Dean Hill Anticline

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The Dean Hill Anticline is an east-west trending fold in the Cretaceous chalk of Hampshire. It lies immediately to the north of the Hampshire Basin and south of Salisbury Plain.

Fold (geology) fold in geology

In structural geology, geological fold occurs when one or a stack of originally flat and planar surfaces, such as sedimentary strata, are bent or curved as a result of permanent deformation. Synsedimentary folds are those due to slumping of sedimentary material before it is lithified. Folds in rocks vary in size from microscopic crinkles to mountain-sized folds. They occur singly as isolated folds and in extensive fold trains of different sizes, on a variety of scales.

The Cretaceous is a geologic period and system that spans 79 million years from the end of the Jurassic Period 145 million years ago (mya) to the beginning of the Paleogene Period 66 mya. It is the last period of the Mesozoic Era, and the longest period of the Phanerozoic Eon. The Cretaceous Period is usually abbreviated K, for its German translation Kreide.

Chalk A soft, white, porous sedimentary rock made of calcium carbonate

Chalk is a soft, white, porous, sedimentary carbonate rock, a form of limestone composed of the mineral calcite. Calcite is an ionic salt called calcium carbonate or CaCO3. It forms under reasonably deep marine conditions from the gradual accumulation of minute calcite shells (coccoliths) shed from micro-organisms called coccolithophores. Flint (a type of chert) is very common as bands parallel to the bedding or as nodules embedded in chalk. It is probably derived from sponge spicules or other siliceous organisms as water is expelled upwards during compaction. Flint is often deposited around larger fossils such as Echinoidea which may be silicified (i.e. replaced molecule by molecule by flint).

Contents

Structure

The anticline runs west 15 kilometres (9.3 mi) from the River Test near Lockerley along the northern rim of the Hampshire Basin, to the south of a narrow strip of palaeogene rocks, the Alderbury-Mottisfont Syncline. [1] [2] At the eastern end under the Test Valley it is cut by the northward-swinging Portsdown Anticline. At the western end to the south-east of Salisbury the structure is cut by the Mere Fault. [3]

Anticline geological term

In structural geology, an anticline is a type of fold that is an arch-like shape and has its oldest beds at its core. A typical anticline is convex up in which the hinge or crest is the location where the curvature is greatest, and the limbs are the sides of the fold that dip away from the hinge. Anticlines can be recognized and differentiated from antiforms by a sequence of rock layers that become progressively older toward the center of the fold. Therefore, if age relationships between various rock strata are unknown, the term antiform should be used.

River Test river in Hampshire, England

The River Test is a river in Hampshire, England. It has a total length of 40 miles (64 km) and it flows through downland from its source near Ashe to its estuary at Southampton, where it converges with the River Itchen to form Southampton Water. In its upper reaches it is a chalk stream, and is used for fly fishing for trout.

Lockerley village in United Kingdom

Lockerley is a village and civil parish in Hampshire, England on the border with Wiltshire. The village lies on the southern bank of the River Dun about two miles upstream from its confluence with the River Test and about 4 kilometres (2.5 mi) east of West Dean which is just over the Wiltshire border. The parish has a population of around 827 people. The nearest town is Romsey, about 8 kilometres (5 mi) to the south-east and is about 13 miles from Salisbury.

In the core the Santonian Newhaven Chalk Formation reaches the surface. [1] [2] In the outer limits near Whiteparish chalk as young as the Campanian Portsdown Chalk Formation is found.

The Santonian is an age in the geologic timescale or a chronostratigraphic stage. It is a subdivision of the Late Cretaceous epoch or Upper Cretaceous series. It spans the time between 86.3 ± 0.7 mya and 83.6 ± 0.7 mya. The Santonian is preceded by the Coniacian and is followed by the Campanian.

Whiteparish village in United Kingdom

Whiteparish is a village and civil parish on the A27 about 7.5 miles (12.1 km) southeast of Salisbury in Wiltshire, England. The village is about 1.5 miles (2.4 km) from the county boundary with Hampshire. The parish includes the hamlets of Cowesfield Green and Newton.

The Campanian is the fifth of six ages of the Late Cretaceous epoch on the geologic timescale of the International Commission on Stratigraphy (ICS). In chronostratigraphy, it is the fifth of six stages in the Upper Cretaceous series. Campanian spans the time from 83.6 to 72.1 million years ago. It is preceded by the Santonian and it is followed by the Maastrichtian.

Hills include Witherington Down, Pepperbox Hill and Dean Hill.

See also

List of geological folds in Great Britain

Related Research Articles

Chalk Group

The Chalk Group is the lithostratigraphic unit which contains the Late Cretaceous limestone succession in southern and eastern England. The same or similar rock sequences occur across the wider northwest European chalk 'province'. It is characterised by thick deposits of chalk, a soft porous white limestone, deposited in a marine environment.

The geology of Hampshire in southern England broadly comprises a gently folded succession of sedimentary rocks dating from the Cretaceous and Palaeogene periods. The lower (early) Cretaceous rocks are sandstones and mudstones whilst those of the upper (late) Cretaceous are the various formations which comprise the Chalk Group and give rise to the county's downlands. Overlying these rocks are the less consolidated Palaeogene clays, sands, gravels and silts of the Lambeth, Thames and Bracklesham Groups which characterise the Hampshire Basin.

