When Somerset lay beneath the sea

The evidence consists of limestone pebbles that carry borings made by molluscs as well as oysters. These pebbles were torn up from the underlying Carboniferous limestone which formed the basic landscape all over Somerset and across the Severn Estuary to South Wales. Beginning at the end of the Triassic period, seas flooded over the whole area, leaving just the tops of the hills showing above the waves. James Ronan, currently studying the Masters in Palaeobiology at the University of Bristol carried out this research last year as an undergraduate - the findings of which are published today in the journal Proceedings of the Geologists' Association . He said: "As the sea flooded around the edges of the Mendips, sea creatures made borings into the limestone seabed to find safety. "Then storms followed and ripped up the limestone seabed, turning it into flat pebbles that contained the borings. The pebbles were dumped and then colonised by oysters before finally being buried." Professor Mike Benton , from Bristol's School of Earth Sciences , led the project.