Late Quaternary sedimentary architecture and depositional history of the Monahans Dune Field, Winkler County, TX.

The Monahans dune field is a Quaternary eolian system on the Southern High Plains in west Texas. Previous work characterizing the Monahans is limited by the depth and spatial coverage of stratigraphic analyses. This study presents the initial results of an ongoing study of the dune system facilitated by the collection and analysis of 81 sonic boreholes (>40 m) and 18 Geoprobe direct push cores (5-19 m). Three-dimensional modeling of these data, and exploratory passive seismic observations reveals a complex depositional record of eolian and palustrine deposition, and pedogenesis. This study analyzes the depositional sequence, geometry and chronology of Blackwater Draw Formation (BWD) and coeval lacustrine sequence. Sonic boring infill logs and geophysical exploration records were used to define the basal depositional surface. The eolian sands and in fill across a northwest to southeast slope thinning eastward to an escarpment and subsurface depressions which are not reflected in the current topography. The chronology of the near-surface stratigraphy was derived from Optically Stimulated Luminescence (OSL) and Thermal Transfer (TT-OSL) Single Aliquot Regeneration (SAR) protocols on quartz grains from in-tact sediment cores. The stratigraphy and chronology of quartz grains from these cores document thirteen eolian deposition phases (EDPs). These phases document a recurring cycle of eolian activity, stabilization and pedogenesis, and erosion. The results of this study provide new insight into sedimentary structures, processes, and depositional history within the Monahans dune system, and relationship with climate variability in the late Quaternary Southern High Plains.