Radiocarbon Ages on Organics From Piedmont Alluvium, Ajo Mountains, Arizona

Pohl, Molly M.

doi:10.1080/02723646.1995.10642557

Cited by 9 publications

(4 citation statements)

References 29 publications

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“…2; Table 2). These features include 14 C-dated alluvial fan surfaces in Las Vegas Valley of southern Nevada (∼9.9 14 C ka; Bell et al, 1998a), Fish Lake Valley of southern Nevada (0.5-6.5 14 C ka; Reheis et al, 1993Reheis et al, , 1995, Silurian Valley of southern California (∼1.8 14 C ka; Anderson and Wells, 2003), Ajo Mountains of southern Arizona (∼2.5 14 C ka; Pohl, 1995), cosmogenic 3 Hedated debris flow boulders in the Grand Canyon of northern Arizona (∼1.5 ka; Cerling, University of Utah, personal communication, 1997), and cosmogenic 36 Cldated Carrizozo lava flows (∼5.2 ka; Dunbar, 2002) and 14 C-dated McCartys lava flows (∼3.0 14 C ka; Laughlin et al, 1994) in central New Mexico.…”

Section: Study Region and Methodsmentioning

confidence: 97%

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Holocene rock varnish microstratigraphy and its chronometric application in the drylands of western USA

Liu

Broecker

2007

Geomorphology

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Section: Study Region and Methodsmentioning

confidence: 97%

“…Given a lag time of ∼200 yr, this suggests an age of ca.1300 YBP for orange layer WH2+, which predates dark layer WH2 and postdates dark layer WH3. Varnish from 14 C-dated alluvial terraces (2630 ± 120 YBP) in the Ajo Mountains of southern Arizona (Pohl, 1995) displays a late Holocene layering sequence LU-1 (WH3+) (Fig. 7F).…”

Section: Age Calibrationmentioning

confidence: 96%

Holocene rock varnish microstratigraphy and its chronometric application in the drylands of western USA

Liu

Broecker

2007

Geomorphology

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“…The first attempt to use cosmogenic nuclides as sediment tracers provided only limiting sediment transport rates on the Ajo Mountain piedmont in Arizona (Pohl, 1995). A later study, at the Iron and Granite Mountains in California, used cosmogenic nuclides as tracers of piedmont sediment from the source basins to more than 5 km down the piedmont (Nichols and others, 2002).…”

Section: American Southwest Piedmontsmentioning

confidence: 97%

Late Quaternary history of the Chemehuevi Mountain piedmont, Mojave Desert, deciphered using 10Be and 26Al

Nichols¹

2005

American Journal of Science

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We used the cosmogenic nuclides, 10 Be and 26 Al, as cosmic-ray dosimeters to track sediment movement across the incised Chemehuevi Mountain piedmont surface. The piedmont extends 12 km from highland source basins to an ephemeral wash at the toe of the piedmont. Nuclide activity in sediment from steep source basins and from the bedrock pediment allows us to estimate rates of sediment generation and thus the rate at which sediment is supplied to the piedmont from weathering rock. Analysis of amalgamated sediment samples, collected along 4-km-long transects spaced at 1 km intervals from the mountain front provide context for understanding nuclide activity in sediment samples collected from two soil pits and demonstrate that sediment steadily moves down the channel network. Samples from the two soil pits allow for estimates of sediment deposition rates and thus further illuminate piedmont history.Model results suggest that the Chemehuevi Mountains are eroding about 40 mm ky ؊1 whereas the mountain-proximal bedrock pediment and the interpiedmont Sawtooth Range are eroding more slowly, 10 to 21 mm ky ؊1 and 9.5 mm ky ؊1 , respectively. Cosmogenic nuclide profiles in two soil pits suggest a complex history of deposition (at rates between 19 to 39 mm ky ؊1 ) and stability over the past 60 ky. A change in process from sediment deposition to sediment transport occurred distally on the piedmont approximately 8 ky ago, while the mid-piedmont piedmont surface has been stable since the mid-Holocene.The incised Chemehuevi Mountain piedmont is changing at rates similar to planar and uniformly active piedmonts such as those adjacent to the Iron and Granite Mountains. All three piedmonts have average sediment grain velocities of decimeters per year, long-term source basin erosion rates between 35 to 40 mm ky, depositional hiatuses around the Pleistocene-Holocene climatic transition from moister to drier conditions, and Pleistocene deposition rates of 18 to 39 mm ky. Such similarity in piedmont behavior, despite clear differences in morphology and appearance, might suggest large scale geologic and climatic controls on the generation, transport and deposition of sediment in the Mojave Desert.

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“…A discussion of dating alluvium in dry environments in the Sonoran Desert of the USA by Pohl (1995) shows that wet sieving of alluvium often provides sufficient organic matter for dating by AMS. Radiocarbon ages obtained show very low standard deviations over periods of 14 ka (<100 years) and the dates obtained are consistent with known rates of soil development in the area.…”

mentioning

confidence: 99%