(Map site 5.) This roadcut along Little Tujunga Canyon Road is of the Mendenhall Gneiss which occurs only on the north side of the San Gabriel fault. Cutting more or less horizontally across the top of the roadcut is a dark gabbroic dike. These dikes are common in the oldest rocks in the San Gabriel Mountains, but do not occur in the younger rocks. They must, therefore, be of an intermediate age.