Dr. Malka Machlus
Earth Institute Contact: Dr. Malka Machlus
Additional External Researchers:
Samual Bowring, MIT
Locations: North America
It has become clear that the Ar-Ar and U-Pb communities are in need of better standards for inter-laboratory comparisons, and these needs are being addressed by the EARTHTIME initiative- a consortium of geochronologists facing the challenge of producing Ar-Ar and U-Pb ages that are accurate at the 1 per mil level. At present there are few standards of Paleozoic age that can be used and we propose to test an ash that has an excellent prospect to fill this gap. The proposed work is to contribute to the goals of the EARTHTIME initiative by testing the suitability of sanidines from the Fire Clay tonstein of the central Appalachian Basin as a Paleozoic monitor standard for 40Ar/39Ar work, and by testing the suitability of its zircons as a U-Pb standard. The published results from this tonstein indicate that the proposed work has a high probability of success. Beyond the goal of developing and distributing standards, this tonstein has potential for contributing to the ongoing comparisons between the U-Pb and 40Ar/39Ar chronometers, and it is a significant ash in the context of placing precise constraints on the Permo-Carboniferous of North America. Ar/Ar dating of single sanidine crystals will be carried in Lamot, and if successful, sanidines will be distributed among other Ar-labs for further inter-lab calibrations (e.g., BGC, Rutgers, MIT). S.A. Bowring (MIT) has agreed to evaluate the suitability of the zircons as a U-Pb standard through the EARTHTIME program, and if suitable, to make it available to other labs. The immediate goal is to test the homogeneity of both systems at the single-grain level.
Cross Cutting Themes:
Climate and Society