| Shulehe alluvial-fan, a large alluvial fan developed in a dry inland region, is located in the range-front of the north Qilian Mountains and the east end of the Alty Tagh fault zone. Much attention has been paid to this alluvial fan due to its great size, special tectonic setting, and approximately 3 km displacement of the fan apex caused by the Altun left-lateral faults. Studies on development and evolution of this young alluvial fan that is continuously growing will make it clear for some important neotectonic problems in the region, such as neotectonic deformation and dynamic mechanism of sedimentary basins related to strike-slip faults, kinematic characteristics of one part of the Altun Fault, the relation of tectonic transform between the Altun strike-slip fault and north Qilian overthrust, etc.Based on previous research results, interpretation of remote sensing images, investigations on Quaternary geology, active tectonics in the region of the Shulehe alluvial fan and its adjacent regions, and dating of late Quaternary sediments, this thesis studies the development of the Shulehe alluvial fan and its response to tectonic activity and characteristics of neotectonic activity in the east end of the Altyn Tagh fault.1. Application of infrared stimulated luminescence (IRSL) dating in late Quaternary proluvial-alluvial sedimentsOptical Stimulated Luminescence (OSL) dating is a technique, also a research field. Its primary supposition, theory and experimental process constrain the source of errors and uncertainties, and determine the basic requirements for sampling. Due to the importance of values of ages in theoretical studies and engineering practice, it is necessary to evaluate objectively the data of ages obtained and use them in geological studies with much caution. Fine grain and multi-aliquot IRSL dating of late Quaternary alluvial-proluvial sediments in the Shulehe region, Gansu indicates that: OSL dating using fine grains found in coarse detrital sediments in region with proluvial-fans is a very simple and easy dating method for late Quaternary sediments in dry and half-dry regions such as northwest China. Abnormal decaying and sensitivity variations of samples are important factors influencing the values of ages, and may lead to underestimation of sample ages. Concerning proluvial sediments, signal zeroing, water content and rate ofenvironmental dose are needed to be determined again. In addition, contents of U and Pb in samples may have climatic implication. Luminescence dating is one of the useful dating techniques for late Quaternary sediments at present. Because this dating technique must settle for the three primary suppositions and there are uncertainties occurring in the process of sample collecting, dealing, measuring and analyzing, much attention must be given to statistical implication of results of dating. Systematic sampling for more samples in more than one or two sections is an important aspect of testing itself. Depositing and forming of each geomorphic unit (terrace, proluvial fan, etc.) is a process bearing possible phase changes and prolonging of time. Therefore,when using OSL ages of sediments, to determine the formation ages of geomorphic units to discuss ages of active faults and to divide tectonic erents, integrated analysis based on field work is necessary, including communication with other reseachers a great extent.2. Ages of layered geomorphic levels in the east end of the Altyn Tagh fault and uplift ratesUplift of the Qilian Mountains and their spreading toward northeast lead to the occurrence of a serial of layered geomorphic levels represented by alluvial-proluvail fans and stream terraces in intermountain basins and range-front plains. Although 10Be and rock varnish dating can be used to determine ages of geomorphic levels, their use is limited in China now. In the studies of ages and uplift rates of geomorphic levels along the Shulehe reaches, methods of OSL and Electron Spin Resonance (ESR) dating are adopted.There are seven terraces of the Shulehe river, w...
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