Preliminary Geologic Map of the Lake Mead 30' X 60' Quadrangle, Clark County, Nevada, and Mohave County, Arizona

Beard, Les P.; Anderson, R. Ernest; Block, Debra L.; Bohannon, Robert G.; Brady, R.J.; Castor, Stephen B.; Duebendorfer, Ernest M.; Faulds, James E.; Felger, Tracey J.; Howard, Keith A.; Kuntz, Mel A.; Williams, V.S.

doi:10.3133/ofr20071010

Cited by 15 publications

(22 citation statements)

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“…Soils at Airport Flat, elevation 450 m, are part of the Cheme series and are formed in mixed alluvium on fan remnants [NRCS Cheme soil series description (NRCS (USDA‐Natural Resources Conservation Service), 2007) and field observations]. Airport Flat was mapped by the USGS (Beard et al. , 2007) as sidestream alluvium (lower Pliocene) and is considered to be the oldest of the three surfaces.…”

Section: Methodsmentioning

confidence: 99%

Pore morphology characteristics of vesicular horizons in undisturbed and disturbed arid soils; implications for arid land management

Yonovitz

Drohan

2009

Soil Use and Management

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We compared the pore morphology of an arid lands vesicular soil horizon in a disturbed and undisturbed state. This surface vesicular horizon is characterized by non‐connected pores that hinder soil water infiltration and thus plays a central role in arid ecosystem hydrodynamics. Disturbance is hypothesized to result in a change in pore morphology that could alter water movement through the horizon and potentially affect ecosystem function. To test this hypothesis, we examined the pore morphology of the vesicular horizon as expressed in area, perimeter, length and width; comparisons were also made for particle size, pH, calcium carbonate equivalent (CCE), electrical conductivity (EC) and the abundance and types of pores in undisturbed soils and adjacent disturbed soils within a year of disturbance. The results indicate no significant differences between treatments in chemistry, particle size or pore morphological measures within a year following disturbance. Vesicles, vughs and interstitial pores were found in vesicular horizons in both treatments and no significant differences in these parameters were found between treatments. Vesicular horizon development may be related to the geological age of the surface materials. Certain old land surfaces are perhaps more susceptible to the formation of vesicular horizons regardless of disturbance. The results suggest that soil functions dependent upon vesicular porosity, for example hydraulic conductivity, may return to a pre‐disturbance condition within one year of disturbance, a finding of importance to the management of arid lands.

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Section: Methodsmentioning

confidence: 99%

Pore morphology characteristics of vesicular horizons in undisturbed and disturbed arid soils; implications for arid land management

Yonovitz

Drohan

2009

Soil Use and Management

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“…During our July 2016 field work, we observed cemented Colorado River gravel of unknown age dipping 12° toward the northwest at lake level (327 m asl and ~105 m above pre-dam river level) in Virgin Basin (at 36.103045°N, 114.466729°W). On the flanks of the northern Black Mountains, Pliocene Colorado River gravels dip 15°-60° away from the core of the range (Longwell, 1936;Beard et al, 2007). On the east flank of the Black Mountains, in the footwall of the Detrital fault system (west side), we (Beard and Felger) found a lag of rounded gravel at elevations as high as 756 m asl using hand-written annotations by R.L.…”

Section: Incision Constraintsmentioning

confidence: 86%

“…In the western Lake Mead area, early Colorado River gravels on the flanks of the northern Black Mountains dip as much as 15° away from the core of the range on the east side and as much as 60° on the west side (Longwell, 1936;Beard et al, 2007). These outcrops, in the hanging wall of range-bounding normal faults, have likely been deformed by normal drag along the Fortification, Kingman Road, and Indian Canyon faults on the west, which we will call the Fortification fault system, and the Detrital and Boulder Wash faults on the east, which we will call the Detrital fault system (Longwell, 1963;Beard et al, 2013).…”

Section: Lower Colorado River Plio-pleistocene Tectonismmentioning

confidence: 99%

“…Downstream from Sandy Point to Hoover Dam, Lake Mead obscures other deposits that might be suitable for calculating incision rates (Beard et al, 2007). Pre-Lake Mead observations by Longwell (1936Longwell ( , p. 1442 indicate that "no remnants of…older cemented [river] gravels were found along the river in the twenty-mile stretch across the Virgin-Detrital trough.…”

