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G.1.3.2 Parachute (:reek Member <br />The Parachute Creek Member is tfie thickest unit in the .Green River <br />Formation. It ranges from less than 200 feet south of the Colorado River, <br />to more than 2,000 feet in the northcentral part of the Piceance Basin. The <br />dominant rock type in the Parachute Creek Member is oil shale. Saline <br />minerals, such as nahcolite and halite, are present with the oil shale in <br />tfie depositional center (northcentral) portion of the basin. The saline <br />minerals were codeposited with oil shale over a period of millions of years, <br />and produced a section of approximately 1,800 feet thick, Subsequent <br />leaching by descending ground waters has reduced the saline section to a <br />thickness of approximately 1,100 feet under the lease area (CEI 1983). <br />The Parachute Creek Member is subdivided into oil shale zones which are <br />designated by the relative richness or leaness of the oil shale. The <br />maximum number of oil-shale zones occur in the northern part of the Piceance <br />Creek Basin where seven rich zones (R-8, R-7, R-6, R-5, R-4, R-3, and R-2) <br />are interstratified with six lean zones (L-7, L-6, L-5, L-4, L-3, and L-2), <br />as illustrated in 1=figure G-5. For example, the R-7 oil shale zone is <br />commonly referred to as the Mahogany Zane, and contains the rich oil shales <br />currently under development in the southern part of the Piceance Creek Basin <br />near Parachute, Colorado. <br />The saline minerals present in the Parachute Creek Member are generally <br />limited to the lower oil shale zones, principally the R-5, L-4, R-4, L-3, <br />and L-2 zones, and parts of the L-5 and R-2 zones. This interval (Zone R-2 <br />up through Zone L-5) is referred to as the Saline Zone (Figure G-5). <br />The Saline Zone reaches a maximum thickness of approximately 1,100 feet <br />under the lease area, and contains four main rock types: oil shale, oil <br />shale with disseminated nahcolite bodies (crystals and crystal aggregates), <br />stratiform (bedded) nahcoite, and stratiform halite, It has been <br />demonstrated that individual horizons of these rock tvoes can be correlated <br />within the Saline Zone, <br />~~ <br />G-8 <br />