Wealden Group

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Wealden Group
Stratigraphic range:
Late Berriasian-Aptian, 140–125  Ma
Cliffs by beach at Bexhill-on-Sea in England - 2008-07-13 D.jpg
Coastal exposure of the Wealden Group near Bexhill-on-Sea
Type Group
Sub-units
Underlies Lower Greensand Group
Overlies Purbeck Group
ThicknessUp to 850 m in Weald Basin, c. 500 m in Wessex basin, few m in marginal areas
Location
Region England
CountryFlag of the United Kingdom.svg  UK
Type section
Named for Weald

The Wealden Group, occasionally also referred to as the Wealden Supergroup, is a group (a sequence of rock strata) in the lithostratigraphy of southern England. The Wealden group consists of paralic to continental (freshwater) facies sedimentary rocks of Berriasian to Aptian age and thus forms part of the English Lower Cretaceous. It is composed of alternating sands and clays. The sandy units were deposited in a flood plain of braided rivers, the clays mostly in a lagoonal coastal plain. [1]

Contents

The Wealden Group can be found in almost all Early Cretaceous basins of England: its outcrops curve from the Wessex Basin in the south to the Cleveland Basin in the northeast. It is not found in northwest England and Wales, areas which were at the time tectonic highs where no deposition took place. The same is true for the London Platform around London and Essex. Offshore, the Wealden Group can reach a thickness of 700 metres. [1] The terms Wealden and Wealden facies are also used as generic terms referring to Early Cretaceous non-marine sequences elsewhere in Europe.

Stratigraphy

The Wealden Group lies stratigraphically on top of the Purbeck Group, which spans the Jurassic-Cretaceous boundary. Within the Wessex Basin, the Wealden Group consists of two formations: the Wessex Formation and overlying Vectis Formation. In the Weald Basin, the Wealden Group consists of four formations: the Ashdown Formation, the Wadhurst Clay Formation, the Tunbridge Wells Sand Formation and the Weald Clay Formation. [2] The lower three formations are sometimes collectively referred to as the Hastings Beds. In Oxfordshire, Buckinghamshire and Wiltshire, the Wealden Group is only found as an outlier on top of hills and only consists of a single formation, the Whitchurch Sand Formation. In Yorkshire, the equivalently aged Speeton Clay Formation, a marine unit, is present.

On top of the Wealden Group is the Lower Greensand Group. The difference between these two groups has been formed by a major eustatic (global) transgression of the sea. The Greensand (Aptian/Albian in age) consists of marine deposits.

The sequence in the Weald Basin has also been described as a supergroup, containing the Weald Clay Group and Hastings Group. [3]

Palaeontology

The Wealden Group forms outcrops covering a large part of south and south-eastern England including the Isle of Wight. It takes its name from the Weald region of Kent, Sussex, Surrey and Hampshire. It has yielded many fossils, including dinosaurs like Iguanodon and Hypsilophodon . [4] Apart from fossils, it shows many other signs of being deposited in a continental environment, such as mudcracks and -in some rare cases- dinosaur footprints. Taxa included in the table below have an uncertain provenance and cannot be placed into one of the constituent formations, thus they are placed here.

Pterosaurs

Pterosaurs reported from the Wealden Group
GenusSpeciesLocationStratigraphic positionMaterialNotesImages
Coloborhynchus C. clavirostris [5]
  • St.-Leonards-on-Sea [5]
Hastings Beds"Anterior portion of rostrum" [5] An ornithocheirid pterosaur.
Coloborhynchus Coloborhynchus piscator jconway.jpg
Coloborhynchus

