Stratigraphy and depositional environment of early Mississippian Joana limestone of east-central Nevada
The Early Mississippian Joana Limestone in the southern Schell Creek and Egan Ranges of east-central Nevada is divided into nine rock types: mudstone, fossiliferous mudstone, wackestone, peloidal wackestone, pelmatozoan wackestone, pelmatozoan packstone, pelmatozoan grainstone, and ooid packstone. From the combined rock type and larger scale outcrop information, three depositional facies were identified: (1) unbedded subtidal, (2) bedded subtidal, and (3) restricted subtidal, each containing a unique set of diagnostic microfacies. Facies thicknesses, lithologies, and contacts with adjacent stratigraphic units indicate a highly varied paleotopography of localized highs and basins during Joana deposition. It is suggested that Waulsortian-type buildups occur downslope of some paleohighs in the unbedded subtidal facies. An age of upper Kinderhookian to lowest Osagean within the Mississippian Period was determined for the Joana, based primarily on conodonts and foraminifera. In the middle beds of the Joana, the previously unreported upper Siphonodella crenulata conodont zone occurs and relates the timing of the Joana to regional geologic events. Color alteration indices of these conodonts are 1.5 to 2, and occur in the oil generation window. Additionally, oil staining was noted in numerous samples primarily from the lower half of the formation, represented by the unbedded subtidal facies. Porosities of the formation are varied, ranging from no visible porosity to over 20% interparticle porosity in some pelmatozoan grainstones.
- Research Organization:
- Univ. of Idaho, Moscow
- OSTI ID:
- 5906536
- Report Number(s):
- CONF-870915-
- Journal Information:
- AAPG (Am. Assoc. Pet. Geol.) Bull.; (United States), Vol. 71:8; Conference: American Association of Petroleum Geologists Rocky Mountain Section meeting, Boise, ID, USA, 13 Sep 1987
- Country of Publication:
- United States
- Language:
- English
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FEDERAL REGION IX
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NORTH AMERICA
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020200* - Petroleum- Reserves
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