According to the British Geological Survey, the primary lithology of the formation consists of "Alternating beds of grey feldspathic, medium-grained turbiditicsandstone and grey siltstone with beds of grey laminated siltstone and silty mudstone."[3] The Birk Knowes site contains fossils from non-marine or marginal marine environment.[4] In 2000, Birk Knowes was closed by the Scottish government agency Scottish Natural Heritage (now NatureScot), due to the theft of specimens from the site by amateur collectors during the preceding decades, who essentially exhausted the fossiliferous deposit. At least some of the fossils ended up in a museum in Berlin, who refused to return them.[5][6][7][8]
