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Geologic map of southern part of Secret Canyon (location shown in lower inset and in Fig. 2), showing fi eld relationships of late Eocene unconformity on either side of Dugout Tunnel fault. Unconformity is on Cambrian Secret Canyon Shale in footwall (green arrow) and on Ordovician Goodwin Formation in hanging wall (blue arrow). Units as high in the section as Eureka Quartzite are locally preserved in hanging wall (red arrow).
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Assessing temporal relationships between foreland and hinterland deformation in foldthrust belts is critical to understanding the dynamics of orogenic systems. In the western U. S. Cordillera, the central Nevada thrust belt (CNTB) has been interpreted as a hinterland component of the Sevier fold-thrust belt in Utah. However, imprecise timing constr...
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Overprinting Cenozoic extension hinders analysis of Cordilleran contractional deformation in the hinterland of the Sevier thrust belt in Nevada. In this study, a 1:250,000 scale paleogeologic map of eastern Nevada, showing spatial distributions of Paleozoic- Mesozoic rocks beneath a Paleogene unconformity, is combined with dip magnitude maps for Pa...
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... Areas extending from northwestern Utah through northeastern Nevada into south-central Idaho (~38°N-43°N, ~113°W-116°W) occupy the Sevier hinterland region of the Cordilleran orogen ( Fig. 1A; e.g., Misch, 1960;. While the location of initial thrusting is unclear (southern Idaho- Royse et al., 1975;Miller, 1980;northeast Nevada-Hodges et al., 1992;Hudec, 1992;west-central Utah-Lawton et al., 1997), compressional deformation propagated eastward with local hindward-directed and out-of-sequence events over late Mesozoic time (Morley, 1988;DeCelles, 1994DeCelles, , 2004Long et al., 2014). Kinematic reconstructions reported from the Sevier type area in west-central Utah (Canyon and Pavant Ranges; Fig. 1A) indicate east-west shortening exceeded 160 km (DeCelles and Coogan, 2006). ...
Polyphase structural mapping and mineral age dating across the Salmon River suture zone in west-central Idaho (Riggins region; ~45°30′N, ~117°W-116°W) support a late Mesozoic history of penetrative deformation, dynamothermal metamorphism, and intermittent magmatism in response to right-oblique oceanic-continental plate convergence (Farallon-North America). High-strain linear-planar tectonite fabrics are recorded along an unbroken ~48 km west-to-east transect extending from the Snake River (Wallowa intra-oceanic arc terrane; eastern Blue Mountains Province) over the northern Seven Devils Mountains into the lower Salmon River Canyon (ancestral North America; western Laurentia). Given the temporally overlapping nature (ca. 145-90 Ma) of east-west contraction in the Sevier fold-and-thrust belt (northern Utah-southeast Idaho-southwest Montana segment), we propose that long-term terrane accretion and margin-parallel northward translation in the Cordilleran hinterland (~41°N-46°N latitude; modern coordinates) drove mid-to upper-crustal shortening >250 km eastward into the foreland region (~115°W-113°W). During accretion and translation, the progressive transfer of arc assemblages from subducting (Farallon) to structurally overriding (North American) plates was accommodated by displacement along a shallow westward-dipping basal décollement system underlying the Cordilleran orogen. In this context, large-magnitude horizontal shortening of passive continental margin strata was balanced by the addition of buoyant oceanic crust-late Paleozoic to Mesozoic Blue Mountains Province-to the leading edge of western Laurentia. Consistent with orogenic float modeling (mass conservation, balance, and displacement compatibility), diffuse dextral-transpressional deformation across the accretionary boundary (Salmon River suture: Cordilleran hinterland) was kinematically linked to eastward-propagating structures on the continental interior (Sevier thrust belt; Cordilleran foreland). As an alternative to noncollisional convergent margin orogenesis, we propose a collision-related tectonic origin and contractional evolution for central portions of the Sevier belt. Our timing of terrane accretion supports correlation of the Wallowa terrane with Wrangellia (composite arc/plateau assemblage) and implies diachronous south-to-north suturing and basin closure between Idaho and Alaska.
