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Lesmahagow

Fossil fish localities

Many important collections of Silurian arthropods and vertebrates have been made near Lesmahagow since the mid to late 1800’s. The Geological Society of Glasgow set up a camp in the 1890’s, which was aptly named “Camp Siluria”, from which members of the society collected a number of rare and complete specimens of fossil fish and eurypterids. It is now very difficult to obtain permission to collect from these rocks as a result of irresponsible collecting which has damaged some important sites. It is still possible to find fossils from these rocks, but all fossils are rare and some may be usefully donated to a museum for research.

A fossil locality near Lesmahagow - one of several localities that yield fossil fish-bearing exposures of Silurian age sedimentary rocks. This image taken in the late 1990's illustrates an operation to rescue scientifically important fossils discarded by irresponsible fossil collectors. © Scottish Natural Heritage.

The Lesmahagow Inlier is a block of Silurian sediments surrounded by sediments of Carboniferous age. The inlier consists of shales and sandstones with occasional pebble conglomerates of a lagoon or lake. The lower parts of the succession contain occasional marine fossils, including trilobites and brachiopods, but the higher parts of the succession lack any evidence of marine incursions becoming influenced more by river and deltaic conditions. The sequence seen here is part of a general regression that can be traced from western Ireland to Scandinavia. The earlier (Cambro-Ordovician) terrane accretion of the Midland Valley Terrane to the Laurentian continent by sinistral strike-slip controlled basin development, sedimentary facies and deformation from Llandovery through until the early Devonian times.