Reevaluation of Late Mesozoic Thrusting in East-Central Nevada

Greg J. Cameron, Alan K. Chamberlain

Late Mesozoic thrust faults occur along a narrow, north-south-trending belt through east-central Nevada. The low-angle faults juxtapose older miogeoclinal Paleozoic rocks onto younger miogeoclinal Paleozoic rocks. The thrust belt can be clearly delineated as far north as the northern Diamond Range and as far south as northwestern Clark County, where the structures merge with the Sevier overthrust belt of southern Nevada and central Utah. In the northern part of the thrust belt, the depositional relationships of the Newark Canyon Formation clearly indicate faulting and attendant folding of Early Cretaceous age. Similarly, the areal relationships of an unnamed Cretaceous-early Tertiary(?) conglomeratic unit in the southern part of the belt suggests a Cretaceous and possibly younger age for deformation there. The thrusting has effectively telescoped the Mississippian Antler basin, as the Mississippian Chainman Shale is consistently the surface of decollement of the structurally lowest exposed thrust. This relationship is important for hydrocarbon exploration as the Chainman is the likely source of oil in the east-central Nevada oil fields. All of these fields lie within the delineated thrust belt.

The exact structural relationship between the east-central Nevada thrust belt and the similar-age Sevier overthrust belt of Utah has yet to be worked out, but it is suggested that prior to middle Tertiary extension, these belts lay side by side, delineating a northeast-trending belt of deformation. Differential Tertiary extension has displaced the hinterland of the thrust belt in a direction counterclockwise from its original position. An estimated 160 km of extension occurred at the latitude of Ely, Nevada.

AAPG Search and Discovery Article #91038©1987 AAPG Annual Convention, Los Angeles, California, June 7-10, 1987.