... The spatial location of the different MCCs in either the hinterland or foreland of the Sevier thrust front ( Fig. 2A) implies that they developed in crust with variable thickness. Support for the Late Cretaceous Nevadaplano orogenic plateau (DeCelles, 2004) with relatively thick crust (~60+ km) in the Sevier hinterland includes observed deeply incised paleovalleys (Henry et al., 2012), geochemical thickness proxies (Chapman et al., 2015), moderate-to-high magnitudes of Mesozoic crustal shortening in the Sevier thrust belt and its hinterland (e.g., Long et al., 2014;Yonkee and Weil, 2015;Zuza et al., 2021), Late Cretaceous deep burial (~7-8 kbar) of supracrustal rocks in exhumed MCCs that supports substantial crustal thickening (Lewis et al., 1999;Hallett and Spear, 2014), reconstructions of Cenozoic extension that imply thickened pre-Cenozoic crust (Coney and Harms, 1984), and stable-isotope paleoaltimetry (e.g., Snell et al., 2014). ...
Metamorphic core complexes (MCC) in the North American Cordillera exhibit a strong dichotomy. Those in the north formed in a thickened orogenic plateau during Paleogene Farallon subduction, are widely spaced (~200 km), and young SW. Conversely, those in the south formed in thinner crust, are closely spaced (~50 km), developed during the Oligocene-Miocene transition to regional transtension, and young NW. Synthesis of magmatism and cooling ages, modeling, and plate reconstructions demonstrate that MCCs could have initiated as buoyant domes driven by lower-crust heating caused by asthenospheric upwelling after Farallon slab rollback. These domes were later exhumed by Miocene extension. The widely spaced Paleogene hinterland domal upwellings and associated mylonites were temporally decoupled from Miocene detachments, manifesting a two-stage development. The closely spaced Oligocene-Miocene foreland MCCs show almost synchronized doming and detachment faulting. The spacing dichotomy of the MCCs reflects the characteristic wavelength of the doming process that was in turn controlled by the thickness and thermal state of the crust.
... Dark orange arrow shows approximate direction of subduction of the Farallon plate (DeCelles, 2004;DeCelles & Graham, 2015). The white box indicates the area of the map shown in (b) Regional tectonic map adapted from Di Fiori et al. (2020); Long, Henry, Muntean, Edmondo, and Cassel (2014), and Long, Henry, Muntean, Edmondo, and Thomas (2014). Gray shading shows the approximate spatial extents of Jurassic-Cretaceous deformational provinces of the North American Cordilleran mountain belt in western United States, while pink shading marks the Sierra Nevada magmatic arc (from Van Buer et al., 2009 Fiori et al., 2021;Long, Henry, Muntean, Edmondo, & Cassel, 2014;Long, Henry, Muntean, Edmondo, & Thomas, 2014;Nolan & Hunt, 1962;Nolan et al., 1974Nolan et al., , 1956. ...
... The white box indicates the area of the map shown in (b) Regional tectonic map adapted from Di Fiori et al. (2020); Long, Henry, Muntean, Edmondo, and Cassel (2014), and Long, Henry, Muntean, Edmondo, and Thomas (2014). Gray shading shows the approximate spatial extents of Jurassic-Cretaceous deformational provinces of the North American Cordilleran mountain belt in western United States, while pink shading marks the Sierra Nevada magmatic arc (from Van Buer et al., 2009 Fiori et al., 2021;Long, Henry, Muntean, Edmondo, & Cassel, 2014;Long, Henry, Muntean, Edmondo, & Thomas, 2014;Nolan & Hunt, 1962;Nolan et al., 1974Nolan et al., , 1956. Sedimentation in the NCF type section basin is attributed to erosion of the eastern flank of the Eureka Culmination, a structural high of the Central Nevada Thrust belt (Figure 1), based on clast and cross-bedding orientations from the NCF type section that indicate an east-flowing fluvial system Fetrow et al., 2020;Long, 2012Long, , 2015Long, Henry, Muntean, Edmondo, & Cassel, 2014;Long, Henry, Muntean, Edmondo, & Thomas, 2014;Long et al., 2015;Vandervoort & Schmitt, 1990). ...
