The landslide on State Route 87 was mapped by Clay Conway of the USGS in 1995 in a geologic map and report (Geology of the Kitty Joe Canyon Area, Mazatzal Mountains, Arizona) to ADOT prior to the rerouting of the highway then. He described landslide deposits (Ql) in the region being up to 120 feet thick.
Ann Youberg here at AZGS superimposed the new highway route onto an airphoto with the Quaternary landslide and talus/colluvium (Qto - "mass wasting") units from Conway's map.
The active area affecting the highway appears to be in the talus/colluvium unit. A larger version of this map and the Conway report will be posted to the AZGS website.