@article{c32461ff6f8c48f98b2ed946e8e380e0,
title = "Rapid Oligocene to Early Miocene Extension Along the Grant Range Detachment System, Nevada, USA: Insights From Multipart Cooling Histories of Footwall Rocks",
abstract = " In Nevada and Utah, the Cordilleran orogen underwent a protracted Cenozoic transition to an extensional setting. However, the geodynamic processes that controlled this transition are poorly understood, in part because the space-time patterns of extension are not known in many areas. Localities of pre-Neogene extension have the potential to elucidate the dynamics of the Cordilleran crust during the final stages of subduction. Here we present data that constrain the timing of extension in the Grant Range in eastern Nevada, which was deformed by a low-angle normal fault system. We present temperature-time histories of eight granite samples exhumed by this fault system, constrained by muscovite 40 Ar/ 39 Ar multi-diffusion domain modeling and fission track and (U-Th)/He ages from zircon and apatite. These data demonstrate rapid cooling (20–35 °C/Myr) from 350–425 to 25–50 °C between 28–31 and 15–19 Ma. The fault system accommodated ~24 km of extension (~115%), and exhumed the granite samples from 7–9 km depths to the near-surface. Rapid Oligocene-early Miocene cooling is interpreted to date the duration of motion on the fault system, and defines an extension rate of 1.5–2.6 km/Myr. This was one of the most significant fault systems active during an episode of spatially distributed late Eocene-Oligocene extension, which overlaps temporally with volcanism generated by slab rollback. Reduced interplate coupling that accompanied slab rollback is interpreted as the primary driver of extension of the Cordilleran plateau during the final stages of subduction. This supports a scenario of orogenic collapse that proceeded in distinct episodes that were initiated by external geodynamic events. ",
keywords = "Basin and Range, Grant Range, Nevadaplano, detachment fault, extension, thermochronology",
author = "Long, {Sean P.} and Heizler, {Matthew T.} and Thomson, {Stuart N.} and Reiners, {Peter W.} and Fryxell, {Joan E.}",
note = "Funding Information: Extension in Nevada and Utah is interpreted to have accommodated the collapse of the Cordilleran orogenic plateau (e.g., Allmendinger, 1992; Colgan & Henry, 2009; Coney & Harms, 1984; DeCelles, 2004). Therefore, analysis of the timing and distribution of extension has the potential to elucidate the geodynamic processes that govern orogenic collapse. However, the transition of the Cordilleran plateau to an extensional regime was complex in space and time, and several aspects of this evolution remain enigmatic (e.g., Dickinson, 2002; Colgan & Henry, 2009; Druschke, Hanson, & Wells, 2009; Henry et al., 2011; Long, 2012; Wells et al., 2012). In particular, the magnitudes, spatial patterns, and driving mechanisms of extension that predates the middle Miocene reorganization of the Pacific-North American plate boundary to a transform system, and the corresponding inception of widespread extension that constructed the Basin and Range Province (e.g., Colgan & Henry, 2009; Dickinson, 2002, 2006; Faulds & Henry, 2008), remain subjects of ongoing debate (e.g., Axen et al., 1993; Best et al., 2009; Druschke, Hanson, & Wells, 2009; Gans et al., 1989; Henry et al., 2011). The Grant Range detachment system provides an important piece of this puzzle, as the results of this study demonstrate that it was one of the most significant fault systems to accommodate extension prior to the middle Miocene. Here the Grant Range fault system is placed in the larger framework of Eocene-Oligocene extension within the Cordilleran orogenic plateau, in order to speculate on the geodynamic processes that contributed to the transition to an extensional regime during the final stages of subduction. This discussion is supported by a compilation of documented sites of Paleogene and older extension across central and eastern Nevada and western Utah (Table 3 and Figure 11). Publisher Copyright: {\textcopyright}2018. American Geophysical Union. All Rights Reserved.",
year = "2018",
month = dec,
doi = "10.1029/2018TC005073",
language = "English (US)",
volume = "37",
pages = "4752--4779",
journal = "Tectonics",
issn = "0278-7407",
publisher = "American Geophysical Union",
number = "12",
}