OPTICALLY STIMULATED LUMINESCENCE DATING OF FENCE ROW DUNES IN WEST TEXAS AND EASTERN NEW MEXICO

Many people have stated that it was not guns or badges that tamed the west, but barbed wire. Certainly it is an ubiquitous feature on the landscape of the Southern Plains. And, like all features in dynamic geomorphologic systems, barbed wire has taken part in shaping its own landscape. In this project, supported by the 2005 "Gladys W. Cole" award from the Quaternary Geology and Geomorphology division, we have used optically stimulated luminescence (OSL) to date sand dunes deposited along fence rows in Cochran County TX and Roosevelt County NM. In addition to fence row dunes, native dunes at each of the two sites were also sampled and dated. OSL results indicate that all dunes sampled experienced deposition in historic times with an average age of 89 ± 8 yrs (AD 1917) with 1 sigma dates for the sample set ranging from AD 1899 to 1935, which is consistent with historical accounts indicating that ranching with extensive fencing was underway in the area by AD 1900 and homesteading had begun at the turn of the century in Roosevelt County NM and in the 1920's in Cochran County, TX. The native dunes, as anticipated, were found to have an internal core of older dune deposits. These natural dune cores yielded OSL ages corresponding to well documented eolian activity periods at circa 800 and circa 2500 yr ago in the Plains. OSL evidence for deposition during the Dust Bowl years was limited at the study sites. Although luminescence signal intensities were very strong, it is possible that due to the extremely low dose rates measured, OSL may not have been able to resolve the 1910's from the 1930's. However, the area may also have been primarily erosional during the Dust Bowl and deposition may truly be absent at these sites. This study helps validate the utility of OSL dating for establishing chronologies and process rates of historic eolian activity in the region.