Subglacial deformation: evidence from microfabric studies of particles and voids in till from the upper Urumqi river valley, Tien Shan, China

• Main Authors: Yi, CL, Cui, ZJ
• Other Authors: Yi, CL (reprint author), Chinese Acad Sci, Inst Geodesy & Geophys, Wuhan 430077, Peoples R China., Chinese Acad Sci, Inst Geodesy & Geophys, Wuhan 430077, Peoples R China., Chinese Acad Sci, Cold & Arid Reg Environm & Engn Res Inst, Lab Ice Core & Cold Reg Environm, Lanzhou 730000, Peoples R China., Peking Univ, Dept Geog, Beijing 100871, Peoples R China.
• Format: Journal/Newspaper
• Language: English
• Published: journal of glaciology 2001
• Subjects: GRAIN-SIZE DISTRIBUTIONS; BED CONDITIONS; MICROSTRUCTURES; DRUMLINS; GLACIER; FABRICS; Journal of Glaciology
• Online Access: https://hdl.handle.net/20.500.11897/389124

Microfabrics formed by flat particles and voids in till samples from the upper Urumqi river valley, Tien Shan, northwestern China, were analyzed using three mutually perpendicular thin sections. Chi-squared tests were used to determine significance levels of the orientations of both particles and voids. The basal tills in an end moraine, on the stoss sides of two roche moutonnees, on the stoss sides of a drumlin with a rock core, and on the lee side of the same drumlin far from the rock core have strong particle and void microfabrics. Field evidence suggests that these tills were deformed in a subglacial setting. Thus, consistent with recent laboratory studies of till fabric development, deformation is believed to be responsible for the strong particle and void microfabrics. in the same end moraine, particle microfabrics in an overlying till were strong, but void microfabrics were weak. This till is believed to have been foamed by dumping and rolling of debris from hill slopes and of ablation moraine from the glacier surface. The weak void microfabric is interpreted to indicate that the till was not consolidated and hence not sheared under the weight of the glacier, despite the strong particle microfabric. Basal tills on the lee sides of the roche moutonnees, and on the lee side of the drumlin but near its core, have weak microfabrics. Geography, Physical Geosciences, Multidisciplinary SCI(E) 7 ARTICLE 159 607-612 47