Paleontological evidence for marine influence during deposition of the Westphalian Coal Measures in the Gulf of St. Lawrence-Sydney Basin region, Atlantic Canada

Abstract

Coal Measures penetrated by oil and gas exploration wells in Gulf of St. Lawrence - Sydney Basin are a regionally mappable seismic facies. The broad extent of this seismic facies has prompted the speculation that it reflects cyclothem deposition, analogous to cyclothem deposits of the Illinois Basin and Mid-Continent Basin region of the United States. This implies that the depositional cycles included periods of marine incursion. Evidence for such incursions, in the form of agglutinated foraminifera assemblages, has been reported from coal-bearing strata of the Sydney Basin, Cape Breton Island. Similar assemblages have now been found in two offshore wells in the Gulf of St. Lawrence. This discovery supports arguments for cyclothymic deposition, enhances the possibility of marine source rocks for hydrocarbon generation, and underlines the need for review of the paleogeographic and depositional history of the Central Maritimes Basin.