... Gray shading shows the approximate spatial extents of Jurassic-Cretaceous deformational provinces of the North American Cordilleran mountain belt in western United States, while pink shading marks the Sierra Nevada magmatic arc (from Van Buer et al., 2009 Fiori et al., 2021;Long, Henry, Muntean, Edmondo, & Cassel, 2014;Long, Henry, Muntean, Edmondo, & Thomas, 2014;Nolan & Hunt, 1962;Nolan et al., 1974Nolan et al., , 1956. Sedimentation in the NCF type section basin is attributed to erosion of the eastern flank of the Eureka Culmination, a structural high of the Central Nevada Thrust belt (Figure 1), based on clast and cross-bedding orientations from the NCF type section that indicate an east-flowing fluvial system Fetrow et al., 2020;Long, 2012Long, , 2015Long, Henry, Muntean, Edmondo, & Cassel, 2014;Long, Henry, Muntean, Edmondo, & Thomas, 2014;Long et al., 2015;Vandervoort & Schmitt, 1990). An estimated 1.1° ± 3.0° (positive northward) apparent latitude shift for the mid-Cretaceous Sierra Nevada (∼100-83 Ma) and negligible apparent rotation of 0.0° ± 4.7° (Hillhouse & Grommé, 2011) indicate that the NCF was deposited at approximately the same latitude as its current position (∼39°N). ...
The North American Newark Canyon Formation (NCF; ∼113–98 Ma) presents an opportunity to examine how terrestrial carbonate facies reflect different aspects of paleoclimate during one of the hottest periods of Earth's history. The lower NCF type section preserves heterogeneous palustrine facies and the upper NCF preserves lacustrine deposits. We combined carbonate facies analysis with δ¹³C, δ¹⁸O, and Δ47 data sets to assess which carbonate facies preserve stable isotope signals that are most representative of climatic conditions. Palustrine facies record the heterogeneity of the original wetland environment in which they formed. Using the pelmicrite facies that formed in deeper wetlands, we interpret a lower temperature zone (35–40°C) to reflect warm season water temperatures. In contrast, a mottled micrite facies which formed in shallower wetlands records hotter temperatures (36–68°C). These hotter temperatures reflect radiatively heated “bare‐skin” temperatures that occurred in a shallow depositional setting. The lower lacustrine unit has been secondarily altered by hydrothermal fluids while the upper lacustrine unit likely preserves primary temperatures and δ¹⁸Owater of catchment‐integrated precipitation. Resultantly, the palustrine pelmicrite and lacustrine micrite are the facies most likely to reflect ambient climate conditions, and therefore, are the best facies to use for paleoclimate interpretations. Average warm season water temperatures of 41.1 ± 3.6°C and 37.8 ± 2.5°C are preserved by the palustrine pelmicrite (∼113–112 Ma) and lacustrine micrite (∼112–103 Ma), respectively. These data support previous interpretations of the mid‐Cretaceous as a hothouse climate and demonstrate the importance of characterizing facies for identifying the data most representative of past climates.
... Areas extending from northwestern Utah through northeastern Nevada into south-central Idaho (~38°N-43°N, ~113°W-116°W) occupy the Sevier hinterland region of the Cordilleran orogen ( Fig. 1A; e.g., Misch, 1960;. While the location of initial thrusting is unclear (southern Idaho- Royse et al., 1975;Miller, 1980;northeast Nevada-Hodges et al., 1992;Hudec, 1992;west-central Utah-Lawton et al., 1997), compressional deformation propagated eastward with local hindward-directed and out-of-sequence events over late Mesozoic time (Morley, 1988;DeCelles, 1994DeCelles, , 2004Long et al., 2014). Kinematic reconstructions reported from the Sevier type area in west-central Utah (Canyon and Pavant Ranges; Fig. 1A) indicate east-west shortening exceeded 160 km (DeCelles and Coogan, 2006). ...
... The character of this proposed thrust system is entirely different from anything observed in the eastern Great Basin. Clear examples of confirmed hinterland thrust faults include those near Eureka, NV (Long et al., 2014, in the White Pine Mountains (Humphrey, 1960;Gans, 2000), and the Confusion Range in western Utah (Greene, 2014). These structures fit within the three large synclinoria (and bounding anticlinoria) located near the Nevada-Utah border (Fig. 1A) (e.g., Hose and Blake, 1976;Gans and Miller, 1983;Welch et al., 2007;Long 2012Long , 2015Greene, 2014). ...
... The Late Cretaceous REWP was located within the inferred Nevadaplano orogenic plateau. At this longitude, Cretaceous thrust structures are preserved to the south, including the Central Nevada thrust belt and Eureka culmination (Long et al., 2014;Di Fiori et al., 2020) and thrust system in the Confusion Range (Greene, 2014). However, these faults involve relatively low magnitude fault-bend fold thrust-fault geometries that did not significant bury the footwall rocks. ...
