Meade Peak Phosphatic Shale Member Research Articles

Gondolellid conodonts and depositional setting of the Phosphoria Formation

The Phosphoria Formation and related rocks were deposited over an 8.9 m.y. interval beginning approximately 274.0Ma and ending approximately 265.1Ma. The Meade Peak Phosphatic Shale Member was deposited in southeastern Idaho and adjacent Wyoming over 5.4 m.y. from approximately 273.2 to 268.6 Ma. The Retort Phosphatic Shale Member was deposited in southwestern Montana and west-central Wyoming over 1.3 m.y. from approximately 267.4 to 266.1Ma. The base of the Roadian Stage of the Middle Permian occurs within the lower phosphate zone of the Meade Peak. The base of the Wordian Stage occurs within the upper phosphate zone of the Meade Peak. The presence of a cool-water brachiopod fauna, cool-water conodont faunas, and the absence of fusulinids throughout the Phosphoria basin indicate the presence of pervasive cool, upwelling waters. Acritarchs are intimately associated with phosphorites and phosphatic shales and may have been the primary organic producer to help drive phosphate production. The gondolellid conodont fauna of the Phosphoria Formation links a geographic cline of Jinogondolella nankingensis from the Delaware basin, West Texas, to the Sverdrup basin, Canadian Arctic, and shows distinct differentiation in species distribution, as do other conodont groups, within the Phosphoria basin. Ten species and two subspecies of gondolellid conodonts are recognized from the Phosphoria Formation and related rocks that belong to Mesogondolella and Jinogondolella.

Kinetics of selenium release in mine waste from the Meade Peak Phosphatic Shale, Phosphoria Formation, Wooley Valley, Idaho, USA

Phosphorite from the Meade Peak Phosphatic Shale member of the Permian Phosphoria Formation has been mined in southeastern Idaho since 1906. Dumps of waste rock from mining operations contain high concentrations of Se which readily leach into nearby streams and wetlands. While the most common mineralogical residence of Se in the phosphatic shale is elemental Se, Se(0), Se is also an integral component of sulfide phases (pyrite, sphalerite and vaesite–pyrite ss) in the waste rock. It may also be present as adsorbed selenate and/or selenite, and FeSe 2 and organo-selenides. Se release from the waste rock has been observed in field and laboratory experiments. Release rates calculated from waste rock dump and column leachate solutions describe the net, overall Se release from all of the possible sources of Se listed above. In field studies, Se concentration in seepage water (pH 7.4–7.8) from the Wooley Valley Unit 4 dump ranges from 3600 µg/L in May to 10 µg/L by Sept. Surface water flow, Q, from the seep also declines over the summer, from 2 L/s in May to 0.03 L/s in Sept. Se flux ([Se] ⁎ Q) reaches a steady-state of < 150 mg/day in 1–4 months, depending upon the volume of Q. Se release (mg/L) follows a first order reaction with a rate constant, k , = 1.35 – 6.35e−3 h − 1 (11.8–55.6 yr − 1 ). Laboratory experiments were performed with the waste shale in packed bed reactors; residence time varied from 0.09 to 400 h and outlet pH ∼ 7.5. Here, Se concentration increased with increasing residence time and release was modeled with a first order reaction with k = 2.19e−3 h − 1 (19.2 yr − 1 ). Rate constants reported here fall within an order of magnitude of reported rate constants for oxidation of Se(0) formed by bacterial precipitation. This similarity among rate constants from both field and laboratory studies combined with the direct observation of Se(0) in waste shales of the Phosphoria Formation suggests that oxidation of Se(0) may control steady-state Se concentration in water draining the Wooley Valley waste dump.

A modern vs. Permian black shale—the hydrography, primary productivity, and water-column chemistry of deposition

The sediment currently accumulating in the Cariaco Basin, on the continental shelf of Venezuela, has an elevated organic-carbon content of approximately 5%; is accumulating under O 2-depleted bottom-water conditions (SO 4 2− reduction); is composed dominantly of foraminiferal calcite, diatomaceous silica, clay, and silt; and is dark greenish gray in color. Upon lithification, it will become a black shale. Recent studies have established the hydrography of the basin and the level of primary productivity and bottom-water redox conditions. These properties are used to model accumulation rates of Cd, Cr, Cu, Mo, Ni, V, and Zn on the seafloor. The model rates agree closely with measured rates for the uppermost surface sediment. The model is applied to the Meade Peak Phosphatic Shale Member of the Phosphoria Formation, a phosphate deposit of Permian age in the northwest United States. It too has all of the requisite properties of a black shale. Although the deposit is a world-class phosphorite, it is composed mostly of phosphatic mudstone and siltstone, chert, limestone, and dolomite. It has organic-carbon concentrations of up to 15%, is strongly enriched in several trace elements above a terrigenous contribution and is black. The trace-element accumulation defines a mean primary productivity in the photic zone of the Phosphoria Basin as moderate, at 500 g m −2 year −1 organic carbon, comparable to primary productivity in the Cariaco Basin. The source of nutrient-enriched water that was imported into the Phosphoria Basin, upwelled into the photic zone, and supported primary productivity was an O 2 minimum zone of the open ocean. The depth range over which the water was imported would have been between approximately 100 and 600 m. The mean residence time of bottom water in the basin was approximately 4 years vs. 100 years in the Cariaco Basin. The bottom water was O 2 depleted, but it was denitrifying, or NO 3 − reducing, rather than SO 4 2− reducing.

