MIDDLE AND LATE PERMIAN PALEONTOLOGY AND STRATIGRAPHY OF THE QUINN RIVER FORMATION, BILK CREEK MOUNTAINS, HUMBOLDT COUNTY, NEVADA

Approximately 200 m of limestone, siltstones, volcaniclastics, siltstones and cherts record deposition in mostly deep marine conditions prior to the Permian-Triassic mass extinction event. The Quinn River Formation potentially records the precursor paleoecologic conditions for the event. Preliminary data collected at the section record: a diverse brachiopod with the most abundant speices beinging Stenoscisma sp, Neophricodothyris sp and a gastropod dominated Middle Permian fauna; a gap in Fossiliferous strata straddling the P/Tr boundary; a prolonged non-fossiliferous stratigraphic interval extending into the Early Triassic; and the return of normal marine conditions in later Early Triassic strata as evidenced by abundant Ammonite fossils. Carbon-Oxygen isotopes show declining trends from the Lower Permian to the Lower Triassic.