San Juan volcanic field
| San Juan volcanic field | |
|---|---|
  San Juan volcanic field Location in Colorado | |
| Location | |
| Location | Colorado, United States |
| Coordinates | 37°53′36″N 106°46′28″W / 37.89333°N 106.77444°WCoordinates: 37°53′36″N 106°46′28″W / 37.89333°N 106.77444°W |
| Geology | |
| Type | Volcanic field |
The San Juan volcanic field, in southwestern Colorado, contains two phases of volcanism.
The earlier volcanism is Oligocene in age, and consists of largely intermediate composition lavas and breccias. A few ash flow tuffs also constitute this phase of volcanism. It probably was related to subduction along the western margin of North America.
The later volcanism is Miocene–Pliocene in age, and is basaltic in composition. It is best interpreted as a partial melt of the lower crust that was erupted onto the surface.[1]
Notable calderas
- La Garita Caldera, size: 35 x 75 km.[2]
- La Garita, North Caldera (Saguache) 37°57′N 106°48′W / 37.95°N 106.8°W
- La Garita, Central Caldera 37°45′34″N 106°56′20″W / 37.759316°N 106.938858°W
- La Garita, South Caldera 37°34′N 107°00′W / 37.56°N 107°W
| Name | Elevation | Coordinates | Age |
| Cochetopa Caldera | - | 38°12′N 106°45′W / 38.2°N 106.75°W[2] | |
| Nelson Mountain Caldera | - | 37°58′N 106°56′W / 37.96°N 106.93°W[2] | |
| Bachelor Caldera | - | 37°49′03″N 106°54′46″W / 37.817378°N 106.912766°W[2] | |
| Creede Caldera | - | 37°45′34″N 106°56′20″W / 37.759316°N 106.938858°W[2] | |
| Lake City calderas | - | 38°01′31″N 107°23′04″W / 38.025377°N 107.384491°W[1] | |
| Platoro calderas | - | 37°21′08″N 106°31′52″W / 37.352147°N 106.530991°W[1] |
See also
References
- ↑ 1.0 1.1 1.2 Lipman, P.W.; Doe, B.R.; Hedge, C.E.; Steven, T.A. (1978). "Petrologic evolution of the San Juan volcanic field, southwestern Colorado: Pb and Sr isotope evidence". Geological Society of America Bulletin 89: 59–82. doi:10.1130/0016-7606(1978)89<59:PEOTSJ>2.0.CO;2. ISSN 0016-7606.
- ↑ 2.0 2.1 2.2 2.3 2.4 Robinson, Joel E.; Dillon R. Dutton; David W. Ramsey; Peter W. Lipman; Tracey J. Felger (2006). Geologic Map of the Central San Juan Caldera Cluster, Southwestern Colorado: Geologic Investigations Series. I-2799. U.S. Geological Survey. Retrieved 2010-05-03.