阿尔金主断裂东端第四纪左行走滑的新证据

NEW EVIDENCE OF QUATERNARY LEFT-LATERAL STRIKE-SLIP MOVEMENT ALONG THE EASTERNMOST SEGMENT OF THE ALTUN FAULT

通过对阿尔金主断裂东端早更新世冲积相砾岩的追踪,发现疏勒河古冲积扇沉积的西边界距现今疏勒河河口约 10km,由此提出了阿尔金主断裂东端第四纪以来左行走滑错动 10km的沉积学新证据。通过对疏勒河河口阶地的分析,认为疏勒河河道沿阿尔金主断裂 2 8km的肘状弯曲除主要反映了断裂的左行走滑外,可能还包含了河流弯折段侧向侵蚀因素的影响。对阿尔金主断裂东端第四纪期间的位错量和走滑速率进行了讨论。

Previous results about the magnitude and rate of strike-slip movement along the eastern segment of the Altun Fault are quite inconsistent with each other. This is mostly because that the Quaternary strike-slip rate was inferred mainly from the offset of drainage system or from interglacial sediments, while these data focused mainly on late Quaternary. Tracing the early Pleistocene alluvial gravel bed outcropped along the easternmost segment of the Altun Fault, we discovered that the western boundary of the ancient alluvial fan deposits of the Shulehe River is now about 10km away from the outlet of the river. We believe that this is an important evidence indicating that the Quaternary left-lateral strike-slip displacement along the easternmost segment of the Altun Fault is about 10km. Basing on the analysis of terraces at the outlet of the Shulehe River, we conclude that the 2.8km elbow-like winding of the Shulehe River channel along the Altun Fault indicates not only the left-lateral strike-slip of the Altun Fault, but also the effect of lateral erosion at the meander reach of the river. The magnitude of the Quaternary dislocation and slip rate along the easternmost segment of the Altun Fault are discussed in this paper as well.