Assessing lithologic discontinuities and parent material uniformity within the Texas sandy mantle and implications for archaeological burial and preservation potential in upland settings

Abstract

Alfisols within the Texas Gulf Coast Plain commonly exhibit textural contrasts between sandy, artifact-bearing A–E horizons (i.e., sandy mantle), and artifact-sterile clay-rich Bt (argillic) horizons. This has invoked debate about parent material uniformity and pedogenic versus geomorphic sandy mantle origins, which has implications for the scientific value of buried archaeological sites. To improve our understanding of archaeological burial in upland settings, we evaluated parent material uniformity within five pedons to distinguish pedogenically derived textural changes from geomorphologically created lithologic discontinuities. Depth trends in clay-free particle size classes and stable/immobile Ti and Zr constituents failed to reveal lithologic discontinuities between the sandy mantle and Bt horizons, and the observed textural differences are interpreted to have resulted from pedogenic processes. This interpretation is supported by clay skins, fine clay increases in Bt horizons, and micromorphological observations. Consequently, artifacts buried in upland summits have likely moved down the soil profile due to biomantle processes. Deep sandy mantle sites, non-parallel contacts between the sandy mantle and Bt horizons, and paleogullies incised into Eocene bedrock are better explained by colluvial/soil creep processes adjacent to summits, where archaeological materials may exhibit preservation potential. No single explanation can account for sandy mantle origins, and we advocate a case-by-case approach.

Textural diversity in selected Retisols in the catena of the Opalenica Plain (western Poland)

“…Results of the Ward clustering confirmed that the profile differences in particle size distribution in Retisols is mainly a result of translocation of the finest particles from the eluvial horizons to illuvial ones (Marcinek and Wioelañska 1984, Komisarek 2000, Komisarek and Sza³ata 2008, although in the pedons studied an abrupt change in particle size distribution is found. This interpretation is in agreement with the results reported by Ahr et al (2012Ahr et al ( , 2013 for sandy mantle Alfisols of the Texas Gulf Coastal Plain. CONCLUSIONS 1.…”

New insights into the origin and evolution of glossic features in coarse‐textured soils in northern lower Michigan (USA)

“…A critical component of pedogenic research is the assessment of potential parent material nonuniformity (i.e., the presence of lithologic discontinuities [LDs]; Ahr et al., 2012; Schaetzl, 1998; Schaetzl, Kasmerchak, et al., 2020). Assessment of parent material uniformity is usually done by examining the vertical distribution of immobile particle size separates, particularly sands, and/or slowly weatherable index elements (e.g., Zr and Ti).…”

“…Because LDs often form as a result of changes in depositional environments, abrupt dissimilarities in the concentration of these components with depth are considered an indicator of parent material nonuniformity (Soil Survey Staff, 2014b). We conducted our evaluation on a pedogenic (mobile) constituent‐free basis, so as to not mathematically bias data on the immobile skeletal fraction (Ahr et al., 2012; Soil Survey Staff, 2014b), by focusing on data from the medium and fine sand subfractions, because of their greater abundance. Additionally, we used Zr and Ti data derived from the pXRF to evaluate index element distribution.…”

“…It is important to reiterate, however, that geochemical analyses were conducted on the whole‐soil material. Thus, we acknowledge the potential for inconsistencies in use of these data, especially Ti (Ahr et al., 2012; Anda et al., 2009; Dąbkowska‐Naskręt & Jaworska, 2001; Sudom & Arnaud, 1971), for identification of LDs, particularly in lower profile horizons that have experienced translocation and/or have not undergone significant leaching.…”