Triassic-Jurassic boundary, and overlying Blue Lias, Pinhay Bay, west of Lyme Regis in the Undercliffs National Nature Reserve and Jurassic Coast World Heritage Site.
Geological Period
Triassic to Cretaceous
Main geological interest
History of geosciences
Stratigraphy and sedimentology
Location
Dorset and East Devon Coast, United Kingdom
50°43’01”N, 002°57’01”W
Triassic-Jurassic boundary, and overlying Blue Lias, Pinhay Bay, west of Lyme Regis in the Undercliffs National Nature Reserve and Jurassic Coast World Heritage Site.
A globally unique near-continuous Mesozoic coastal succession exemplified by the classic Lower Jurassic of Lyme Regis.
The Jurassic Coast uniquely exposes an almost continuous Mesozoic sequence. It is renowned for its contribution to Earth science with over 300 years of research exemplified by the marine Lower Jurassic of the Lyme Regis area. A prolific source of invertebrate and vertebrate fossils (first collected by Mary Anning and including many type specimens), this sequence is fundamental to our modern understanding of Lower Jurassic stratigraphy spanning end Triassic (Rhaetian) and Lower Jurassic (Hetangian-Pliensbachian) marine strata, which document environment, climate and sea level change over this interval.
Recent discoveries (Jurassic Coast Collection): exceptionally preserved Ichthyosaurus communis from the Blue Lias Formation (found and prepared by Fiann Smithwick).
- Geological description
The Jurassic Coast World Heritage Site exposes an outstanding sedimentary succession displaying 185 million years of the Earth’s history – a near-continuous Mesozoic stratigraphical record. This encompasses the transition from terrestrial to marine Triassic (Gallois, 2019) and Jurassic strata, and culminates in the Upper Cretaceous Chalk (Mortimore, 2019) and the iconic Old Harry Rocks.
This coastline provides “one of the finest sections of marine Jurassic rocks anywhere in the world” (Callomon and Cope, 1995) – a statement exemplified by global reference sections in the marine Lower Jurassic at Lyme Regis. This area is noted for its prolific invertebrate (including a near complete Jurassic ammonite zonation) and marine reptile fossil fauna, first collected by Mary Anning (1799-1847). Today, housed in museums the world over, Mary Anning’s discoveries included the world’s first complete pleisosaur, many complete ichthyosaurs and fossil fish, and the first British pterosaur. She collaborated and corresponded with many contemporary scientists inspiring the world’s first published palaeoecological reconstruction, De la Beche’s Duria antiquior.
Fundamental to our modern biostratigraphy for the Lower Jurassic (Simms et al., 2004) Lyme Regis remains one of the most readily accessible and studied sources of Lower Jurassic marine fossils in the world (Jurassic Coast Trust, 2021).
- Scientific research and tradition
This actively eroding coast has contributed to geoscience for over 300 years, from the earliest collections of Mary Anning and the descriptions of William Buckland and Henry de la Beche. Today the Jurassic Coast is considered by geologists as one of the most significant teaching and research sites in the world.
Mary Anning (1799-1847) with her dog Tray looking eastwards towards Lyme Regis and Golden Golden Cap (Artist unknown, Natural History Museum, London).
- Reference
Callomon, J.H. and Cope, J.C.W. (1995) ‘The Jurassic Geology of Dorset.’, in P.D. Taylor (ed.) Field Geology of the British Jurassic. Geological Society, London, pp. 51–103.
Gallois, R. (2019) ‘The stratigraphy of the Permo-Triassic rocks of the Dorset and East Devon Coast World Heritage Site, U.K.’, Proceedings of the Geologists’ Association, 130(3), pp. 274–293. Available at: https://doi.org/10.1016/j.pgeola.2018.01.006.
Jurassic Coast Trust (2021) The Jurassic Coast Collection: year 1 report, p. 135. Available at: https://indd.adobe.com/view/06b9ab57-534b-4997-89b3-2d7c1d3cb27b.
Mortimore, R.N. (2019) ‘Late Cretaceous stratigraphy, sediments and structure: Gems of the Dorset and East Devon Coast World Heritage Site (Jurassic Coast), England’, Proceedings of the Geologists’ Association, 130(3), pp. 406–450. Available at: https://doi.org/10.1016/j.pgeola.2018.05.008.
Simms, M.J. et al. (2004) British Lower Jurassic Stratigraphy. Peterborough: Joint Nature Conservation Committee (Geological conservation review series, 30).
- Author(s)
Jonathan Larwood.
Natural England. United Kingdom.
