Single and Multigrain Quartz-Luminescence Dating of Irrigation-Channel Features in Santa Fe, New Mexico

Acequias (irrigation channels and ditches) were used by Spanish settlers, their descendants, and Native Americans in New Mexico. Several Such features were recently excavated in Santa Fe, but material for numeric dating was difficult to find. Therefore, for this high-energy-deposition irrigation-feature setting we applied optically stimulated luminescence (OSL) sediment dating methods to determine the timing of last. filling of some of these acequias. We report multigrain single-aliquot quartz (MGSAQ) OSL dating results and the first single-gram quartz (SGQ) OSL dating results for irrigation features. One sample yielded an average age of 96 +/- 13 yr, consistent with the maximum expected age of 127 yr (before 2007). An OSL age of 175 +/- 15 yr for another sample delimits a sedimentation event since the first, construction of that feature ca. 300 yr ago. A sample known to be younger than 400-450 yr but predating the mid-19th century gave an SGQ age of 376 +/- 31 yr. These results indicate that: (1) Regional quartz in New Mexico is highly favorable to OSL dating; (2) in this setting, SGQ OSL dating is preferred to MGSAQ dating; and (3) for the last. 500-600 yr, SGQ OSL dating in such settings is preferred to C-14 dating because OSL dating lacks those ambiguities inherent in converting C-14 ages to calendar years. (C) 2009 Wiley Periodicals, Inc.