Late Paleozoic coastal plain paleosols: Geochemical insights into soil genesis, provenance, and paleoclimate within paleoequatorial Pangea, Paradox Basin, USA

Abstract

Studies of ancient drylands can enhance our understanding of ecosystem responses to changing climate, but reconstructing deep-time dryland environments using paleosols is challenging because these fossil soils are often weakly developed and many proxies are not equilibrated to past climate. Paleosols from the uppermost Honaker Trail Formation and lower Cutler beds (Rico and Halgaito Formations) span the Pennsylvanian-Permian transition within the Paradox Basin of southeast Utah (USA) and are an ideal setting to explore dryland paleoenvironments. Integration of bulk oxide, micro-XRF, and stable isotopic data allows for assessments of paleoclimate, provenance, and pedogenic processes. Ti/Al ratios track a broadly consistent provenance while Ti/Zr trends follow allochthonous dust contributions, possibly indicating a shift in paleowinds near the Rico-Halgaito boundary that is supported by Ti/Zr and Zr/Hf ratios from within-zircon analysis. Carbon isotopic data suggest pedogenic carbonate formation under conditions of low soil productivity while modeled MAP estimates reveal an average of 409 mm/yr ± 209. Evaluation of MAT and MAP relationships suggests that Inceptisols identified within this study could represent ancient Aridisols. We conclude that dry climatic conditions promoted an unstable landscape for the region encompassing the study interval while also precluding hydrolysis and leaching, resulting in weakly developed paleosols with abundant carbonate features and red coloration. These findings are consistent with other work from the region, pointing to dry conditions and shifting paleowinds within paleoequatorial Pangea during the Pennsylvanian-Permian transition.