ABSTRACT: Quantitative biostratigraphy finds useful applications in chronostratigraphy and time scale calibration. Fixing the Global Stratotype Section and Point (GSSP) is made more objective if correlation potential of alternative boundary levels is compared using the Unitary Association (UA) method. The base of the Ladinian (Middle Triassic) GSSP is a case in which not the regionally most easily correlatable ammonoid datum was selected. Radio-isotopic dates are often obtained outside the province where the primary standard biozonation is established, introducing a correlation uncertainty into time scale calibration. In the Early Jurassic, an uncertainty of approximately one standard ammonoid substage is demonstrated using the UA method, if using a North American U-Pb date requires correlation with the northwest European zonation. The resolution of the time scale was significantly improved for the Ordovician and Silurian by employing constrained optimization to construct a global sequence of graptolite bioevents. Interpolation between the available U-Pb dates is possible by scaling using the assumption of near-constant sedimentation rate in pelagic facies. Future uses of quantitative biostratigraphy may include exploitation of large paleontologic databases (e.g. the Paleobiology Database) and contribution to the generation of dynamic, interactive geologic time scales.


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