1980-07-11_REVISION - M1977493 (8)

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4. GEOLOGY, GLACIATION AND EROSION AT CLIMAX 4. 1 GENERAL GEOLOGY The generalized geology in the area of Climax is shown in Appendix G. This geology map was compiled from maps by Vaughn Surface , 1971 and Ogden Tweto, 1974 . Because of the diversity of rock types, ages of rock units, and abundant faulting and folding , the area is geologi- cally complex. Precambrian Rocks Precambrian units consist of crystalline metamorphic rocks, correlated with the Idaho Springs Formation and Silver Plume Granite . Metamorphic rocks are thought to be of metase- dimentary origin and are divided into graulite, gneissic and migmatite units. The Silver Plume Granite is present in three textural varieties, all of which are of similar composition (quartz monzonite to granite) . The three varities include a trachitoid phase, a fine to medium grained equigranular phase and a pegmatitic phase . The granite occurs as stocks, dikes and sills intruding the Idaho Springs Formation. Paleozoic Rocks The thick sedimentary rock sequence in the area is Paleozoic in age. The general stratigraphic sequence for these sediments is given in Table 4 . 1 . The majority of sedimentary rocks observed in the area belong to either the Minturn or Maroon Formation. Only small isolated patches of the other Paleozoic units have been found in the area. Stratigraphic continuity is limited by movement along the numerous faults. Many of the sedimentary rocks have undergone some metamorphic alterations. Tertiary Intrusive Rocks Intrusive rocks of tertiary age occur as dikes, sills and stocks. They are generally quartz monzonites in composi- tion. Major outcropping stocks are the Humbug , Tucker Moun- tain, Chalk Mountain and English Gulch stocks. Numerous sills 4-1