Phosphoria formation

Limits of Phosphoria, Park City, and Embar formations 

The Phosphoria Formation was originally thought to have formed as cold P-rich waters were delivered via upwelling to the continental shelf margin analogous to modern systems such as the one of the Peru-Chile coast. 

However, more recent research has shown that the Phosphoria Sea was more likely a relatively shallow (less then 200 m deep), semi-restricted epicontinental embayment (Hiatt and Budd 2001 and references therein). Within this restricted sea, phosphorite formation occurred primarily in the deeper portions of the basin, although phosphorites also formed in the shallower waters (Hiatt and Budd 2001). 

Modern models of the Phosphoria Basin generally depict a warm, shallow sea. Based on the presence of contemporaneous evaporites and organic carbon levels as high as 32.9%, Stephens and Carroll (1999) developed a model for a system with both salinity stratified waters and upwelling (Fig. 7). Analysis of 6 0p values have shown water temperatures during phosphogenesis to have been temperate (14-26°C) in the deeper zones of the Phosphoria Sea and between 30-37°C in the shallower waters, which 

Many questions remain regarding the relationship of the Phosphoria Formation in size and age to other phosphorites. Estimates of the rate of burial of P in Phosphoria sediments relative to the total P-flux into the contemporary oceans vary widely (Trappe 1994) with estimates of 0.8 % (Filippelli and Delaney 1992), 4% (Herring 1995), and 10% (Arthur and Jenkyns 1981). The largest values are comparable to the burial rates of P relative to P-flux rates at the modem analogs off Pern and Namibia, suggesting that the burial rate of the Phosphoria Formation was less important than the extent and duration of phosphogenesis (Trappe 1994). 

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Hagiwara (2000) completed a reconnaissance survey of Se isotope variation in marine sediments and sedimentary rocks (Table 4). The most important observation was a lack of strong enrichment in lighter isotopes in most shale samples and three Black Sea sediments. It appears that near-surface alteration has altered Se isotope ratios in some cases. All of the Phosphoria formation samples were probably altered by deep groundwater or hydrothermal... 

Phosphorite Belkinsk Altai Sayan, Siberia, former USSR Phosphorite Bone Valley Formation, Florida, USA Phosphorite Brazil 3 samples Phosphorite Duwi Formation Egypt 18 samples Phosphorite Karatau, Kazakhstan Phosphorite Oulad Abdoun Basin, Morrocco Phosphorite Phosphoria Formation Montana, Idaho, Wyoming, and Utah, USA 60 samples Phosphorite southeast Jordan 3 beds... 

Gulbrandsen, R.A. (1966) Chemical composition of phosphorites of the Phosphoria Formation. Geochimica et Cos-mochimica Acta, 30, 769-78. 

Knudsen A. C. and Gunter M. E. (2002) Sedimentary phosphorites—an example Phosphoria formation, southeastern Idaho USA. In Reviews in Mineralogy Vol. 48. Phosphates—Geochemical, Geobiological, and Materials Importance (eds. M. J. Kohn, J. Rakovan, and J. M. Hughes). Mineralogical Society of America, Washington, DC, pp. 361-389. 

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). 

IV = Modal values (except means average) for the Phosphoria Formation, according to Gulbrandsen (1966). 

Cook, P.J., 1970. Repeated diagenetic calcitization, phosphatization and silification in the Phosphoria Formation. Bull. Geol. Soc. Am., 81 2107—2116. 

Geological Setting and Geochemistry of Oil Shales in the Permian Phosphoria Formation... 

The Permian Phosphoria Formation in the northwestern Interior United States contains two phosphatic and organic-ncarbon-rich shale members, the Meade Peak Phosphatic Shale Member and the Retort Phosphatic Shale Member. Ihese rocks were formed at the periphery of a foreland basin between the Paleozoic continental margin and the North American cratonic shelf. The concentration, distribution, and coincidence of phosphorite, organic carbon, and many trace elements within these shale members probably were coincident with areas of optimum trophism and biologic productivity related to areas of upwelling. In the Phosphoria sea upwelling is indicated to have occurred by sapropel that was deposited adjacent to shoals near the east flank of the depositional basin. 

The Phosphoria Formation was deposited in a foreland basin between the Continental margin and the North American cratonic shelf. This foreland basin, which is here defined by the area of deposition of the two organic-ncarbon-rich mudstone members of the Phosphoria (fig. 1), has been named the Sublett basin (8)5 and it covers an extensive area of approximately 400,000 knr (about 700 km by 600 km). The basin has a northwest-southeast-trending axis and seems to have been deepest in central Idaho where deep-water sedimentary rocks equivalent to the Phosphoria Formation are exceptionally thick. The depth decreased toward the shelves and land areas indicated in figure 1. The deepest part of the Sublett... 

The southwest limit of the Sublett basin in Nevada was along the Humboldt highland (17). The Humboldt highland was the principal source of terrigenous sediments incorporated in the Murdock Mountain Formation (18), which is equivalent to the lower part of the Phosphoria Formation (fig. 2). 

Figure 4. Isopach map of Meade Peak (left) and Retort (right) Members of the Phosphoria Formation contour interval is 10 m. Principal overthrust faults of the Sevier thrust belt indicated by barbed line isopachs and faults are dashed where uncertain.

Phosphoria Formation directly above the Meade Peak (26). 

MAUGHAN Permian Phosphoria Formation Trace Metals... 

Petroleum generation from the Phosphoria Formation has been investigated and a total yield of 30.7 x 109 metric tons is estimated by Claypool and others (4 p. 118). The bulk of the... 

Figure 10. Plot comparing organic carbon and bitumen (left), and phosphorus to organic carbon, bitumen, and hydrocarbons (right) in samples from Meade Peak and Retort Members of the Phosphoria Formation. Values in percent for organic carbon and phosphorus are from Maughan (11) bitumen and...

Oil that has been discovered and produced from the Pennsylvanian Tensleep Sandstone (fig 11), the probable Lower Permian part of the Weber Sandstone in northwestern Colorado, and the middle Permian Park City Formation in central Wyoming probably has been derived from the Phosphoria Formation. Oil in the Lower Permian upper member of the Minnelusa Formation in northeastern Wyoming may have migrated into these reservoirs from the Phosphoria source beds, but carbonaceous beds in the middle member of the Minnelusa are a more likely source Cheney and Sheldon (33) speculated that petroleum originated in the organic-carbon-rich shale beds of the Phosphoria Formation and that the oil... 

Figure 11. Relation of oil reservoirs (solid patterns) in Pennsylvanian Tensleep Sandstone to carbonaceous shale beds of the Permian Phosphoria Formation and to inferred maximum depth of burial (thickness of Mesozoic rocks, in kilometers) shown by solid lines and supplementary 2.5- and 3,5-km thickness shown by dashed line.

J. Stewart Williams provided me an introduction to the Phosphoria Formation in both classroom and field. E. D. McKee, S. 

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