Quantitative analysis of fluvial paleohydraulics and intra-channel belt stratal preservation: lower Wasatch Formation, Utah, USA

This article uses measurements from five fluvial channel belts of the Paleocene lower Wasatch Formation to quantitatively document the transience or persistence of flow velocities recorded in stratigraphy at the bedset scale. We use facies proportions and sedimentary structures coupled with a paleoflow velocity workflow to calculate the mean flow velocity for each bedset. Flow velocity measurements were analyzed using a lattice approach that documents either persistence or transience of mean flow velocities, which, in turn was combined with facies trends to infer perennial and ephemeral flow conditions during the deposition of the channel belt. All five channel belts have significant spatial dependence of mean flow velocities. Based on short-range spatial dependence, we infer perennial flow conditions in both laterally and downstream-accreting channel belts, and ephemeral flow conditions in two downstream-accreting channel belts. The remaining channel belt only has short-range spatial dependence as intra channel-belt erosion has completely destroyed any intermediate and long-range flow velocity dependence within the channel belt. Furthermore, we document that intra channel-belt stratal preservation comes at the expense of basin-scale stratal preservation, meaning high channel migration rates destroy basin-scale architecture (stacking patterns) by channel scouring while preserving intra channel-belt morphodynamics at the bedset scale.