Pedostratigraphic influence of late-Quaternary sediments and paleosols on headwall and sidewall canyon morphology in the Arikaree Breaks, Central Great Plains

Abstract

Pedostratigraphy exerts considerable influence on landscape evolution and morphology in the Central Great Plains. Few locations are as well suited to undertake a soil-geomorphic study in this area as the Arikaree Breaks (hereafter ‘Breaks’) of northwestern Kansas and adjacent parts of Nebraska and Colorado. The Breaks are a network of impressive box canyons, which formed through erosion of a late-Quaternary loess-mantled landscape and underlying Late Cretaceous Pierre Shale and are a product of the Arikaree and Republican River watersheds eroding into the uplands of the High Plains. The primary objective of this study was to assess the influence of late-Quaternary sediments, soils, and paleosols on canyon headwall and sidewall morphology. Soil properties determined included rubification index, particle-size distribution, bulk density, dry rupture resistance, organic carbon, calcium carbonate equivalent, pH, electrical conductivity, and horizon development index. Three landform morphology properties were used in this study—surface slope, concavity, and roughness—and were measured with terrestrial laser scanning. A secondary objective was to provide detailed documentation of physical and chemical pedostratigraphic properties and pedogenic morphological development of Central Great Plains sediments (loess and sand), soils, and paleosols. Correlations and predictive statistical relationships indicated that the influence of pedostratigraphic unit and horizon-scale variability of soil properties on surface slope and concavity was muted by hydrological processes at the headwall of the canyon which appeared to control gross wall morphology and retreat as the canyon lengthened and advanced into the uplands. However, surface roughness of the headwall section was influenced by soil properties at the horizon scale. The influence of pedostratigraphic unit and horizon-scale variability of soil properties on surface slope, concavity, and roughness in the sidewall section exhibited stronger roles than in the headwall section in dictating fine-scale morphology and sidewall retreat as the canyon widened and advanced towards other adjacent first-order canyons. Based on the relationships observed in this study, the distinctions between primary influences controlling headwall and sidewall morphology and retreat at different scales are important to consider when predicting canyon and gully development in Central Great Plains sediments, soils, and paleosols and in landscape evolution modeling of canyons and gullies in other areas where thick and highly variable pedostratigraphy is geographically extensive.