High-Resolution Dating of Key Beds

Constraining rates of Earth surface processes, such as sedimentation or volcanic eruption, is one of the fundamental problems in many fields of the earth sciences. Estimating sedimentation rate can be done by dating eruptions of interlayered volcanic ash beds. Constructing high-precision geochronology for such strata has been done primarily by U-Pb dating of zircon and 40Ar/39Ar dating of sanidine. The results have been used to constrain stage boundaries and to estimate rates of surficial processes, including the rate of Cambrian biological diversification and evolution, and the tempo of the end Permian mass extinction.

I would like to work on establishing a time scale and a correlation for continent successions based on the 40Ar/39Ar dating and characterization of altered ash beds interlayered throughout the sedimentary succession. Ordovician strata, widely distributed in the North America are unique in paleontological and physical features, have been exceptionally well studied, and the absolute timing and rate of the sedimentation will provide important insight into near surface processes that operated during the Early Paleozoic. Ordovician K-bentonites are also distributed in the Eastern Europe, therefore it may be possible to test inter-continental correlation between Laurentia and Baltoscandia by constraining the eruption ages.

Another interesting research subject is dating young volcanic samples. Ever improved 40Ar/39Ar and (U-Th)/He techniques allow for dating relatively young, even historical volcanic eruptions. To successfully date such young samples, it is essential to use high-resolution techniques to detect small amounts of the daughter elements, 40Ar and 4He, and to avoid possible bias due to air contamination. Dating archaeologically important localities would be possible if the samples contain K- or (U,Th)- rich phases.

Related publications:
Min K, Reiners PW, Wolff J, Mundil R, Winters LR (in press) (U-Th)/He dating of volcanic phenocrysts with high-U-Th inclusions, Jemez Volcanic Field, New Mexico. Chemical Geology

Min K, Renne PR and Huff WD (2001) 40Ar/39Ar dating of Ordovician K-bentonites in Laurentia and Baltoscandia. Earth and Planetary Science Letters, v. 185, p. 121-134.