DISTRIBUTION PATTERNS OF CISURALIAN AMMONOIDS OF NORTHERN PANGAEA

This study investigates the Cisuralian ammonoid distribution patterns across Northern Pangaea. Specific areas in the study will include West Texas and Kansas, Nevada, the Canadian Arctic basin, and the Ural Mountains. Ammonoid distribution patterns during the Asselian, Sakmarian, and Artinskian time indicate a possible segregation into equatorial, transitional or temporal, and boreal realms. These distribution patterns and subsequent ocean circulation resulted in a unique occurrence of ammonoids within the temporal localities along the western margin of North America, including locations in Nevada. During the Cisuralian, the western margin of North America consisted of a series of marine basins and associated islands. One of these basins, the Dry Mountain Trough (DMT), is particularly important to our understanding of ammonoid paleogeographies. In general, the ammonoid faunas within the Dry Mountain Trough consist of cosmopolitan and endemic species from either boreal or equatorial realms. More specifically, the Portuguese Springs community consists partially of Nevadoceras steelei, Bamyaniceras sp., Akmilleria n.sp., Properrinites n.sp., Crimites elkoensis, Neocrimites n.sp., and Almites sp. representing an equatorial, warm water realm. Whereas the Beck Springs fauna, including Uraloceras nevadense, Uraloceras involutum, Metalegoceras baylorense, Crimites elkoensis, and Neocrimites n.sp., is indicative of boreal, cool water environments. The purpose of this study is to prepare a series of paleogeographic maps of Northern Pangaea that depict the distribution of these specific genera. These maps will assist in the understanding of migration and evolutionary patterns.