Topographic Thresholds and Soil Preservation along the Southern High Plains Eastern Escarpment, Northwest Texas, USA

Abstract

The eastern escarpment of the Southern High Plains (USA) is today a semi-arid erosional landscape delineated by canyon breaks and topographic relief. A series of buried soils were identified, described, and sampled at 19 soil profile localities exposed along terraces of the South Fork of the Double Mountain Fork of the Brazos River (South Fork) and two associated tributaries (Spring Creek and Macy 285 drainage). Radiocarbon dating revealed late-Pleistocene to early Holocene (~12,580–9100 14C B.P.), middle-Holocene (~6025–4600 14C B.P.), and late-Holocene (~2000–800 14C B.P.) buried soils. The late-Pleistocene to middle-Holocene soils were preserved only at higher elevations within the upper section of the South Fork and Spring Creek. A topographic position analysis was conducted using GIS to identify and examine the impacts of a soil topographic threshold on the preservation and distribution of buried soils within this geomorphic system. Above the identified ~810 m threshold, lateral migration of channels was constrained. Extensive channel migration below the threshold removed older terraces that were replaced with late-Holocene terraces and associated buried soils. Landscape topography constraints on geomorphic processes and soil formation impacted the preservation of archaeological sites in this semi-arid region.

Late Quaternary Stratigraphy and Geochronology of the Spring Creek Drainage along the Southern High Plains Eastern Escarpment, Northwest Texas

“…Radiocarbon dating involved organic sediments (Table A1 in Appendix A), charcoal (Table A2), and bone (Table A3), totaling 85 samples. From those dated samples, only 5 (5.9%) have been cited previously (four in Murphy et al [8], Macy Locality 100 profile A, Table A1; and one in Conley et al [2], Macy Locality 10 profile B, Table A1). The current radiocarbon results, then, provide a 94.1% increase in dated samples for the transect area.…”

“…Unit 4 rests conformably on unit 3 (middle fluvio-lacustrine unit). This upper fluviolacustrine unit is composed primarily of silty clay to silty loam sediments, with interspersed pedogenic soft secondary carbonate masses and root tracings [1,2]. A buried soil delineates the upper boundary and represents a period of landscape stability.…”

“…From a landscape perspective, the preservation of these older sediments was controlled by local topography. This topographic control also affected the broader regional soils record [1,2,22,29].…”

“…Over the past 11 years, research activities in the uppermost reaches of Spring Creek on the eastern edge of the Southern High Plains, Texas, have identified, explored, and excavated a series of Late Pleistocene vertebrate faunal localities and Holocene archaeological sites [1][2][3][4][5][6][7][8]. In addition to faunal and cultural studies, the research effort also has involved intensive investigation of associated Spring Creek depositional patterns.…”

“…Instead, The research reported here expands the initial work in upper Spring Creek (e.g., [1,8]) based on additional profiles, stratigraphic refinement, and an increased number of radiocarbon dates. Of the 19 localities in Conley [1] and Conley et al [2], only one (Macy Locality 10) is within the Spring Creek Valley. The previous study of that one profile has identified a buried soil and provided a radiocarbon date from the A-horizon of the buried soil.…”