Paper No. 2
Presentation Time: 8:25 AM


CRAMER, Bradley D., Department of Earth and Environmental Sciences, University of Iowa, 121 Trowbridge Hall, Iowa City, IA 52242, SCHMITZ, Mark D., Department of Geosciences, Boise State University, 1910 University Drive, Boise, ID 83725-1535, HUFF, Warren D., Department of Geology, University of Cincinnati, PO Box 210013, Cincinnati, OH 45221-0013, BERGSTROM, Stig M., School of Earth Sciences, The Ohio State University, Columbus, OH 43210-1308 and KOLATA, Dennis R., Illinois State Geological Survey, Prairie Research Institute, University of Illinois, 615 E. Peabody Dr, Champaign, IL 61820,

Advances in geochronometry during the previous decade revolutionized our ability to determine numerical time in the ancient past. Similarly, major advances in chronostratigraphy revolutionized our ability to determine relative time in the ancient past as well, particularly through the use of integrated high-resolution biostratigraphy and high-resolution (often cm-scale) chemostratigraphy. Until recently however, these two communities were mostly independent from one another and the potential resolving power of integrating their efforts in deep time has been largely underutilized.

Integration in deep time of the two communities through the EARTHTIME Project and the International Geoscience Programme (IGCP) Project 591 during recent years have begun to demonstrate the resolving power of fully integrated geochronometry and chronostratigraphy and have begun to open new lines of inquiry for the deep time geoscience community. High resolution chronostratigraphically controlled high-precision geochronometric ages recently produced for the Silurian Period demonstrate that global chronostratigraphic correlation within the Milankovitch band (<400kyr) is regularly achievable for Paleozoic strata, provide considerable improvement to the calibration of the Silurian Time Scale, and provide some of the first high-precision determinations of rates of biogeochemical change during major Paleozoic global change events.

Here, we present two new chronostratigraphically controlled, high-precision U/Pb (zircon) dates from volcanic ash deposits from the Ludlow Series (Silurian System) of Podolia, Ukraine. These new dates effectively bracket the largest perturbation of the global carbon cycle (Lau Excursion) and help to constrain one of the most rapid increases in 87Sr/86Sr (Ludlow Rise), during the past 500 Myr. These new dates demonstrate rates of geochemical change during the Silurian Period that significantly exceed model predictions challenging our understanding of the Paleozoic Earth system and demonstrating the potential of the Deep Time Earth History Revolution.