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The Saline Zone is overlain by a 300 to 400-foot thick sequence of oil shale known <br />as the Leached Zone. This interval, which usually includes part of the L-5 zone and <br />all of the R-6 zone, B-Groove, R-7 zone, and part of the R-8 zone, once contained <br />numerous horizons of stratiform nahcolite and halite and nonstratified nahcolite (in <br />oil shale). Circulating groundwaters in the geologic past dissolved the saline <br />minerals and produced numerous dissolution vugs, cavities, breccias and rubble, as <br />well as subsidence of rocks above the Leached Zone. Today, the Leached Zone is <br />characterized by thin oil shale horizons containing numerous dissolution features <br />that are interbedded with more massive oil shales containing only joints and <br />partings. <br />The Mahogany Zone (R-7 zone) of the Parachute Creek Member averages about <br />175 feet thick in the Lease area and consists of rich-to moderate-grade oil shale, <br />volcanic tuff and some marlstone. The lower one-third contains numerous <br />dissolution vugs, fractures, cavities and rubble zones. The Mahogany Zone is <br />overlain by the A-Groove, a 16-foot thick interval of marlstone and silty marlstone, <br />and the R-8 oil shale zone. The R-8 oil shale zone consists of approximately 176 <br />feet of low to moderate-grade oil shale units interbedded with marlstone, siltstone <br />and volcanic tuff. Both the A-Groove and R-8 zone contain dissolution features. <br />The Uinta Formation, along with a tongue of Green River Formation (Thirteenmile <br />Creek), dominates surface outcrops on the Lease. Most exposures consist of <br />sandstone, siltstone or marlstone and belong to either the Tu4 or Tu5 units of the <br />Uinta Formation. In total, the Uinta Formation has an average thickness of about <br />1,142 feet in the Lease area. Included in this sequence are three tongues of Green <br />River Formation (including Thirteenmile Creek). The Uinta Formation rests <br />conformably on the R-8 zone of the Parachute Creek Member of the Green River <br />Formation. <br />Structurally, the north-central Piceance Creek Basin consists of a series of <br />northwest-southeast trending anticlines and synclines which are superimposed on <br />the overall basinal setting. One of these structures, the South Rangely Syncline, <br />Daub & Associates, Inc. Page 4-5 NSI Mine Plan 2010 Rev. <br />Printed: 7/5/2010 Section 4 Geology