Subsurface to Surface Correlation of the Tensleep Sandstone in the West Flank of the Pryor Mountains in Carbon County, Montana

The Pennsylvanian Tensleep Sandstone is an eolian and nearshore marine/sabka quartz arenite unit with prominent outcrops along the western Pryor/Bighorn Mountain front east of Red Lodge, MT. Regionally, the formation represents one of the largest ergs in the global geologic record. High permeability makes it an important oil and gas reservoir and aquifer in south central Montana and throughout much of Wyoming. The Tensleep Sandstone’s high percentage of quartz content and grain roundness, due to its eolian origin, makes it a prospective source for natural proppant sand. Three continuous 4-inch cores were obtained during a cooperative project between Montana Tech and industry partners. Using stratigraphic sections, cores, thin sections, and x-ray fluorescence (XRF) analysis, the usefulness and economic feasibility of the Tensleep Sandstone as a minable hydraulic fracture proppant was explored. Usefulness depends on cementation, grain shape, grain size, and depth from surface of the prospective zone. Grain shape and size were determined by thin sections, sieving, and stereomicroscope analysis. Analysis of 20 disaggregated sand samples has shown that as much as 30 percent of the grain sizes fall between 30-50 mesh (medium- to finegrained sand size) and about 45 percent of the grain sizes fall between 70–140 mesh (very fine-grained sand to coarse silt), grain sizes appropriate for some hydraulic fracture operations. Core descriptions and XRF data display the distribution of lithology and cementation. Core descriptions and XRF data display the distribution of lithology and cementation. Elemental (XRF) analyses help to delineate more pure quartz sands from those with grain fractions reflecting fine-grained clastic and evaporitic inputs. The core and nearby stratigraphic sections are used to quantify the amount of overburden and the 3 amount of resource in the area. Initial results show favorable crush strength and useable grain size and shape.

The Problem of the Tensleep Sandstone

Sandstone is probably one of the most important groups of rocks in existence today. The economic importance of so insignifi­cant a thing as a mass of sand grains grows with the true reality of the situation. By increasing our knowledge of grains of sand, or particles of sandstone in all their ram­ifications, it would undoubtedly reflect upon our everyday life by increasing commercial possibilities of an undevel­oped natural resource of Montana.

Stratigraphic and palaeoenvironmental significance of a Pennsylvanian (Upper Carboniferous) palynoflora from the PiauFormation, Parnaba Basin, northeastern Brazil

A well-preserved palynoflora is reported from within a cored interval of a coal-exploratory borehole (1-UN-23-PI of the Geological Survey of Brazil) in the southern part of the Parnaiba Basin, northeastern Brazil. The sample studied is from the lower portion of the Piaui Formation. Its palynoflora is characterized by particular abundance of the trilete cavate/pseudosaccate miospores Spelaeotriletes triangulus Neves and Owens, 1966 and S. arenaceus Neves and Owens, 1966, together with cingulizonate forms mainly attributable to Vallatisporites Hacquebard, 1957 and Cristatisporites R. Potonie and Kremp emend. Butterworth et al., 1964. Radially and bilaterally symmetrical monosaccate pollen grains are also well-represented, chiefly by Plicatipollenites Lele, 1964 and Potonieisporites Bhardwaj, 1954, respectively. Taeniate grains (i.e., monosaccates and bisaccates) are relatively minor constituents of the palynoflora; no marine microplankton were encountered. Several species are described in detail : the trilete apiculate spores Brevitriletes levis (Balme and Hennelly) Bharadwaj and Srivastava, 1969 and Horriditriletes uruguaiensis (Marques-Toigo) Archangelsky and Gamerro, 1979; and the taeniate pollen grains Meristocorpus ostentus sp. nov. and Lahirites segmentatus sp. nov. A Pennsylvanian (Late Carboniferous : late Westphalian) age is adduced for the palynoflora via its correlation with part of the Tapajos Group (specifically, the upper Itaituba Formation) of the Amazonas Basin in northern Brazil. The entirely land-derived palynomorphs, associated with abundant plant debris, corroborate previous suggestions that the lower part of the Piaui Formation accumulated in a nonmarine setting under conditions of aridity.

Some notes on Pennsylvanian Crustaceans in the Illinois basin / Frederick R. Schram --.

v.35:no.3(1976)

Pennsylvanian invertebrates of the Mazon Creek area, Illinois / Eugene S. Richardson, Jr. --

v.12:no.2(1956)

Cervifurca nasuta n. gen. et sp. : an interesting member of the Iniopterygidae (Subterbranchialia, Chondrichthyes) from the Pennsylvanian of Indiana, U.S.A. / Rainer Zangerl --.

n.s. no.35(1997)

Pennsylvanian invertebrates of the Mazon Creek area, Illinois. Trilobitomorpha arthropleurida, Eugene S. Richardson, Jr. --

v.12:no.5(1959)

Pennsylvanian invertebrates of the Mazon Creek area, Illinois : Eurypterida / Erik N. Kjellesvig-Waering --

v.12:no.6(1963)

Pennsylvanian invertebrates of the Mazon Creek area, Illinois / Eugene S. Richardson, Jr. --

v.12:no.4(1956)

Pennsylvanian invertebrates of the Mazon Creek area, Illinois / Eugene S. Richardson, Jr. --

v.12:no.1(1956)

A new hydrozoan from the Pennsylvanian of Illinois / [by] Matthew H. Nitecki -- and Eugene S. Richardson, Jr. --

v.30:no.1(1972)

Pennsylvanian invertebrates of the Mazon Creek area, Illinois: the Essex fauna and medusae / Ralph Gordon Johnson -- and Eugene S. Richardson, Jr. --

v.12:no.7(1968)

Pennsylvanian invertebrates of the Mazon Creek area, Illinois / Eugene S. Richardson, Jr. --

v.12:no.3(1956)

Paraparchites mazonensis n. sp. (Ostracoda) from Middle Pennsylvanian ironstone concretions of Illinois / I. G. Sohn --.

v.37:no.2(1977)