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<br />• thickness from 6.2 to 11.8 feet.' Nahcolite in this layer averages about 60 percent by <br />weight. The Multi Mineral Corporation' opened a small entry within the Horse <br />Draw Mine in the Love Bed at a depth of 1,840 feet. Horse Draw Mine was located <br />about 6,500 feet southwest of monitoring well 20-1. The Love Bed at monitoring <br />well 20-1 is estimated to be approximately 1,700 feet below the ground surface. <br />Garden Gulch Member Douglas Creek Member, and Anvil Points Members The <br />Douglas Creek and Garden Gulch Members contain sandstone, siltstone, marlstone, <br />algal limestone, and some lean, clay-rich oil shale. The Douglas Creek Member is <br />approximately 800 feet thick, and the Garden Gulch Member is about 700 feet thick <br />(Bradley 1931). The Anvil Points Member is similar in composition and is actually a <br />lateral correlative of the Douglas Creek and Garden Gulch Members, as well as being <br />part of the lower Parachute Creek Member. <br />Clay-rich oil shale is abundant in the Garden Gulch Member. Its mineralogical <br />composition includes quartz, illite, dolomite, and albite. These rocks are believed to <br />have been deposited in a freshwater lacustrine environment (Pitman 1982, Dyni <br />1981). This would explain the high concentrations of illite, which is geochemically <br />unstable in alkaline aquatic settings. The high clay content results in a relatively <br />impermeable stratigraphic sequence that generally impedes the movement of <br />groundwater between the Green River Formation and the underlying rock <br />formations. <br />Although fossils are rare in the Garden Gulch Member, it is known to contain a few <br />ostracods, gar scales, fish, and leaves. The Douglas Creek Member contains <br />abundant fossils, including ostracods, gastropods, and pelecypods. The remains of <br />fish, turtles, crocodiles, and leaves are also found occasionally (Newman 1980). <br />Wasatch and Lower Tertiary Formations <br />The Wasatch Formation may reach a maximum thickness of 5,500 feet, making this <br />stratigraphic sequence the thickest Tertiary unit in the Piceance Creek Basin. In the <br />southern and eastern portion of the basin, the Wasatch Formation has been <br />subdivided into the Shire, Molina, and Atwell Gulch Members. The Shire Member <br />has variegated siltstone, claystone, and sandstones. The Molina Member is <br />dominated by massive, cross-stratified sandstone. The basal Atwell Gulch Member <br />is composed of variegated siltstone and claystone (Donnell 1961). The Wasatch <br />Formation is undivided in the northern part of the basin. <br />The base of the Tertiary section is composed of a conglomerate formerly called the <br />Ohio Creek Formation, which overlays Cretaceous rocks of the Mesa Verde Group <br />' This layer was the stratigraphic datum used by the USGS studies of John Dyni and the Multi <br />Mineral Corporation investigations at the U.S. Bureau of Mines (USBM) Horse Draw Ivline <br />Research Facility. <br />' The Multi Mineral Corporation was an early partner in the Yankee Gulch Joint Venture Leases. <br />American Soda has since acquired Multi Minerals' interests in the leases. <br />American Soda. L.L.P. '7_'7 <br />Commercial Mme Plan <br />August 18. 1998 <br />