River- and wave-dominated depositional systems of the Upper Cretaceous Dunvegan Formation, northwestern Alberta

This paper documents the detailed sedimentological aspects of the Dunvegan Formation based on examination of about 130 core and 500 well logs. Nineteen facies have been grouped into 7 successions. In combination with sand isolith maps, these facies successions are further linked into lithofacies assemblages that define distinct, large-scale depositional systems. Facies Successions 1, 2, and 3 coarsen upward and represent the progradation of storm-dominated shorefaces, riverdominated delta lobes, and mixed-influence deltaic lobes, respectively. Facies Successions 4, 5, and 6 fine upward and comprise the deposits of fluvial-dominated distributaries, estuaries, and barrier inlets. Facies Succession 7 is irregular and comprises the deposits of the delta plain, including interdistributary bays and lagoons. Facies Successions 2, 4, and 7 define the river-dominated deltaic depositional systems, which show lobate geometries fed by channelized shoestring sands. The wave-dominated deltas also show lobate geometries but are characterized by a linkage of Successions 1, 5, and 7, which show more marine influence. The wave-influenced deltas are characterized by a linkage of Successions 3, 4, and 7 and are intermediate in shape and facies between the wave-dominated and river-dominated end members. The wave-dominated barriers are elongate and oriented shore parallel, and are characterized by a linkage of Successions 1, 6, and 7. The Dunvegan Formation cannot be characterized as a single delta. Rather, it is interpreted here as a stacked series of different types of depositional systems. These prograded to the southeast, with shorelines trending approximately northeast-southwest. Overall there apppears to be a decrease in the importance of fluvial processes upward.