ABSTRACT
Rock Types ....................................................................... 371 11.5 Concluding Remarks ................................................................................. 374 References ............................................................................................................. 375
Phosphatic shales, originally deposited in shallow, Permian seas in southeast Idaho, contain economically mineable concentrations of phosphate (Moyle and Piper, 2004). The phosphate ore deposits are hosted by the Meade Peak member of the Permian Phosphoria Formation. The Meade Peak member is sandwiched between overlying chert caprock (Rex chert member) and underlying dolomitic limestone (Grandeur dolostone member). Within the Meade Peak there are upper and lower ore zones with a middle unit of shale that is discarded. Waste rock from mining operations (e.g., middle waste shale, other sedimentary units such as chert, limestone, and dolostone) are placed in large waste rock dumps adjacent to or near surface-mined open trenches. Some of these dumps are cross-valley lls in natural catchments containing intermittent or permanent streams (Amacher et al., 1995).
