New &lt;sup&gt;40&lt;/sup&gt;Ar/&lt;sup&gt;39&lt;/sup&gt;Ar isotopic dates from Miocene volcanic rocks in the Lake Mead area and southern Las Vegas Range, Nevada

Harlan, Stephen S.; Duebendorfer, Ernest M.; Deibert, Jack E.

doi:10.1139/cjes-35-5-495

Cited by 4 publications

(6 citation statements)

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“…The sudden onset of extension in the central Basin and Range at ca. 15 Ma is well documented, with rapid extension beginning in the Eldorado Mountains and surrounding area Gans and Bohrson, 1998) Harlan et al, 1998). The resolution of faster rates of slip on detachment faults within the Colorado River Extensional Corridor beginning at 15 ± 1 Ma fi ts well with this scenario, providing the fi rst evidence for increased extension rates in the southern Basin and Range at this time.…”

Section: Mamentioning

confidence: 60%

Late-stage evolution of the Chemehuevi and Sacramento detachment faults from apatite (U-Th)/He thermochronometry--Evidence for mid-Miocene accelerated slip

Carter

Kohn

Foster

et al. 2006

Geological Society of America Bulletin

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The unique low-temperature sensitivity of the apatite (U-Th)/He (AHe) technique provides valuable new information relating to the late-stage thermal evolution of metamorphic core complexes in the southern Basin and Range Province. In all the ranges studied, the data show greater complexity than previously seen from other thermochronometers. In the Chemehuevi and northern Sacramento Mountains, a trend of decreasing ages toward the northeast applies only for the structurally shallowest parts of the footwall. This is followed by essentially age-invariant segments of 15 ± 1 Ma, refl ecting an increase in the rate of detachment fault movement. The timing of the change suggested by the data agrees with recently published AHe results from the nearby Harcuvar Mountains, located ~125 km to the southeast, suggesting that an underlying regional mechanism triggered this change. Plate reconstructions indicate that the Pioneer-Mendocino fracture zone migrated northward through the area at this time, leaving a slab window in its wake. We suggest that the additional heat applied to the base of the lithosphere from the slab window resulted in mechanical weakening of the area and that this, combined with the extensional strain regime present, resulted in an increased rate of slip within the actively extending metamorphic core complexes. This agrees well with timing constraints for extension onset in the central Basin and Range Province of southern Nevada, and suggests that weakening of the southern Basin and Range Province at 15 ± 1 Ma was partially responsible for the onset of extension in the central Basin and Range. These fi ndings demonstrate that improved constraints on changes in extension rate within the Basin and Range Province should be possible through the application of the AHe technique to other metamorphic core complex footwalls.Keywords: metamorphic core complexes, Basin and Range Province, low-angle normal faults, (U-Th)/He, low-temperature thermochronology.

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Section: Mamentioning

confidence: 60%

Late-stage evolution of the Chemehuevi and Sacramento detachment faults from apatite (U-Th)/He thermochronometry--Evidence for mid-Miocene accelerated slip

Carter

Kohn

Foster

et al. 2006

Geological Society of America Bulletin

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“…12 Ma. That projected basal age for the Muddy Creek Formation is almost certainly too old, for the underlying "red sandstone unit" of Bohannon (1984) has yielded multiple isotopic ages (N = 8) of 11.9-10.05 Ma (Harlan et al, 1998;Castor et al, 2000;Beard et al, 2007) where exposed within and near White Basin (Fig. 2), ~40 km south-southwest of the test well.…”

Section: Muddy Creek Formation Agementioning

confidence: 99%

“…3) is a heterogeneous assemblage of alluvial and lacustrine deposits interpreted as the record of locally developed basins of internal drainage fi lled with sediment derived from bounding uplands or deposited in basinal lakes that developed downslope from clastic aprons shed from bounding uplands (Bohannon, 1983(Bohannon, , 1984Lamb et al, 2005). Strata of the Horse Spring Formation encountered in the test well (Bohannon et al, 1993) include only the uppermost Lowell Wash Member, dated elsewhere at 14-12 Ma (Harlan et al, 1998;Beard et al, 2007;Lamb et al, 2010), and the lowermost Rainbow Gardens Member, dated elsewhere at 24-18 Ma (Beard, 1996;Beard et al, 2007Beard et al, , 2010, suggesting that an intraformational unconformity spanning ~5 m.y. breaks the Horse Spring succession in the subsurface of the Virgin River depression.…”

