| Surface Macrofabric of Boulder Dominated Desert Mountain Slopes, California, USA |
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| 作者姓名： | Donald A. FRIEND |
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| 作者单位： | Department of |
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| 摘 要： | Introduction Studies on microfabric and macrofabric are common, spanning from the sedimentology of fine grained rock to fabric analyses of glacial and periglacial deposits. These studies generally focus on one deposit that is all the same age. This study is unique in that identical measures of fabric were taken on a series of like deposits on the steep slopes (~25° to ~35°) of rhyolite domes in eastern California (Figures 1 and 2) whose maximum possible age stretches over a one-million-year…
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| 关 键 词： | 美国 漂石 沙漠 地质构造 |
| 文章编号： | 1672-6316（2005）03-0181-12 |
| 收稿时间： | 2005-06-01 |
| 修稿时间： | 2005-07-28 |
Surface macrofabric of boulder dominated desert mountain slopes, California, USA |
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| Donald A. FRIEND.Surface Macrofabric of Boulder Dominated Desert Mountain Slopes, California, USA[J].Journal of Mountain Science,2005,2(3):181-192. |
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| Authors: | Donald A Friend |
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| Institution: | (1) Department of Geography, Minnesota State University, 7 Armstrong Hall, 56001-6026 Mankato, MN, USA |
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| Abstract: | Rhyolite domes formed over a million year continuum in eastern California are used to study boulder dominated slopes. Slopes
in this study are steep (∼25° to ∼35°) and are made of coarse boulder sized blocks. These slopes include well varnished vertically
oriented colluvial deposits that have been likened to relict periglacial stone stripes, or as indicated in this study, are
the result of ongoing desert slope processes. The deposits are common throughout the arid southwestern US, but their morphometric
character, fabric, and rates of formation have not been assessed systematically. Results indicate that boulder deposits examined
here are remnant from the original surface formed during volcanic eruption and that these boulder slope deposits evolve slowly.
Grain size, grain shape and grain angularity do not change significantly from genesis to ∼0.6 Ma; trends in the data change
markedly after that time. Mean eigenvectors indicate a fabric oriented downhill, parallel to the slope, consistent with the
visual impression that long thin to plate-like rocks orient themselves similarly; however, fabric is actually randomly dispersed,
similar to that at slope genesis, as indicated by the eigenvalue analysis resultants ofC andK. Interestingly, grains remain or become more angular over the million-year time scale of the study as they decrease in size,
indicating active in situ weathering processes on individual grains; this result is counter to the common assumption that
as grains weather they become more rounded over time. |
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| Keywords: | Boulder-fields desert-slopes macrofabric |
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