Evidence for an early Neoglaciol glacier advance from rock glaciers Rind Lake sediments in the Sierra Nevada, California, USA

被引:50
作者
Konrad, SK [1 ]
Clark, DH [1 ]
机构
[1] Univ Washington, Dept Geol Sci, Seattle, WA 98195 USA
关键词
D O I
10.2307/1551975
中图分类号
X [环境科学、安全科学];
学科分类号
08 ; 0830 ;
摘要
Lichenometric ages of active glacigenic rock glaciers and Matthes (Little Ice Age) moraines, together with sediment cores from basins below these landforms, provide evidence for a glacier advance similar to 3000 yr ago in the Sierra Nevada, California. Diameters of the largest lichens (70-108 rmn) on the Mendel rock glacier indicate that it began forming well before the onset of the Little Ice Age (LIA) (similar to 700 yr BP). Smaller Lichens (30-45 mm) on the Matthes moraines of Darwin and Conness glaciers suggest that they formed during the LIA. The apparent lack of pre-LIA Holocene moraines below "clean" glaciers in the Sierra Nevada demonstrates that the pre-LIA Neoglacial advance must have been less extensive than the Matthes advance. Sediment cores recovered below Matthes glacial deposits provide additional support for a pre-LIA Neoglacial advance. Three cares from a meadow directly below the Powell rock glacier record grus deposition (suggesting nonglacial, summer-dominant mass wasting) between about 5300 and 3600 C-14 yr BP (similar to 6000-3900 cal yr BP), and alternating gyttja and silt (suggesting cooler, winter-dominated precipitation) after about 3600 C-14 yr BP (3900 cal yr BP). A lake core from below Conness Glacier shows a transition from higher-organic sediments (10-16% total organic carbon) to lower-organic sediments (2-4% total organic carbon) at approximately 3200 C-14 yr BP (3400 cal yr BP), suggesting formation and growth of the glacier in the cirque at that time.
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页码:272 / 284
页数:13
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