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418 results on '"Kubik, Peter W."'

43. Calibrating a long-term meteoric 10Be delivery rate into Western US glacial deposits through a comparison of complimentary meteoric and in situ-produced 10Be depth profiles

Author

Clow, Travis, Willenbring, Jane K., Schaller, Mirjam, Blum, Joel D., Christl, Marcus, Kubik, Peter W., and Blanckenburg, Friedhelm

Subjects
TheoryofComputation_ANALYSISOFALGORITHMSANDPROBLEMCOMPLEXITY
Abstract

Meteoric 10Be (10Bemet) concentrations in soil profiles great potential as a geochronometer and a tracer of Earth surface processes, particularly in fine-grained soils lacking quartz that would preclude the use of in situ-produced 10Be (10Bein situ). One prerequisite for using this technique for accurately calculating rates and dates is constraining the delivery, or flux, of 10Bemet to a site. However, few studies to date have quantified long-term (i.e. millennial) delivery rates. In this study, we compared existing concentrations of 10Bein situ with new measurements of 10Bemet in soils sampled from the same depth profiles to calibrate a long-term 10Bemet delivery rate. We did so on the Pinedale and Bull Lake glacial moraines at Fremont Lake, Wyoming (USA) where age, grain sizes, weathering indices, and soil properties are known, as are erosion/denudation rates calculated from 10Bein situ. After ensuring sufficient beryllium retention in each profile, solving for the delivery rate of 10Bemet via Monte Carlo simulations, and normalizing to Holocene-average paleomagnetic intensity, we calculate best-fit fluxes of 0.92 (+/− 0.08) × 106 and 0.71 (+0.09/−0.08) × 106 atoms cm−2 y−1 to the Pinedale and Bull Lake moraines, respectively, and compare these values to two widely-used 10Bemet delivery rate estimation methods. Accurately estimating 10Bemet flux using these methods requires careful consideration of spatial scale as well as temporally varying parameters (e.g. paleomagnetic field intensity) to ensure the most realistic estimates of 10Bemet-derived erosion rates in future studies.

Published
2020

49. Constraining the timing of the most recent cataclysmic flood event from ice-dammed lakes in the Russian Altai Mountains, Siberia, using cosmogenic in situ [sup.10]Be

Author

Reuther, Anne U., Herget, Jurgen, Ivy-Ochs, Susan, Borodavko, Pavel, Kubik, Peter W., and Heine, Klaus

Subjects
Lakes -- Reports, Floods -- Analysis, Earth sciences
Abstract

Ice-dammed lakes were repeatedly formed in intermontane basins in the Russian Altai Mountains throughout the Pleistocene. These cataclysmic outburst floods, caused by ice-dam failures, were documented as Earth's largest flood waves by other geoscientists. Using in situ [sup.10]Be, we successfully dated surfaces of flood-associated boulders located in a former lake basin and downvalley from a former ice dam. Our precise surface exposure ages suggest that all boulders were associated with the most recent out of a number of cataclysmic floods that occurred at 15.8 [+ or -] 1.8 ka. The field location of the boulders implies that they were deposited by the largest late Pleistocene flood that drained the Chuya-Katun Lake completely following initial dam failure. A published reconstruction of the late glacial paleoenvironment in the vicinity of the former ice dam indicates that dam failure was likely a result of climatically induced downwasting of glaciers. The failure of the ice dam provides more evidence for the timing of widespread warming during the late glacial in southern Russia. This flooding event in the headwaters of the Ob River coincides with a freshwater peak as recorded in isotopic records of the Kara Sea and the Arctic Ocean. Keywords: Altai Mountains, [sup.10]Be, outburst flood, paleolake.

Published
2006

50. Geomorphological evidence and cosmogenic [sup.10]Be/[sup.26]Al exposure ages for the Last Glacial Maximum and deglaciation of the Antarctic Peninsula Ice Sheet

Author

Bentley, Michael J., Fogwill, Christopher J., Kubik, Peter W., and Sugden, David E.

Subjects
Ice sheets -- Research, Geomorphological research, Earth sciences
Abstract

This paper presents the first systematic attempt to map the Last Glacial Maximum (LGM) configuration of the southern and central parts of the Antarctic Peninsula Ice Sheet, and to determine the timing of onshore ice-sheet retreat. Geomorphologic evidence shows that the LGM ice sheet expanded to form two ice domes in Palmer Land and merged with an expanded and thicker West Antarctic Ice Sheet in the Weddell Sea. Ice from the Antarctic Peninsula merged with Alexander Island ice in George VI Sound. Cosmogenic [sup.10]Be and [sup.26]Al data from 29 erratics on nunataks yield model ages between 7.2 ka and older than 1 Ma. The data set contains a high proportion of erratics with evidence of nuclide inheritance. Once these ages have been excluded, the cosmogenic ages suggest that thinning of the west side of the Antarctic Peninsula Ice Sheet to near-present configuration was almost complete by the early Holocene. These data, combined with previously published [sup.14]C data, exclude the possibility that the west side of the Antarctic Peninsula Ice Sheet has been thinning throughout the Holocene, as has been demonstrated for some other sectors of the West Antarctic Ice Sheet. On the east side of the Antarctic Peninsula, ice-sheet thinning was under way prior to the early Holocene, but our data do not constrain the ice-sheet behavior more recently than 7.2 ka. Keywords: glacial geology, Antarctic Peninsula. ice sheets, deglaciation, cosmogenic isotopes.

Published
2006

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