Wessex Formation

Wessex Formation
Stratigraphic range: Late BerriasianBarremian, 140–125 Ma
West of Chilton Chine - geograph.org.uk - 1378519.jpg
Exposure of the Wessex Formation west of Chilton Chine
TypeGeological formation
Unit ofWealden Group
Sub-unitsCoarse Quartz Grit (in Dorset)
UnderliesVectis Formation
OverliesDurlston Formation
Thicknessup to 1000 m near Swanage
Lithology
Primarymudstone
Othersandstone, ironstone & conglomerate
Location
RegionSouthern England
Country UK
ExtentDorset, Isle of Wight, offshore Wessex Basin
Type section
Named forWessex
Named byDaley and Stewart
LocationBacon Hole, Mupe Bay
Year defined1979
IOW geology.svg
Exposure of the Wessex and Vectis Formations on the South Coast of the Isle of Wight, shown in turquoise, exposures in Dorset not shown.

The Wessex Formation is a fossil-rich English geological formation that dates from the Berriasian to Barremian stages (about 145–125 million years ago) of the Early Cretaceous. It forms part of the Wealden Group and underlies the younger Vectis Formation and overlies the Durlston Formation.[1] The dominant lithology of this unit is mudstone with some interbedded sandstones. It is 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.

Nomenclatural History

The Wessex Formation has historically alternately been called the "Variegated Marls And Sandstones", a name used by W. J. Arkell in his 1947 map of the Isle of Purbeck[2] as well as the "Wealden Marls" [3] It was given its current formal name by Daley and Stewart in 1979[4]

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