Clay coatings from a modern soil chronosequence: A tool for estimating the relative age of well-drained paleosols

Abstract

Blue light optically stimulated luminescence (OSL) dates obtained from upland and terrace soil profiles in southeastern Mississippi have been used to generate a model for illuvial clay accumulation in deeply weathered, subtropical soils (e.g. Ultisols). The illuvial clays developed in upland vs. alluvial terrace soils of southeastern Mississippi are distinct in terms of thickness and total volume of translocated clay. The coatings in the Mississippi soils are also an analogue for clay coatings observed in mid-Cretaceous paleosols of North America. Many of the Cretaceous paleosols had a polygenetic history. The relative age of the well-drained phase of pedogenic development, characterized by illuvial clay accumulations, may be estimated using the model generated from the Mississippi soils. As many of the mid-Cretaceous paleosols mark unconformities, it would be beneficial to estimate the duration of the hiatuses. Three geomorphic surfaces characterize the landscape of southeastern Mississippi: uplands, stream-cut terraces, and modern alluvium. The present floodplain, has poorly developed soils, and lacks illuvial accumulations. Soils developing in the uplands have abundant and prominent illuvial clay coatings up to 2 mm thick, while the terraces have minor clay coatings less than 1 mm thick.