F.M. Phillips, M.G. Zreda, S.S. Smith, New Mexico Tech

D. Elmore, P.W. Kubik, University of Rochester

R.I Dorn, Arizona State University

D.J. Roddy, USGS Flagstaff, AZ

Geochimica et Cosmochemica Acta 55 (991) 2695-2698

Using cosmogenic 36Cl buildup and rock varnish radiocarbon, we have measured the exposure age of rock surfaces at Meteor Crater, Arizona. Our 36Cl measurements on four dolomite boulders ejected from the crater by the impact yield a mean age of 49.7 +- 0.85 ka, which is in excellent agreement with an average age of 49 +- 3 ka obtained from thermoluminescence studies on shock-metamorphosed dolomite and quartz. Tbese ages are supported by undetectably low 14C in the oldest rock varnish sample.