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首页> 外文期刊>Journal of geophysical research. Earth Surface: JGR >Quantifying regolith erosion rates with cosmogenic nuclides ~(10)Be and ~(26)Al in the McMurdo Dry Valleys, Antarctica
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Quantifying regolith erosion rates with cosmogenic nuclides ~(10)Be and ~(26)Al in the McMurdo Dry Valleys, Antarctica

机译：用南极麦克默多干旱谷中的宇宙成因核素〜（10）Be和〜（26）Al量化go石侵蚀速率

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The McMurdo Dry Valleys, Antarctica (MDV) are among the oldest landscapes on Earth, and some landforms there present an intriguing apparent contradiction such that millions of years old surface deposits maintain their meter-scale morphology despite the fact that measured erosion rates are 0.1-4 m Ma~(-1). We analyzed the concentration of cosmic ray-produced ~(10)Be and ~(26)Al in quartz sands from regolith directly above and below two well-documented ash deposits in the MDV, the Arena Valley ash (~(40)Ar/~(39)Ar age of 4.33 Ma) and the Hart ash (K-Ar age of 3.9 Ma). Measured concentrations of ~(10)Be and ~(26)Al are significantly less than expected given the age of the in situ air fall ashes and are best interpreted as reflecting the degradation rate of the overlying sediments. The erosion rate of the material above the Arena Valley ash that best explains the observed isotope profiles is 3.5 ± 0.41 X 10~(-5) g cm~(-2) yr~(-1) (～0.19 m Ma~(-1)) for the past ～4 Ma. For the Hart ash, the erosion rate is 4.8 ± 0.21 x 10~(-4) g cm~(-2) yf~(-1) (～2.6 m Ma~(-1)) for the past ～I Ma. The concentration profiles do not show signs of mixing, creep, or deflation caused by sublimation of ground ice. These results indicate that the slow, steady lowering of the surface without vertical mixing may allow landforms to maintain their meter-scale morphology even though they are actively eroding.
机译：南极麦克默多干旱谷（MDV）是地球上最古老的景观之一，那里的某些地貌呈现出令人着迷的明显矛盾，因此尽管测得的侵蚀速率为0.1-，但数百万年的地表沉积物仍保持其米级形态。 4 m Ma〜（-1）。我们分析了MDV中两个有据可查的灰分沉积物正上方和下方的重粉岩石英球中宇宙射线产生的〜（10）Be和〜（26）Al的浓度，这是竞技场谷灰（〜（40）Ar / 〜（39）Ar年龄4.33 Ma）和Hart灰（K-Ar年龄3.9 Ma）。考虑到原位空气落灰的年龄，测得的〜（10）Be和〜（26）Al浓度显着低于预期，最好解释为反映了上覆沉积物的降解速率。可以最好地解释所观察到的同位素分布的阿雷纳河谷火山灰上方物质的侵蚀速率为3.5±0.41 X 10〜（-5）g cm〜（-2）yr〜（-1）（〜0.19 m Ma〜（- 1））过去〜4 Ma。对于哈特灰，过去〜I Ma的侵蚀速率为4.8±0.21 x 10〜（-4）g cm〜（-2）yf〜（-1）（〜2.6 m Ma〜（-1））。浓度曲线没有显示出由于冰的升华引起的混合，蠕变或放气的迹象。这些结果表明，在不进行垂直混合的情况下，缓慢，稳定地降低地表可能使地貌即使在受到侵蚀的情况下仍能保持其米级形态。

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