This map is a result of a study of the geology and mineral resource potential of the San Carlos Indian Reservation (Reservation) for the San Carlos Apache Tribe. The map provides new information on the geology of an area that contains the boundary between the Basin and Range Province on the south and the mountainous terrain that, in this part of Arizona, borders the southern structural margin of the Colorado Plateaus Province (herein referred to as the Colorado Plateau) on the north. In particular the map shows the great variety of Tertiary volcanic and sedimentary rocks typical of the northern part of the Basin and Range Province in east-central Arizona and the structural complications resulting from Cenozoic extension. Geology depicted in this map may aid in the interpretation of mineral resources between the copper mining areas of the Globe-Miami district to the west of the Reservation and the Morenci district to the east.