There is a long-standing discrepancy for numerous North American Cordillera metamorphic core complexes between geobarometric pressures recorded in the exhumed rocks and their apparent burial depths based on palinspastic reconstructions from geologic field data. In particular, metamorphic core complexes in eastern Nevada are comprised of well-documented ~12–15 km thick Neoproterozoic–Paleozoic stratigraphy of Laurentia's western passive margin, which allows for critical characterization of field relationships. In this contribution we focus on the Ruby Mountain–East Humboldt Range–Wood Hills–Pequop Mountains (REWP) metamorphic core complex of northeast Nevada to explore reported peak pressure estimates versus geologic field relationships that appear to prohibit deep burial. Relatively high pressure estimates of 6–8 kbar (23–30 km depth, if lithostatic) from the lower section of the Neoproterozoic–Paleozoic passive margin sequence require burial and or repetition of the passive margin sequence by 2–3× stratigraphic depths. Our observations from the least migmatized and/or mylonitized parts of this complex, including field observations, a transect of peak-temperature (Tp) estimates, and critical evaluation of proposed thickening/burial mechanisms cannot account for such deep burial. From Neoproterozoic–Cambrian (Ꞓ) rocks part of a continuous stratigraphic section that transitions ~8 km upsection to unmetamorphosed Permian strata that were not buried, we obtained new quartz-in-garnet barometry via Raman analysis that suggest pressures of ~7 kbar (~26 km). A Tp traverse starting at the same basal Ꞓ rocks reveals a smooth but hot geothermal gradient of ≥40 °C/km that is inconsistent with deep burial. This observation is clearly at odds with thermal gradients implied by high P-T estimates that are all ≤25 °C/km. Remarkably similar discrepancies between pressure estimates and field observations have been discussed for the northern Snake Range metamorphic core complex, ~200 km to the southeast. We argue that a possible reconciliation of long-established field observations versus pressures estimated from a variety of barometry techniques is that the rocks experienced non-lithostatic tectonic overpressure. We illustrate how proposed mechanisms to structurally bury the rocks, as have been invoked to justify published high pressure estimates, are entirely atypical of the Cordillera hinterland and unlike structures interpreted from other analogous orogenic plateau hinterlands. Proposed overpressure mechanisms are relevant in the REWP, including impacts from deviatoric/differential stress considerations, tectonic mode switching, and the autoclave effect driven by dehydration melting. Simple mechanical arguments demonstrate how this overpressure could have been achieved. This study highlights that detailed field and structural restorations of the least strained rocks in an orogen are critical to evaluate the tectonic history of more deformed rocks.
... These faults exhibit relatively little displacement relative to the Sevier fold-andthrust belt farther east (Figs. 1B-1D;Armstrong, 1968;Gans and Miller, 1983;DeCelles and Coogan, 2006;Long 2012Long , 2015Long , 2019Long et al., 2014;Greene, 2014). Long (2015) suggested that the Central Nevada thrust belt, Eastern Nevada fold belt, and Western Utah thrust belt collectively record long-lived and low-magnitude (a few tens of kilometers) shortening across the region of their development, but, as a package, all of these rocks were transported over 220 km eastward during Sevier thrusting. ...
