基于宇生核素10Be的西秦岭北缘流域侵蚀速率空间分布研究

Catchment erosion rates across a landscape can be determined by in situ cosmogenic nuclide 10Be abundances of active channel deposits. Along with the widespread availability of digital elevation models, quantification of the erosion rates provides an opportunity to make ignificant progresses on the relationship between geomorphic characteristics and the catchment erosion rate. The northern West Qinling, located in the uplifting outmost northeastern Tibetan Plateau, is an ideal laboratory for studying active deformation and landscape evolution during late enozoic. Focusing on the 10Be-derived catchment erosion rates, our present proposal will study 20 tributary drainage basins along the southern Weihe River drainage basin in the northern flank of the West Qinling. The target would be fixed on the catchment-erosion rates along different regions. Furthermore, we will determine spatial distribution of 10Be-derived catchment erosion rates along the northern West Qinling. In addition to these studies, we will analyze the series of controlling factors of the catchment erosion within the drainage basin. Finally, the results will be of great help to study the late Cenozoic landscape evolution of the northern West Qinling.

通过测定原地宇生核素10Be浓度可以反演汇水流域盆地尺度侵蚀速率，探讨地貌特征对流域尺度侵蚀的控制作用。地处青藏高原东北缘的西秦岭北缘造山带，位于特殊大陆动力学环境形成的特定构造-地貌转换区域，东西两段分别受控于走滑断裂和正断裂，是定量分析流域侵蚀速率空间分布和构造变形与地貌演化相互作用的理想地区之一。本申请拟以流域盆地尺度侵蚀速率为切入点，基于原地宇生核素10Be这一关键技术手段，对西秦岭北缘渭河流域南侧的20个亚流域系统进行流域盆地尺度侵蚀速率研究，探讨该地区侵蚀速率的空间格局分布及控制因素，项目成果最终为探讨西秦岭北缘构造活动的地貌响应等科学问题奠定基础。

通过测定原地宇生核素10Be浓度可以反演汇水流域盆地尺度侵蚀速率，探讨地貌特征对流域尺度侵蚀的控制作用。地处青藏高原东北缘的西秦岭北缘造山带，位于特殊大陆动力学环境形成的特定构造-地貌转换区域，东西两段分别受控于走滑断裂和正断裂，是定量分析流域侵蚀速率空间分布和构造变形与地貌演化相互作用的理想地区之一。本项目以流域盆地尺度侵蚀速率为切入点，基于原地宇生核素10Be这一关键技术手段，对西秦岭北缘渭河流域南侧的28个亚流域系统进行流域盆地尺度侵蚀速率研究，获得其10Be浓度为4.26E5-1.47E5 atom/g，由其计算这一地区千年尺度流域侵蚀速率。这一地区东西向地形起伏梯度大，降水和岩性变化弱，使得我们能够对地形与流域侵蚀速率的关系进行探讨。我们获得的侵蚀速率为43.4-139 m/Ma，小于zheng et al.(2006)获得的临近区域六盘山地区的0.5-0.6mm/a的剥露时间速率，同时也远小于王修喜等（2006）基于磷灰石裂变径迹估算的六盘山平均剥蚀速率0.34和1.05mm/a。将所获得的流域地貌特征参数和现有研究成果进行对比分析，结合所获得的28个亚流域侵蚀速率，揭示地貌特征与侵蚀速率的关系，特别关注坡度、起伏、河流陡峭系数等，获得了研究区域地貌特征与流域盆地尺度侵蚀速率之间的变化关系。成果可为探讨西秦岭北缘构造活动的地貌响应等科学问题奠定基础。