Beginning of Mesozoic marine overstep of the Mendips: The Rhaetian and its fauna at Hapsford Bridge, Vallis Vale, Somerset, UK

One of the most dramatic environmental changes in the Mesozoic history of Europe was the switch from terrestrial to marine deposition marked by the Rhaetian Transgression, 205 Ma. Beginning with this event, the Mendip Hills, composed primarily of uplifted and folded Lower Carboniferous limestones, w...

Full description

Saved in:
Bibliographic Details
Published in:Proceedings of the Geologists' Association 2020-10, Vol.131 (5), p.578-594
Main Authors: Ronan, James, Duffin, Christopher J., Hildebrandt, Claudia, Parker, Adam, Hutchinson, Deborah, Copp, Charles, Benton, Michael J.
Format: Article
Language:English
Subjects:
Bristol
Chondrichthyes
Osteichthyes
Penarth Group
Rhaetian
Rhaetian bone bed
Westbury Formation
Citations: Items that this one cites
Items that cite this one
Online Access:Get full text
Tags: Add Tag
No Tags, Be the first to tag this record!
Description
Summary:One of the most dramatic environmental changes in the Mesozoic history of Europe was the switch from terrestrial to marine deposition marked by the Rhaetian Transgression, 205 Ma. Beginning with this event, the Mendip Hills, composed primarily of uplifted and folded Lower Carboniferous limestones, were flooded in a stepwise manner from the Late Triassic to mid Cretaceous. The basal Rhaetian beds at the eastern end of the Mendips (Hapsford Bridge, Vallis Vale) lie directly on Carboniferous limestone, which was bored, indicating it functioned as a hardground. Bored pebbles were then eroded, transported, encrusted with bivalves, and deposited in marine muds in the lower parts of the Westbury Formation. At certain levels also, suspended mini-conglomerates within finer-grained sediments suggest continuing storm activity. The Hapsford Bridge Rhaetian bone bed includes microvertebrate remains of four species of sharks and two species of bony fishes, all of them typical of Rhaetian-aged bone beds. The invertebrate fauna is especially rich, including bivalves and echinoids, as well as trace fossils. Unusual elements are barnacles and a possible belemnite.
ISSN:0016-7878
DOI:10.1016/j.pgeola.2020.02.005