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Saline minerals are generally limited to the lower part of the Parachute Creek Member, principally the R-5, L-4, R-4, L-3, R-3 and L-2 oil shale zones, and part of the L-5 and R-2 oil shale zones. Scattered occurrences of dawsonite and nahcolite may occur in higher zones of the Parachute Creek Member; however, they are not important economically. The main mass of saline minerals (i.e., the Saline Zone) reaches a maximum thickness of about 1,100 feet (Dyni, 1974a, 1981). This horizon contains four main rock types: oil shale, oil shale with disseminated nahcolite bodies (crystals and crystal aggregates), stratiform nahcolite and stratiform halite. Dyni (1974a, 1981) has demonstrated that individual horizons of these rock types can be correlated within the Saline Zone. Stratiform halite and nahcolite are generally most easily correlated, though horizons of oil shale with abundant disseminated nahcolite also make excellent marker beds. Dyni (1981) has established a descriptive nomenclature for the most important nahcolite, halite and nahcolitic oil shale horizons in the Saline Zone (Figure 4-8); this system will be used in this document. Halite in the Saline Zone is not found below the R-5 oil shale zone. It is primarily concentrated in two major horizons, one at the base of the L-5 zone, called the "Upper Salt", and the second at the base of the R-5 oil shale zone, the "Lower Salt". Other horizons of halite occur between the two massive salts but they are subordinate in thickness. Within the "Upper' and "Lower" Salts, halite is usually interbedded with thin horizons of nahcolitic oil shale, nahcolite and halitic nahcolite. Halite and nahcolite may exhibit complex lateral facies variations. These variations, which have important economic implications, will be discussed in detail in later sections of this document. Daub & Associates, Inc. Page 4-22 NSI Mine Plan 2010 Rev. Printed: 7/5/2010 Section 4 Geology