Cambrian sandstones

The Rose Run Sandstone is the best characterized of the Cambrian sandstones because it is also an oil and gas reservoir (Fig. 3). It is also the only one of the Cambrian sandstones that is known to retain its sandstone composition in the eastern part of the state rather than passing laterally into carbonate. The Rose Run Sandstone is a sandy layer in the middle of the Knox Dolomite (Fig. 4), which across much of eastern Ohio lies at depths suitable for injection of supercritical C02 (Fig. 3). The Rose Run Sandstone was deposited in a passive margin phase of the Appalachian Basin and consists of interbedded layers of carbonate, primarily dolos-tone, and sandstone (Fig. 5). The sandstone is compositionally mature, consisting largely of quartz. Subordinate reactive minerals are the alkali feldspars and locally abundant glauconite (Fig. 5). Dolomite and quartz are the dominant cements (Janssens 1973 Riley et al. 1993). 

Fig. 6. Cross-section for central Ohio. Cambrian sandstones that are candidates for C02 storage are shaded (after Gupla Bair 1997) (PA, Pennsylvania for location of cross-section, see Fig. 3).

The mineral content of the Rose Run Sandstone is similar to other deep formations that are being considered for sequestration of C02, including other Cambrian sandstones deep beneath Ohio (Janssens 1973) and the glauconitic sandstone in the Alberta Basin of Canada (Gunter et al. 1993). Like the Rose Run, these... 

A simplified stratigraphic section through the study area is presented in Fig. lb. In the study area, Precambrian rocks are overlain by a thick succession of Cambrian sandstones. The sandstones are in turn overlain by the Ordovician Prairie du Chien Group, the St. Peter Sandstone, and the Sinnipee Group (Fig. lb). The Prairie du Chien Group consists of dolomitized oolitic limestones, muddy facies, and stromatohtes, with cyclic interbedded thin sandstones and shales. A majorunconformity (Tippecanoe... 

Moderate and low arsenic concentrations are found in numerous wells in the FRV, irrespective of the presence of the SCH in the open interval of the well. These levels of arsenic in ground water do not correlate to the intersection of the SCH with the static water level (Fig. 8), indicating that the sulfide oxidation initiated by oxygen introduced at the borehole does not cause all arsenic occurrences. Tfiere is no single stratigraphic unit that controls the low to moderate concentrations wells with open intervals in the Sinnipee Group, the St. Peter Sandstone, the Prairie du Chien Group or the Cambrian sandstones are all affected. 

The calculation of the hydrological parameters necessary for establishing the above-mentioned silica balance appears to be a rather complicated problem as intergranular pressure solution leads to a dynamic reduction in rock mass and volume and frequently also to a lowering of the porosity. These parameters have been simulated for different petrophysical and geochemical conditions. The first results show that for the large amount of secondary silica observed to become exported, 0.5 x io -o.5 x lo cm of water is required for every cm of the Cambrian sandstones of the Oued el-Mya Basin. If we assume, on the other hand, that the quartz cement in the Ordovician sandstones from Ahnet Mouy-dir resulted within the rocks themselves from pressure solution then the water flux necessary was small or virtually nil and this formation approached an isochemical system. 

The Permian cover rests unconformably on a schistose Pre-cambrian basement with rhyolitic tuff, sometimes overlain by Cambrian sandstones and dolomite. The Permian of Lodeve, which is roughly 2000 m thick, is mainly composed of 600-700m of Autunian sediments (lower third, grey middle, grey and red upper third, red) and 1300m of slightly unconform-able, entirely red, Saxonian sediments. With the exception of... 

Bendigo is a classic example of a low-sulphide gold-quartz deposit located in a folded sequence of sandstone and shale of the Cambrian-Ordovician age (Ramsay et al. 1998 Goldberg et al. 2007). Regional soil geochemistry covers an area of 4,000 km. Sampling Grid 5x5 km. 134 samples were collected as can be seen in Fig. 2, titanium anomalies form sub-... 

