Chlorine-36 in Fossil Rat Urine: An Archive of Cosmogenic Nuclide Deposition During the Past 40,000 Years

• DOI: 10.1126/science.277.5325.538
• Publication Date: 2002-07-27T09:44:47Z
• Authors: Mitchell A. Plummer; Fred M. Phillips; June Fabryka-Martin; H. J. Turin; Peter E. Wigand; Pankaj Sharma
• Keywords: Cosmogenic nuclide; Deposition; Nuclide; Carbon fibers

Knowledge of the production history cosmogenic nuclides, which is needed for geological and archaeological dating, has been uncertain. Measurements chlorine-36/chlorine ( 36 Cl/Cl) ratios in fossil packrat middens from Nevada that are radiocarbon-dated between about 38 thousand years ago (ka) present showed Cl/Cl were higher by a factor 2 before ∼11 ka. This raises possibility rates just close Pleistocene up to 50% than suggested carbon-14 calibration data. The discrepancy could be explained addition low–carbon-14 carbon dioxide atmosphere during period, would have depressed atmospheric radiocarbon activity. Alternatively, climatic effects on Cl deposition may enhanced ratios.