Ostracoderm tubercles were recovered from the lower portion of two Black River Group sections between Montreal and Quebec City. Some of these fish remains seem identical to tubercles of Astraspis desiderata from the Harding Sandstone of Colorado. The age of the Quebec remains is questionably earliest Blackriveran or basal Caradocian of the European standard. The remains were found in sandy carbonates probably laid down in the supratidal to shallow marine environments. It is concluded that these remains may represent part of a continent-wide, biostratigraphically useful vertebrate fauna and that bulk sampling and acid residuing might be a technique whereby sparse, fragmentary, earliest Paleozoic fish remains could be found.
Carbonates of the Middle Ordovician Black River Group across the outcrop in southern Ontario have a fabric of elongate particles trending consistently in NW–SE and NE–SW directions. The origin of the fabric is considered primarily resulting from longshore currents in a shallow basin influenced by tidal activity. Insoluble residues constitute a small portion of the rock mass, but contain a wide range of mineral species. Although their distribution is sporadic, suites of minerals east and west of Marmora contain distinctive species. Generally, the detrital minerals seem to reflect the Precambrian source area to the north of the Paleozoic outcrop. A higher concentration of anhydrite to the east is interpreted as indicative of an area of more restricted marine conditions.
The unconformable character and paleogeographic significance of the Chazy-Black River group contact, Montréal area, southwestern Quebec