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

, the Bagshot Beds are a series of

sand Sand is a granular material composed of finely divided mineral particles. Sand has various compositions but is defined by its grain size. Sand grains are smaller than gravel and coarser than silt. Sand can also refer to a textural class ...

s and

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 pa ...

s of shallow-water origin, some being fresh-water, some marine. They belong to the upper

Eocene The Eocene ( ) Epoch is a geological epoch that lasted from about 56 to 33.9 million years ago (mya). It is the second epoch of the Paleogene Period in the modern Cenozoic Era. The name ''Eocene'' comes from the Ancient Greek (''ēṓs'', ...

formation of the

London London is the capital and List of urban areas in the United Kingdom, largest city of England and the United Kingdom, with a population of just under 9 million. It stands on the River Thames in south-east England at the head of a estuary dow ...

and Hampshire basins, in

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 ...

and derive their name from Bagshot Heath in Surrey. They are also well developed in

Hampshire Hampshire (, ; abbreviated to Hants) is a ceremonial and non-metropolitan county in western South East England on the coast of the English Channel. Home to two major English cities on its south coast, Southampton and Portsmouth, Hampshire ...

Berkshire Berkshire ( ; in the 17th century sometimes spelt phonetically as Barkeshire; abbreviated Berks.) is a historic county in South East England. One of the home counties, Berkshire was recognised by Queen Elizabeth II as the Royal County of Ber ...

and the

Isle of Wight The Isle of Wight ( ) is a county in the English Channel, off the coast of Hampshire, from which it is separated by the Solent. It is the largest and second-most populous island of England. Referred to as 'The Island' by residents, the Is ...

. The following divisions are generally accepted: *Upper Bagshot Beds — Barton sand and Barton clay. *Middle Bagshot Beds — Bracklesham Beds. *Lower Bagshot Beds — Bournemouth Beds and Alum Bay Beds. The lower division consists of pale-yellow, current-bedded sand and

loam Loam (in geology and soil science) is soil composed mostly of sand ( particle size > ), silt (particle size > ), and a smaller amount of clay (particle size < ). By weight, its mineral composition is about 40–40–20% concentration of sand–si ...

, with layers of pipeclay and occasional beds of

flint Flint, occasionally flintstone, is a sedimentary cryptocrystalline form of the mineral quartz, categorized as the variety of chert that occurs in chalk or marly limestone. Flint was widely used historically to make stone tools and start ...

pebbles. In the London basin, wherever the junction of the Bagshot beds with the London clay is exposed, it is clear that no sharp line can be drawn between these formations. The Lower Bagshot Beds may be observed at Brentwood, Billericay and High Beach in

Essex Essex () is a Ceremonial counties of England, county in the East of England. One of the home counties, it borders Suffolk and Cambridgeshire to the north, the North Sea to the east, Hertfordshire to the west, Kent across the estuary of the Riv ...

; outliers, capping hills of

London clay The London Clay Formation is a marine geological formation of Ypresian (early Eocene Epoch, c. 56–49 million years ago) age which crops out in the southeast of England. The London Clay is well known for its fossil content. The fossils from ...

, occur at

Hampstead Hampstead () is an area in London, which lies northwest of Charing Cross, and extends from the A5 road (Roman Watling Street) to Hampstead Heath, a large, hilly expanse of parkland. The area forms the northwest part of the London Borough o ...

Highgate Highgate ( ) is a suburban area of north London at the northeastern corner of Hampstead Heath, north-northwest of Charing Cross. Highgate is one of the most expensive London suburbs in which to live. It has two active conservation organisat ...

and Harrow. In Surrey, considerable tracts of London clay are covered by heath-bearing Lower Bagshot Beds, as at

Weybridge Weybridge () is a town in the Borough of Elmbridge in Surrey, England, around southwest of central London. The settlement is recorded as ''Waigebrugge'' and ''Weibrugge'' in the 7th century and the name derives from a crossing point of the ...

Aldershot Aldershot () is a town in Hampshire, England. It lies on heathland in the extreme northeast corner of the county, southwest of London. The area is administered by Rushmoor Borough Council. The town has a population of 37,131, while the Alder ...

Woking Woking ( ) is a town and borough status in the United Kingdom, borough in northwest Surrey, England, around from central London. It appears in Domesday Book as ''Wochinges'' and its name probably derives from that of a Anglo-Saxon settlement o ...

etc. The Ramsdell clay, N.W. of

Basingstoke Basingstoke ( ) is the largest town in the county of Hampshire. It is situated in south-central England and lies across a valley at the source of the River Loddon, at the far western edge of The North Downs. It is located north-east of Southa ...