Dinosaurs

Dinosaurs reported from the Wealden Group
GenusSpeciesLocationStratigraphic positionMaterialNotesImages
Thecospondylus [6] T. horneri [6] Hastings Beds"Internal mold of sacrum." [7] Dubious genus that has been variously classified as either a saurischian or ornithischian. [8] It is currently only tentatively regarded as dinosaurian. [6]
Thecospondylus.jpg
Therosaurus [9] T. anglicus [9]
  • West Sussex [9]
Altispinax [10] A. dunkeri [10] Hastings Beds"Dorsal vertebrae." [11]
Becklespinax.jpg
Haestasaurus [12] H. becklesii [10] Hastings BedsForelimbA ?basal macronarian

Haestasaurus.PNG

Pleurocoelus [13] P. valdensis [13] A dubious basal titanosauriform [13]
Turiasauria IndeterminateHasting beds? [14] Vertebra [14]
Theropoda Indeterminate
  • West Sussex, East Sussex, Kent [15]
Xenoposeidon X. proneneukosA rebbachisaurid sauropod

Wealden elsewhere in Europe

The term "Wealden" and "Wealden facies" has been applied to other Lower Cretaceous sequences in Europe, including the "German Wealden", comprising the Berriasian aged Bückeberg Formation of the Lower Saxony Basin [16] and in Belgium, where "Wealden facies" has been used as a term to refer to the Barremian-Aptian aged sequences of the Mons Basin, including the Sainte-Barbe Clays Formation where large numbers of Iguanodon were found in the 19th century. [17]

Related Research Articles

<i>Valdosaurus</i> Extinct genus of dinosaurs

Valdosaurus is a genus of bipedal herbivorous iguanodont ornithopod dinosaur found on the Isle of Wight and elsewhere in England, Spain and possibly also Romania. It lived during the Early Cretaceous.

<span class="mw-page-title-main">Weald Clay</span> Geological formation in England

Weald Clay or the Weald Clay Formation is a Lower Cretaceous sedimentary rock unit underlying areas of South East England, between the North and South Downs, in an area called the Weald Basin. It is the uppermost unit of the Wealden Group of rocks within the Weald Basin, and the upper portion of the unit is equivalent in age to the exposed portion of the Wessex Formation on the Isle of Wight. It predominantly consists of thinly bedded mudstone. The un-weathered form is blue/grey, and the yellow/orange is the weathered form, it is used in brickmaking.

<i>Eotyrannus</i> Extinct genus of dinosaurs

Eotyrannus is a genus of tyrannosauroid theropod dinosaur hailing from the Early Cretaceous Wessex Formation beds, included in Wealden Group, located in the southwest coast of the Isle of Wight, United Kingdom. The remains (MIWG1997.550), consisting of assorted skull, axial skeleton and appendicular skeleton elements, from a juvenile or subadult, found in a plant debris clay bed, were described by Hutt et al. in early 2001. The etymology of the generic name refers to the animal's classification as an early tyrannosaur or "tyrant lizard", while the specific name honors the discoverer of the fossil.

<span class="mw-page-title-main">Purbeck Group</span> Stratigraphic Group in England

The Purbeck Group is an Upper Jurassic to Lower Cretaceous lithostratigraphic group in south-east England. The name is derived from the district known as the Isle of Purbeck in Dorset where the strata are exposed in the cliffs west of Swanage.

<i>Yaverlandia</i> Extinct genus of dinosaurs

Yaverlandia is a genus of maniraptoran dinosaur. Known from a partial fossil skull found in Lower Cretaceous strata of the Wessex Formation on the Isle of Wight. it was described as the earliest known member of the pachycephalosaurid family, but research by Darren Naish shows it to have actually been a theropod, seemingly a maniraptoran. The type species is Y. bitholus.

<span class="mw-page-title-main">Lohan Cura Formation</span> Geologic formation in Argentina

The Lohan Cura Formation is a geologic formation with outcrops in the Argentine provinces of Río Negro, Neuquén, and Mendoza. It is the second oldest Cretaceous terrestrial formation in the Neuquén Basin.

