UPPER TRIASSIC TETHYAN REEF FAUNAS IN THE BLUE MOUNTAIN PROVINCE, WALLOWA TERRANE, NORTHEASTERN OREGON

Reefs are high-diversity, laterally zoned, biologically accommodated assemblages with biotic framework. During the Late Norian, scleractinian corals flourished and created extensive reef systems around the Triassic tropics. Norian-age reef-like assemblages are present in three localities within the Wallowa terrane. The first being Black Marble Quarry which is located in the northern Wallowa Mountains and Summit Point and Red Gulch situated in the southern Wallowa Mountains. The Martin Bridge and Hurwal Formations are part of the Wallowa terrane, one of numerous island arcs of the North American Cordillera, which display rocks ranging from Upper Triassic to Lower Jurassic. The Triassic portion contains scleractinian corals, sponges and rare reef-like structures which date closely to the Carnian-Norian boundary. The Norian reef-like assemblages currently exposed in the Wallowa terrane display great similarities with a newly discovered fauna in the adjacent Huntington terrane. These faunas occur in the Summit Point and Red Gulch localities and show possible links with the Wallowa terrane as well as other Cordilleran terranes, especially Wrangellia. Most of the reef faunas existed at low latitudes and share similarities with distant taxa from the western Tethys (Northern Limestone Alps). Wallowa, and possibly Huntington corals, belong to Tethyan faunas which dispersed across the Panthalassa Ocean. However, due to the dynamic nature of paleogeography associated with terranes, this hypothesis needs revision. Most faunas in the Wallowa terrane are early Norian, while identical species from the western Tethys are considerably younger. Additional sampling and analysis of the Wallowa and Huntington fossils and refined dating will assist in understanding differences between the Blue Mountains region and the Tethys. Further paleontological research will focus on the taxonomy of the reef faunas, improving biostratigraphic correlations, and understanding the paleogeography of the Wallowa and Huntington terranes and their relationships to other Cordilleran terranes and the distant Tethys.