A Cretaceous chronostratigraphic database: construction and applications

Abstract

Timing and rates of tectonic events, evolutionary processes, and oceanographic and paleoclimatic changes must be based on high-precision numerical age calibration of stages defined in Global Stratotype and Section Points (GSSPs). The Cretaceous Chronostratigraphic Database (CRETCSDB3) is an objective, testable database that calibrates select Cretaceous events and enables high-resolution chronostratigraphic correlations. CRETCSDB3 is a compilation of more than 3500 taxa and marker beds in nearly 300 published sections calibrated to a mega-annum (Ma) scale. The database spans the Jurassic/Cretaceous and the Cretaceous/Paleogene boundaries. Construction of CRETCSDB3 began by plotting bioevents in the Kalaat Senan, Tunisia, Cenomanian-Turonian section 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 to constrain the accuracy of the numerical scale. Ranges of first and last occurrences are calibrated to mega-annums of Cretaceous stages defined by GSSPs or reference sections. This database serves as a look-up table for interpolation and age calibration of other stratigraphic sections. The age ranges of some taxa and marker beds are preliminary and may be extended as new sections are added to the database. CRETCSDB3 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 97.88±0.69 Ma Clay Spur Bentonite in Wyoming by sequence stratigraphy and cosmopolitan dinoflagellates. The inconsistency between this age and the current 100.5 Ma date of the 2012 Geologic Time Scale remains to be evaluated independently.