Section: Wider Perspectivesmentioning

confidence: 99%

Detrital-zircon U-Pb evidence precludes paleo–Colorado River sediment in the exposed Muddy Creek Formation of the Virgin River depression

et al. 2014

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“…16-13 Ma to the south of Lake Mead and in the eastern Lake Mead region (Anderson et al, 1972;Faulds et al, 1992Faulds et al, , 2008Faulds et al, , 2010Beard, 1996;Duebendorfer and Sharp, 1998) and ca. 13-9 Ma in the western Lake Mead area (Duebendorfer and Simpson, 1994;Harlan et al, 1998;Castor et al, 2000). Extension had generally ceased by ca.…”

Section: Lake Mead Regionmentioning

confidence: 99%

Paleogeographic implications of late Miocene lacustrine and nonmarine evaporite deposits in the Lake Mead region: Immediate precursors to the Colorado River

et al. 2016

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Thick late Miocene nonmarine evaporite (mainly halite and gypsum) and related lacustrine limestone deposits compose the upper basin fill in half grabens within the Lake Mead region of the Basin and Range Province directly west of the Colorado Plateau in southern Nevada and northwestern Arizona. Regional relations and geochronologic data indicate that these deposits are late synextensional to postextensional (ca. 12-5 Ma), with major extension bracketed between ca. 16 and 9 Ma and the abrupt western margin of the Colorado Plateau established by ca. 9 Ma. Significant accommodation space in the half grabens allowed for deposition of late Miocene lacustrine and evaporite sediments. Concurrently, waning extension promoted integration of initially isolated basins, progressive enlargement of drainage nets, and development of broad, low gradient plains and shallow water bodies with extensive clastic, carbonate, and/or evaporite sedimentation. The continued subsidence of basins under restricted conditions also allowed for the preservation of particularly thick, localized evaporite sequences prior to development of the through-going Colorado River. The spatial and temporal patterns of deposition indicate increasing amounts of freshwater input during the late Miocene (ca. 12-6 Ma) immediately preceding arrival of the Colorado River between ca. 5.6 and 4.9 Ma. In axial basins along and proximal to the present course of the Colorado River, evaporite deposition (mainly gypsum) transitioned to lacustrine limestone progressively from east to west, beginning ca. 12-11 Ma in the Grand Wash Trough in the east and shortly after ca. 5.6 Ma in the western Lake Mead region. In several satellite basins to both the north and south of the axial basins, evaporite deposition was more extensive, with thick halite (>200 m to 2.5 km thick) accumulating in the Hualapai, Overton Arm, and northern Detrital basins. Gravity and magnetic lows suggest that thick halite may also lie within the northern Grand Wash, Mesquite, southern Detrital, and northeastern Las Vegas basins. New tephrochronologic data indicate that the upper part of the halite in the Hualapai basin is ca. 5.6 Ma, with rates of deposition of ~190-450 m/m.y., assuming that deposition ceased approximately coincidental with the arrival of the Colorado River. A 2.5-km-thick halite sequence in the Hualapai basin may have accumulated in ~5-7 m.y. or ca. 12-5 Ma, which coincides with lacustrine limestone deposition near the present course of the Colorado River in the region. The distribution and similar age of the limestone and evaporite deposits in the region suggest a system of late Miocene axial lakes and extensive continental playas and salt pans. The playas and salt pans were probably fed by both groundwater discharge and evaporation from shallow lakes, as evidenced by sedimentary textures. The elevated terrain of the Colorado Plateau was likely a major source of water that fed the lakes and playas. The physical relationships in the Lake Mead region suggest that thick nonmarine evapori...

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New <sup>40</sup>Ar/<sup>39</sup>Ar isotopic dates from Miocene volcanic rocks in the Lake Mead area and southern Las Vegas Range, Nevada

Cited by 4 publications

References 0 publications

Late-stage evolution of the Chemehuevi and Sacramento detachment faults from apatite (U-Th)/He thermochronometry--Evidence for mid-Miocene accelerated slip

Late-stage evolution of the Chemehuevi and Sacramento detachment faults from apatite (U-Th)/He thermochronometry--Evidence for mid-Miocene accelerated slip

Detrital-zircon U-Pb evidence precludes paleo–Colorado River sediment in the exposed Muddy Creek Formation of the Virgin River depression

Paleogeographic implications of late Miocene lacustrine and nonmarine evaporite deposits in the Lake Mead region: Immediate precursors to the Colorado River

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