Intrachannel Architecture, Channel-Margin Geometry and Evolution of a Deep-water Slope Channel-Levee Complex: Isaac Channel 3, Neoproterozoic Windermere Supergroup, Canada

Navarro, Lilian L.¹, Zishann A. Khan¹, R. William C. Arnott¹ (1) University of Ottawa, Ottawa, ON

Deep-water slope channels of the Windermere turbidite system were developed on a Neoproterozoic passive-margin basin during the break-up of western Canada and formation of the proto-Pacific Ocean. At Castle Creek South, Isaac Channel 3 (IC3) represents a channel-levee complex, which is up to 80 m thick and at least 1.6 km wide, bounded on both sides by genetically-related levee deposits. The base of IC3 is an asymmetrical, composite surface with a terraced geometry along its northwest margin and an interfingered/serrated geometry along its southeast margin. These observed differences are interpreted to be the result of differences in the nature of sediment transport and deposition along the outer- and inner-bend margins, respectively, of a sinuous deep-sea channel.

Based on the integration of outcrop data from measured logs and mapping, IC3 was subdivided into four main vertically-stacked channel units that show a lateral offset toward the northwest. Channel units are separated by laterally-correlative, erosion surfaces overlain by bypass-dominated, thin-bedded turbidites or mudstone-clast breccia associated with major incision/reincision periods. Channel-fill deposits of the lower channel unit are dominated by amalgamated conglomerate/sandstone, and channel fills in the middle and upper units consist mostly of semi-amalgamated sandstone with fine sandstone/siltstone interbeds. From channel axis to margins a distinct lateral trend is recognized over short distances (i.e. <100 m), in which coarse-grained strata tend to thin and fine and become increasingly interstratified with thin-bedded facies.

Vertical and lateral variations recognized in IC3 indicate changes (i.e. increasing/decreasing sediment caliber, flow size, sand/mud ratio) in flow or slope conditions through time. IC3 provides new insights into the processes related to the inception, migration and evolution of deep-water slope-channel systems.