LUMINESCENCE DATING OF ANTHROPOGENIC FEATURES OF THE SAN LUIS VALLEY: WHAT TO KNOW BEFORE, DURING, AND AFTER SAMPLING

Humans have hunted, gathered, and left signs of their presence in the San Luis Valley of Colorado from well over 11,000 years ago to recent times. Many of the older features that remain are intriguing and include cairns, effigies, stone circles and walls, and rock art. Modern human curiosity over the age of some of these structures has brought about increased study and dating of the objects using the well-established methods of radiocarbon, dendrochronology, and relative dating.

Optically stimulated luminescence (OSL) dating has been used in the San Luis Valley for dating of the Great Sand Dunes (Forman et al 2006, Madole et al 2008), lunettes around the dunes (Brunhart-Lupo 2012), past earthquake reoccurrence at fault scarps (Crone et al 2006), and future work on fluvial terraces of the Rio Grande. Although OSL is commonly used at other archeological sites throughout the country (Topper, Buttermilk Creek, Cactus Hill, etc.), within the San Luis Valley it has not been applied because of the abundance of organic remains for radiocarbon or lack of money for OSL dating. At other sites, most of the OSL ages are obtained from sediment or ceramics, with the occasional stone tool (if heated at some point); however, if one thinks “outside of the box” then endless possibilities become available. OSL has been used to date the time of emplacement for teepee rings, stone walls, stone huts, earthen mounds, and cairns.

What should archeologists or Quaternary geologists know about the luminescence technique before determining whether the site they have found would be suitable for OSL dating? What would be important to have at the site and what could be unimportant or missing and still guarantee an effective outcome? Using two case histories of structures that were dated in 2011 and 2012, the appropriate steps and procedures will be explained and a template will be given for the successful dating paradigm.