Weydale Quarry

Also within

Caithness County

Condition (NatureScot)

Geology & landscape

Mining / Industrial: Quarry · Geological Period: Devonian · Rock Type: Siltstone

Description

Weydale Quarry Weydale Quarry SSSI lies 4km southeast of Thurso, Caithness. The site has been notified due to the exposure of a layer of sedimentary rock which contains fossil fish. The fossil fish bed has been exposed here as a result of quarrying to extract flagstones. The 1.3m-thick bed of laminated siltstone that contains the fossil fish is exposed in the rock face at the northern end of the quarry. The fish bed at Weydale dates from the Middle Devonian geological time period, approximately 380 million years ago, when the area we know as Caithness was a large inland lake. This quarry forms part of a network of sites across northern Scotland where Middle Devonian fossil fish beds have been exposed. These sites differ in the age of their fossil-bearing rocks and therefore present different snapshots of fish evolution. Weydale’s fish beds occur at the junction between the Mey subgroup and Ham Scarfskerry subgroup of the Upper Caithness Flagstone Group and it is the only quarry in Caithness yielding characteristic fish species from this point in the rock sequence. Well-preserved specimens of two fish species, Dipterus valenciennesi and Osteolepis panderi, occur commonly, and fossils of Thursius pholidotus and Homosteus milleri have also been found at Weydale. This site is of national importance in the study of early vertebrate evolution.