Petrology of the Deschambault Formation, Trenton group, St. Lawrence lowland of Quebec.

The Deschambault Formation of the St. Lawrence lowland of Quebec was investigated and defined by T. H. Clark during the course of mapping the geology of this area. The large fauna of this formation indicates that its age is middle Ordovician, being time equivalent to the Hull stage of the Trenton series (Clark, in press, a). The limestones of the Deschambault outcrop in a discontinuous belt on the northwest side of the St. Lawrence River from Montreal to a point just beyond Quebec City (Figure 1). Stratigraphic sections are exposed only in quarries and river channels because of the thick overburden formed by Pleistocene glacial deposits. Such outcroppings are readily accessible. [...