Constraining Sediment Dispersal Processes in a Siltstone-Dominated Clastic Wedge

Recent studies in fine-grained formations (i.e., mudstone and siltstone deposits) have highlighted a range of physical processes that disperse and re-distribute fine-grained sediment in marine settings. However, linking quantified dispersal patterns to paleocurrent trends to highlight the role of multidirectional dispersal processes in fine-grained successions is often challenging due to the poor preservation potential of paleocurrent indicators in outcrops and limited lateral extent in subsurface datasets.

Detailed characterization of well-preserved outcrops of an up to 300 meter-thick, mixed-carbonate–siliciclastic, siltstone-dominated prograding clastic wedge succession of the Lower Triassic Sulphur Mountain Formation (Southern Alberta, Canada) allowed for analysis from a broad range of bedforms and erosional features. Based on 600+ paleocurrent data, two dominant sediment transport directions were observed—(1) Basinal-directed dispersal processes by episodic storm and sediment gravity flow processes, omnipresent fair-weather conditions, and shallow-water shelf channels; and (2) Oblique dispersal along the continental shelf and slope inferred from current and starved ripples paleocurrent trends. These contrasting dispersal trends highlight the complex spatial interplay between downslope sedimentation and more continuous oblique sediment reworking by ocean currents during fair weather conditions. Central to this theme is that fine-grained sediment distribution occurs over a wide area both basinward and laterally along the shelf and slope in the clastic wedge. Accordingly, these trends provide a rare archive of the three-dimensionality of dispersal processes that re-distributed fine-grained sediment, which corroborate with the complex nature of sediment dispersal patterns observed in modern continental margins.