GENERAL32961

• Permit No: M1999002
• IBM Index Class Name: General Documents
• Doc Date: 8/18/1998
• Doc Name: COMMERCIAL MINE PLAN SUBMITTED TO BLM SECTION 7
• Media Type: D
• Archive: No

• minerals. Dolomite in saline shales tends to have an increased substitution of iron
for magnesium (Desborough 1978, Cole and Picard 1978). A few thin beds of clay-
rich oil shale are found near the base of the Parachute Creek Member (Pitman 1982,
Dyni 1981). The principal fossils associated with the Parachute Creek Member are fly
larvae and gar scales. Ostracods and leaves are occasionally found (Newman 1980).
The Parachute Creek Member is generally considered to comprise three distinct
zones referred to as the Mahogany, Leached, and Saline Zones.
Mahogany Zone -The Mahogany Zone is a rich oil shale interval that
behaves as a leaky semi-confining layer in the hydrogeologic cycle. The Mahogany
Zone is about 180 feet thick and is located between two thin layers of lean oil shale
known as the A-Groove (above) and the B-Groove (below). The A-Groove is about
15 feet thick at monitoring well 20-1, and the B-Groove is about 23 feet thick.
Leached Zone -For the purposes of this document, the stratigraphic interval
between the Mahogany Zone and the Saline Zone is referred to as the Leached Zone,
a badly degraded oil shale zone. Some documents refer to this interval as "the
upper leached portion of the saline facies of the Saline Zone of the Parachute Creek
Member." This document treats the Leached Zone separately because all soluble
saline minerals such as halite and nahcolite have been removed by the percolation
of groundwater through this zone. The leached shale is badly fractured and contains
• numerous interstratified horizons of breccia, rubble, vugs, collapse intervals, and
cavities. The Leached Zone in the central and north-central Piceance Creek Basin is
known to extend well above the Mahogany Zone, up into the upper Parachute
Creek Member. The mineralogy of leached oil shale is similar to saline oil shale
except for the absence of nahcolite and halite.
Saline Zone -The Saline Zone has significant concentrations of nahcolite,
dawsonite, and halite. The Saline Zone is separated from the Leached Zone by a
well-defined contact known as the Dissolution Surface. The Dissolution Surface is
reported to be located at 1,404 feet below the ground surface at monitoring well 20-1.
Although monitoring well 20-i did not penetrate the entire thickness of the Saline
Zone, the base of the Saline Zone was estimated to be at approximately 2,170 feet
based on data from other nearby core holes (Dyni 1981). The base of the Saline Zone
in core hole 17-1, approximately 1.5 miles north of monitoring well 20-1, is
estimated to be at approximately 2,727 feet.
Stratigraphic analyses of the Saline Zone have shown that various oil shale zones,
along with nahcolite, dawsonite, and halite horizons, are laterally continuous over
long distances. One of the most widespread thick beds of microcrystalline nahcolite
is the Love Bed, which underlies a minimum area of 60 square miles and ranges in
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American Soda, L.L.P. 7-6
Commercial Mine Plan
August 18, 1998