Lithofacies of the Pennsylvanian Osha Canyon Formation at the type section, Jemez Mountains, New Mexico
— Karl Krainer and Spencer G. Lucas

The Pennsylvanian Osha Canyon Formation at the type section in the Jemez Mountains (northern New Mexico) is a 27.3-m thick succession composed of fossiliferous marly shale with intercalated limestone beds and a mixed  siliciclasticcarbonate sandstone bed on top. Limestone is represented by bioclastic grainstone, locally grading into packstone. The mixed siliciclastic-carbonate sandstone forming the uppermost part of the section contains up to 20% skeletal grains. Sediments of the Osha Canyon Formation were deposited in a shallow-marine shelf environment with normal salinity. Fossiliferous marly shales indicate low-energy conditions below wave base; intercalated limestone beds and sandstone on top were deposited under highenergy conditions above wave base. Deposition of the Osha Canyon Formation occurred during a period of relative tectonic quiescence with some weak tectonic pulses, which probably caused minor sea-level changes. Increased siliciclastic influx in the upper part of the Osha Canyon Formation points to increased tectonic activity.