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• Salt Wash (Jms) <br />The Salt Wash Member of the Morrison Formation consists of lenticular sandstone beds (about 60%) <br />and lesser amounts of red mudstone and shale (about 40%). The lenticular and cross-bedded <br />sandstones, which are usually very fine-to-fine grained, indicate deposition in a fluvial environment. <br />The member is exposed as a series of strong ledges and slopes containing white to light gray or light <br />brown to rusty red and fine- to medium-grained sandstone. The sandstone units crop out as cliffs or <br />rims while the mudstones form slopes. In the upper part of the Salt Wash, the numerous channel <br />sandstones have coalesced into a relatively thick unit referred to as the Top Rim, which hosts the ore <br />deposits in the Beaver Mesa area. Similarly, there is a thick sequence of channel sandstones at the base <br />of the member called the Bottom Rim. Usually there are several thinner sequences or individual <br />channel sandstones in the central part of the member, which are termed Middle Rim sands. Both the <br />Middle and Bottom Rim sands also locally host uranium vanadium deposits. The Salt Wash is in <br />excess of 300 feet in thickness within the Whirlwind claim block. <br />Summerville Formation (Js) <br />• This is a remarkably even-bedded, thin-bedded unit that forms slopes. It is primarily reddish-brown <br />sandy or silty shales, but some beds are greenish-gray. Thin beds of red and green chert are <br />widespread. In this area the formation is about 90 feet thick (Cater, 1955). The top is often channeled <br />by the sandstones at the base of the Salt Wash Member, but it may be difficult to locate if Salt Wash <br />mudstones rest directly on the Summerville shales. This formation is an aquiclude (Blanchard, 1990) <br />separating the occasional aquifers of the Morrison Formation from the Entrada aquifer. <br />Colluvial and Landslide Deposits <br />Slopes below the Burro Canyon rim contain landslide deposits that often cover all of the Brushy Basin <br />and parts of the Salt Wash Member. As shown on Figure G4, colluvial and landslide deposits are <br />present locally along the canyon walls. These deposits consist of sandstone fragments in a matrix of <br />reddish-brown and light green mudstone and clay. <br />4.2 Geologic Structure <br />The Whirlwind area lies in the northwest-trending Sagers Wash Syncline formed between the <br />Uncompahgre Uplift and the La Sal Mountain intrusion. The Beaver Mesa mining area is structurally <br />• simple compared with much of the surrounding region. The rocks dip gently (160 feet per mile, 1° 45', <br />Whirlwind Mine 07 (rev. April 08) G-5 <br />