Seven distinctive lithologie units are recognized and described from the Charlo – Upsalquitch Forks area, northern New Brunswick. Four of these units are equated with the Matapedia Limestone and the Limestone Point, La Vieille, and Bryant Point formations of adjacent areas. In addition three new units are defined, described, and placed in the local and regional stratigraphic framework. These are the informally named Siltstone Unit, Grit Unit, and Conglomerate Unit.Although the lithofacies and biofacies changes of the area are rapid and complex the sedimentologic and paleoecologic evidence indicates a dominantly shallowing trend throughout the Late Ordovician to at least Middle Wenlock times. A reversal of this trend during the Early Wenlock in the northeast part of the area is indicated by the deeper water facies of the lower La Vieille Formation.