@article{ee0fe3d609ca479fb6168c92ca948561,
title = "New Approach to the Radiocarbon Dating of Rock Varnish, with Examples from Drylands",
abstract = "New electron microscope observations reveal that organic inclusions are often trapped in pockets under rock varnish. Accelerator radiocarbon dating of subvarnish organic detritus provides a new method of constraining when a rock was exposed by cultural or geomorphic processes. Applications are exemplified for human artifacts and landforms found in drylands. Three radiocarbon dates from 30,000 to 36,000 yr B.P. indicate rock engravings in South Australia are among the oldest art yet found in the world and show that humans migrated into what is now the “arid zone” of Australia at least 10,000 years earlier than previously thought. The first direct age control on Nazca geoglyphs and subterranean irrigation aqueducts in southern Peru indicate manufacture around 1400 to 2100 yr B.P. Geoglyphs along the Colorado River were made before 1100 yr B.P. Artifacts from a quarry site in the Mojave Desert, California, yield minimum 14C ages from 3700 to 26,000 yr B.P.",
keywords = "AMS, Colorado River, Mojave Desert, Nazca, Peru, South Australia, alluvial fans, archeology, desert, geoglyphs, geornorphology, human migration, petroglyphs, pukios, radiocarbon dating, rock engravings, rock varnish",
author = "Ronald Dorn and Clarkson, {Persis B.} and Nobbs, {Margaret F.} and Loendorf, {Lawrence L.} and Whitley, {D. S.}",
note = "Funding Information: tial Young Investigator Award and Arizona State University Faculty Grant-in-Aid (Dorn), Social Sciences and Humanities Research Council of Canada Grant #410-89-0642 (Clarkson), Australian Institute for Torres Straight Islander and Aboriginal Studies (Nobbs), and the University of North Dakota (Loen-dorf ). National Science Foundation Grant EAR 84- 08163 paid for the Arizona State University microprobe. This work would not have been possible without accelerator radiocarbon measurements by Isotrace, New Zealand Department of Scientific and Industrial Research Nuclear Science Group, Beta Analytic and Eidgenossiche Technische Hochschule University in Zurich, and the University of Arizona. We thank B. Trapido for graphical assistance; M. Anders, F. Budinger, J. Clark, D. Donahue, D. Dorn, W. Craf, D. Hanna, C. Vance Haynes, D. Krinsley, B. Johnson, A.J.T. Jull, J. Lancho, R. Morrison, C. Lewis, J. Nobbs, M. Owen, P. Pitluga, H. Silverman, K. Schreiber, L. Toolin, P. Trusty, and A. Watchman for discussions, laboratory, and field assistance; anonymous reviewers for an improved way to present this material; and H. Casey for permission to use Figure 4e. Peruvian samples were collected under permit issued to Clarkson by the lnstituto Nacional de Cultura of Peru. California samples were collected at the request of G. Hillier, BLM desert district manager. Funding Information: Funded by National Science Foundation Presiden-",
year = "1992",
month = mar,
day = "1",
doi = "10.1111/j.1467-8306.1992.tb01902.x",
language = "English (US)",
volume = "82",
pages = "136--151",
journal = "Annals of the Association of American Geographers",
issn = "0004-5608",
publisher = "Taylor and Francis Ltd.",
number = "1",
}