New Mexico Geological Society Annual Spring Meeting — Abstracts

The Mescalero Sands is a sand sheet of eolian origin that occurs between the Pecos River valley and the caprock escarpment of the Ogallala Fm. in southeastern New Mexico. The sand sheet formed on the eroded surface of the Mescalero paleosol, a regional petrocalcic soil that may have developed largely during the Sangamonian. The sand sheet incorporates two distinct eolian sand units, the older accumulating 90 to 70 ka directly on the eroded Mescalero paleosol and the younger one accumulating 9 to 5ka on top of the older sand; their ages are provided by optically stimulated luminescence. The older sand unit is derived from the Ogallala. During the time interval between deposition of the older and younger eolian units, a noncalcic red argillic soil developed on the older sand; the noncalcic character of the paleosol may be in response to the mesic climate of the Wisconsinan. Small parabolic and shrub-coppice dunes mark the modem surface of the sand sheet; luminescence ages of one coppice dune place it wholly within the 20^th century, and cesium-137 content indicates that the upper 22 cm of the coppice dune accumulated since 1954.