<span class="mw-page-title-main">Arundel Formation</span> Geological formation in Maryland

The Arundel Formation, also known as the Arundel Clay, is a clay-rich sedimentary rock formation, within the Potomac Group, found in Maryland of the United States of America. It dates to the Early Cretaceous, and is of late Aptian or early Albian age. This rock unit had been economically important as a source of iron ore, but is now more notable for its dinosaur fossils. It is named for Anne Arundel County, Maryland.

<span class="mw-page-title-main">London Basin</span> The basin of river Thames in London

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.

<span class="mw-page-title-main">Wessex Formation</span> Early Cretaceous geological formation in England

The Wessex Formation is a fossil-rich English geological formation that dates from the Berriasian to Barremian stages of the Early Cretaceous. It forms part of the Wealden Group and underlies the younger Vectis Formation and overlies the Durlston Formation. The dominant lithology of this unit is mudstone with some interbedded sandstones. It is part of the strata of the Wessex Basin, exposed in both the Isle of Purbeck and the Isle of Wight. While the Purbeck sections are largely barren of vertebrate remains, the Isle of Wight sections are well known for producing the richest and most diverse fauna in Early Cretaceous Europe.

The Vectis Formation is a geological formation on the Isle of Wight and Swanage, England whose strata were formed in the Barremian, approximately 125 million years ago. The environment of deposition was that of a freshwater coastal lagoon with occasional marine influence after the early Aptian marine transgression, transitioning from the floodplain environment of the underlying Wessex Formation. The primary lithology is of laminated grey mudstones. The Vectis Formation is composed of three geological members: the Shepherds Chine member, the Barnes High Sandstone member, and the Cowleaze Chine member. It is overlain by the fully marine Atherfield Clay Formation, part of the Lower Greensand Group. Dinosaur remains are among the fossils that have been recovered from the formation.

<span class="mw-page-title-main">Urbión Group</span>

The Urbión Group is a geological group in Castile and León and La Rioja, Spain whose strata date back to the Early Cretaceous (late Hauterivian to late Barremian. The formations of the group comprise a sequence of brown limestones in a matrix of black silt, sandstones, claystones and conglomerates deposited under terrestrial conditions, in alluvial fan and fluvial environments.

<span class="mw-page-title-main">Lower Greensand Group</span> Geological unit

The Lower Greensand Group is a geological unit present across large areas of Southern England. It was deposited during the Aptian and Albian ages of the Early Cretaceous. It predominantly consists of sandstone and unconsolidated sand that were deposited in shallow marine conditions.

<span class="mw-page-title-main">Geology of East Sussex</span> Overview of the 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.

<span class="mw-page-title-main">Tunbridge Wells Sand Formation</span> Stratigraphic Unit in England

The Tunbridge Wells Sand Formation is a geological unit which forms part of the Wealden Group and the uppermost and youngest part of the unofficial Hastings Beds. These geological units make up the core of the geology of the Weald in the English counties of West Sussex, East Sussex and Kent.

<span class="mw-page-title-main">Ashdown Formation</span> Geological unit of the Lower Cretaceous

The Ashdown Formation is a geological unit, which forms part of the Wealden Group and the lowermost and oldest part of the now unofficial Hastings Beds. These geological units make up the core of the Weald in the English counties of East Sussex and Kent.

<span class="mw-page-title-main">Wadhurst Clay Formation</span>

The Wadhurst Clay Formation is a geological unit which forms part of the Wealden Group and the middle part of the now unofficial Hastings Beds. These geological units make up the core of the geology of the High Weald in the English counties of West Sussex, East Sussex and Kent.

The Phu Phan Formation is an Early Cretaceous geologic formation in Thailand. Fossil theropod tracks have been reported from the formation.

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 Sainte-Barbe Clays Formation is a geological formation in Belgium. It is found in localised areas of the northern margin of the Mons Basin, alongside the equivalently aged Hautrage and Baudour Clay Formations. It is Upper Barremian-Lower Aptian in age. It predominantly consists of laminated clay, with some lignite. It is well known for the "Iguanodon sinkhole" locality near Bernissart where many specimens of Iguanodon bernissartensis were described by Louis Dollo in the late 19th century.

