EVIDENCE FOR AN ALBIAN HUDSON ARM CONNECTION BETWEEN THE CRETACEOUS WESTERN INTERIOR SEAWAY OF NORTH AMERICA AND THE LABRADOR SEA
T. S. White, B. J. Witzke, and G. A. Ludvigson
Numerous researchers have alluded to a Cretaceous Hudson Arm connection between the Labrador Sea and the North American Western Interior Seaway. However, the evidence for this connection has been circumstantial. In this talk we present sedimentary geochemical data which are indicative of marine influence in the Albian Mattagami Fm of the Moose River Basin, James Bay Lowlands, Ontario. Dinoflagellate-bearing laminated mudstones of the Mattagami Fm, previously interpreted as freshwater in nature, contain a record of marine influence which we attribute to the existence of a Hudson Arm. This reinterpretation is based on relationships between total iron, pyritic sulfur and organic matter in the sediments. Relatively high quantities of labile organic matter (TOC >5% and HI >400) and pyrite (%FeS2 >0.5%, and up to 2%) are associated with mudstone horizons that are reported to contain dinoflagellates. The dinoflagellate genus has been described in coeval marine-influenced strata in the Kiowa Shale and Muddy Fm in the central United States. The facies association between dinoflagellate-bearing mudstones, fluvial sandstones, and early pyrite mineralization, are interpreted to indicate deposition in an estuary. Furthermore, we use the association between the estuarine fill deposits and coeval kaolinitic mudrock paleosols in the Moose River Basin, and in similar deposits in Quebec and Labrador, to reconstruct the southern shoreline of the Albian Hudson Arm Seaway. We suggest the Hudson Arm marine connection between the Labrador Sea and the Western Interior Seaway may be related to the complex interplay between regional extension associated with rifting between Labrador and Greenland, and the passage of eastern North America over one or more hotspots in the Cretaceous.