Shadows of the Shinarump?

Sentinel Mesa and the Big Chief make their appearance on the northern extremes of Arizona's Monument Valley. The Navajo name for the valley is Ts Bil` Ndzisgail (Valley of the Rocks.) The area is part of the Colorado Plateau. The floor is largely Cutler Red siltstone deposited by the meandering rivers that carved the valley. The valley's vivid red color comes from iron oxide exposed in the weathered siltstone. The darker, blue-gray rocks in the valley get their color from manganese oxide. Between 1948 and 1967, the southern extent of the Monument Upwarp was mined for uranium, which occurs in scattered areas of the Shinarump siltstone; vanadium and copper are associates with uranium in some of these deposits. April 26, 2009