Littorina sp., Periwinkle

Onoba semicostata

Significance: the raised beaches of East Lothian contain many shell fragments that provide important information about past marine environments

The oldest marine sediments known in East Lothian date from the period of ice retreat, when arctic seas filled the outer part of the Firth of Forth. These deposits occur at or below present sea level and so tend only to be seen in excavations. The clays of the former Portobello brick works, up to 30 m thick, yielded bones of an arctic seal.

Much more accessible are the molluscs in the pebble-rich deposits of the Main Postglacial Raised Beach. Here large numbers of shells of periwinkle, whelk and limpet can be recovered which match the species found currently on these rocky shorelines. The fossils show that the sea water temperature around 5500 years ago was similar to that of today.

In the sandy and muddy sediments of equivalent age around Tyne Mouth there are many tiny whelks and snails, including Onoba semicostata, Rissoa parva interrupta.

Raised beaches of the Firth of Forth   sea level change

Key sites  Belhaven   Chapel Point