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Glacially‐crushed quartz grains in late Quaternary deposits in the Virunga Mountains, Rwanda ‐indicators of wind transport from the north?

 

作者: WILLIAM C. MAHANEY,  

 

期刊: Boreas  (WILEY Available online 1990)
卷期: Volume 19, issue 1  

页码: 81-89

 

ISSN:0300-9483

 

年代: 1990

 

DOI:10.1111/j.1502-3885.1990.tb00424.x

 

出版商: Blackwell Publishing Ltd

 

数据来源: WILEY

 

摘要:

Quartz sand grains in late Quaternary deposits of the Virunga Mountains, northwestern Rwanda, were found to contain glacial‐crushing microtextures. Glacially‐crushed subangular grains generally lack sharp edges, and carry mainly low frequency, linear crushing features. Because there are no known tills in the Virunga Volcanoes (and because quartz is rare in volcanic terrain), it is likely the grains were delivered by aeolian transport from the Ruwenzori Massif, ‐150 km to the north. All the grains studied are consistent with crushing under low shear stress, and over short transport distances, in alpine glaciers. An increase in the percentage of glacially‐crushed quartz from Holocene to Pleistocene beds likely reflects on the increased strength of the paleowind system (trade winds) during the last glacial maximum. Alternatively, it could reflect on the increased source area for glacially‐crushed grains resulting from an increase in the extent of the Afroalpine belt during the last g

 

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