FROM RESTRICTED SEA TO COASTAL FLOODPLAIN: A REVIEW OF OSTRACODE PALEOECOLOGY FROM THE CARBONIFEROUS MARITIMES BASIN, ATLANTIC CANADA

The Carboniferous strata of the Maritimes Basin in Eastern Canada are characterized by rapidly changing environments of limited temporal and spatial stability. Factors that fostered paleoenvironmental change in the basin included local tectonics, global eustatic fluctuation, and a variable semi-arid to humid climate. Consequently, it is possible to recognize freshwater, brackish, marine, and hypersaline paleoenvironments in the Maritimes Basin, which makes the region an ideal place to study ostracode paleoecology. Due to their tolerance for a wide variety of environmental conditions, ostracodes have been found in almost all of these types of paleoenvironments.

The Carboniferous strata of the Maritimes Basin can be divided into three divisions. In the lower part of the Lower Carboniferous, the Horton Group of Nova Scotia contains siliciclastic muds and sands that were deposited in a marginal sea of lowered salinity. Ostracodes found in these strata include the eurytopic paraparchitaceans, marine beyrichiaceans and carbonitaceans of non-marine affinity. In the upper part of the Lower Carboniferous, the Windsor Group of Nova Scotia and the Codroy Group of Newfoundland contain mixed carbonates, siliciclastics, and evaporites. Ostracodes include normal marine faunas with paleocopes, bairdiaceans and hollinomorphs, chemosynthetic faunas comprised of the eurytopic paraparchitaceans, and brackish environments associated with kloedenellaceans. In the Upper Carboniferous, the Joggins Formation of Nova Scotia contains siliciclastics, carbonates, and coals that were deposited on a low-gradient coastal floodplain. Ostracodes include exclusively freshwater carbonitaceans.

Since the ostracodes are found in a wide variety of paleoenvironments, they can be used to track first order environmental change in the Maritimes Basin. The developmental history of the basin demonstrates a progression from an initial flooding stage, to the development of restricted seaways with local hydrothermal activity, and a final stage involving the progradation and aggradation of coal swamps.