Section: Incision Constraintsmentioning

confidence: 99%

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Insights into post-Miocene uplift of the western margin of the Colorado Plateau from the stratigraphic record of the lower Colorado River

et al. 2019

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The spatial and temporal distribution of Pliocene to Holocene Colorado River deposits (southwestern USA and northwestern Mexico) form a primary data set that records the evolution of a continental-scale river system and helps to delineate and quantify the magnitude of regional deformation. We focus in particular on the age and distribution of ancestral Colorado River deposits from field observations, geologic mapping, and subsurface studies in the area downstream from Grand Canyon (Arizona, USA). A new 4.73 ± 0.17 Ma age is reported for a basalt that flowed down Grand Wash to near its confluence with the Colorado River at the eastern end of what is now Lake Mead (Arizona and Nevada). That basalt flow, which caps tributary gravels, another previously dated 4.49 ± 0.46 Ma basalt flow that caps Colorado River gravel nearby, and previously dated speleothems (2.17 ± 0.34 and 3.87 ± 0.1 Ma) in western Grand Canyon allow for the calculation of long-term incision rates. Those rates are ∼90 m/Ma in western Grand Canyon and ∼18–64 m/Ma in the eastern Lake Mead area. In western Lake Mead and downstream, the base of 4.5–3.5 Ma ancestral Colorado River deposits, called the Bullhead Alluvium, is generally preserved below river level, suggesting little if any bedrock incision since deposition. Paleoprofiles reconstructed using ancestral river deposits indicate that the lower Colorado River established a smooth profile that has been graded to near sea level since ca. 4.5 Ma. Steady incision rates in western Grand Canyon over the past 0.6–4 Ma also suggest that the lower Colorado River has remained in a quasi–steady state for millions of years with respect to bedrock incision. Differential incision between the lower Colorado River corridor and western Grand Canyon is best explained by differential uplift across the Lake Mead region, as the overall 4.5 Ma profile of the Colorado River remains graded to Pliocene sea level, suggesting little regional subsidence or uplift. Cumulative estimates of ca. 4 Ma offsets across faults in the Lake Mead region are similar in magnitude to the differential incision across the area during the same approximate time frame. This suggests that in the past ∼4 Ma, vertical deformation in the Lake Mead area has been localized along faults, which may be a surficial response to more deep-seated processes. Together these data sets suggest ∼140–370 m of uplift in the past 2–4 Ma across the Lake Mead region.

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“…Field measurements were conducted for a total of 363 days (almost 1 year) at Nellis Dunes Recreation Area (NDRA), Nevada, USA (Figure 2). NDRA lies 6 km north‐east of the city of Las Vegas in the north‐eastern portion of the Las Vegas Valley referred to as the Nellis basin (Beard et al ., 2007).…”

Section: Geographical and Sedimentological Settingsmentioning

confidence: 99%

Gross erosion, net erosion and gross deposition of dust by wind: field data from 17 desert surfaces

Buck

2010

Earth Surf Processes Landf

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Wind erosion measurements were carried out in Nellis Dunes Recreation Area, southern Nevada, USA. Gross erosion (the total mass of sediment effectively blown away from a surface), gross deposition (the total mass of sediment effectively depositing on a surface) and net erosion (the difference in sediment mass before and after an event) were measured for 1 year, on 17 different types of surfaces developed on loose dune sand, compacted sand, loose silt, compacted and/or aggregated silt, rock-covered sands and silts, mixtures of sand, silt and clay, exposed petrocalcic horizons, gravelly substrata and bedrock. Results showed that net erosion, which is the type of erosion measured in field and laboratory experiments, strongly differs from gross erosion. Activity on a surface is much higher than classic net erosion measurements suggest. Future studies on wind erosion should better acknowledge the distinction between the two types of process. Also, a grain diameter of maximum susceptibility to wind erosion ('optimum deflation diameter') near 70 mm as proposed by the aeolian literature only exists for net wind erosion. No such optimum diameter was found for gross wind erosion within the particle range 0-100 mm delineating the transport modes of suspension and modified saltation. In addition, desert surfaces predominantly composed of sand did not show an optimum deflation diameter (for net erosion) around 70 mm. Instead, there was a preferential grain size around 15 mm at which particles were most vulnerable to net emission. Desert surfaces poor in sand showed the classic value of 70 mm. This suggests that interactions exist between the type of surface and the susceptibility of particles to wind erosion. This study is solely based on field data. Although results are supported by two previous wind tunnel studies, more wind tunnel experiments documenting the interactions between gross erosion and gross deposition are necessary.

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Preliminary Geologic Map of the Lake Mead 30' X 60' Quadrangle, Clark County, Nevada, and Mohave County, Arizona

Cited by 15 publications

References 0 publications

Pore morphology characteristics of vesicular horizons in undisturbed and disturbed arid soils; implications for arid land management

Pore morphology characteristics of vesicular horizons in undisturbed and disturbed arid soils; implications for arid land management

Insights into post-Miocene uplift of the western margin of the Colorado Plateau from the stratigraphic record of the lower Colorado River

Gross erosion, net erosion and gross deposition of dust by wind: field data from 17 desert surfaces

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