Paper No. 28-6
Presentation Time: 3:25 PM
THE ANTLER OROGENY RECORDED IN DETRITAL MULTI-MINERAL U-PB GEOCHRONOLOGY, SOUTHERN NEVADA
The Antler orogeny was a Devonian-Mississippian (~325-375 Ma) mountain building event that occurred along the western margin of North America, which trends NNE-SSW from southeastern Idaho to southeastern California. The initiation of the Antler orogeny occurred during 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. The RMA thrusting caused a flexure response in the continental crust and resulted in the formation of the adjacent Antler Foreland basin. The significance of the Antler orogeny led to decades of research but a consensus on both the origin of the RMA and driving tectonic forces has yet to be made. End-member models for the potential source of the RMA includes local derivation from southwestern Laurentia, versus far traveled exotic source that involves peri-Gondwana or Northern Laurentia derivations. Additionally, proposed mechanisms for RMA emplacement are also debated, with end-member models including eastward subduction driving the closure of a back-arc basin, or westward subduction resulting in emplacement of the Antler as an accretionary prism with or without a terminal arc collision. To test these models, we sampled upper Paleozoic sedimentary rocks along a transect spanning SE-SW 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 fold and thrust belt, and the Antler overlap sequence. We will compare the Paleozoic basin sample age distributions against a suite of new modern river sand samples that drain numerous Precambrian basement and lower Paleozoic sedimentary sources that potentially eroded into the Antler Foreland basin. Samples taken across the RMA-Antler foreland basin system were separated for multi-mineral U-Pb geochronology of detrital apatite, rutile, and zircon. Applying several geochronometers will allows us to better understand crustal terranes (sources) in terms of temperatures, magmatism, and metamorphism and provide new constrains to help resolve the proposed end-member tectonic models.