GENERAL39079 - Laserfiche WebLink

Home Browse Search

' Pikeview Quarry Environmental Assessment Page 26 characterized by broad dissected bench-like erosional swfaces that descend in steps to the= plains. At the eastern edge of the Front Range, Pikes Peak and the Rampart Range, composed of pink, coarse grained Precambrian granite, rise steeply above the plains to the 14, ] ] 0-foot summit of Pikes Peak. Thick layers of sediments deposited in intermountain basins befi~re the mountains of the Front Range were formed are evident in the Florissant Fossil Beds, Manitou Pazk, and South Pazk to the west. ' The proposed project azea is composed of Pikes Peak Granite and sedimentary limestone beds. Pikes Peak Granite is a coarse pink biotite ofpre-Cambrian age. The rock is coarse-grained, composed of alkalic feldspar, quartz and biotite. Its color is due to the , abundance of feldspaz. Quartz is less abundant, and biotite is relatively rare. Pikes Peak Granite weathers in huge round masses, so chazacteristic that it may be , recognized from a distance. Boulders have broken away from dome-like outcrops, and rocks up to 20 feet in diameter have fallen from the ledges. The mesh of coazse interlocking grains is easily ruptwed by frost, and the rock is broken into pieces by disintegration, forming chazacteristic gravel. Durutg the Pliocene epoch, the granite block that lies just west of the plains was ' uplifted to an elevation of about 9,500 feet, forming the Front Range of the Rocky Mountains. There was also movement within the granite block itself. The part of the Pikes Peak mass south of the Ute Pass Fault was uplifted to about 12,000 feet, thousands of feet ' above the granite adjoining it to the north. Areas of glacial drift are chiefly terminal moraines of local valley glaciers. They are r made up almost wholly of Pikes Peak granite, and contain only small amounts of Cripple Creek and Windy Point granites. The material consists of angular fragments of many sizes, the largest being 8 to 10 feet in diameter. ' Glaciers were formed dwing [he Pleistocene era in the valleys leading away from the summit of Pikes Peak at an altitude of 12,750 feet and lower, moving downstream a distance ' of fow miles in some cases. The lower limit of ice work is at an elevation of about 9,500 feet. The ice reached a maximum thickness of nearly 350 feet in some of the valleys. The ' higher slopes of Pikes Peak were covered with snow, but the summit was not glaciated. 1 he , ice sculpturing of the mountain did not proceed far enough to reduce its mass greatly. (USDA Forest Service, 1971) , The sedimentary beds (limestone) of Pikeview Quarry were geologically uplifted and subjected to contact metamorphism by the intrusion of the Pikes Peak Granite. As a result, these bedded deposits strike generally north-south and dip steeply toward the east. 3.2.2 Topography and Soils ' The Pikeview Quarry occupies an azea of 210 acres in altitudes ranging from 6,880 feet to 7,825 feet. Most of the mining activities occw at 7,] 00 to 7,500 feet, in large flat ' areas. The mining activities along the west side of the quarry extended all the way to the Hydrosphere Resource Consultants, 100? Walnut Street Suite 200, Boulder, CO 80302 1