SEDIMENT STATE SYSTEM THEORY FOR FLUVIAL-SOURCED BORDERING DUNE FIELDS, MID-CONTINENT NORTH AMERICA

Fluvial-sourced boarding dune fields are found in proximity to large alluvial rivers throughout the non-glaciated region of mid-continent North America. Geochronological data constrain the formation of these dune fields to the latest Pleistocene and early Holocene, with subsequent middle and late Holocene reactivations in response to widespread regional droughts. Though prehistoric drought likely played a significant role in the development of dunes visible today, the influx of sediment from alluvial sources, or lack there of, should not be overlooked as a significant factor influencing construction and subsequent reactivation of these landscapes. This research presents a new spatial-temporal sediment state system theory for fluvial-sourced bordering dune fields in the mid-continent North America, supported by geomorphic and chronologic evidence. This theory proposes high sediment flux at the end of the Pleistocene as the principle driver for dune construction and activity at that time, not drought. As sediment flux decreased, dune fields reached equilibrium state throughout the early Holocene, causing widespread landscape stability. Dune field destabilization and reactivation during the middle and late Holocene correspond to periods of low sediment flux, and, therefore, represent a landscape response to drought. Limited pulsed sediment flux in some rivers during the Holocene may explain the lack of regional correlation evident in some aeolian-derived drought chronologies.