, belongs to this formation. In the Isle of Wight, the lower division is well exposed at Alum Bay (200 m.) and White Cliff Bay (140 ft.). Here it consists of unfossiliferous sands (white, yellow, brown, crimson and every intermediate shade) and clays with layers of

lignite Lignite, often referred to as brown coal, is a soft, brown, combustible, sedimentary rock formed from naturally compressed peat. It has a carbon content around 25–35%, and is considered the lowest rank of coal due to its relatively low heat ...

and ferruginous

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 silicat ...

. Similar beds are visible at

Bournemouth Bournemouth () is a coastal resort town in the Bournemouth, Christchurch and Poole council area of Dorset, England. At the 2011 census, the town had a population of 183,491, making it the largest town in Dorset. It is situated on the English ...

and in the neighborhood of

Poole Poole () is a large coastal town and seaport in Dorset, on the south coast of England. The town is east of Dorchester and adjoins Bournemouth to the east. Since 1 April 2019, the local authority is Bournemouth, Christchurch and Poole Counc ...

, Wareham, Corfe Castle and

Studland Studland is a village and civil parish on the Isle of Purbeck in Dorset, England. The village is located about north of the town of Swanage, over a steep chalk ridge, and south of the South East Dorset conurbation at Sandbanks, from which it ...

. The leaf-bearing clays of Alum Bay and Bournemouth are well known and have yielded a large and interesting series of plant remains, including ''

Eucalyptus ''Eucalyptus'' () is a genus of over seven hundred species of flowering trees, shrubs or mallees in the myrtle family, Myrtaceae. Along with several other genera in the tribe Eucalypteae, including '' Corymbia'', they are commonly known as ...

'', '' Caesalpinia'', ''

Populus ''Populus'' is a genus of 25–30 species of deciduous flowering plants in the family Salicaceae, native to most of the Northern Hemisphere. English names variously applied to different species include poplar (), aspen, and cottonwood. The we ...

'', ''

Platanus ''Platanus'' is a genus consisting of a small number of tree species native to the Northern Hemisphere. They are the sole living members of the family Platanaceae. All mature members of ''Platanus'' are tall, reaching in height. All excep ...

'', ''Sequoia'', ''

Aralia ''Aralia'' , or spikenard, is a genus of the family Araliaceae, consisting of 68 accepted species of deciduous or evergreen trees, shrubs, and rhizomatous herbaceous perennials. The genus is native to Asia and the Americas, with most specie ...

'', '' Polypodium'', '' Osmunda'', '' Nipadites'' and many others. The clays of this formation are of great value for pottery manufacture; they are extensively mined near Wareham and Corfe, whence they are shipped from Poole and are consequently known as 'Poole clays'. Alum was formerly obtained from the clays of Alum Bay; and the lignites have been used as fuel near Corfe and at Bovey. The Bracklesham Beds are sometimes classed with the overlying Barton clay as Middle Bagshot. In the London basin the Barton Beds are unknown. In Surrey and Berkshire, the Bracklesham Beds are from 20 to 50 ft. thick; in Alum Bay they are 100 ft., with beds of lignite in the lower portion; and about here they are sharply marked off from the Barton clay by a bed of conglomerate formed of flint pebbles. The Upper Bagshot Beds, Barton sand and Barton clay, are from 140 to 200 ft. thick in the Isle of Wight. The Agglestone (or Haggerstone) rock and Puckstone rock, near Studland in

Dorset Dorset ( ; archaically: Dorsetshire , ) is a county in South West England on the English Channel coast. The ceremonial county comprises the unitary authority areas of Bournemouth, Christchurch and Poole and Dorset. Covering an area of , ...

are formed of large indurated masses of the Lower Bagshot beds that have resisted the weather; Creechbarrow near Corfe is another striking feature due to the same beds. Many of the

sarsen Sarsen stones are silicified sandstone blocks found in quantity in Southern England on Salisbury Plain and the Marlborough Downs in Wiltshire; in Kent; and in smaller quantities in Berkshire, Essex, Oxfordshire, Dorset, and Hampshire. Geo ...

stones or greywethers of S.E. England have been derived from Bagshot strata.

References

{{EB1911 article with no significant updates Geologic formations of England Paleogene England Ypresian Stage Geography of Surrey