RECONSTRUCTING BAR AND CHANNEL MORPHODYNAMICS FROM ANCIENT RIVER DEPOSITS (Invited Presentation)
Here, we use new paleomorphodynamic measures to reconstruct and compare ancient bar and channel characteristics in a range of Mesozoic and Cenozoic river deposits in the western United States. We first identify avulsion-generated channel-belt deposits, then we evaluate individual bar elements specifically focusing on bar preservation, bar persistence (defined as the relative distance a bar deposit migrated with a coherent form), and bar stacking within a given channel belt. Collectively these measures allow us to compare relative avulsion frequency, relative channel migration, relative bar stability, and the prevalence of forced vs. free bars among different deposits.
This work demonstrates that bar and channel deposits vary widely across ancient fluvial systems, even among systems with similar sand-body dimensions, basin-scale architecture, and overall sand:mud ratios. These measurements allow us to compare detailed aspects of channel morphodynamics to long-term avulsion and floodplain-accumulation patterns in an effort to understand how the process of river meandering is linked to larger-scale fluvial landscape dynamics.