basin and range
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2022 ◽  
Author(s):  
Jens-Erik Lund Snee ◽  
Elizabeth L. Miller

ABSTRACT The paleogeographic evolution of the western U.S. Great Basin from the Late Cretaceous to the Cenozoic is critical to understanding how the North American Cordillera at this latitude transitioned from Mesozoic shortening to Cenozoic extension. According to a widely applied model, Cenozoic extension was driven by collapse of elevated crust supported by crustal thicknesses that were potentially double the present ~30–35 km. This model is difficult to reconcile with more recent estimates of moderate regional extension (≤50%) and the discovery that most high-angle, Basin and Range faults slipped rapidly ca. 17 Ma, tens of millions of years after crustal thickening occurred. Here, we integrated new and existing geochronology and geologic mapping in the Elko area of northeast Nevada, one of the few places in the Great Basin with substantial exposures of Paleogene strata. We improved the age control for strata that have been targeted for studies of regional paleoelevation and paleoclimate across this critical time span. In addition, a regional compilation of the ages of material within a network of middle Cenozoic paleodrainages that developed across the Great Basin shows that the age of basal paleovalley fill decreases southward roughly synchronous with voluminous ignimbrite flareup volcanism that swept south across the region ca. 45–20 Ma. Integrating these data sets with the regional record of faulting, sedimentation, erosion, and magmatism, we suggest that volcanism was accompanied by an elevation increase that disrupted drainage systems and shifted the continental divide east into central Nevada from its Late Cretaceous location along the Sierra Nevada arc. The north-south Eocene–Oligocene drainage divide defined by mapping of paleovalleys may thus have evolved as a dynamic feature that propagated southward with magmatism. Despite some local faulting, the northern Great Basin became a vast, elevated volcanic tableland that persisted until dissection by Basin and Range faulting that began ca. 21–17 Ma. Based on this more detailed geologic framework, it is unlikely that Basin and Range extension was driven by Cretaceous crustal overthickening; rather, preexisting crustal structure was just one of several factors that that led to Basin and Range faulting after ca. 17 Ma—in addition to thermal weakening of the crust associated with Cenozoic magmatism, thermally supported elevation, and changing boundary conditions. Because these causal factors evolved long after crustal thickening ended, during final removal and fragmentation of the shallowly subducting Farallon slab, they are compatible with normal-thickness (~45–50 km) crust beneath the Great Basin prior to extension and do not require development of a strongly elevated, Altiplano-like region during Mesozoic shortening.


2022 ◽  
Author(s):  
N. Midttun ◽  
et al.

<div>Text: Additional explanation of the methods used to recalculate the Ar/Ar ages of Gutenkunst (2006), Saylor and Hodges (1994), and Saylor (1991). Figure S1: Analytical plots recalculated from <sup>40</sup>Ar/<sup>39</sup>Ar data originally produced by Gutenkunst (2006). Figure S2: Scans of a large scale map and seven isochron plots for five samples provided by B. Saylor (personal commun., 2015). Table S1: Detrital zircon U-Pb analytical data. Table S2: Zircon (U‐Th)/He analytical data. Table S3: Analytical data for <sup>40</sup>Ar/<sup>39</sup>Ar ages of Gutenkunst (2006).<br></div>


2021 ◽  
Author(s):  
Miles McCoy-Sulentic ◽  
Diane Menuz ◽  
Rebecca Lee

Wetlands in the arid Central Basin and Range (“Central Basin”) ecoregion of Utah are scarce but provide important functions including critical habitat for wildlife including Species of Greatest Conservation Need and migratory birds, water quality improvement, and recreational and aesthetic values. The Utah Geological Survey (UGS) conducted a study in 2019 and 2020 to better understand the location, type, condition, and potential function of wetlands in the ecoregion. This study focused on areas in the Great Salt Lake and Escalante Desert-Sevier Lake (“Sevier Basin”) HUC6 watersheds within the Central Basin to complement previous work by the UGS that focused on other watersheds in the ecoregion.


Geosphere ◽  
2021 ◽  
Author(s):  
Nikolas Midttun ◽  
Nathan A. Niemi ◽  
Bianca Gallina

