The Accumulation of Cosmogenic Chlorine-36 in Rocks: a Method for Surface Exposure Dating

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Science  03 Jan 1986:
Vol. 231, Issue 4733, pp. 41-43
DOI: 10.1126/science.231.4733.41


Because of the reaction of cosmic rays with elements in minerals, chlorine-36 accumulates in rocks exposed at the earth's surface. This suggests that the ratio of chlorine-36 to stable chloride can be used as a geochronometer. Reasonable agreement has been obtained between measurements of chlorine-36 in volcanic rocks of known age and calculations of chlorine-36 production based on rock composition and cosmicray flux. The buildup of chlorine-36 should be a useful means for measuring the surface exposure time of young volcanic rocks and geomorphic features in the age range of 103 to 106 years.