Red Crag Formation

Red Crag Formation
Stratigraphic range: Late Pliocene - Early Pleistocene ~3.3–2.5 Ma PreꞒ Ꞓ O S D C P T J K Pg N ↓
Red Crag at Bawdsey Cliff in Suffolk
Type	Geological formation
Unit of	Crag Group
Sub-units	Sizewell Member
Underlies	Norwich Crag Formation
Overlies	Coralline Crag Formation or London Clay (unconformity)
Thickness	up to 20 metres (70 ft), locally up to 45 m, offshore up to 70 m
Lithology
Primary	Sand
Location
Region	Europe
Country	England

The Red Crag Formation is a geological formation in England, deposited from the latest Pliocene to the earliest Pleistocene (Gelasian).^[1] It outcrops in south-eastern Suffolk and north-eastern Essex. The name derives from its iron-stained reddish colour and crag which is an East Anglian word for shells. It is part of the Crag Group, a series of notably marine strata which belong to a period when Britain was connected to continental Europe by the Weald–Artois Anticline, and the area in which the Crag Group was deposited was a tidally dominated marine bay.^[2] This bay would have been subjected to enlargement and contraction brought about by transgressions and regressions driven by the 40,000-year Milankovitch cycles.

The sediment in the outcrops mainly consists of coarse-grained and shelly sands that were deposited in sand waves (megaripples) that migrated parallel to the shore in a south-westward direction.^[3] The most common fossils are bivalves and gastropods^[4] that were often worn by the abrasive environment.^[2] The most extensive exposure is found at Bawdsey Cliff, which is designated a Site of Special Scientific Interest (SSSI);^[5] here a width of around 2 kilometres (1.2 miles) of Crag is exposed. At the coastline by Walton-on-the-Naze, remains of megalodon were found.^[6]

The Red Crag Formation at depth in eastern Suffolk clearly has one member, the Sizewell Member, a coarse shelly sand with thin beds of clay and silt.^[7] It was interpreted as having been deposited in large scale sand waves where the sea bed was deeper. The overlying Thorpeness Member, was provisionally assigned to the Red Crag based on its lithology but there is more evidence to suggest that it is part of the Norwich Crag Formation.

It has been proposed that the Red Crag started in the late Pliocene and to have possibly extended up into the early Pleistocene, but there is disagreement on more precise dating. According to the British Geological Survey,^[8] the Red Crag sits within a segment of time from about 3.3 to 2.5 mya. It is considered that the Red Crag at Walton-on-the–Naze is the oldest and that it was deposited in only a few decades at some time between 2.9 and 2.6 mya.^[9] This has led to the UK stratigraphic stage name Waltonian, which is usually correlated with the final Pliocene Reuverian Stage in the Netherlands.^[10] While the precise age of the formation is uncertain, it is generally suggested that deposition of the formation as a whole spanned around 600-800,000 years.^[1] There are difficulties in reconciling how the Red Crag equates with international chronological stages. In particular, the start and end dates are poorly defined due to the general paucity of age-diagnostic stratigraphic indicators and the fragmentary nature of the geology. It can also be difficult to separate the Red Crag from the overlying Norwich Crag Formation.

The base of the formation contains a nodule-rich bed (termed the "Nodule Bed", or "Coprolite Bed") with fossils including terrestrial vertebrates (as well as marine fossils such as those of whales and shark teeth), some of which were reworked from deposits considerably older than the Red Crag Formation itself and often display abrasion and polish indicating reworking.^[11] While some of these animals are as old as the Eocene (such as Hyracotherium and Coryphodon, originating from the London Clay),^[12] most originate from the Pliocene and late Miocene, at least as early as MN 11-12, around 9-7 million years ago in the case of some species.^[11] The presence of monkeys and other thermophilic species implies that during the late Miocene-early Pliocene, the region was probably considerably warmer than today, and had a subtropical climate.^[11] During the Late Pliocene, the region is thought to have had a temperate climate.^[13] The Red Crag also contains Early Pleistocene fossils of animals similar in age to the formation itself, though terrestrial vertebrate fossils from the rest of the Red Crag are considerably rarer than those from the nodule bed.^[12] The phosphatic nodules and bones in the bed were historically during the mid-late 19th century ground up on industrial scales to use as fertilizer.^[14]

Genus/species	Locality	Notes	Image
"Mammut" borsoni[12][13]	Nodule Bed	A member of the family Mammutidae, closely related to the American mastodon (Mammut americanum). One of the largest land mammals ever, originates from Pliocene deposits
Anancus arvernensis[11]	Nodule Bed and higher stratigraphic layers	A "tetralophodont gomphothere", related to elephants, dating to the Pliocene-Early Pleistocene
Mammuthus rumanus[13]		The oldest mammoth species known outside of Africa, dating to the Pliocene
Mammuthus meridionalis[15]		A large mammoth dating to the Early Pleistocene

