Stratigraphy of Paleozoic rocks in the Carlin-Pinon Range area, Nevada

Abstract

Paleozoic rocks are exposed over slightly more than one-quarter of the re~ion here designated as the Carlin-Pinon Range area, which includes four 15-minute quadrangles that cover about 925 square miles in northeastern Nevada. Paleozoic rocks crop out mostly along the Pinon Range, trending north through the central part of the area, in the northeastern part of the area, and in isolated ridges and hills. Strata ranging in age from Ordovician through Permian make up the stratigraphic section of Paleozoic units. Two prominent unconformities separate these units into three major sequences: (1) Ordovician to upper Upper Devonian, (2) Lower Mississippian to Middle Pennsylvanian, and (3) Upper Pennsylvanian to Upper Permian. Rocks forming sequence 1 consist essentially of two different facies and differ strikingly from the other two sequences. Sequences 2 and 3 are somewhat similar lithologically; the older parts of both are composed in part of sedimentary rocks deposited during major uplift of the source areas of the sediments. Formations in sequence 1 consist of an autochthonous carbonate assemblage deposited in a miogeosyncline, an allochthonous siliceous assemblage deposited in a eugeosyncline to the west, and an allochthonous transitional assemblage. The oldest strata in the carbonate assemblage are of Ordovician age, consist of gray dolomite with interbeds of shale in the upper part, and are assigned to the Pogonip Group; these beds, incompletely exposed in a very small area, are about 350 feet thick with their base unexposed. Overlying the Pogonip and also exposed over only a small area is the Eureka Quartzite, which consists of 70 feet of obscurely stratified, thin-and thick-bedded white quartzite. Regionally, the basal contact of the Eureka is an uncomformity; in the area of this report it is poorly exposed but seems conformable. The Hanson Creek Formation overlies the Eureka on what appears to be a conformable contact; regionally, however, this contact also is an unconformity. The Hanson Creek is composed of 150 feet of thin-to thick-bedded black and gray dolomite; a persistent yellowishweathering limy siltstone and silty limestone unit marks the top of the formation. Poorly preserved fossils from this formation suggest that it is both Middle and Late Ordovician in age. Ordovician units of the siliceous (western) assemblage in the mapped area are the Valmy and Vinini Formations. These two formations are time-equivalent and are similar l.ithologically in containing black shale and chert. The Valmy west of the area of the present report, however, also contains much quartzite and greenstone: On the basis of quartzite and greenstone content along with shale and chert., about. 150 feet of strata at the northern end of the Sulphur Spring Range is placed in t.he Valmy Formation. Graptolites date these beds as Middle Ordovician. The dominantly black chert, shale, and mudstone that make up the Vinini Formation in this area are probably AI A2 STRATIGRAPHY OF PALEOZOIC ROCKS, CARLIN-PINON RANGE AREA, NEVADA thickness of t...

Late Cenozoic paleogeographic evolution of northeastern Nevada: Evidence from the sedimentary basins

“…10; Smith and Ketner, 1976;Smith and Howard, 1977). In the Huntington Creek area, sedimentation began shortly before 15.4 Ma and continued to after 9.9 Ma (Table 1; Perkins et al, 1998).…”

“…In most places, the age of extension can only be constrained to between the late Eocene and middle Miocene (Smith and Ketner, 1976;Smith and Howard, 1977;Wallace, 1993Wallace, , 2003c. At Mule Canyon (Fig.…”

“…With the exception of these basal conglomerates, ash-rich units generally are more common in the lower half of the section, and beds are thin bedded and laterally continuous. The sediments have increasingly more epiclastic materials upsection (Smith and Ketner, 1976), and they include sandstone, pebble-rich sandstone, and conglomerate. Clasts were derived from (Fig.…”

Phosphatic Permian rocks of the Adobe Range, Nevada, and their environment of deposition

“…A thick sequence of Permian rocks is exposed in and near the southern end of the Adobe Range (Dott, 1958;Fails, 1960;Ketner, 1970Ketner, , 1973bSmith and Ketner, 1975)-Its abundant fauna of conodonts, pelecypods, and brachiopods indicate the middle and upper beds are correlative with the Phosphoria Formation. These beds are composed mainly of quartz-silty and sandy calcarenite, quartz siltstone and fine-grained quartz sandstone, and chert.…”

“…Permian rocks are widespread in central Elko County, Nevada, and have been described in several publications (Dott, 1955;Fails, 1960;Churkin and Kay, 1967;Coash, 1967;Ketner, 1970Ketner, , 1973aKetner, , 1973bSmith and Ketner, 1975;and Coats and Gordon, 1972), but heretofore little notice has been taken of their phosphate content. Close observation reveals that all of the younger Permian rocks of this area are remarkably phosphatic.…”