Stop the press: the Jurassic Coast starts in the Permian. A Geologists’ Association field meeting report of a two-day excursion to the South Devon Coast with Prof John CW Cope

This Geologists’ Association field meeting followed the publication of Professor John Cope’s Geologists’ Association (GA) Guide No 73, Geology of the South Devon Coast (https://geologistsassociation.org.uk/guidesales.html; £9 for members and £12 for non-members), which was reviewed in Issue 50 of this magazine. It is also the companion to GA Guide No 22, Geology of the Dorset Coast. John retired in 2003 after lecturing at Swansea and Cardiff universities. Since then, he has been an Honorary Research Fellow at the National Museum Wales in Cardiff, and has a wide field experience in the UK and Europe, with publications covering many fossil groups over a wide stratigraphical range. Most recently he has been working on redrawing the geological map of South Wales, the subject of an upcoming GA lecture. And, each year, for the past six years, he has provided weekend geological trips to the West Country.

Fig. 1. Prof Cope demonstrates bedding and cleavage.

We met up at Meadfoot Strand to the east of Torquay Harbour. Our mission for the weekend was to examine the complex Devonian succession in the Torbay area and its unconformable relationship to the Permo-Triassic cover. Of great interest was the marine Devonian, first described by Adam Sedgwick, assisted by Roderick Impey Murchison, who finally realised that these facies were contemporaneous with the familiar Old Red Sandstone found north of the Bristol Channel. Since then, the Devonian Stages have been named after rocks in the Czech Republic, Germany and Belgium. The base of the Devonian was the first ‘Global Boundary Stratotype Section and Point’ (GSSP), defined by graptolite zones at Klonk, in the Prague Basin of the Czech Republic – a great geological name.

The area has much to offer enthusiasts of structural geology because the Devonian strata have been tectonised by the closure of the Rheic Ocean during the Variscan orogeny. The story has only been unravelled in the last 50 years. First, sediments filled a series of basins caused by crustal extension; the basement beneath the Devonian rocks may well be a massif of Precambrian mica-schist. Then, from the Early Carboniferous, continental collision caused a series of major thrust structures that progressively moved northward. As a consequence, what Carboniferous rocks were deposited in the Torbay area were rapidly stripped off and the Devonian was covered by sediments from the Permo-Triassic.


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