Twyford, Hampshire village and civil parish in Hampshire, England

Twyford is a village and civil parish in Hampshire, England, approximately three miles south of Winchester and near the M3 motorway and Twyford Down. In 2001, the population of the parish was 1,456. The village and parish are on the left bank of the Itchen, which passes through nearby watermeadows, and has been important economically for its residents.

Fair Oak village in the United Kingdom

Fair Oak, Hampshire is a large village on the outskirts of Eastleigh, and near Southampton and Winchester. Its parish incorporates the neighbouring village of Horton Heath, which lies to the south.

Owslebury village in the United Kingdom

Owslebury is a village and civil parish in the county of Hampshire, in the south of England approximately 5 miles (8.0 km) outside Winchester. It lies within the administrative district of the City of Winchester.

Compton and Shawford civil parish in the City of Winchester, Hampshire, England

Compton and Shawford is a civil parish in the City of Winchester, Hampshire, England. The word compton means village in a combe and aptly describes the settlement as it primarily consists of a long street on the side of a chalk valley.

Beacon Hill, Warnford, Hampshire is a chalk hill in the South Downs on the boundary of the parishes of Warnford and Exton. Part of the hill is a national nature reserve and 44.8 hectares biological SSSI, first notified in 1979.

Chilcomb village in the United Kingdom

Chilcomb is a small village and civil parish in the English county of Hampshire 3 miles (4.8 km) east of Winchester and includes the South Downs Way long distance footpath.

St. Catherines Hill, Hampshire hillfort in Hampshire

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London Basin

The London Basin is an elongated, roughly triangular sedimentary basin approximately 250 kilometres (160 mi) long which underlies London and a large area of south east England, south eastern East Anglia and the adjacent North Sea. The basin formed as a result of compressional tectonics related to the Alpine orogeny during the Palaeogene period and was mainly active between 40 and 60 million years ago.

Hampshire Basin

The Hampshire Basin is a geological basin of Palaeogene age in southern England, underlying parts of Hampshire, the Isle of Wight, Dorset, and Sussex. Like the London Basin to the northeast, it is filled with sands and clays of Paleocene and younger ages and it is surrounded by a broken rim of chalk hills of Cretaceous age.

Geology of East Sussex

The geology of East Sussex is defined by the Weald–Artois anticline, a 60 kilometres (37 mi) wide and 100 kilometres (62 mi) long fold within which caused the arching up of the chalk into a broad dome within the middle Miocene, which has subsequently been eroded to reveal a lower Cretaceous to Upper Jurassic stratigraphy. East Sussex is best known geologically for the identification of the first dinosaur by Gideon Mantell, near Cuckfield, to the famous hoax of the Piltdown man near Uckfield.

The Winchester-East Meon Anticline is one of a series of parallel east-west trending folds in the Cretaceous chalk of Hampshire. It lies at the western end of the South Downs, immediately to the north of the Hampshire Basin and south-east of Salisbury Plain.

The Winchester-King's Somborne Syncline is one of a series of parallel east-west trending folds in the Cretaceous chalk of Hampshire. It lies at the western end of the South Downs, immediately to the north of the Winchester-East Meon Anticline and east of Salisbury Plain.

The Stockbridge Anticline is one of a series of parallel east-west trending folds in the Cretaceous chalk of Hampshire. It lies at the western end of the South Downs, immediately to the north of the Winchester-King's Somborne Syncline and east of Salisbury Plain.

The Micheldever Syncline is one of a series of parallel east-west trending folds in the Cretaceous chalk of Hampshire. It lies at the western end of the South Downs, immediately to the north of the Stockbridge Anticline and east of Salisbury Plain.

The Alderbury-Mottisfont Syncline is an east-west trending fold in the Cretaceous chalk of Hampshire. It lies to the north of the Dean Hill Anticline and south of Salisbury Plain.

The geology of West Sussex in southeast England comprises a succession of sedimentary rocks of Cretaceous age overlain in the south by sediments of Palaeogene age. The sequence of strata from both periods consists of a variety of sandstones, mudstones, siltstones and limestones. These sediments were deposited within the Hampshire and Weald basins. Erosion subsequent to large scale but gentle folding associated with the Alpine Orogeny has resulted in the present outcrop pattern across the county, dominated by the north facing chalk scarp of the South Downs. The bedrock is overlain by a suite of Quaternary deposits of varied origin. Parts of both the bedrock and these superficial deposits have been worked for a variety of minerals for use in construction, industry and agriculture.

The Portsdown Anticline is a north-facing geological fold of Tertiary age affecting rocks in Hampshire, southern England. This upfold of the local sedimentary rock sequence is paralleled by the Bere Forest/Chichester Syncline (downfold) about 2km to its north and a postulated deep fault to the north again. Further west, this major east-west structure adopts more of a NW - SE alignment. At the surface the Portsdown Anticline is seen to affect the Chalk rocks of Late Cretaceous age at Ports Down though it is known to also affect the underlying Jurassic strata.

This article describes the geology of the New Forest, a national park in Hampshire, in southern England.

References

  1. 1 2 Salisbury (Map). 1:50000. British Geological Survey England and Wales. British Geological Survey. 2005. ISBN   0-7518-3425-4.
  2. 1 2 Winchester (Map). 1:50000. British Geological Survey England and Wales. British Geological Survey. 2002. ISBN   0-7518-3340-1.
  3. ↑ Melville, R.V. (1982). Hampshire Basin and adjoining areas. British Regional Geology (4 ed.). British Geological Survey. ISBN   0852726503.
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