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.
Highlights
The threshold concept is commonly used for discerning the impact of geomorphic processes on landscape evolution [1,2,3]
This study examines the geographic distribution of late-Quaternary buried soils developed in common parent materials in the ecotonal area between the Southern High Plains and westernmost Rolling Plains near Post, Texas (USA)
The general soil threshold model developed from this study indicates a crossover in pedogensis or soil/landscape preservation at a certain elevation, with the late-Pleistocene to early Holocene soil and middle-Holocene ULS soil restricted to the upper reaches of the drainage system, and late-Holocene soils found in both the upper and lower reaches
Summary
The threshold concept is commonly used for discerning the impact of geomorphic processes on landscape evolution [1,2,3]. This study examines the geographic distribution of late-Quaternary buried soils developed in common parent materials in the ecotonal area between the Southern High Plains and westernmost Rolling Plains near Post, Texas (USA). The aims of this study are to: (1) identify whether a threshold impacts the formation and preservation of soils within the research area; and (2) develop a model that integrates the results of the initial study [22] and current study to provide a better understanding of regional geomorphic processes and their impact on landscape evolution and the archaeological record. A combination of particle size, calcium carbonate equivalence (CCE), total organic carbon content (OCC), and thin-section analyses were conducted at 16 of the 19 profiles to confirm field descriptions and to delineate episodes of parent material deposition. Additional laboratory analysis of total carbon and total nitrogen has been determined by a LECO truspec CN analyzer
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