We addressed fundamental questions about the lithology, age, structure, and thermal evolution of the deep crust of the retroarc hinterland of the North American Cordilleran orogen through systematic investigation of zircons from Cretaceous plutons in the Snake Range and Kern Mountains of east-central Nevada. Geochronological (U-Pb) and geochemical (trace element, O and Hf isotopes) characterization of pre- and synmagmatic growth domains of zircons, coupled with traditional petrologic methods (petrography, field relationships, and whole-rock major-element, trace-element, and Sr-Nd and Pb isotope geochemistry), fingerprinted temporal variations in crustal contributions to magmatism. The samples are typical felsic, peraluminous Cordilleran interior granitoids that formed between 102 ± 2 Ma and 71 ± 1 Ma (95% confidence). Over the entire time span of magmatism, 87Sr/86Srinitial, εNd(t), 208Pb/204Pb, and εHf(t) exhibit incrementally more “crustal” ratios. The oldest and youngest samples, respectively, predate and postdate all published timing constraints of Cretaceous peak metamorphism in the region and exhibit the least and most radiogenic whole-rock isotopic results in the study (87Sr/86Srinitial = 0.7071 vs. 0.7222; εNd(t) = −3.4 vs. −18.8; 208Pb/204Pb = 38.8 vs. 40.1). Accordingly, the least intrasample variability of εHf(t), δ18OZrc, and trace-element ratios in magmatic zircon domains is also observed in these oldest and youngest samples, whereas greater intrasample variability is observed in intermediate-age samples that intruded during peak metamorphism. The geochemistry of zircon growth in the intermediate-age samples suggests assimilation of partially molten metasedimentary crust led to increased heterogeneity in their magma chemistry. Interaction of magmas with distinctive crust types is indicated by contrasts between four categories of inherited zircon observed in the studied intrusions: (1) detrital zircon with typical magmatic trace-element ratios; (2) zircon derived from high-grade 1.8–1.6 Ga basement; (3) zircon with anomalously low δ18O of uncertain origin, derived from 1.7/2.45 Ga basement (or detritus derived thereof); and (4) zircon from variably evolved Jurassic–Early Cretaceous deep-seated intrusions. The progression of zircon inheritance patterns, correlated with evolving geochemical signatures, in Late Cretaceous granitic plutons is best explained by early, relatively primitive intrusions and their penecontemporaneously metamorphosed country rock having been tectonically transported cratonward and superposed on older basement, from which the later, more-evolved Tungstonia pluton was generated. This juxtaposition consequentially implies tectonic transport of synorogenic plutonic rocks occurred in the Cordilleran hinterland during the Sevier orogeny as a result of the interplay of retroarc magmatism and convergent margin tectonism.
... To the west of the Sevier fold-thrust belt, a broad region of the Cordilleran retroarc in eastern Nevada and westernmost Utah is often referred to as the "Sevier hinterland" (e.g., Armstrong, 1972). Upper-crustal shortening, though likely of a low magnitude (a few tens of km), was diffusely distributed across the Sevier hinterland, and it was accommodated by east-vergent thrust systems in central Nevada and western Utah and a broad region of open folds in eastern Nevada (e.g., Gans and Miller, 1983;Taylor et al., 2000;Long, 2012Greene, 2014;Long et al., 2014aLong et al., , 2014bDi Fiori et al., 2020) (Fig. 1). By the late stages of Cordilleran shortening in the Late Cretaceous-Paleogene, the Sevier hinterland in eastern Nevada is interpreted to have been a high-elevation (~2.2-3.5 km) plateau ("Nevadaplano"), which was underlain by ~50-60-km-thick crust (e.g., Coney and Harms, 1984;Allmendinger, 1992;DeCelles, 2004;Cassel et al., 2014;Snell et al., 2014;Chapman et al., 2015;Long, 2019). ...
... Retro-deformation of a cross section through the Diamond Mountains, Fish Creek Range, and Mahogany Hills by Long (2019) illustrated the geometry of the Eureka Culmination, a 20-km-wide, open anticline interpreted as a faultbend fold that structurally elevated Cambrian to Permian sedimentary rocks above an east-vergent, subsurface thrust fault (Long et al., 2014a) (Fig. 7). The timing of construction of the culmination is constrained by syn-contractional deposition of the ca. ...
... The timing of construction of the culmination is constrained by syn-contractional deposition of the ca. 114-99 Ma Newark Canyon Formation on its eastern limb (Long et al., 2014a;Di Fiori et al., 2020). The Paleogene unconformity in the Diamond Mountains and Fish Creek Range is subhorizontal and overlies complexly deformed Cambrian to Permian rocks. ...