Genus/species	Locality	Notes	Image
Proboscidipparion sp.[16]	Nodule Bed	Known from teeth. A three toed equine belonging to the extinct tribe Hipparionini. Suggested to be Pliocene in age. Previously referred to as "Hipparion" crassum. Although previously hipparionine teeth remains from the Red Crag have been attributed to other genera, including Plesiohipparion and Hipparion sensu lato, a 2021 paper suggested that all hipparionine remains from the Red Crag may represent Proboscidipparion.[16]
Plesiohipparion rocinantis[17]	Nodule Bed	A three toed equine belonging to the extinct tribe Hipparionini. Suggested to be late Pliocene in age
Equus major[17]		A large equine of Early Pleistocene age
Stephanorhinus etruscus[13]		A rhinoceros belonging to the extinct genus Stephanorhinus, dating to the Late Pliocene-Early Pleistocene
Tapirus arvernensis[13]	Nodule Bed	An extinct tapir belonging to the genus Tapirus, dating to the Pliocene
Dasychoerus arvernensis[11]	Nodule Bed	An extinct swine (Suidae) dating to the Late Pliocene (MN zone 16),[11] related to living African giant forest hogs.[18]
Hippopotamodon sp.[11]	Nodule Bed	A swine (Suidae) either representing the species H. erymanthius or H. major, likely originate from the Late Miocene (MN zone 11-12, around 9-7 million years ago).
Parabos sp.[13]		A bovine
Cervus perrieri[13][15]	Nodule Bed	A large deer dating to the Pliocene, also known as Praeelaphus perrieri
Metacervocerus pardinensis[13][15]	Nodule Bed	A medium sized deer dating to the Pliocene, also referred to as Cervus pardinensis
Procapreolus cusanus[13][15]	Nodule Bed	A small deer dating to the Pliocene
Eucladoceros falconeri[15]	Red Crag proper	A deer of Early Pleistocene age
Gazella sp.[12]		A gazelle of Early Pleistocene age
Leptobos etruscus[19]	Nodule Bed	A bovine of Pliocene age closely related to living bison.

Genus/species	Locality	Notes	Image
Mesopithecus sp.[11]	Nodule Bed	Known from a single tooth. A monkey belonging to the subfamily Colobinae, related to living African colobus monkeys and Asian langurs. Possibly of Late Miocene-Early Pliocene age.
Macaca sp.[11]		An indeterminate macaque known from a tooth, possibly of Early Pliocene age. Has affinities with the Barbary macaque (Macaca sylvanus), which has a fossil record in Europe spanning the Pliocene and into the Pleistocene.

Genus/species	Locality	Notes	Image
Hystrix sp.[12]		An Old World porcupine, of Early Pleistocene age
Castor fiber[12]		Commonly known as the Eurasian beaver, species extant, remains are of Early Pleistocene age
Trogontherium minus [20]	Nodule Bed	A member of the beaver family (Castoridae) belonging to the extinct genus Trogontherium, of Pliocene-Early Pleistocene age

Genus/species	Locality	Notes	Image
Parailurus anglicus[11]		A member of the family Ailuridae, closely related to the living red panda, of Pliocene age
Pliocrocuta perrieri[21]		A large bone cracking hyena, of Pliocene-Early Pleistocene age
Ursidae indet.[21]		A large bear
Ontocetus emmonsi[22]		An extinct genus of pinniped in the family Odobenidae, related to the living walrus. Known from tusks. Previously referred to as Odobenus huxleyi and Trichecodon huxleyi

Genus/species	Locality	Notes	Image
Otodus megalodon[27]		Known from a tooth. A giant macropredatory shark, the largest shark ever
Micromesistius poutassou[28]		Known from an otolith. Commonly known as blue whiting, species extant

Over 240 mollusc species have been described from the Red Crag, making the table below only a small fraction of the total number of invertebrates.^[29]

Genus/species	Locality	Notes	Image
Glycymeris glycymeris[30]		Commonly known as a "dog cockle", belongs to the bittersweet clam family Glycymerididae, species extant
Tapes [31]		A saltwater clam
Spisula[31]		A surf clam
Macoma[31]		A saltwater clam, includes extinct species
Mya arenaria[30]		Commonly known as the soft-shell clam, species extant
Mytilus edulis[30]		Commonly known as the blue mussel, species extant
Varicorbula gibba[31]		A bivalve commonly known as a basket shell, species extant
Venerupis [31]		A bivalve commonly known as carpet shells
Neptunea contraria[31]		A true whelk, species extant though with a much more southerly modern range
Nucella lapillus[30]		Commonly known as the dog whelk, species extant
Cerastoderma edule[30]		Known as the common cockle, species extant
Anomia[31]		A saltwater clam,
Buccinum[31]		A true whelk
Capulus[31]		A cap snail
Calyptraea chinensis[30]		A superficially limpet-like gastropod, commonly known as the Chinese hat snail, species extant
Emarginula crassa[30]		A species of keyhole limpet, still extant
Venus casina[30]		A saltwater clam, species extant
Aporrhais pespelecani[30]		A gastropod, species extant
Turritella communis[30]		A sea snail, species extant
Euspira catena[30]		A sea snail, commonly known as the large necklace shell, species extant
Colus gracilis[30]		A sea snail, species extant
Ensis[31]		A razor clam
Terebratula[31]		A terebratulid brachiopod

• Cromer Forest Bed fossiliferous Pleistocene deposit in Norfolk, England

• Lee, J. R.; Woods, M. A.; Moorlock, B. S. P., eds. (2015). British Regional Geology: East Anglia (5th ed.). British Geological Survey. ISBN 978-0-85272-823-9.

51°59′58″N 1°25′16″E / 51.9994°N 1.4211°E / 51.9994; 1.4211