The mineralized district is restricted by two main strike-slip faults of Kubanan to the east and Posht e Bdam to the west (Fig. la). The host rocks are a thick sequence of Upper Precambrian-Cambrian rhyolite, tuff, alkali granite, syenite, mafic dykes, magnetitite, dolomite, gypsum, limestone, black shale, and sandstone. The Upper Percambrian-Cambrian sequence is overlain unconformably by Mesozoic and... 

Riley, R. A., Harper, J. A., Baranoski, M. T., Laughrey, C. D. Carlton, R. W. 1993. Measuring and Predicting Reservoir Heterogeneity in Complex Deposystems The Late Cambrian Rose Run Sandstone of Eastern Ohio and Western Pennsylvania. Appalachian Oil and Natural Gas Research Consortium, Morgantown, West Virginia. 

Cambrian, Franconia Formation (sandstone), Norwalk, Wise., U.S.A. Schneider (1927) analyst T.B. Brighton. 

Gilkeson RH, Cowart JB. 1987. Radium radon and uranium isotopes in groundwater from Cambrian-Ordovician sandstone aquifers in Illinois USA. In Graves B, ed. Radon in ground water, radon, radium and other radioactivity in ground water Hydrogeologic impact and application to indoor airborne contamination Proc National Water Well Association conference, Somerset, NJ, April 7-9, 1987. Chelsea, MI Lewis Publishers, Inc., 403-422. 

Fishman N. S. (1997) Basin-wide fluid movement in a Cambrian paleoaquifer evidence from the Mt. Simon sandstone, Illinois and Indiana. In Basin-wide Diagenetic Patterns Integrated Petrologic, Geochemical, and Hydro-logic Considerations (eds. I. Montanez, J. M. Gregg, and K. L. Shelton). Society for Sedimentary Geology (SEPM), Tulsa, OK, vol. 57, pp. 221-234. 

Cambrian Shalk>w marine ) sandstone Lower Paleozoic sandstone aquifer ... 

Fishman, N. S., 1997, Basin-wide fluid movement in a Cambrian paleoaquifer Evidence from the Mt. Simon Sandstone, Illinois and Indiana. 

Weaver, T. R., and Bahr, J. M., 1991, Geochemical evolution in the Cambrian-Ordovician sandstone aquifer, eastern Wisconsin. 1. Major ion and radionuclide distribution Ground Water, v. 29, no. 3, p. 350-356. 

The majority of magnesite production in Russia is situated around Satka, Ufa Province, in the southern Urals. The magnesite is contained in 14 bodies within two parallel series of lenses forming a belt some 5 miles long. The belt is composed of late Precambrian to Cambrian dolomite, marl, sandstone, slate, and phyllite some 300-500 m thick. The individual magnesite bodies are up to 2000 m in length. 

In the study region the paleogeographic history may be subdivided into two stages, viz. the Lower Cambrian characterized by predominantly continental environments and the Middle Cambrian with transitional and marine sedimentation. The Lower Cambrian is represented by alluvial and proluvial deposits, conglomerates, pebble beds and coarse angular and poorly sorted sandstones. 

Judging from the mineral composition of the shales in which such secondary transformations would be reduced to a minimum there could have been only 15-30% detrital illite as a primary constituent in the sandstones of the Hassi Messaoud field whereas the amount of illite detected in the Cambrian siltstones is 30-50%. Consequently, only 1% of secondary quartz could have resulted from the transformation of illite to kaolinite. Thus, widely developed kaolinization of illite and feldspars is accompanied by the liberation of silica in the form of silicic acid which is mostly consumed in the formation of overgrowth on quartz grains. The extent of this silicification, however, is controlled by other factors the chemical nature of the environment created and especially the permeability of the rocks. The lower the permeability, the more intense silicification will be. 

The circumstances above explain why there is little evidence of pressure solution even in Cambrian, Ordovician and other sandstones buried to 5 000 m and more. The large amount of authigenic quartz viewed in cathodoluminescence microscopy, despite little evidence of pressure solution criteria, suggests that a more appropriate mechanism for silica authigenesis in sandstones needs to be identified. 

Lower Palaeozoic (or Primary) Cambrian 500 Sandstones, slates, siliceous grits 1... 

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