Upper Jurassic mollusks from eastern Oregon and western Idaho

Jurassic ammonites of early Callovian age occur throughout more than 13,000 feet of strata exposed along and near the South. Fork of the John Day River near Izee in east-central Oregon. They occur also in several hundred feet of dark shale exposed along Dennett Creek near Mineral, Idaho. Other ammonites of early Oxfordian age were found in Idaho about 400 feet above the base of 1,000 feet of tough noncalcareous black shale exposed in the canyon of the Snake River near the northeast corner of Oregon and the southeast corner of Washington. These Oxfordian ammonites were collected in Idaho about one-third of a mile east of the Snake River. The black shale in which they occur is well exposed on the Oregon side of the canyon.