SEM Analysis of Quartz Sand Grain Surface Textures Indicates Alluvial/Colluvial Origin of the Quaternary "Glacial" Boulder Clays at Huangshan (Yellow Mountain), East-Central China

Authors

P. E. Helland, University of Nebraska-Lincoln
Pei-Hua Huang, University of Science and Technology of China
Robert F. Diffendal Jr., University of Nebraska-LincolnFollow

Document Type

Article

Date of this Version

1-1-1997

Citation

Quaternary Research (1997) 48: 177-186, article no. QR971916

Comments

Copyright © 1997, University of Washington. Used by permission.

Abstract

Geomorphic features and Pleistocene deposits on Huangshan have been attributed to glaciation. Recent reassessment questions this interpretation. As part of the reassessment, quartz sand grains from deposits identified as glacial boulder clays (till composed of boulders in a clay or silt matrix) were analyzed by scanning electron microscope for evidence of their sedimentary history. Surface textures found on the boulder-clay grains were compared with those on grains with known sedimentary histories including glacial, grus, colluvial, and alluvial grains. The analysis shows that the grains lack typical glacial textures. The surface textures present indicate a complex history. Non-uniformly weathered grain surfaces point to chemical weathering of the source rock. This is supported by the deep weathering of the nonquartz clasts in the sand-sized fraction as well as in boulders at the outcrops. The close correspondence in surface-texture frequencies with those of the alluvial grains indicates an alluvial component to the grains' history. The similarity with the colluvial grains and the outcrops' structures suggest an alluvia/colluvial origin for the deposits. The history indicated by the surface textures agrees with the recent reassessment of the geomorphic features and points to warm climatic conditions in east-central China for at least part of the Pleistocene.