Profile of a paleo-orogen: High topography across the present-day Basin and Range from 40 to 23 Ma

Abstract

Records of past topography connect Earth's deep interior to the surface, reflecting the distribution of heat and mass, past crustal structure, and plate interactions. Many tectonic reconstructions of the North American Cordillera suggest the presence of an Altiplano-like plateau in the location of the modern Basin and Range, with conflicting timing and mechanisms for the onset of surface-lowering extension and orogen collapse. Here we show, through a paleotopographic profile, that from the Eocene to the Oligocene a high, broad orogen stretched across Nevada, with a distinct crest that divided a continuous westward-draining slope extending to central California from an internally drained eastern Nevada plateau. This paleo-orogen maintained demonstrably higher-than-modern elevations, reaching 3500 m in the late Oligocene. Despite the long-term high gravitational potential energy of the crust supporting this topography, surfacelowering extension did not occur until the transition to a transform margin changed the external kinematic framework of the system. Maximum surface lowering was spatially decoupled from brittle upper crustal extension, requiring a large component of mid-crustal flow.

Fluid–Rock Interaction and Strain Localization in the Picacho Mountains Detachment Shear Zone, Arizona, USA

“…Modern δ 2 H composition of precipitation in the Tucson basin area ranges from −38‰ (summer) to −61‰ (winter; Kalin, ; Simpson et al, ). Although no Miocene meteoric water composition is available for Arizona, late Oligocene δ 2 H of precipitation ranges from about −60 to −70‰ in the Great Basin area (Cassel et al, ). In addition, δ 2 H fluid of −40‰ calculated from synkinematic muscovites from the Buckskin Mountains detachment (Arizona) is interpreted to reflect isotope composition of mid Miocene rainfalls sourced near sea level (Gébelin et al, ).…”

“…Although such values are not diagnostic of a specific fluid reservoir, they are consistent with fluids of metamorphic origin (Figure ; Gregory, ; Kerrich & Rehrig, ). It is also possible that these values reflect a mixing relationship between metamorphic fluids and meteoric fluid during the early Miocene, when southern Arizona was located near sea level (e.g., Cassel et al, ; Friedman et al, ; Gébelin et al, ). It is therefore possible that the PMDSZ recorded a late stage meteoric overprint as temperature decreased, when hydrogen isotope exchange was still ongoing but oxygen isotope exchange ceased.…”

“…Tectonics O H2O values reflect a mixing relationship between metamorphic fluids and meteoric fluid during the early Miocene, when southern Arizona was located near sea level (e.g., Cassel et al, 2014;Friedman et al, 2002;Gébelin et al, 2012). It is therefore possible that the PMDSZ recorded a late stage meteoric overprint as temperature decreased, when hydrogen isotope exchange was still ongoing but oxygen isotope exchange ceased.…”

Middle Miocene to Holocene tectonics, basin evolution, and paleogeography along the southern margin of the Snake River Plain in the Knoll Mountain–Ruby–East Humboldt Range region, northeastern Nevada and south-central Idaho

“…1A; Henry, 2008). The Nevadaplano formed as a consequence of Mesozoic to Paleogene tectonic convergence and crustal thickening along the western margin of North America (e.g., DeCelles, 2004;Henry, 2008;Cassel et al, 2014). During this period of convergence, northeastern Nevada formed part of the hinterland of the Sevier fold and thrust belt and underwent Jurassic and Cretaceous thrust faulting, plutonism, metamorphism, and as much as ~30 km of tectonic burial of Paleozoic basement (e.g., Hodges et al, 1992;Camilleri and Chamberlain, 1997;McGrew et al, 2000;Hallett and Spear, 2014).…”

Rapid Oligocene to Early Miocene Extension Along the Grant Range Detachment System, Nevada, USA: Insights From Multipart Cooling Histories of Footwall Rocks

“…Eocene‐Oligocene extension has also been documented (e.g., Gans & Miller, ; Gans et al, , ; Druschke, Hanson, & Wells, ; Evans et al, ; Lee et al, ; Long & Walker, ), and was often associated spatially and temporally with the Great Basin ignimbrite flare‐up, a NE to SW sweep of silicic volcanism interpreted to have accompanied post‐Laramide slab rollback (Figure a; e.g., Dickinson, ; Humphreys, ). The initiation of widespread extension that formed the Basin and Range Province, which is attributed to establishment of the San Andreas transform system (e.g., Atwater, ), was not until the middle Miocene (e.g., Cassel et al, ; Colgan & Henry, ; Dickinson, ).…”