LATE PALEOZOIC DEFORMATION IN THE NORTHERN ADOBE RANGE, ELKO COUNTY, NEVADA

Several late Paleozoic deformation events are recorded in the northern Adobe Range in addition to the post-Early Triassic deformation recognized by Ketner and Ross (1990). Some of these correlate with late Paleozoic deformation events recently recognized in the southern Adobe Range in Carlin Canyon. The northern Adobe Range provides a rare opportunity to study mid- to late Paleozoic deformation in an area where Permian and Triassic rocks are preserved, so the geometry and kinematics of both pre- and post-Early Triassic deformation can be determined.

The Mississippian to Permian sedimentary section includes several angular unconformities representing deformation events. South of Coal Mine Canyon there is an angular unconformity within the Mississippian (C2), placing gently dipping conglomerate over steeply dipping shale, and another unconformity (P1 or P2) placing homoclinal Permian chert, sandstone, conglomerate and limestone over beveled open folds in the Mississippian conglomerate. These units are overlain by Late Permian to Early Triassic shale and carbonate. In Coal Canyon (northwest of Coal Mine Canyon), both the Mississippian shale and rocks of the Antler allochthon are beveled and depositionally overlain by the Permian units. There are additional depositional breaks within and above the Permian section and a significant pre-Triassic unconformity.

There are several distinct deformation events recorded in the Paleozoic section. The lower angular unconformity in Coal Mine Canyon and folded lower- to middle-Mississippian section records deformation within the Mississippian, while the upper unconformity records deformation in rocks as young as Permian. The rocks of the Antler allochthon are thrust over Mississippian shale of the Antler foreland basin in Coal Canyon, and the thrust is unconformably overlain by Permian rocks; the thrusting could be correlative to either unconformity. Map patterns also suggest open folding and beveling of Permian units under the Early Triassic section. All of these predate deformation recorded by the Early Triassic section.