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in the northern portion of the embayment ranges from 35 to 150 feet and the unit <br />disconformably underlies the Morrison. <br />Morrison Formation - This formation commonly contains massively bedded lenticular <br />sandstones, light gray limestones, light green marls and varicolored sand shales. Lateral <br />changes are extreme in the Morrison and few beds can be traced more than 200 yards <br />along the outcrop. Lenses and channel fills are common. The thickness ranges from 100 <br />to a maximum of 4~0 feet in the Garden Park area. The Morrison disconformably <br />underlies the Lytle Sandstone member of the Purgatoire Formation. <br />Structural Setting <br />The Park Center Well is within the Canon City embayment which is a structural re-entrant <br />located in the extreme southwestern corner of the Denver Basin. The embayment is bounded on <br />the west and southwest by the Wet Mountains, on the north and northeast by the Front Range and <br />on the east by the Brush Hollow horst (southern plunge of the Front Range}. The embayment was <br />developed during the Paleozoic age with recurrent movement during the Laramide along similar <br />trends. High angle reverse faults and thrusts now characterize the margins of the embayment, <br />especially in the northern portion, Fourmile Creek graben. The southern and western portion of <br />the embayment is dominated by the elongated northwest-southeast trending Canon City-Florence <br />basin. The current embayment is the result of east west compressional forces during the Laramide <br />which resulted in the post-Cretaceous folding and faulting of the area (Gerhard, 196. <br />The Canon City-Florence Basin (Chandler Syncline) is an asymmetrical basin with steeply <br />dipping sedimentary strata along its western margin and gently dipping beds on its eastern flank <br />(figure 4). The axis of the syncline parallels the Wet Mountains, from its northern termination by <br />the southern end of Front Range southward to its termination by a thrust of Pre-Cambrian rocks <br />onto the Cretaceous sediments and termination of the axis by the fault. The Chandler syncline is <br />doubly plunging from both the north and south to its deepest point just south of the city of Canon <br />City. Dips within the basin vary from a maximum of up to 45 degrees along the western flank to <br />nearly horizontal along the basin axis and less than 10 degrees along the eastern flank. <br />The Fourmile Creek graben is a V-shaped structure beginning approximately 4 miles southwest of <br />Cripple Creek and extends about 14 miles south to were the graben opens to its maximum extent <br />of 10 miles in width. The graben is characterized by steeply dipping reverse and normal faults <br />which bound the structure along both the east (Garden Park Thrust, Cooper Mountain Fault) and <br />the west (Twin Mountain Fault). The southern termination of the graben is considered to be <br />represented by a semicircle of Niobrara outcrops around the north lobe of the Canon City- <br />Florence basin. <br />Hydrost~tig_r~ohic Units <br />The Morrison and Ralston Creek Formations are generally sequences of impermeable siltstones, <br />claystones and shales with minor lenses of permeable beds that occur locally, and cannot be <br />traced over long distances. The Ralston Creek Formation includes a massive gypsum section <br />interbedded with siltstones or shales which are of low hydraulic conductivity and forms an <br />3 <br />