Named for exposures at Coon Hollow, Wallowa Co, OR. Type section is on ridge south of Little Cougar Creek, southern Nez Perce Co, ID. These areas lie in the Eastern Columbia basin. Cross section. Weathers rapidly. Exposed as rounded slopes. Both contacts are angular unconformities. Lower contact revised. Overlies the newly named Wild Sheep Formation of Seven Devils Group in north part of area. Overlies the newly named Kurry Creek Member of the newly named Doyle Creek Formation at Pittsburg Landing, Idaho Co, ID. Underlies Columbia River Basalt Group. Consists mostly of black to brown mudstone, minor siltstone and sandstone, rare conglomerate beds and breccia about 600 m thick. A basal conglomerate has clasts mostly sedimentary origin and rarely volcanic origin. Fossils rare; Oxfordian ammonite found 125 m above base. Callovian ammonite found in exposures near Pittsburg Landing. Composite graphic section.

Source: GNU records (USGS DDS-6; Denver GNULEX).