Ashgill Layer

Ashgill Layer

 

(named after the settlement of Ashgill, Great Britain), the uppermost layer of the Ordovician system. In typical locations it is composed of shalelike clays with trilobites and graptolites. It is divided into two zones according to the graptolite composition: Dicellograptus complonatus and D. anceps. Deposits of the Ashgill layer are known in Western Europe, non-Soviet Asia, and North America; in the USSR they are found in Kazakhstan, Siberia, and the northeast.