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7 <br />tributaries. Locally, folds associated with salt intrusions and <br />lacoolithic mountains modify the gently dipping regional structure. <br />The major tributaries of the Colorado River in the vicinity of <br />the lease are the Dolores River and San Miguel River, see Fig. 1. The <br />San Miguel River generally follows the northwest structure trend. The <br />Dolores River, Colorado River and several of their tributaries are <br />superposed streams. In many places these streams cut across the <br />structural trends. <br />The principal geomorphic features of the region are (1) the <br />canyons of the Dolores and San Miguel Rivers; (2) the Paradox Valley <br />and other northwest - trending salt anticline valleys; (3) mesas which <br />lie in the syncline areas between the salt anticlines; (4) the <br />Uncompahgre Plateau; and (5) the LaSal Mountains which have resulted <br />from the intrusion of a lacoolith in Tertiary time. <br />The canyon of the San Miguel River is located about 8 miles <br />northeast of the Paradox Valley. The Dolores River, which is about <br />10 miles northwest of the lease, crosses the Paradox Valley at a right <br />angle to its northwest trend. The Uncompahgre Plateau is located <br />about 25 miles northeast of the Paradox Valley, and the LaSal <br />Mountains lie about 15 miles northwest of the northwestern end of the <br />Valley. <br />Stratigraphy: The region to the southwest of the Uncompahgre Plateau <br />lies in the Paradox structural basin which covers much of Southwestern <br />Colorado and Southeastern Utah. The Paradox Basin contains a thick <br />section of sedimentary rocks which overlie Precambrian crystalline <br />