Algal Bioherms of the Upper Gull River Formation (Middle Ordovician) near Kingston, Ontario

Twelve stratigraphic sections, that lie within a 15 to 20 ft section (4.6 to 6 m) of upper Gull River limestone, were measured within an area of 400 square miles (1000 km2) near Kingston, Ontario.Sedimentation was cyclic and a series of recessive, clastic layers alternating with resistant carbonate units was deposited. Two carbonate units, low in the measured section, contain here and there stromatolites of the LLH-S variety. Above these, a third carbonate layer contains LLH-S stromatolites which appear to persist throughout the area. A fourth carbonate unit above these includes scattered occurrences of stromatolites developed about colonies of Tetradium cellulosum.A brief description of the algal stromatolites occurring in the measured stratigraphic section is presented, and from adjacent lithologies an environment of growth in shallow, semi-restricted marine waters is postulated.