Permian sediments

Very slow deposition rates are necessary to create economic-grade phosphorites. Slansky (1986) estimates sediment accumulation rates of economic-grade phosphorites between 2x10 and 1x10 years per meter of deposit. This slow deposition rate is seen in Permian sediments of the Rocky Mountains where the Phosphoria Formation is about 30 m thick in the most phosphatic zone, whereas the same time period is represented by over 1000 m in non-phosphatic sections of the Permian in the Rocky Mountains. 

According to the adsorbed complex the salinity of the sea must have been normal. Frequent variations of Fe /Fe are evidence of an oxidizing/reducing environment. From the end of the Carboniferous onwards the Oued el-Mya region, like the rest of the Sahara, was subjected to continental conditions probably as a result of the Hercynian orogeny. Permian sediments are entirely lacking from the study area. 

Lukacs E. and Florjancic A. P. Uranium ore deposits in the Permian sediments of northwest Yugoslavia. InFormation of uranium ore deposits (Vienna IAEA, 1974), 313-29. 

The basement is made up of crystalline schists of the meso-metamorphic Somes Series. Sedimentation started during Permian with detritic deposits interbedded with rhyolites. The overlying Triassic deposits are unconformable and include detritic formations (Lower Triassic) and massive layers of carbonate rocks (Middle Triassic). The absence of the Upper Triassic is due to the uplift of the region during the Kimmeric tectonic phase. 

Figure 10.12. A. Carbon isotopic composition of major groups of higher plants and autotrophic microorganisms compared with oxidized carbon (CO2, HCO3, CC>32 )- The triangles are mean values. (After Holser et al 1988 Schidlowski, 1988). B. Sulfur isotopic composition of bacteriogenic sulfide in modern marine anaerobic sediments (open bars, 1-6) and in the Permian Kupferschiefer (black bar, 7) compared with oxidized sulfate of modem (1-6) and Permian seawater (+11 %o). The black triangles are mean values. (After Holser et al., 1988.)...

The Period-averaged mass ratio of calcite to dolomite (Figure 10.29) is relatively high for Cambrian, Permian, and Tertiary System rocks, whereas this ratio is low for Ordovician through Carboniferous age sediments and rises in value from the Triassic through the Recent. The generalized sea level curve of Vail et al. 

In Figure 10.30 the survival rate of the total sedimentary mass for the different Phanerozoic systems is plotted and compared with survival rates for the total carbonate and dolomite mass distribution. The difference between the two latter survival rates for each system is the mass of limestone surviving per unit of time. Equation 10.1 is the log linear relationship for the total sedimentary mass, and implies a 130 million year half-life for the post-Devonian mass, and for a constant sediment mass with a constant probability of destruction, a mean sedimentation rate since post-Devonian time of about 100 x 1014 g y 1. The modem global erosional flux is 200 x 1014 g y-1, of which about 15% is particulate and dissolved carbonate. Although the data are less reliable for the survival rate of Phanerozoic carbonate sediments than for the total sedimentary mass, a best log linear fit to the post-Permian preserved mass of carbonate rocks is... 

The connection between weathering, evaporation, bacterial activity in marine sediments in shallow water areas and stable sulfur isotope distribution was studied by Holser and Kaplan (1966), Nielsen and Ricke (1969), Nielsen (1968), and Eremenko and Pankina (1972). The sulfur isotope ratios of evaporite sulfates show enrichment of 34S in the Devonian deposits (5 +23 °/oo), a pronounced dip in the Permian ( 5 +12 °/oo), values of +20 °/oo in the Triassic, a fall (+17 to +15 °/oo) in the Jurassic and Cretaceous, stabilizing in the Tertiary to the Recent value of +20 °/oo. 

Cullers R. L. (1994a) The controls on the major and trace element variation of shales, siltstones, and sandstones of Pennsylvanian-Permian age from uplifted continental blocks in Colorado to platform sediment in Kansas, USA. Geochim. Cosmochim. Acta 58, 4955-4972. 

Even more surprising is the presence of the diunsaturated acid 18 2 in all coal samples studied. The presence of diunsaturated acids is indeed highly unusual because of their inherent instability under geological conditions. Itihara et al. (42) have reported the presence of 18 2 in a fossil walnut stone of estimated age one million years (Pleistocene), but this appears to be the first report of a diunsaturated acid in a sediment or coal from the Eocene epoch or the Permian period. 

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