Triassic Woodside Shale, TRw, and Thaynes Formation, TRt, including its massive limestone bed outcrops are shown in the images below.
Above: Mill Creek Canyon takes an abrupt right-angle turn from NW to SW at the Elbow Fork tributary junction. The abruptness of the deflection is due to regional slope helped by the erosion resistance of the massive limestone beds of the Thaynes Formation.
Left: Massive limestone beds of the Thaynes Formation, TRt. Elbow Fork is a Trail Head for the Lambs Canyon, Mount Aire, and the Pipeline trails. The Pipeline Trail is the dirt pathway into a "tunnel" of evergreens in the image. View is downcanyon.