Geologic mapping, measured sections, and geochronologic data elucidate the tectono-stratigraphic development of the Titus Canyon extensional basin in Death Valley, California, and provide new constraints on the age of the Titus Canyon Formation, one of the earliest syn-extensional deposits in the central Basin and Range. Detrital zircon maximum depositional ages (MDAs) and compiled 40Ar/39Ar ages indicate that the Titus Canyon Formation spans 40(?)–30 Ma, consistent with an inferred Duchesnean age for a unique assemblage of mammalian fossils in the lower part of the formation. The Titus Canyon Formation preserves a shift in depositional environment from fluvial to lacustrine at ca. 35 Ma, which along with a change in detrital zircon provenance may reflect both the onset of local extensional tectonism and climatic changes at the Eocene–Oligocene boundary. Our data establish the Titus Canyon basin as the southernmost basin in a system of late Eocene extensional basins that formed along the axis of the Sevier orogenic belt. The distribution of lacustrine deposits in these Eocene basins defines the extent of a low-relief orogenic plateau (Nevadaplano) that occupied eastern Nevada at least through Eocene time. As such, the age and character of Titus Canyon Formation implies that the Nevadaplano extended into the central Basin and Range, ~200 km farther south than previously recognized. Development of the Titus Canyon extensional basin precedes local Farallon slab removal by ca. 20 Ma, implying that other mechanisms, such as plate boundary stress changes due to decreased convergence rates in Eocene time, are a more likely trigger for early extension in the central Basin and Range.


2021 ◽  
Vol 7 (45) ◽  
Author(s):  
Katharine M. Loughney ◽  
Catherine Badgley ◽  
Alireza Bahadori ◽  
William E. Holt ◽  
E. Troy Rasbury

Energies ◽  
2021 ◽  
Vol 14 (21) ◽  
pp. 7186
Author(s):  
Leslie Allen Mowbray ◽  
Michael L. Cummings

Hot springs in the Alvord/Pueblo valleys in southeastern Oregon are analogous to Basin-and-Range hydrothermal systems where heat source and permeable pathways are met through crustal thinning. Silica sinter deposition at Mickey Springs, Alvord Valley, predates the late Pleistocene high stand of pluvial Lake Alvord. At Borax Lake, Pueblo Valley, sinter deposition occurred during the Holocene. This study examines the evolution of springs at Mickey Springs, where three morphologies of sinter are present: (1) basalt clasts surrounded by sinter in interbedded conglomerate and sandstone, (2) pool-edge and aprons of sinter surrounding depressions (12–32 m diameter), and (3) quaquaversal sinter mounds with pool-edge sinter. The oldest sinter occurs in silica-cemented conglomerate and sandstone, where deposition occurred prior to 30 kya. Deposition around broad depressions and mounds occurred after 30 kya but before water levels began to rise in pluvial Lake Alvord. Thermoluminescence dates suggest sinter deposition ceased before 18 kya when silt and clay filled inactive vents and buried aprons. A few mounds hosted active springs after sinter deposition ceased but while submerged in pluvial Lake Alvord. Now, high-temperature springs, steam vents, and mud pots are concentrated in a 50 × 50 m area near the southern edge of the spring area.


2021 ◽  
Author(s):  
N. Midttun ◽  
et al.

<div>Text: Additional explanation of the methods used to recalculate the Ar/Ar ages of Gutenkunst (2006), Saylor and Hodges (1994), and Saylor (1991). Figure S1: Analytical plots recalculated from <sup>40</sup>Ar/<sup>39</sup>Ar data originally produced by Gutenkunst (2006). Figure S2: Scans of a large scale map and seven isochron plots for five samples provided by B. Saylor (personal commun., 2015). Table S1: Detrital zircon U-Pb analytical data. Table S2: Zircon (U‐Th)/He analytical data. Table S3: Analytical data for <sup>40</sup>Ar/<sup>39</sup>Ar ages of Gutenkunst (2006).<br></div>


2021 ◽  
Author(s):  
N. Midttun ◽  
et al.

<div>Text: Additional explanation of the methods used to recalculate the Ar/Ar ages of Gutenkunst (2006), Saylor and Hodges (1994), and Saylor (1991). Figure S1: Analytical plots recalculated from <sup>40</sup>Ar/<sup>39</sup>Ar data originally produced by Gutenkunst (2006). Figure S2: Scans of a large scale map and seven isochron plots for five samples provided by B. Saylor (personal commun., 2015). Table S1: Detrital zircon U-Pb analytical data. Table S2: Zircon (U‐Th)/He analytical data. Table S3: Analytical data for <sup>40</sup>Ar/<sup>39</sup>Ar ages of Gutenkunst (2006).<br></div>


Geosphere ◽  
2021 ◽  
Author(s):  
Michelle M. Gavel ◽  
Jeffrey M. Amato ◽  
Jason W. Ricketts ◽  
Shari Kelley ◽  
Julian M. Biddle ◽  
...  

