USING TLS TO ASSESS THE INFLUENCE OF LATE-QUATERNARY SEDIMENTS AND PALEOSOLS ON CANYON DEVELOPMENT IN THE CENTRAL GREAT PLAINS

The Arikaree Breaks of NW Kansas and adjacent parts of Nebraska and Colorado are a network of spectacular box canyons, which formed through erosion of a late-Quaternary, loess-mantled landscape and underlying Late Cretaceous Pierre Shale. These canyons provide an excellent setting in which to 1) construct a detailed chronostratigraphy of loess deposits and paleosol formation (~400 k-year record), and 2) test the hypothesis that specific stratigraphic units (loess deposits and intercalated paleosols, aeolian sand, basal shale) are critical to controlling canyon development and morphology in this landscape. This research integrates a detailed chronostratigraphy utilizing OSL and AMS ¹⁴C dating with TLS and sedimentologic and pedologic data to develop a conceptual model of canyon evolution. This project is being conducted in a first-order box canyon of the larger Hay Canyon system and has resulted in the delineation of five distinct morphologic zones, from headwall (Zone 1) to mouth (Zone 5). Canyon morphology along this axis (Zones 1-5) is influenced by Pierre Shale, aeolian sand probably deflated from the Ogallala Formation (Miocene-Pliocene), probable pre-Illinoian loess and soils, Loveland Loess and the Sangamon Soil (Illinoian), Gilman Canyon Formation loess and soils (middle Wisconsinan), Peoria Loess (late Wisconsinan), and Bignell Loess and fill (Holocene). Along the axis, headwalls dissecting upland loess transition to increased Pierre Shale exposure towards the canyon mouth. TLS is being used to assess pedostratigraphic controls on canyon development through the analysis of headwall and sidewall slopes and surface morphology. The linear profiles of slopes transition from simple (steep) convex profiles in Zone 1 to complex concave profiles in Zone 5. Description and sampling of stratigraphic and pedologic data by horizon for Zones 1, 3, and 5 are being correlated with linear profiles and surface roughness metrics obtained from TLS data to derive a model of canyon evolution along the canyon axis. In sum, this research is being conducted in an effort to better understand landscape response to climate change, internal system adjustments, and stratigraphic control on canyon development and morphology.