Grès dévoniens du puits n° 8 de Liévin à Avion (Pas-de-Calais, France) : contexte historique et nouveaux restes de vertébrés

Abstract

The Liévin shaft n° 8 of the Nord – Pas-de-Calais coal basin worked as a ventilation shaft from 1948 to 1982. Collections of Early Devonian vertebrates, made both in situ during boring of the shaft, and later on its slag heap, included mostly pteraspidid heterostracans, plus a few remains of cyathaspidiforms, osteostracans, as well as thelodont and acanthodian scales. In 1982, vertebrates were collected on its slag heap. They came from the subsurface Lochkovian, lower Pernes Formation. They include Heterostraci (Traquairaspididae indet., Rhinopteraspis crouchi, Pteraspididae indet.), Osteostraci (Cephalaspis sp.) and ‘actinolepid’ Arthrodira (Kujdanowiaspis? sp.). These are dated of the R. crouchi Biozone, and correlated to the ‘middle’ Lochkovian. As in the Liévin shaft n° 6, it corresponds to the highest diversity for the latest Silurian-Early Devonian sequence of vertebrates in Artois (northern France). This peak is known worldwide.