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During the last glacial maximum (LGM), the western Uinta Mountains of northeastern Utah were occupied by the Western Uinta Ice Field. Cosmogenic Be-10 surface-exposure ages from the terminal moraine in the North Fork Provo Valley and paired Al-26 and Be-10 ages from striated bedrock at Bald Mountain Pass set limits on the timing of the local LGM. Moraine boulder ages suggest that ice reached its maximum extent by 17.4 +/- 0.5 ka (+/- 2 sigma). Be-10 and Al-26 measurements on striated bedrock from Bald Mountain Pass, situated near the former center of the ice field, yield a mean Al-26/Be-10 ratio of 5.7 +/- 0.8 and a mean exposure age of 14.0 +/- 0.5 ka, which places a minimum-limiting age on when the ice field melted...
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The Colorado River system in southern Utah and northern Arizona is continuing to adjust to the baselevel fall responsible for the carving of the Grand Canyon. Estimates of bedrock incision rates in this area vary widely, hinting at the transient state of the Colorado and its tributaries. In conjunction with these data, we use longitudinal profiles of the Colorado and tributaries between Marble Canyon and Cataract Canyon to investigate the incision history of the Colorado in this region. We find that almost all of the tributaries in this region steepen as they enter the Colorado River. The consistent presence of oversteepened reaches with similar elevation drops in the lower section of these channels, and their coincidence...
Cosmic-ray-produced 10Be and 26Al in riverborne quartz sediment are commonly used to estimate average catchment-scale erosion rates. Likewise, the concentrations of these nuclides in ancient sediments, stored in a depositional basin, carry a record of past erosion rates in the sediment source area. This is important because such a record could be compared to records of climate change or tectonic events to elucidate relationships between climate, tectonics and erosion. If the sediments are shielded from the cosmic-ray flux after deposition, for example in deep water, their nuclide concentrations need only be corrected for radioactive decay since deposition in order to determine past erosion rates. Where sediment...
    map background search result map search result map Rapid incision of the Colorado River in Glen Canyon - insights from channel profiles, local incision rates, and modeling of lithologic controls Rapid incision of the Colorado River in Glen Canyon - insights from channel profiles, local incision rates, and modeling of lithologic controls