Geologic Setting of Petroleum Source Rocks in Permian Phosphoria Formation: ABSTRACT

The Permian Phosphoria Formation in the northwestern interior United States contains two phosphatic and organic-carbon-rich shale members--the Meade Peak Phosphatic Shale Member and the Retort Phosphatic Shale Member. These 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. Upwelling is indicated to have occurred in the Phosphoria sea by the presence of sapropel that was deposited adjacent to shoals near the east flank of the depositional basin. Maximum organic-carbon concentration is as much as 30 wt. % in the organically richest beds in the shale members and the maximum average in each member is about 10 wt. %. A close association occurs in the distribution of the organic carbon, silver, chromium, molybdenum, nickel, titanium, vanadium, and zinc. Phosphorous differs slightly from the distribution of organic carbon and by contrast seems typically associated with copper, lanthanum, neodymium, strontium, yttrium, and ytterbium. Burial of the sapropelic muds by Triassic and younger sediments and the consequent rise in ambient temperature has led to catagenesis of hydrocarbons from the kerogen in these rocks. In some areas of southwestern Montana, hydrocarbons have not been generated; however, burial has been minimal and temperatures have remained low. Consequently, these rocks remain organic-rich shales that have the potential for producing synthetic oil and gas. End_of_Article - Last_Page 942------------

Phosphorite, Organic Carbon, and Hydrocarbons in Permian Phosphoria Formation, Western United States: ABSTRACT

The Permian Phosphoria Formation in the northwestern interior United States contains two phosphatic and organic carbon-rich shale members that include both phosphorite and petroleum source beds. The association suggests an intimate relation between factors which generate phosphorite deposits and hydrocarbon source beds. The two members, the Meade Peak Phosphatic Shale Member and the Retort Phosphatic Shale Member, were deposited at the periphery of a foreland basin between the Cordilleran geosyncline and the North American craton. The concentration, distribution, and coincidence of phosphorite, organic carbon, End_Page 746------------------------------ and many of the trace elements within these shale members probably were coincident with areas of optimum trophism and biologic productivity. The paleogeographic relations suggest that the trophic regions were areas of upwelling in the Phosphoria sea adjacent to shoals near the eastern flank of the basin. The richest phosphorite beds, mostly pelletoidal, are near the base and the top of each shale member, and the organic carbon and the residual hydrocarbon contents of the phosphorite beds are low in comparison to the other strata. The beds richest in organic carbon are near the middle part of both members, where phosphorite content is low and residual hydrocarbon content is high. The deposition of both phosphorite and organic matter that is precursor to petroleum seems to be directly r lated to areas of inferred upwelling and biomass concentration, but the sediments have been differentiated into dominantly phosphorite beds and dominantly petroleum source beds by chemical or mechanical factors. End_of_Article - Last_Page 747------------

Selenium Concentrations in Phosphorus Fertilizer Materials and Associated Uptake by Plants

AbstractThe Se concentration of seven Florida Land Pebble deposit phosphate rocks ranged from 0.7–7.0 ppm. The range was 1.4–178 ppm Se in seven samples from the western phosphate field. The Meade Peak phosphatic shale member of the Phosphoria formation contains more Se than rock from other phosphatic formations. Normal and concentrated superphosphates made from phosphatic rocks containing 100 ppm Se can be expected to contain about 60 and 40 ppm Se, respectively. Laboratory‐prepared concentrated superphosphate containing 23 ppm Se applied to an alkaline soil that normally produced alfalfa (Medicago sativa L.) low in Se at a rate of 156 ppm P increased Se concentration in alfalfa above the minimal requirements to protect livestock from white muscle disease. Concentrated superphosphate and single superphosphate prepared from phosphate rock containing 178 ppm Se and applied at a rate of 80 ppm P increased the Se concentration in alfalfa compared to the same amount of P applied as Se free concentrated superphosphate. Normal phosphate fertilizer practices can provide required Se for livestock provided the fertilizer is prepared from phosphate rock containing sufficient Se.