Late Quaternary stratigraphy and chronology by thermal-transfer optically stimulated luminescence dating of quartz grains for the Monahans eolian system, Winkler County, Texas.

Abstract

The Monahan's eolian system in west Texas is studied using sixteen Geoprobe cores, >5 m-long, providing a new stratigraphic record for the past 500 ka. The oldest part of the record >100 ka was dated using the novel thermal-transfer optically stimulated luminescence (TT-OSL) method. The TT-OSL emissions show sensitivity to solar resetting, with >90% diminution of signal in 48 hr. Several quartz separates were dated using both TT-OSL and OSL-SAR methods within the age range of 60 to 250 ka and there was concordance at two sigma errors between these optical dating methods. Pedosedimentary analysis of the cores in combination with strategic luminescence dating reveals nine Eolian Depositional Phases (EDP) spanning 80 yr to 515 ka. Among the six older EDP (>70 ka), there appears to be more subsequent pedogenesis forming indurated Bk soils, while the three younger (<60 ka) EDP exhibit mostly weak soil development.