Portland Group (geology)

Portland Group
Stratigraphic range: Tithonian
Cliffs of the Portland Stone Formation on the western side of Portland Bill
TypeGroup
Sub-unitsPortland Stone Formation,
Portland Sand Formation
UnderliesPurbeck Group
OverliesKimmeridge Clay Formation
Thicknessup to 75 metres (250 ft)
Lithology
PrimaryLimestone, sandstone
OtherMudstone, micrite
Location
RegionEngland
Country UK
ExtentDorset
Type section
Named forIsle of Portland

The Portland Group (defining the Portlandian) is a Late Jurassic (Tithonian) lithostratigraphic group (a sequence of rock strata) in South East England.[1] The name is derived from the Isle of Portland in Dorset where the strata are exposed and have been extensively worked. Rocks of this age have in the past been called the Portlandian stage by geologists, which corresponds with the late Tithonian stage of the internationally used geological timescale.

  1. ^ "BGS Lexicon of Named Rock Units - Result Details". webapps.bgs.ac.uk. Retrieved 30 May 2024.