The Rossport Formation stratotype, located on Channel Island near Rossport, Ontario, may be subdivided into eight distinct lithostratigraphic units. The lower six units, which belong to the Lower Member of the formation, consist primarily of dolomite, sandy dolomite, and arenite. The Central Member is composed of cryptalgal and banded chert-carbonate, and the Upper Member consists of crudely banded dolomite. The red colouring of the carbonates is due to a diagenetic hematization process.
The Rossport Formation, at Channel Island, appears to be representative of a Neohelikian shallow shelf sea environment which became shallower and more restricted as deposition progressed.