Looking down secondary pore throats in Mississippian siliciclastic sandstones of eastern Nevada: Predicting porosity by low-power microscopy
- Geological Survey, Menlo Park, CA (United States)
Mississippian sandstones in eastern Nevada consist of quartz, chert, and lithic detritus shed from erosion of the Roberts Mountain allochthon. Deposited in a marine flysch-trough and a variety of peripheral nonmarine environments, the sandstones reflect a complex history of compaction and cementation. The utility of studying sandstone pores in color impregnated thin sections and in images created with the scanning electron microscope (SEM) is well documented in geologic literature. However, low-power binocular microscopic examination of hand specimens cut with a petrographic diamond saw is a simple and inexpensive alternative for observing the number and type of pore throats, fractures, and presence or absence of quartz overgrowths. The low-power microscope technique is especially useful for observing pores formed by dissolution of rock fragments. Facets of quartz overgrowths and pitted quartz facets are also clearly visible using the low-power technique. Petrographic microscopy of non-calcareous, color-impregnated thin sections indicates porosity in the Mississippian sandstones of eastern Nevada was first reduced by mechanical compaction and (or) precipitation of authigenic cements such as quartz, calcite and dolomite. In rocks of moderate thermal maturity, secondary porosity results from dissolution of argillaceous and carbonaceous sedimentary rock fragments, and in some cases, by dissolution of earlier formed calcareous cement.
- OSTI ID:
- 5025497
- Report Number(s):
- CONF-9305259-; CODEN: GAAPBC
- Journal Information:
- Geological Society of America, Abstracts with Programs; (United States), Vol. 25:5; Conference: 89. annual meeting of the Cordilleran Section and the 46th annual meeting of the Rocky Mountain Section of the Geological Society of America (GSA), Reno, NV (United States), 19-21 May 1993; ISSN 0016-7592
- Country of Publication:
- United States
- Language:
- English
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