The Geomagnetic Reversal Time Scale is now one of the most useful and firmly established components of chronostratigraphic correlation, at least for times younger than mid-Jurassic. Over the past 10 years, significant extensions of this have been made to earlier times by studying the magnetostratigraphy of well- dated, fossiliferous strata in multiply-overlapping sections. We propose to extend our existing studies over the next 3 years to the Precambrian-Cambrian, Cambrian-Ordovician, Ordovician- Silurian, and the Silurian-Devonian. Although a long-range goal of these efforts is to determine whether or not it is possible to establish a zone-by-zone magnetostratigraphy for the entire Paleozoic, the period boundaries are logical places to start due to the intensive efforts of biostratigraphers searching for global boundary stratotype sections. These boundaries often correspond to times of great evolutionary diversification and/or extinction, and results from the proposed work could find immediate application in measuring the isochrony of extinction and proposed global climatic events, as well as verifying the utility of carbon-isotopic stratigraphy.
