Original paper

Improved resolution and quantified stratigraphic uncertainty time scales of the future

Sadler, Peter M.; Cooper, Roger A.


By using automated procedures for compositing and scaling, we build a time scale for the Ordovician and Silurian from the stratigraphic range-ends of over 1,500 graptolite species from over 214 measured sections worldwide. The global scaled composite sequence of range-end events and embedded radiometrically dated levels, achieves a resolution that is ten times better than can be achieved by using fossil zones. When the graptolite zone boundaries are located in the composite, error bars on individual zone boundaries can be estimated in m.y. By integrating composites based on conodont bioevents, the graptolite time scale can be extended into younger, and older, periods. This approach to time scale building offers major improvements in resolution and quantification of error in Paleozoic time scales, using existing biostratigraphy and radiometric data.


ordoviciansiluriancalibrationtime scale developmentresolutionuncertainty