The region oscillated between terrestrial and shallow ocean conditions during the Paleozoic as multi-cellular life became common and three major orogenies to the east shed sediments before North America became part of the supercontinent Pangaea.
[1][2] The oldest rocks in Arizona likely date to the late Archean or early Proterozoic, although evidence of earlier geology was overwritten during the Yavapai orogeny and the Mazatzal orogeny—major mountain building events 1.8 to 1.6 billion years ago.
In Arizona, these veins commonly host exotic minerals including beryllium and tantalum, and elements like lithium, bismuth, uranium and tungsten.
The major Grenville orogeny in the east of the Proto-North American continent impacted areas as far west as Arizona, producing large rift basins between 1.2 and 1 billion years ago.
The Great Unconformity is a famous gap in the stratigraphic record of the Grand Canyon of 900 million years between Proterozoic granitic rocks and Cambrian marine sediments.
These, in turn, are overlain by sandstone, siltstone and shale deposited under near-shore conditions, which were covered over 515 to 488 million years ago by limestone, traced with worm boreholes, as well as thin beds of conglomerate.
Due to uplift during the Taconic orogeny, the sea retreated and Arizona returned to continental conditions during the Ordovician and Silurian leaving few rocks from these time periods.
During the Devonian, Arizona alternated between marine and continental conditions, as a subduction zone and volcanic island arc appeared in the area of Nevada.
The Martin Formation in southern Arizona contains limestone, sandstone, shale and chert deposited in the Late Devonian and laden with fish and invertebrate fossils.
Subsequent erosion has generated large caves in the limestone, including Kartchner Cavern in Cochise County and the Grand Canyon's Vesey's Paradise.
During the Pennsylvanian and the Permian, the final assembly of the Appalachian Mountains to the elevation of the Himalayas occurred with the Alleghanian orogeny and the formation of the supercontinent Pangaea.
Glaciation of the southern hemisphere raised and lowered sea levels in Arizona, creating the ledge and slope topography common in the Grand Canyon, Sedona and Monument Valley, with alternating layers of siltstone, limestone, sandstone, dolomite and shale.
As the oceanic plate subsided under North America, it generated partial melting conditions that formed volcanoes on the surface in California and Arizona.
The main Laramide phase from 79 to 67 million years ago created massive volcanic centers, which erupted huge volumes of andesite and rhyolite ash.
[4] Due to flat subduction during the final phase of the Laramide orogeny from 54 to 43 million years ago in the Eocene epoch of the Cenozoic, deep intrusion of granite and pegmatite took place, 23 kilometers below the surface.
Granitic plutons tended to form near well-developed crush zone and often have tungsten and quartz rich veins in garnet-muscovite granitoids and pegmatite dikes.
During the Eocene, Oligocene and Miocene, the Mid-Tertiary ignimbrite flare-up, a mountain building event tied to the Farallon Plate, erupted huge quantities of volcanic ash.
The eruptions are believed to have been partly the result of increasing steep slab subduction into the mantle and magmatic activity shifted from the east to the west, bringing with it changes in mineralogy and rock types.
In the last 14 million years of the Miocene, Pliocene, Pleistocene and the current Holocene, the subducting Farallon slab was cut off by strike-slip motion on the San Andreas Fault, coupled with a transform boundary.
Basalt intruded into the basins and evaporites and other sediments accumulated, including salt beneath Phoenix, clay and zeolites in the Bowie area and gypsum in both the San Pedro and Verde valleys.
[6] The USGS published research in 1997, examining the Pennsylvanian and Permian age sandstone, limestone and siltstone underlying Flagstaff and the southern Colorado Plateau, which forms a complex regional aquifer with poorly understood groundwater flow.
The Ray, Miami, Pinto Valley, Morenci, Safford, Carlota, Superior and Resolution mines are examples of open-pit extraction sites for copper in east-central Arizona.
The Aravapai, Castle Dome, California, Middle Pass, Swisshelm and Ash Peak mining districts all resulted from the Mid-Tertiary mountain building event.