APPEKUNNY FORMATION.
Lying on top of the Altyn are 3,000 or more feet of prevailing greenish shales and argillites[2] comprising the Appekunny formation. Slabs of these rocks, because of their great hardness, have been used as flagstones in the walks at the Many Glacier Ranger Station and adjacent Park Service residential area. Mud cracks and ripple marks are common. The formation is prominent on the side of Singleshot Mountain near the St. Mary entrance to the park, and everywhere immediately overlying the lighter-hued Altyn along the east edge of the Lewis Range where, especially when seen from a distance, it appears to have a purplish color. It also outcrops along the western base of the Livingstone Range ([Figure 3]D), but such exposures are as a rule obscured by a cover of dense forest. Accessible outcrops can readily be examined along Going-to-the-Sun Highway for several miles east of Sun Point and near McDonald Falls, and also along the lower part of the Grinnell Glacier trail.