The Bracklesham Group (formerly Bracklesham Beds), in
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 ...
, is a series of
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
marl
Marl is an earthy material rich in carbonate minerals, clays, and silt. When hardened into rock, this becomes marlstone. It is formed in marine or freshwater environments, often through the activities of algae.
Marl makes up the lower part o ...
s, with sandy and
lignitic beds, in the middle
Eocene
The Eocene ( ) Epoch is a geological epoch (geology), epoch that lasted from about 56 to 33.9 million years ago (mya). It is the second epoch of the Paleogene Period (geology), Period in the modern Cenozoic Era (geology), Era. The name ''Eocene' ...
of the
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 yo ...
and
London Basin
The London Basin is an elongated, roughly triangular sedimentary basin approximately 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 compre ...
of
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 ...
.
The type section of the Bracklesham Group is the sea cliffs at
Whitecliff Bay
Whitecliff Bay is a sandy bay near Foreland which is the easternmost point of the Isle of Wight, England, about two miles south-west of Bembridge and just to the north of Culver Down. The bay has a shoreline of around and has a popular sandy ...
on 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 Isle of ...
, and it is also well developed on the mainland. The Group gets its name from a section at
Bracklesham in
Sussex
Sussex (), from the Old English (), is a historic county in South East England that was formerly an independent medieval Anglo-Saxon kingdom. It is bounded to the west by Hampshire, north by Surrey, northeast by Kent, south by the English ...
. The thickness of the deposit is around 120 m.
Fossil
A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserved ...
mollusca
Mollusca is the second-largest phylum of invertebrate animals after the Arthropoda, the members of which are known as molluscs or mollusks (). Around 85,000 extant species of molluscs are recognized. The number of fossil species is esti ...
are abundant, and
fossil fish
The evolution of fish began about 530 million years ago during the Cambrian explosion. It was during this time that the early chordates developed the skull and the vertebral column, leading to the first craniates and vertebrates. The first fish ...
are to be found, as well as ''
Palaeophis
''Palaeophis'' ('ancient snake') is an extinct genus of marine snake that is the type genus of the extinct snake family Palaeophiidae.
Described species within this genus lived in the Eocene epoch, with some unnamed or questionable records from ...
'', a sea-snake, and ''
Puppigerus
''Puppigerus'' is an extinct genus of sea turtle from the Eocene. It is known from finds in the United States, the United Kingdom, Belgium, Denmark, and Uzbekistan.
Taxonomy
''Puppigerus'' was described by Edward Drinker Cope in 1870. As of 1997 ...
'', a
sea turtle
Sea turtles (superfamily Chelonioidea), sometimes called marine turtles, are reptiles of the order Testudines and of the suborder Cryptodira. The seven existing species of sea turtles are the flatback, green, hawksbill, leatherback, loggerhead, ...
.
Nummulite
A nummulite is a large lenticular fossil, characterized by its numerous coils, subdivided by septa into chambers. They are the shells of the fossil and present-day marine protozoan ''Nummulites'', a type of foraminiferan. Nummulites commonly vary ...
s and other
foraminifera
Foraminifera (; Latin for "hole bearers"; informally called "forams") are single-celled organisms, members of a phylum or class of amoeboid protists characterized by streaming granular Ectoplasm (cell biology), ectoplasm for catching food and ot ...
also occur.
The Bracklesham Group lies between the
Barton Clay above and the Bournemouth Beds,
Lower Bagshot, below. In the London Basin, these beds are represented only by thin sandy clays in the Middle Bagshot group. In the
Paris Basin
The Paris Basin is one of the major geological regions of France. It developed since the Triassic over remnant uplands of the Variscan orogeny (Hercynian orogeny). The sedimentary basin, no longer a single drainage basin, is a large sag in the cr ...
the "Calcaire grossier" lies upon the same geological horizon.
References
;Attribution
* This cites:
**F. Dixon, ''Geology of Sussex'' (new ed., 1878)
**F. E. Edwards and
SV Wood, ''Monograph of Eocene Mollusca'', Palaeontographical Soc. vol. i. (1847–1877)
**''Geology of the Isle of Wight'', ''Mem. Geol. Survey'' (2nd ed., 1889)
**C. Reid, ''The Geology of the Country around Southampton'', Mem. Geol. Survey (1902).
New Forest Geology Guide
Geological groups of the United Kingdom
Eocene Series of Europe
Paleogene England
Lithostratigraphy of England
{{UK-geologic-formation-stub