The Basin and Range and Rio Grande rift (RGR) are regions of crustal extension in southwestern North America that developed after Laramide-age shortening, but it has not been clear whether onset and duration of extension in these contiguous extensional provinces were the same. We conducted a study of exhumation of fault blocks along a transect from the southeastern Basin and Range to across the RGR in southern New Mexico. A suite of 128 apatite and 63 zircon (U-Th)/He dates (AHe and ZHe), as well as 27 apatite fission-track (AFT) dates, was collected to investigate the cooling and exhumation histories of this region. Collectively, AHe dates range from 3 to 46 Ma, ZHe dates range from 2 to 288 Ma, and AFT dates range from 10 to 34 Ma with average track lengths of 10.8–14.1 µm. First-order spatiotemporal trends in the combined data set suggest that Basin and Range extension was either contemporaneous with Eocene–Oligocene Mogollon-Datil volcanism or occurred before volcanism ended ca. 28 Ma, as shown by trends in ZHe data that suggest reheating to above 240 °C at that time. AHe and ZHe dates from the southern RGR represent a wider range in dates that suggest the main phase of cooling occurred after 25 Ma, and these blocks were not reheated after exhumation. Time-temperature models created by combining AHe, AFT, and ZHe data in the modeling software HeFTy were used to interpret patterns in cooling rate across the study area and further constrain magmatic and/or volcanic versus faulting related cooling. The Chiricahua Mountains and Burro Mountains have an onset of rapid extension, defined as cooling rates in excess of &gt;15 °C/m.y., at ca. 29–17 Ma. In the Cookes Range, a period of rapid extension occurred at ca. 19–7 Ma. In the San Andres Mountains, Franklin Mountains, Caballo Mountains, and Fra Cristobal range, rapid extension occurred from ca. 23 to 9 Ma. Measured average track lengths are longer in Rio Grande rift samples, and ZHe dates of &gt;40 Ma are mostly present east of the Cookes Range, suggesting different levels of exhumation for the zircon partial retention zone and the AFT partial annealing zone. The main phase of fault-block uplift in the southern RGR occurred ca. 25–7 Ma, similar to what has been documented in the northern and central sections of the rift. Although rapid cooling occurred throughout southern New Mexico, thermochronological data from this study with magmatic and volcanic ages suggest rapid cooling was coeval with magmatism in the Basin and Range, whereas in the Rio Grande rift cooling occurred during an amagmatic gap. These observations support a model where an early phase of extension was facilitated by widespread ignimbrite magmatism in the southeastern Basin and Range, whereas in the southern Rio Grande rift, extension started later and continues today and may have occurred between local episodes of basaltic magmatism. These differences in cooling history make the Rio Grande rift tectonically distinct from the Basin and Range. We infer based on geologic and thermochronological evidence that the onset of extension in the southern Rio Grande rift occurred at ca. 27–25 Ma, significantly later than earlier estimates of ca. 35 Ma.


Geosphere ◽  
2021 ◽  
Author(s):  
Michael C. Say ◽  
Andrew V. Zuza

The spatial distribution and kinematics of intracontinental deformation provide insight into the dominant mode of continental tectonics: rigid-body motion versus continuum flow. The discrete San Andreas fault defines the western North America plate boundary, but transtensional deformation is distributed hundreds of kilometers eastward across the Walker Lane–Basin and Range provinces. In particular, distributed Basin and Range extension has been encroaching westward onto the relatively stable Sierra Nevada block since the Miocene, but the timing and style of distributed deformation overprinting the stable Sierra Nevada crust remains poorly resolved. Here we bracket the timing, mag­nitude, and kinematics of overprinting Walker Lane and Basin and Range deformation in the Pine Nut Mountains, Nevada (USA), which are the western­most structural and topographic expression of the Basin and Range, with new geologic mapping and 40Ar/39Ar geochronology. Structural mapping suggests that north-striking normal faults developed during the initiation of Basin and Range extension and were later reactivated as northeast-striking oblique-slip faults following the onset of Walker Lane transtensional deformation. Conformable volcanic and sedimentary rocks, with new ages spanning ca. 14.2 Ma to 6.8 Ma, were tilted 30°–36° northwest by east-dipping normal faults. This relationship demonstrates that dip-slip deformation initiated after ca. 6.8 Ma. A retrodeformed cross section across the range suggests that the range experienced 14% extension. Subsequently, Walker Lane transtension initiated, and clockwise rotation of the Carson domain may have been accommodated by northeast-striking left-slip faults. Our work better defines strain patterns at the western extent of the Basin and Range province across an approximately 150-km-long east-west transect that reveals domains of low strain (~15%) in the Carson Range–Pine Nut Mountains and Gillis Range surrounding high-magnitude extension (~150%–180%) in the Singatse and Wassuk Ranges. There is no evidence for irregular crustal thickness variations across this same transect—either in the Mesozoic, prior to extension, or today—which suggests that strain must be accommodated differently at decoupled crustal levels to result in smooth, homogenous crustal thickness values despite the significantly heterogeneous extensional evolution. This example across an ~150 km transect demonstrates that the use of upper-crust extension estimates to constrain pre-extension crustal thickness, assuming pure shear as commonly done for the Mesozoic Nevadaplano orogenic plateau, may not be reliable.


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