The geology of the Black River group in the vicinity of Montreal.

Abstract

The rocks of the Black River Group (Middle Ordovician) in the vic1nity of Montreal outcrop in a narrow belt which traverses the Island of Montreal, lIe Bizard, and lIe Jesus. They comprise three formations, the Pamella, Lowville, and Leray. The Pamelia formation is ten feet thick and is made of impure dolomltic limestones and shaly limestones; the Lowville is sixteen feet thick and is made of fine-grained and olitic, dove, thin-bedded limestones with frequent shaly partings; the Leray is twenty-two feet thick and consists of thick beds of black, light-weathering limestone, containing nodules of chert and irregularly horizontal streaks of brownish, sandy material. The formations thin out eastward, and probably were deposited in a narrow arm of the Black River sea, extending from ottawa towards and beyond Montreal. [...