Spatial and Temporal Stratal Evolution of an Ancient Deep-Marine Channel-Levee Complex, Neoproterozoic Isaac Formation, Windermere Supergroup, British Columbia, Canada

Abstract

At the Castle Creek study area a superbly exposed slope channel system (Isaac channel complex 1; ICC1) crops out. ICC1 is ~ 220 m thick, exposed 5 km along strike and consists of four vertically-stacked channel units (LC, UC1-UC3). Based on lithological changes and grain size analysis, two styles of channel fills and stacking patterns are recognized – a disorganized stack of aggradational channel fills (LC, UC1 and UC2) and an organized lateral-offset stack of laterally accreting channel fills (UC3). Changes in channel stacking pattern are interpreted to be related to the combined effects of long- and short-term changes in relative sea level (RSL) that controlled the granulometric make-up and volumetric potential of shelf sediment storage. Episodes of abundant coarse shelf sediment caused flows to adopt a plug-like density structure that promoted riverine-like lateral accretion in channel bends. Conversely, when sediment was sourced principally from the hinterland, flows were highly stratified, which promoted channel aggradation.