Abstract
Interbasinal stratigraphic correlation provides the foundation for all consequent continental-scale geological and paleontological analyses. Correlation requires synthesis of lithostratigraphic, biostratigraphic and geochronologic data, and must be periodically updated to accord with advances in dating techniques, changing standards for radiometric dates, new stratigraphic concepts, hypotheses, fossil specimens, and field data. Outdated or incorrect correlation exposes geological and paleontological analyses to potential error. The current work presents a high-resolution stratigraphic chart for terrestrial Late Cretaceous units of North America, combining published chronostratigraphic, lithostratigraphic, and biostratigraphic data. 40Ar / 39Ar radiometric dates are newly recalibrated to both current standard and decay constant pairings. Revisions to the stratigraphic placement of most units are slight, but important changes are made to the proposed correlations of the Aguja and Javelina formations, Texas, and recalibration corrections in particular affect the relative age positions of the Belly River Group, Alberta; Judith River Formation, Montana; Kaiparowits Formation, Utah; and Fruitland and Kirtland formations, New Mexico. The stratigraphic ranges of selected clades of dinosaur species are plotted on the chronostratigraphic framework, with some clades comprising short-duration species that do not overlap stratigraphically with preceding or succeeding forms. This is the expected pattern that is produced by an anagenetic mode of evolution, suggesting that true branching (speciation) events were rare and may have geographic significance. The recent hypothesis of intracontinental latitudinal provinciality of dinosaurs is shown to be affected by previous stratigraphic miscorrelation. Rapid stepwise acquisition of display characters in many dinosaur clades, in particular chasmosaurine ceratopsids, suggests that they may be useful for high resolution biostratigraphy.
Highlights
In 1952, Cobban and Reeside [1] published a grand correlation of Cretaceous rocks of the Western Interior of central and southern North America, including both marine and terrestrial units, and biostratigraphic ranges for a variety of invertebrates and vertebrates
Broad-scale correlations akin to that of Cobban and Reeside [1] are less common, but examples include Krystinik and DeJarnett [2], Sullivan and Lucas [3, 4], Miall et al [5], and Roberts et al [6]. Construction of these kinds of correlation charts is built upon a great wealth of literature; the product of dedicated work by generations of stratigraphers working in the Western Interior
The value of such analyses is inherently dependent upon the accuracy of the plotted taxa, which in turn depend upon the accuracy of the stratigraphic correlations of the formations from which their fossils were recovered
Summary
In 1952, Cobban and Reeside [1] published a grand correlation of Cretaceous rocks of the Western Interior of central and southern North America, including both marine and terrestrial units, and biostratigraphic ranges for a variety of invertebrates and vertebrates Such interbasinal correlation diagrams are enormously useful for making stratigraphic comparisons between units and similar style diagrams have become commonplace in the geological literature. A simple example is that of time-calibrated phylogenies, where the stratigraphic positions of individual taxa are superimposed on phylogenetic trees These are becoming much more prominent in the dinosaur literature Precise dating of geological formations is especially critical for testing anagenesis or cladogenesis in dinosaurs [8, 11], but when specimens are very similar in age, imprecision of only a few hundred thousand years is often enough to completely reverse paleobiological interpretation
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