From abstract: Jurassic ammonites of late Bathonian to middle Callovian Age have been found in 12,000-13,000 feet (3,660-3,960 m) of strata exposed in the area near and south of Izee and Seneca in east-central Oregon. Ammonites of early Callovian Age and possibly also late Bathonian Age occur in several hundred feet of black shale exposed along Dennett Creek near Mineral, Idaho. Early Callovian ammonites also occur in similar black shale exposed on the Oregon side of Snake River Canyon about 32 miles (52 km) south of the northeast corner of Oregon.