Mountains as a separate formation that had not been included in the established stratigraphic system defined by Abraham Gottlob Werner, he named it "Jura-Kalkstein" in 1799.
The name "Jura" is derived from the Celtic root *jor via Gaulish *iuris "wooded mountain", borrowed into Latin as a place name, evolved into Juria and Jura. The Jurassic period is divided into three epochs: Early and Late. In stratigraphy, the Jurassic is divided into the Lower Jurassic, Middle Jurassic, Upper Jurassic series of rock formations known as Lias and Malm in Europe; the separation of the term Jurassic into three sections originated with Leopold von Buch. The faunal stages from youngest to oldest are: During the early Jurassic period, the supercontinent Pangaea broke up into the northern supercontinent Laurasia and the southern supercontinent Gondwana; the Jurassic North Atlantic Ocean was narrow, while the South Atlantic did not open until the following Cretaceous period, when Gondwana itself rifted apart. The Tethys Sea closed, the Neotethys basin appeared. Climates were warm, with no evidence of a glacier having appeared; as in the Triassic, there was no land over either pole, no extensive ice caps existed.
The Jurassic geological record is good in western Europe, where extensive marine sequences indicate a time when much of that future landmass was submerged under shallow tropical seas. In contrast, the North American Jurassic record is the poorest of the Mesozoic, with few outcrops at the surface. Though the epicontinental Sundance Sea left marine deposits in parts of the northern plains of the United States and Canada during the late Jurassic, most exposed sediments from this period are continental, such as the alluvial deposits of the Morrison Formation; the Jurassic was a time of calcite sea geochemistry in which low-magnesium calcite was the primary inorganic marine precipitate of calcium carbonate. Carbonate hardgrounds were thus common, along with calcitic ooids, calcitic cements, invertebrate faunas with dominantly calcitic skeletons; the first of several massive batholiths were emplaced in the northern American cordillera beginning in the mid-Jurassic, marking the Nevadan orogeny. Important Jurassic exposures are found in Russia, South America, Japan and the United Kingdom.
In Africa, Early Jurassic strata are distributed in a similar fashion to Late Triassic beds, with more common outcrops in the south and less common fossil beds which are predominated by tracks to the north. As the Jurassic proceeded and more iconic groups of dinosaurs like sauropods and ornithopods proliferated in Africa. Middle Jurassic strata are neither well studied in Africa. Late Jurassic strata are poorly represented apart from the spectacular Tendaguru fauna in Tanzania; the Late Jurassic life of Tendaguru is similar to that found in western North America's Morrison Formation. During the Jurassic period, the primary vertebrates living in the sea were marine reptiles; the latter include ichthyosaurs, which were at the peak of their diversity, plesiosaurs and marine crocodiles of the families Teleosauridae and Metriorhynchidae. Numerous turtles could be found in rivers. In the invertebrate world, several new groups appeared, including rudists (a reef-formi