Late Quaternary sinistral slip rate along the Altyn Tagh fault and its structural transformation model

摘要

Based on technical processing of high-resolution SPOT images and aerophotos, detailed mapping of offset landforms in combination with field examination and displacement measurement, and dating of offset geomorphic surfaces by using carbon fourteen (~(14)C), cos-mogenic nuclides (~(10)Be+~(26)Al) and thermoluminescence (TL) methods, the Holocene sinistral slip rates on different segments of the Altyn Tagh Fault (ATF) are obtained. The slip rates reach 17.5 ±2 mm/a on the central and western segments west of Aksay Town, 11+-3.5 mm/a on the Subei-Shibaocheng segment, 4.8+-1.0 mm/a on the Sulehe segment and only 2.2 +- 0.2 mm/a on the Kuantanshan segment, an easternmost segment of the ATF. The sudden change points for loss of sinistral slip rates are located at the Subei, Shibaocheng and Shulehe triple junctions where NW-trending active thrust faults splay from the ATF and propagate southeastward. Slip vector analyses indicate that the loss of the sinistral slip rates from west to east across a triple junction has structurally transformed into local crustal shortening perpendicular to the active thrust faults and strong uplifting of the thrust sheets to form the NW-trending Danghe Nanshan, Daxueshan and Qilianshan Ranges. Therefore, the eastward extrusion of the northern Qing-hai-Tibetan Plateau is limited and this is in accord with "the imbricated thrusting transformation-limited extrusion model".