ABSTRACT: Stratigraphy of Devonian-Mississippian Rocks, Northern Pinon Range, Southwestern Elko County, Nevada
IVERSON, BRIAN G., University of Nevada at Reno, Reno, NV
The Pinon Range in southwestern Elko County, Nevada, exposes rocks along the eastern edge of the Roberts Mountains thrust. This study clarifies the difference in the Upper Devonian and Mississippian siliciclastics in the northern Pinon Range. The Woodruff, Pilot, Webb, Dale Canyon, and Chainman formations are somewhat similar lithologically and often are difficult to separate in the field. The siliciclastics of the Lower Mississippian Dale Canyon Formation were deposited in front of the advancing Roberts Mountains allochthon and were overridden by the allochthon in several places in the Pinon Range. The siliciclastics of the Upper Mississippian Chainman Formation were deposited after cessation of thrusting of the Roberts Mountains allochthon. These two formations are very similar lith logically, but can be separated on the basis of age and proportion of sandstone/conglomerate to shale. The Lower Mississippian Webb formation is compositionally indistinguishable from, and coeval with, the lower part of the Dale Canyon Formation. On the basis of age and lithology, rocks belonging to the Pilot Shale and to the Woodruff Formation were identified and separated from rocks previously mapped as the Webb Formation. This revised stratigraphy greatly simplifies geologic interpretations in the northern Pinon Range.