Portland Group (geology)
The Portland Group (defining the Portlandian) is a Late Jurassic (Tithonian) lithostratigraphic group (a sequence of rock strata) in South East England. 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.
| Portland Group | |
|---|---|
| Stratigraphic range: | |
Cliffs of the Portland Stone Formation on the western side of Portland Bill | |
| Type | Group |
| Sub-units | Portland Stone Formation, Portland Sand Formation |
| Underlies | Purbeck Group |
| Overlies | Kimmeridge Clay Formation |
| Thickness | up to 75 metres (250 ft) |
| Lithology | |
| Primary | Limestone, sandstone |
| Other | Mudstone, micrite |
| Location | |
| Region | England |
| Country | UK |
| Extent | Dorset |
| Type section | |
| Named for | Isle of Portland |
This article is issued from Wikipedia. The text is licensed under Creative Commons - Attribution - Sharealike. Additional terms may apply for the media files.