Crustal temperature conditions can strongly influence the evolution of deformation during orogenesis. The Sevier hinterland plateau in Nevada and western Utah (“Nevadaplano”) experienced a Late Cretaceous episode of shallow-crustal metamorphism and granitic magmatism. Here, we investigate the thermal history of the Nevadaplano by measuring peak thermal field gradients attained in the upper 10–20 km of the crust along an east-west transect through nine ranges in eastern Nevada and western Utah, by integrating Raman spectroscopy of carbonaceous material thermometry and published conodont alteration indices with reconstructed cross sections. Thermal field gradients of 29 ± 3 °C/km were obtained in the House and Confusion Ranges in westernmost Utah. The Deep Creek, Schell Creek, and Egan Ranges in easternmost Nevada yielded elevated gradients of 49 ± 7 °C/km, 36 ± 3 °C/km, and 32 ± 6 °C/km, respectively. Moving westward, the White Pine, Butte, Pancake, and Fish Creek Ranges exhibit gradients typically between ~20–30 °C/km. The elevated thermal gradients in easternmost Nevada are interpreted to have been attained during ca. 70–90 Ma granitic magmatism and metamorphism and imply possible partial melting at ~18 km depths. Our data are compatible with published interpretations of Late Cretaceous lithospheric mantle delamination under the Sevier hinterland, which triggered lower-crustal anatexis and the resulting rise of granitic melts. The lack of evidence for structures that could have accommodated deep burial of rocks in the nearby Northern Snake Range metamorphic core complex, combined with thermal gradients from adjacent ranges that are ~1.5–3 times higher than those implied by thermobarometry in the Northern Snake Range, further highlights the debate over possible tectonic overpressure in Cordilleran core complexes. Cross-section retro-deformation defines 73.4 ± 4.6 km (76 ± 8%) of extension across eastern Nevada and 15 km of shortening in the Eastern Nevada fold belt.
... Numerous studies have focused on understanding the deformational history of the later stages of the North American Cordillera orogen, including thin-skinned Cretaceous-Paleogene Sevier fold-and-thrust belt development and the commonly thick-skinned, basement-uplift-involving Paleogene Laramide deformation (e.g., Dickinson and Snyder, 1978;Jordan, 1981;Livaccari et al., 1981;Allmendinger et al., 1983Allmendinger et al., , 1987DeCelles et al., 1995;DeCelles and Coogan, 2006;Greene, 2014;Long et al., 2014Long et al., , 2015Long, 2015;Copeland et al., 2017;Axen et al., 2018). This deformation is associated with crustal thickening of the Great Basin region as part of the interpreted Late Cretaceousearly Cenozoic Nevadaplano orogenic plateau (e.g., DeCelles, 2004;Snell et al., 2014;Chapman et al., 2015). ...
... A longstanding dilemma in Cordilleran tectonics has revolved around the apparent lack, or relative insignificance, of Cretaceous deformation in the hinterland of the Sevier fold and thrust belt across present-day Nevada, including much of the proposed Nevadaplano (e.g., Long, 2012;Long et al., 2014). This has led to debate regarding the evolution of a Cordilleran orogenic plateau. ...
... It also remains unclear how the various Cordilleran domains were kinematically and/or dynamically connected, such as the magmatic arc, retroarc thrust belt, and the thrust belt's hinterland (e.g., Dickinson and Snyder, 1978;Bird, 1998;DeCelles, 2004;DeCelles and Graham, 2015;Anderson, 2020). This apparent lack of Cretaceous hinterland deformation may either result from the concentration of deformation at rarely exposed mid-crustal levels (e.g., Miller and Hoisch, 1995; or overprinting by Cenozoic extension that can be documented through systematic field mapping and structural restorations (e.g., Greene, 2014;Long et al., 2014). ...
