A CRETACEOUS CHRONOSTRATIGRAPHIC DATABASE: CONSTRUCTION AND APPLICATIONS
The CRETCSDB1 is a compilation of more than 3400 taxa and marker beds in more than 295 published sections calibrated to a mega-annum scale. The database spans the Jurassic/Cretaceous and the Cretaceous/Paleogene boundaries. The first step in calibrating bioevents to a time scale in the CRETCSDB1 was to graph the Cenomanian-Turonian section at Kalaat Senan, Tunisia, to the 1989 time scale. The sedimentology, sequence stratigraphy, and biostratigraphy of this section were precisely documented and stage boundaries defined biostratigraphically. Additional sections with radiometrically dated beds were graphed in successive steps to refine the mega-annum accuracy of the numerical scale. The ranges of first and last occurrences are calibrated to mega-annums of Cretaceous stages defined by GSSPs or reference sections. The age ranges of some taxa and marker beds are preliminary and may be extended as new sections are added to the database. This database is a look-up table or a source for various quantitative methods of interpolation and calibration of other stratigraphic sections.
The CRETCSDB1 tested the numeric age calibration of the Albian/Cenomanian boundary. This boundary in North Texas accurately correlates with the GSSP in France by ammonites, planktic foraminifers and dinoflagellates. This stage boundary in North Texas correlates with the 97.17±0.69 Ma Clay Spur Bentonite in Wyoming by sequence stratigraphy and cosmopolitan dinoflagellates. The inconsistency between this age and the current 99.6 Ma date remains to be evaluated independently.