ABSTRACT: Tectonic Influence on the Pennsylvanian-Permian Paleogeography of the Great Basin
SNYDER, WALTER S., C. SPINOSA, DORA M. GALLEGOS, and DAVID L. SCHWARZ, Boise State University, Boise, ID
The Pennsylvanian-Permian paleogeography of the Great Basin reflects tectonic disruption of the miogeocline and Antler highlands. This tectonism postdates the Antler orogeny and apparently predates the latest Permian-Early Triassic Sonoma orogeny. The Antler highlands was not a solid wall of orogenic mountains, but a series of islands and seaways that connected the tectonically active foreland with the paleoPacific. These open passageways facilitated some faunal exchange with the paleoPacific, but did not preclude the development of endemic North American forms. East of the Antler highlands, discrete tectonic phases can be identified by uplifts, folding, normal faulting, tilting, and basin formation. These tectonic phases have been termed the (1) Oquirrh (Morrowan-middle Desmoinesian) (2) Humboldt (Late Pennsylvanian); (3) Dry Mountain (middle Wolfcampian-middle Leonardian); and (4) Ishbel (Late Permian). West of the Antler highlands, the effects of this tectonism on the Havallah-Schoonover basin is unclear. Parts of this basin became structurally incorporated into the Golconda allochthon (terrane) during the Sonoma orogeny. The marked increase of Lower Permian carbonate turbidites within some of the Golconda allochthon structural units probably reflects increased tectonism within the Antler highlands. Although discussion continues about orogenic status of this tectonism, we prefer to abandon the concept of the proposed "Humboldt orogeny.- The relationship of the Permian tectonic phases with the Sonoma orogeny are similarly open to debate; emplacement of the Golconda allochthon may record the last phase ("Golconda phase-) of protracted and genetically associated continental margin tectonism.