Controls on the stratigraphic development of the Triassic Fundy Basin, Nova Scotia: implications for the tectonostratigraphic evolution of Triassic Atlantic rift basins

Abstract

Abstract: The Late Triassic synrift succession of the Minas sub-basin (Bay of Fundy, Nova Scotia) includes a fluvio-alluvial fan-dominated unit (lower and middle Wolfville Formation), a transitional fluvio-playa unit (upper Wolfville Formation) and an upper playa-dominated package (Blomidon Formation). We describe the facies development in the 240 m thick upper Wolfville Formation, examine vertical facies stacking patterns and develop a depositional model for this succession. The unit comprises channelized and unconfined fluvial deposits interbedded with aeolian and playa sediments that grade upward into playa deposits. The succession comprises progradational and retrogradational fluvial packages and thin aggradational playa claystones. Comparison with 11 other Atlantic margin continental Triassic rift basins allows an assessment of the controls that govern rift basin development. The transition from fluvial to playa or lacustrine conditions occurs in all basins at different times. The lack of synchronicity indicates that global climate change was not a controlling factor. We suggest that the fluvial to lacustrine or playa transition was due to a decrease in source area relief related to a decline in regional tectonic activity, and that the basin was hydrologically closed throughout sedimentation. This tectonostratigraphic model may be appropriate for other Triassic basins developed along the Atlantic margin.