Cordilleran Section - 97th Annual Meeting, and Pacific Section, American Association of Petroleum Geologists (April 9-11, 2001)

Paper No. 0
Presentation Time: 8:30 AM


HANGER, Rex A., Department of Geography and Geology, Univ of Wisconsin - Whitewater, 800 West Main Street, Whitewater, WI 53190,

During the Permian, faunas of the west coast of Pangea were dominated by brachiopods, corals, fusulinids, bryozoans and mollusks. West of the coast, in ancient Panthalassa, assorted island arc terranes were populated by coeval faunas of similar higher level taxonomic compositions. Important differences are the presence of both Asiatic and endemic taxa in the terrane faunas. Such data were important in the groundbreaking interpretations of "exotic", far-travelled nature for the terranes. Unfortunately, the presence of a single, or very few, taxa often led to an "exotic" label, despite a preponderance of faunal elements that were congeneric, or even conspecific, with those of the West coast of Pangea. Modern statistical methods more often confused the situation, rather than clearing it up as different methods can be 'picked' to give different results. Probabilistic methods are superior to all others because they test against a null hypothesis of random distribution of taxa in space, and they assess significance in similarity/dissimilarity. Using databases of brachiopods and bryozoans, plus supplemental data from corals and fusulinids, probabilistic similarity analyses considering complete faunas, and not just 'select' taxa, reveal a pattern of northern hemisphere, statistically similar Pangean West coast affinities for most terranes. These results are consilient with recent geochemical and paleomagnetic data. "Exotic" interpretations for terrane paleogeography are thus not always warranted, especially after the Early Permian.