Carbonicola fossil

Fossil of a fresh water mussel, Carbonicola.  Fresh water mussel beds fossilised in coal measures are an indication that the region was once part of a coastline.   Fossils are remains of plants or animals which are preserved in rocks.  These ones are from the carboniferous or Coal Age, 300 million years ago when Upper Nithsdale was below a shallow coral sea, which then drained away leaving the area a marshy coastal jungle.   Productive coal measures are the major source of fossils such as these.  They indicate estuary conditions, with the sea slowly receding, and fresh water marshes developing.   As this area has long been the scene of mining activity its geological past can be deciphered in great detail.  The first geological survey of the Sanquhar Basin was in 1867, and since then it has been famous for its exposures of fossil layers.