This study will provide new technologies to directly date sedimentary sequences. Proof of the concept will come from dating Neoproterozoic black shales in Grand Canyon via in situ U/Th-Pb microprobe dating of authigenic grains that were precipitated by microbial processes near the time of lithification. New technologies will minimize electron beam diameter, count rate, background regression, conductive coating, interference correction, and error estimation. Geologic applications include precise dating of Neoproterozoic C-isotope excursions.
