Clarach Bay just north of Aberystwyth is a 1st class exposure of Silurian rocks on the seashore. The rocks are mudstones, grits and sandstones deposited on a deep sea floor, 428-443 million years ago. The rocks are folded and faulted and contain some fossils mainly rather amorphous corals.

Photo: The glacial sands, gravels and tills are in the upper part of the cliff,. The so-called Aberystwyth grits are in the foreground.