AN  INTEGRATED PETROLEUM  EVALUATION OF NORTHEASTERN  NEVADA


Introduction Evaluation Prospects


 

 

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AUGUSTA SEQUENCE

The Triassic Augusta Sequence was defined for a thick sequence of units comprising much of the section at Augusta Mountain in the northern Augusta Mountains, along the Lander-Pershing County boundary (Muller and others, 1951). In Lander County, the Augusta Sequence is composed of the following units in ascending order; the Detrital Unit, Favret, Panther Canyon, Augusta Mountain, Cane Spring, and Osobb Formations.

Only the Panther Canyon and Augusta Mountain Formations are recognized in the evaluation area and are described in detail in this report. The other formations which comprise the Augusta Sequence to the west of the study area are briefly summarized below.

The Detrital unit is 2,550 feet in thickness (Stewart and McKee, 1977). It is composed mainly of pebble conglomerate containing chert, quartzite and sandstone clasts from 1 to 2 inches to boulder size, greenish or reddish-gray siltstone, and very fine-grained platy sandstone, with minor amounts of tuff. This unit unconformably overlies the Permian Havallah Formation and is exposed only in the New Pass Range (Stewart and McKee, 1977).

The Favret Formation (Muller and others, 1951) conformably overlies the Detrital Unit and is about 600-800 feet of dark-gray to black, thin-bedded, platy limestone, and interbedded black, calcareous, bituminous shale, and red and tan siltstone. It is exposed in the New Pass Range, Augusta Mountains and northern Fish Creek Mountains (Stewart and McKee, 1977).

The Cane Spring Formation (Muller and others, 1951) is mainly a thick-bedded to massive, medium-gray limestone and dolomite with minor shale, siliceous conglomerate, and impure thin-bedded limestone. It is about 1,500 feet in thickness on the west side of the Augusta Mountains and about 500 feet thick in the northern Fish Creek Mountains (Stewart and McKee, 1977). The Cane Spring Formation rests conformably on the Augusta Mountain Formation and is overlain conformably by the Osobb Formation.

The Osobb Formation (Muller and others, 1951) is the uppermost Triassic unit of the Augusta Mountain Sequence. It is composed of fine to medium-grained, well-sorted and cross-bedded, quartz sandstone with a carbonate matrix, and minor interbedded shale, and massive thick-bedded limestone (Ferguson and others, 1951). The Osobb is 2,500 feet thick in the Augusta Mountains, and about 500 feet in the northern Fish Creek Mountains where it has been contact metamorphosed (Stewart and McKee, 1977).


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