Occurrences of closely related, terrestrial vertebrates at mid- latitudes in North America and Asia suggest that Alaska was part of an intercontinental route of overland dispersal and supported diverse faunas during the late Cretaceous. Until recently the composition of these faunas was unknown. Discovery of concentrations of dinosaur fossils on the Alaskan North Slope opens the possibility for the first assessment of the composition of this Cretaceous fauna. Field work in this area will allow thorough sampling of the vertebrate fauna preserved in North Slope localities. Members of the U.S. Geological Survey are investigating the invertebrate paleontology, paleobotany, tephrachronology, and magnetostratigraphy of this geological section. Correlated with these and other lines of investigation, the occurrences should yield information on the tolerances of some dinosaurs to extremes in temperature and light conditions. Most current hypotheses concerning dinosaurian extinction invoke either catastrophic or gradual environmental change as a causal factor. Determination of the probable ranges of environmental tolerance of Alaskan dinosaurs will contribute to the evaluation of these hypotheses.
