Phosphoria Formation, western

Maughan EK (1980) Relation of phosphorite, organic carbon and hydrocarbons in the Permian Phosphoria Formation, western USA. In Geologic comparee des gisements de phosphates et de petiole. Doc B.R.G.M 24 63-91... 

It is easily identified by its optical or X-ray diffraction characteristics as it is always well crystallized. The apatite formed at low temperatures, however, is not well crystallized. For example, the phosphate species in the Phosphoria Formation of western US, though a calcium apatite containing a wide range of other elements, is very hne grained and associated with many other hne-grained or poorly crystalline materials, i.e., clays (Gulbrandson, 1966). It is this low-temperature, poorly crystalline form of calcium apatite that is found in biomineralized tissues. The bioapatite, predominantly a hydroxylapatite, has a formula that can be written as Ca5(P04,C03)3 (OH, F, Cl, CO3). 

One concern surrounding Gulbrandsen s work was that the samples he analyzed came from different regions within the Phosphoria Formation, which leaves the possibility that different weathering patterns have affected the eastern and western portions of the Phosphoria Formation to produce the results Gulbrandsen reported. Current work on the Meade Peak Member of the Phosphoria Formation (Knudsen and Gunter 2002) supports Gulbrandsen s (1970) theory. 

Figure 6. Geographic extent of western phosphate fields, and the Permian Phosphoria Formation (modified from Herring 1995).

Meade Peak Phosphatic Shale Member, Phosphoria Formation Carbonaceous marine shales, western U.S. 

Phosphorites that are richest and thickest and contain the most uranium are the miogeosynclinal type deposited on the outer parts of continental shelves where upwelling of deep marine waters has occurred. These waters were saturated with respect to phosphate and were probably the source of the phosphate in the phosphorites. These phosphorites are commonly present in thick miogeosynclinal sequences, where they are associated with carbonates, black shale, chert, carbonaceous mudstone and minor amounts of mudstone. " The Phosphoria Formation of the western U.S.A. is an example. 

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