Geological history of the Chiricahua Mountains

Chiricahua Mountains
Portal Peak in the Chiricahua Mountains as seen from Rodeo to the east
Highest point
Peak	Chiricahua Peak
Elevation	9,759 ft (2,975 m)
Coordinates	31°50′47″N 109°17′28″W / 31.84639°N 109.29111°W / 31.84639; -109.29111
Dimensions
Length	35 mi (56 km) NW, then SW
Width	21 mi (34 km) (arc-shape)-N-S
Geography
Chiricahua Mountains in Arizona
Country	United States
State	Arizona
Regions	Madrean Sky Islands (northeast)-Sonoran Desert (northwest)-Chihuahuan Desert
County	Cochise
Communities	Willcox, AZ-NW Douglas, AZ-S Rodeo, NM-E Portal, AZ-(NE foothills)
Range coordinates	31°56′N 109°23′W / 31.93°N 109.38°W / 31.93; -109.38Coordinates: 31°56′N 109°23′W / 31.93°N 109.38°W / 31.93; -109.38
Borders on	Dos Cabezas Mountains-NW San Simon Valley-NE & E San Bernardino Valley-SE Pedregosa Mountains-S Sulphur Springs Valley-NW, W & SW

The Geologic history of the Chiricahua Mountains concerns the Chiricahua Mountains, an inactive volcanic range located in Coronado National Forest of southeastern Arizona, in the United States. They are part of an "archipelago" of mountain ranges known as the sky islands that connect the Sierra Madre Occidental in Mexico with the Rocky Mountains. The Chiricahua Mountains are home to a number of unusual geologic features associated with the Turkey Creek Caldera, some of which are protected by Chiricahua National Monument. The landscape has been dominantly shaped by faulting due to Basin and Range extension during the Miocene, volcanic activity, and erosion.

During the Precambrian, the southwestern coastline of North America extended as far north as the present-day borders of Wyoming and Colorado. Continental growth began around 1.8 billion years ago as a sequence of island arcs (separated by seas) moved to the northwest and accreted onto the edge of North America. By 1.4 Ga, most of Arizona had been added to the continent.

Paleozoic deposition in southeast Arizona occurred from about 510 to 251 Ma in a passive margin setting. Throughout this time, the area was covered by an ancient sea and thick layers of limestone and sandstone were deposited.Permian-aged strata rich in fossil brachiopods, echinoid spines, and gastropods are the only Paleozoic rocks exposed in the Chiricahua Mountains, and reflect a shallow-marine coral reef environment. These rocks are also the oldest known rocks exposed in the Chiricahuas and were formed around 280 Ma.