COLLABORATIVE RESEARCH: Middle Miocene Biogeography and Biostratigraphy in the Northern Rocky Mountains of Idaho, Montana, and Wyoming

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This project continues work on the effect of middle Miocene tectonism on mammalian biogeographic patterns in the northern Rocky Mountains. The project will test hypotheses concerning the concordance between morphologic patterns, biogeographic patterns and development of the Mid-Tertiary unconformity in Idaho, Montana, and Wyoming. The study will focus on interpreting the geochronologic and biogeographic patterns of the geomyoid rodents (gophers, kangaroo rats, and such) from Barstovian deposits in 5 intermontane basins. Geomyoid rodents are the focus because they underwent a pronounced radiation just after the unconformity developed. Computerized imaging and Geographic Information System techniques, combined with a cladistic approach, will be used to analyze the biogeographic meaning of the abundant geomyoid dental remains from well-dated horizons in each of the basins, as well as appropriate comparative material from other localities in the Great Plains and Great Basin. The research is of widespread interest in (1) identifying the interplay between geologic and biotic processes on a timescale that has received little attention (2-3 million years); (2) applying new paleontological techniques (imaging and GIS) that allow us to address problems of interest to both paleontologists (evolution, speciation) and geologists (chronology of basin formation) and (3) refining links of the magnetostratigraphic, vertebrate biochronologic, and radiometric time scales in the middle Miocene, which is critical for understanding the tectonic evolution of the northern Rockies.