The Jackson Mountains are located in the western Great Basin in Humboldt County, northwest Nevada. The range contains a late Paleozoic to Mesozoic depositional sequence. This sequence records sedimentation, volcanism and deformation in a back-arc setting. The Mississippian to late Early Permian McGill Canyon Formation was deposited in basinal to slope to distal shelf environments, dominated by hemipelagic and turbiditic facies. In the Permian there was an volcanic arc andesite component, and a nearby contemporaneous carbonate platform shed olistostromes into the unit. The McGill Canyon was laid down in an area between the McCloud arc and the Havallah back-arc basin. The late Middle Triassic to middle Norian Bliss Canyon Formation was laid down in basinal to fore-reef to carbonate platform to lagoonal to terrigenous littoral environments. Both of these formations are of flap sequences deposited on an east-facing, back-arc margin. The Bliss Canyon represents the western margin of the Early Mesozoic marine basin of the western Great Basin. From the late Norian to the Bathonian, several stages of subearial volcanism and alluvial epiclastic sedimentation laid down the Happy Creek Formation, a thick arc andesite volcanic pile. The Happy Creek is part of the Early Mesozoic Cordilleran magmatic arc province. In the Bathonian, this volcanic pile was cut by a conjugate sinistral high-angle wrench fault system as volcanism waned. During the Callovian, sediments of the King Lear Formation filled in and then overlapped the wrench basins. These sediments were derived from the east, where a west-vergent thrust system was active. This phase of thrusting ceased by the Oxfordian. Arc-related silicic volcanism and alluvial to fluvial sedimentation within the King Tear continued into the Aptian, when the thrusts were reactivated during a second phase. Both phases of thrusting verged both east and west. Stocks, dikes and sills of the Early Mesozoic Intrusive suite are comagmatic with the volcanism in the Happy Creek and King Lear, and intrude the sedimentary units. This suite both plugs and is truncated by the wrench faults and the first phase of thrusting, but is cut by the second phase. The Jackson Mountains are part of the Black Rock terrane in northwest Nevada. Within this terrane, the rocks share a common tectonic history and stratigraphy distinct from the neighboring terranes, and are separated from them by Mesozoic thrust and strike-slip faults.
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Geology of the Jackson Mountains, northwest Nevada
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