The Ruby Mountains–East Humboldt Range–Wood Hills–Pequop Mountains (REWP) metamorphic core complex, northeast Nevada, exposes a record of Mesozoic contraction and Cenozoic extension in the hinterland of the North American Cordillera. The timing, magnitude, and style of crustal thickening and succeeding crustal thinning have long been debated. The Pequop Mountains, comprising Neoproterozoic through Triassic strata, are the least deformed part of this composite metamorphic core complex, compared to the migmatitic and mylonitized ranges to the west, and provide the clearest field relationships for the Mesozoic–Cenozoic tectonic evolution. New field, structural, geochronologic, and thermochronological observations based on 1:24,000-scale geologic mapping of the northern Pequop Mountains provide insights into the multi-stage tectonic history of the REWP. Polyphase cooling and reheating of the middle-upper crust was tracked over the range of <100 °C to 450 °C via novel 40Ar/39Ar multi-diffusion domain modeling of muscovite and K-feldspar and apatite fission-track dating. Important new observations and interpretations include: (1) crosscutting field relationships show that most of the contractional deformation in this region occurred just prior to, or during, the Middle-Late Jurassic Elko orogeny (ca. 170–157 Ma), with negligible Cretaceous shortening; (2) temperature-depth data rule out deep burial of Paleozoic stratigraphy, thus refuting models that incorporate large cryptic overthrust sheets; (3) Jurassic, Cretaceous, and Eocene intrusions and associated thermal pulses metamorphosed the lower Paleozoic–Proterozoic rocks, and various thermochronometers record conductive cooling near original stratigraphic depths; (4) east-draining paleovalleys with ~1–1.5 km relief incised the region before ca. 41 Ma and were filled by 41–39.5 Ma volcanic rocks; and (5) low-angle normal faulting initiated after the Eocene, possibly as early as the late Oligocene, although basin-generating extension from high-angle normal faulting began in the middle Miocene. Observed Jurassic shortening is coeval with structures in the Luning-Fencemaker thrust belt to the west, and other strain documented across central-east Nevada and Utah, suggesting ~100 km Middle-Late Jurassic shortening across the Sierra Nevada retroarc. This phase of deformation correlates with terrane accretion in the Sierran forearc, increased North American–Farallon convergence rates, and enhanced Jurassic Sierran arc magmatism. Although spatially variable, the Cordilleran hinterland and the high plateau that developed across it (i.e., the hypothesized Nevadaplano) involved a dynamic pulsed evolution with significant phases of both Middle-Late Jurassic and Late Cretaceous contractional deformation. Collapse long postdated all of this contraction. This complex geologic history set the stage for the Carlin-type gold deposit at Long Canyon, located along the eastern flank of the Pequop Mountains, and may provide important clues for future exploration.
... In this study, we focus on the CNTB, which is defined as a system of north-striking, east-vergent thrust faults and folds that branches northward off of the Sevier fold-thrust belt in southern Nevada (Figure 1) Long, 2012;Long, Henry, Muntean, Edmondo, & Cassel, 2014;Long & Walker, 2015;Taylor et al., 1993;Taylor et al., 2000). Based on cross-cutting relationships, deformation in most places in the CNTB can only be broadly bracketed between the Pennsylvanian-Permian and the Eocene (Nolan, 1962;Taylor et al., 1993;Taylor et al., 2000;Vandervoort & Schmitt, 1990). ...
... Further to the south in Nevada and Utah, three structural provinces have been defined in the Sevier hinterland ( Figure 1): The CNTB; the eastern Nevada fold belt; and the western Utah thrust belt. The CNTB branches off the Sevier fold-thrust belt in southern Nevada, and contains north-striking, east-vergent thrust faults and folds (Long, Henry, Muntean, Edmondo, & Cassel, 2014;Taylor et al., 2000). The Early Cretaceous NCF is exposed in several areas within and to the north of the CNTB. ...
... In the northern part of the CNTB and proximal areas to the north, isolated exposures of the Early Cretaceous NCF (Figures 2 and 3), a terrestrial sedimentary unit postulated to have been deposited during regional thrust faulting and folding (e.g., Druschke et al., 2011;Fouch et al., 1979;Hose, 1983;Nolan et al., 1956;Vandervoort & Schmitt, 1990), offer the opportunity to further constrain CNTB deformation timing. Recent studies of the type-locality of the NCF in the southern Diamond Mountains (Figure 2) Long, Henry, Muntean, Edmondo, & Cassel, 2014) have documented that the NCF was deposited and deformed during construction of an east-vergent CNTB anticline named the Eureka culmination. Geologic mapping and U-Pb zircon geochronology showed that the NCF type-section exposure was deposited during growth of east-vergent folds and motion on associated thrust faults in the eastern limb of the culmination between ∼114 and <∼99 Ma . ...
