Wealden Group


The Wealden Group, occasionally also referred to as the Wealden Supergroup, is a group in the lithostratigraphy of southern England. The Wealden group consists of to continental 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.
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.. 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 Wealden 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. 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.
On top of the Wealden Group is the Lower Greensand Group. The difference between these two groups has been formed by a major eustatic transgression of the sea. The Greensand 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.

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. 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

Dinosaurs