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• or subcrops principally in the central portion of the lease. <br />Poison Canyon Formation - The youngest bedrock formation outcropping <br />on the lease tract is the Poison Canyon Formation. Overlying the <br />Raton, the Poison Canyon has in some literature teen combined <br />with the Raton into the Arapahoe formation. Although both units <br />contain the characteristic yellow-brown cross-stratified sandstones, <br />the Poison Canyon can be distinguished and separated from underlying <br />beds by its basal conglomerate. The Poison Canyon outcrops in the <br />center of the Chandler Syncline on the eastern portion of the <br />Cribbs-Jackson lease. Due to erosion of the exposed beds, a complete <br />section of the Poison Canyon formation does not occur in the area. <br />Terrace Deposits - Unconformably overlying the Tertiary and <br />Cretaceous bedrock formations and capping the gently sloping mesas <br />• are Pleistocene deposits known as the Rocky Flats Alluvium and the <br />Verdos Alluvium. These terrace deposits consist of poorly consolidated, <br />~ poorly sorted aggregations of silts, sands, and cobbles. Both deposits <br />vary considerably in thickness, however, they normally range 15-20 feet <br />thick. Although once deposited over most of the lease area, recent <br />streams have dissected these terraces exposing the underlying bedrock <br />in numerous channels. <br />Structure <br />The controlling structural feature in the area of the lease <br />holdings is the Wet Mountain Thrust. The Wet Mountain fault <br />formed by the thrust is a low angle reverse fault running generally <br />northwest to southeast along the flank of the Wet Mountains. Along this <br />fault the Precambrian gneiss is adjacent to and over much younger <br />. Cretaceous age sediments. Drag along the lower block o= the fault <br />created a downwarping of the sediments to the east of t^e thrust <br />resulting in the development of the Chandler Syncline. <br />~3 <br />