WHICH SCALES OF STRATAL ARCHITECTURE ARE RELEVANT TO HYPORHEIC-ZONE PROCESSES?

Processes within the hyporheic zone are influenced by connected high-permeability pathways, if extant within fluvial bedforms, which create zones of greater flow. Recent work on modern rivers and ancient sediments has led to a conceptual model of the hierarchy of fluvial forms within channel-belts of gravelly braided rivers, and the corresponding scales of heterogeneity within the stratal architecture. The channel belts are composed of compound bars and channels. Compound bars are composed of unit bars and are often cut by cross-bar channels. Unit bars are built from the deposits of various bedforms, with those of dunes representing the greatest volumetric proportion. Stratasets of open-framework gravel formed with dune migration are the highest permeability strata within the hyporheic zone. The connectivity of open framework gravel stratasets changes across the scales of the fluvial forms and associated scales of stratal architecture. A model for this hierarchical stratal architecture, created using a geometric simulation methodology, will be used within a flow model of the hyporheic zone as described in a related presentation by Zhou, Ritzi, Dominic, and Soltanian.