Summer Coon Volcano

The mid-Tertiary-age Summer Coon composite cone in Colorado, mapped by Lipman (1968), is a deeply dissected cone in which the nearly circular complex of stocks is exposed, as are the radial dikes shown in Fig. 7.19. These silicic dikes are as much as 4.8 km long and 60 m wide. Remnants of the cone consist of interbedded tuff-breccias and lava flows of mafic to intermediate

Fig. 7.19
Geologic map and cross section of the mid-Tertiary-age Summer Coon
composite cone in Colorado. This is a deeply dissected cone in which both the
nearly circular complex of stocks and the radial dikes are exposed.
(Adapted from Lipman, 1968.)

compositions. The symmetry of the dike complex reflects fracturing and dike emplacement controlled by stress around the central pluton or plutons and little superimposed tectonic control. The volcano's location on thick continental crust makes the Summer Coon volcano model more similar to volcanoes of the Andean altiplano than to the island arc volcanoes.