Documenting the spatio‐temporal progression of deformation within fold‐thrust belts is critical for understanding orogen dynamics. In the North American Cordillera, the geometry, magnitude, and timing of contractional deformation across a broad region of Nevada known as the “Sevier hinterland” has been difficult to characterize due to minimal exposures of syn‐contractional sedimentary rocks and overprinting of Cenozoic extension. To address this, we present geologic mapping and U‐Pb zircon geochronology from three exposures of the Cretaceous Newark Canyon Formation (NCF) in central Nevada. In the Cortez Mountains, NCF deposition between ∼119 and 110 Ma is hypothesized to be related to generation of relief by thrusting/folding to the west. In the Fish Creek Range, NCF deposition between ∼130 and 100 Ma was related to motion on an east‐vergent thrust fault. In the Pancake Range, NCF deposition is bracketed between ∼129 and 66 Ma and post‐dated east‐vergent folding. We incorporate these timing constraints into a compilation of deformation timing in the Sevier hinterland. Late Jurassic (∼165 and 155 Ma) shortening, which is largely post‐dated shortening in the Luning‐Fencemaker thrust belt to the west and pre‐dated initial deformation in the Sevier fold‐thrust belt to the east, is interpreted to represent diffuse, low‐magnitude deformation that accompanied eastward propagation of the basal Cordilleran décollement. Cretaceous (∼130 and 75 Ma) hinterland shortening, which includes deformation associated with NCF deposition, was contemporaneous with shortening in the Sevier fold‐thrust belt. This is interpreted to represent long‐duration strain partitioning between the foreland and hinterland during continued coupling above the basal décollement and the progressive westward underthrusting of thick North American lower‐middle crust.
... Most contractional structures in the REWP have been assumed to be Late Cretaceous on the basis of prograde metamorphic ages [50], voluminous Late Cretaceous leucogra-nites interpreted as crustal melts due to crustal thickening [25,36,37,52], metamorphic zircon rims [53], ca. 83 Ma Lu-Hf garnet ages from the Wood Hills [54], and coeval shortening in the Sevier fold-thrust belt to the east [55,56]. ...
... The Windermere thrust sheet would have been >15 km thick, 50 km wide (N-S direction), and overthrust the REWP with a transport-parallel distance of 70+ km. This geometry is entirely atypical of contractional structures in eastern Nevada (e.g., [21,52,126]) and dissimilar to typical thrust sheets mapped or geophysically imaged in other hinterland regions, such as in Tibet and the Andes (e.g., [83,[127][128][129][130][131][132]). In summary, the lack of field evidence, our refined Jurassic age for the Independence thrust, and T p data from the Pequop Mountains all make the Cretaceous Windermere thrust hypothesis insubstantial. ...
... In the Ruby Mountains-East Humboldt Range, this includes thrust faults that have been folded and intruded by Late Cretaceous peraluminous melts (e.g., [25,45]). Across central Utah and Nevada, upper crustal shortening was pervasive (e.g., [52,56,124,126,142]) (Figure 1(b)). Taken together, this suggests that shortening strain at REWP latitudes occurred either (1) progressively from the Middle Jurassic to Late Cretaceous or (2) as two punctuated pulses of Jurassic and Cretaceous deformation (Figure 1(b)). ...
Mesozoic crustal shortening in the North American Cordillera’s hinterland was related to the construction of the Nevadaplano orogenic plateau. Petrologic and geochemical proxies in Cordilleran core complexes suggest substantial Late Cretaceous crustal thickening during plateau construction. In eastern Nevada, geobarometry from the Snake Range and Ruby Mountains-East Humboldt Range-Wood Hills-Pequop Mountains (REWP) core complexes suggests that the ~10–12-km-thick Neoproterozoic-Triassic passive-margin sequence was buried to great depths (>30 km) during Mesozoic shortening and was later exhumed to the surface via high-magnitude Cenozoic extension. Deep regional burial is commonly reconciled with structural models involving cryptic thrust sheets, such as the hypothesized Windermere thrust in the REWP. We test the viability of deep thrust burial by examining the least-deformed part of the REWP in the Pequop Mountains. Observations include a compilation of new and published peak temperature estimates (n=60) spanning the Neoproterozoic-Triassic strata, documentation of critical field relationships that constrain deformation style and timing, and new 40Ar/39Ar ages. This evidence refutes models of deep regional thrust burial, including (1) recognition that most contractional structures in the Pequop Mountains formed in the Jurassic, not Cretaceous, and (2) peak temperature constraints and field relationships are inconsistent with deep burial. Jurassic deformation recorded here correlates with coeval structures spanning western Nevada to central Utah, which highlights that Middle-Late Jurassic shortening was significant in the Cordilleran hinterland. These observations challenge commonly held views for the Mesozoic-early Cenozoic evolution of the REWP and Cordilleran hinterland, including the timing of contractional strain, temporal evolution of plateau growth, and initial conditions for high-magnitude Cenozoic extension. The long-standing differences between peak-pressure estimates and field relationships in Nevadan core complexes may reflect tectonic overpressure.