References

  1. 1 2 Jackson (2008)
  2. Hopson PM, Wilkinson IP, Woods MA (2008). "A stratigraphical framework for the Lower Cretaceous of England" (PDF). British Geological Survey Research Report , RR/08/03. British Geological Survey.
  3. Benson RB, Brusatte SL, Hutt S, Naish D (2009). "A new large basal tetanuran (Dinosauria: Theropoda) from the Wessex Formation (Barremian) of the Isle Of Wight, England". Journal of Vertebrate Paleontology. 29 (2): 612–615. Bibcode:2009JVPal..29..612B. doi:10.1671/039.029.0202. S2CID   83869634.
  4. Weishampel et al. (2004)
  5. 1 2 3 Rodrigues T, Kellner AW (2013). "Taxonomic review of the Ornithocheirus complex (Pterosauria) from the Cretaceous of England". ZooKeys (308): 1–112. Bibcode:2013ZooK..308....1R. doi: 10.3897/zookeys.308.5559 . PMC   3689139 . PMID   23794925.
  6. 1 2 3 4 "10.21 Kent, England; 1. Hastings Beds"in Weishampel, et al. (2004). Page 559.
  7. "Table 2.1," in Weishampel, et al. (2004). Page 26.
  8. Huene, 1909. Skizze zu einer Systematik und Stammesgeschichte der Dinosaurier [Sketch of the systematics and origins of the dinosaurs]. Centralblatt für Mineralogie, Geologie und Paläontologie. 1909, 12-22.
  9. 1 2 3 4 "10.18 West Sussex, England; 1. Hastings Beds" in Weishampel, et al. (2004). Page 559.
  10. 1 2 3 4 5 6 "10.19 East Sussex, England; 1. Hastings Beds" in Weishampel, et al. (2004). Page 559.
  11. "Table 4.1," in Weishampel, et al. (2004). Page 73.
  12. Paul Upchurch, Philip D. Mannion & Michael P. Taylor (2015) The Anatomy and Phylogenetic Relationships of “Pelorosaurus“ becklesii (Neosauropoda, Macronaria) from the Early Cretaceous of England. PLoS ONE 10(6): e0125819. doi:10.1371/journal.pone.0125819 http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0125819
  13. 1 2 3 "10.19 East Sussex, England; 1. Hastings Beds" and "10.18 West Sussex, England; 1. Hastings Beds" in Weishampel, et al. (2004). Page 559.
  14. 1 2 Mannion PD (24 January 2019). "A turiasaurian sauropod dinosaur from the Early Cretaceous Wealden Supergroup of the United Kingdom". PeerJ. 7: e6348. doi: 10.7717/peerj.6348 . PMC   6348093 . PMID   30697494.
  15. "10.19 East Sussex, England; 1. Hastings Beds" and "10.18 West Sussex, England; 1. Hastings Beds" and "10.21 Kent, England; 1. Hastings Beds"in Weishampel, et al. (2004). Page 559.
  16. Richter, Annette (2012). "The 'German Wealden' and the Obernkirchen Sandstone – an Introduction". Dinosaur Tracks 2011: an international symposium, Obernkirchen, April 14-17, 2011 : abstract volume and field guide to excursions. Göttingen: Universitätsverlag Göttingen. ISBN   978-3-86395-105-4. OCLC   852208407.
  17. Dejax, J.; Pons, D.; Yans, J. (1 April 2007). "Palynology of the dinosaur-bearing Wealden facies in the natural pit of Bernissart (Belgium)" (PDF). Review of Palaeobotany and Palynology. Aspects of the Jurassic and Cretaceous palynology. 144 (1): 25–38. Bibcode:2007RPaPa.144...25D. doi:10.1016/j.revpalbo.2005.10.004. ISSN   0034-6667.

Further reading

See also