Lower Triassic Deltas Along an Arid Coastline of Western Pangea: Insights on the Coastal Dynamics of the Lower Triassic Montney Formation of the Western Canada Sedimentary Basin and Its Impact on Depositional Processes

Arid coastal environments encompass a complex array of depositional environments associated with aeolian, fluvial and shallow marine deposits, which are preserved in the rock record as a mosaic of interfingering facies. Shifting of facies, both temporally and spatially, in conjunction with local and regional unconformities, makes stratigraphic correlations difficult, especially within subsurface datasets. The Lower Triassic Montney Formation in the Western Canada Sedimentary Basin presents evidence of a dynamic coastal depositional systems along a 200 km transect of the northwestern margin of Pangea. Previous studies have interpreted that the paleogeography of 32–34° N latitude and arid climate during deposition, fostered moderate seasonality and the development of perennial and ephemeral rivers/deltas. However, within the study area, at least two thick and extensive delta systems developed in this region. Centrally located is a 5–20 m thick fluvial-dominated delta with interbedded very fine sandstone and siltstone. This fluvial-dominated delta likely supplies sediment to a northern wave-dominated delta/strandplain complex composed of a 5–10 m thick succession of very fine sandstone with planar laminae, through cross stratification and massive bedding. Within the southern area, a storm-dominated delta has <1m thick beds of sandstone and siltstone with common Bouma sequences. Through facies mapping, an evolution and extent of these depositional environments can be constructed to show the dynamic nature of the marginal marine systems along arid coastlines and their contribution of sediment delivery to the offshore environments.