Fabric analysis of till clasts in the upper Urumqi River, Tian Shan, China

摘要

In-situ measurement of clast fabric within till and other sediment was performed at locations in Hayisa (HY), Upper-Wangfeng (UW), Lower-Wangfeng (LW) and Balatigou (BL), in the upper Urumqi River in the Tian Shan of NW China. Subglacial tills have stronger fabric of both a-axis and a-B-plane than supraglacial till. This can be explained as a result from the different stress and transport histories of till clasts. The preferred orientation of a-axes of till fabrics intersect the former ice-flow direction at a sharp angle (62 ± 16°); whereas the a-B-plane, with its normal intersecting the former ice-flow at 84 ± 4°, is oriented approximately parallel to the ice flow direction. Thereby, subglacial relief appears to strongly influence the till fabric. In particular, the a-axis fabric is more sensitive to landforms than that of the a-b plane. In simple straight troughs, such as the Wangfeng Valley, fabric varies little. In the complex section of the trough, such as the Hayisa Lipolith, fabric characteristics are different at different sites of the Hayisa Drumlin. The fabric data can be used to understand glacial sedimentary processes in the study area.