Gold in Triassic Redbeds

摘要

Varying amounts of very finely-divided gold can be found in redbeds of Triassic age throughout the world, and many attempts have been made to recover the gold. The iron oxides which a)'e responsible for the red colors appear to have been related to the breakup of the Gondwanaland supercontinent during the Triassic period, some 180 to 240 million years ago. The iron oxides, along with gold, were probably belched out of the many volcanoes which existed at that time, in the form "of volcanic ash and dust. Triassic redbeds in the United States consist primarily of sandstone, siltstone, and shale, and form spectacular panoramas of cliffs and canyons on the Colorado Plateau, a vast region which includes large portions of Utah, Colorado, Arizona, and New Mexico. In much of the region, the Triassic can be divided into three units: a thick lower unit, the Moenkopi Formation; a relatively thin middle unit, the Shinarump Conglomerate; and a thick upper unit known as the Chinle Formation. Areas underlain by Triassic redbeds are shown in black on the accompanying map.