Stratigraphy and Petroleum Potential of the Mississippian Chainman Shale and Diamond Peak Formation, East-Central Nevada

JACARUSO, THOMAS J., Fuel Resources Development Company, Denver, CO

An eastward-thinning and shallowing-upward Middle and Late Mississippian group of sedimentary rocks accumulated east of the Antler orogenic highland. The Chainman Shale consists of fine-grained siliciclastic and carbonate rocks deposited in deep-water and slope environments; it ranges from 400 ft thick in the east to 2400 ft thick in the west, where it interfingers with the Diamond Peak Formation. Fine- to coarse-grained siliciclastic and carbonate rocks up to 5100 ft thick comprise the Diamond Peak Formation and were deposited in submarine fan, fluvial, shoreline, and deltaic settings. In the eastern Antler basin, up to 600 ft of medium-grained siliciclastic strata, the Scotty Wash Quartzite, represent deposition in shelf and deltaic environments.

The Chainman, Diamond Peak, Scotty Wash, and Pennsylvanian Ely Limestone comprise two unconformity-bounded stratigraphic sequences. Sequence 1 strata (Diamond Peak/Chainman) were deposited in an asymmetric basin formed by subsidence due to thrust loading, which controlled sedimentation. An unconformity formed by uplift associated with thrust-load relaxation separates the sequences. Sequence 2 strata (Diamond Peak/Scotty Wash/Ely) were deposited in a symmetric, shallow to emergent setting where variation in subsidence and sediment supply controlled sedimentation.

Mississippian sandstone reservoir quality is a function of depositional environment, with maximum porosity occurring in Diamond Peak shoreline strata (sequence 2) in the central Antler basin. Organic carbon and maturation data suggest the Chainman Shale is presently generating hydrocarbons capable of sourcing structural-, stratigraphic-, and unconformity-controlled traps in east-central Nevada.

AAPG Search and Discovery Article #91010©1991 AAPG Rocky Mountain Section Meeting, Billings, Montana, July 28-31, 1991 (2009)