title: Antler Foreland Basin Evolution Recorded in Detrital Zircon U-Pb Geochronology
Creators: name: Duncan, James
Publisher: name: University of Nevada, Las Vegas
Year: 2022

description: The Antler orogeny was a Devonian-Mississippian (375-320 Ma) mountain building event that occurred along the western Laurentian margin. The initiation of the Antler orogeny is marked by the emplacement of the Roberts Mountain Allochthon (RMA) that thrust Cambrian-Devonian deep water marine siliciclastic rocks 100 km eastward onto the western Laurentian margin. Shortening related to the Antler orogeny deformed RMA strata and caused a flexural response in the continental crust that resulted in the formation of the adjacent Antler Foreland basin. The paleogeographic history of the RMA strata and tectonic drivers for the Antler orogeny are still debated. Proposed models suggest that the RMA strata are either exotic rocks derived from northwestern Laurentian, peri-Gondwana, or peri-Baltica affinities, or simply the distal, deep-water equivalents to southwest Laurentian passive margin sequences. To test these models, I sampled Paleozoic sedimentary rocks along a transect spanning SE-NW Nevada. Samples were chosen based on spatial relationships covering major provinces associated with the Antler orogeny such as the cratonal region, distal and proximal Antler foreland basin, hinterland sources within the Antler fold and thrust belt, and the Antler overlap sequence. The overarching goal of this study is to better understand the shift in sedimentary provenance from passive margin sedimentation to Antler foreland basin development. Then, I use the new detrital zircon data to compare Paleozoic stratigraphy in southern Nevada with previously published data in central Nevada and Utah, and southern and northern California to better discriminate between proposed origins and tectonic models for the Antler orogeny and associated RMA strata. My findings include: (1) Ubiquitous Paleoproterozic provenance signature appear in both allochthonous RMA and autochthonous passive margin strata suggesting that northern Peace River Arch cratonic sediments were dispersed southward via longshore transport in oceanic basins along western Laurentia, which indicates a non-exotic origin for the RMA strata across the Great Basin; (2) Antler foreland basin deposits record the recycling of RMA strata in the Antler orogenic interior, which exhibits spatially heterogeneous detrital zircon age distributions with the presence of southern Laurentian signatures in the southern Antler foreland basin and the absence of these same signatures in northern sections; (3) Paleozoic aged zircons are observed in Antler foreland basins deposits providing evidence for coeval magmatism during the Antler orogeny. Presence of young ages in the foreland basin supports tectonic models in which non-collisional or collision-related subduction margin generated the Antler orogeny; and (4) Additionally, the observed Paleozoic detrital zircon ages in the southern proximal Antler foreland basin were likely derived from Klamath Mountains and northern terranes to the west as opposed to the previously interpreted long-traveled continental sediment dispersal pathways from eastern Appalachian sources.