The Cambrian Fauna of the Leny Limestone, Perthshire, Scotland

Abstract

Dark limestones in the old quarries at Leny, Perthshire contain sparse beds with tiny fossils. They are poorly preserved and, though barely affected by the Ordovician Grampian Event tectonism, there is some taphonomic distortion and many are corroded along stylolitised horizons. The fauna mainly comprises trilobites of two types, open-ocean miomerids and polymerid shelf dwellers. Miomerids Condylopyge cf. eli and Kiskinella cristata indicate a stratigraphical position equivalent to the base of the paradoxidid Amgan Stage of Siberia; traditionally regarded as ‘Middle Cambrian’. However, the bulk of the Leny miomerids, notably species of Pagetides, are forms described from the outer edge of Laurentia, within the Bonnia–Olenellus Zone, where it is considered to be ‘Lower Cambrian’. The Leny polymerids were likely transported off-shelf and some are conspecific with taxa in the Laurentian allochthonous Quebec and New York successions of the Early–Middle Ordovician (Taconic) Appalachian Orogen. The Leny Limestone and Shale Member of the Keltie Water Grit Formation is part of the Dalradian Supergroup deposited in an off-shelf Caledonide Grampian Terrane of the Humber Tectonostratigraphical Zone, midway between the North American successions and the Greenland Caledonides.

Additional to the trilobites, brachiopods, sponges, hyoliths, bradoriids and a selection of indeterminable organic fragments occur; none of which has any particular age significance.