活动造山带地区河流阶地与下切速率及其时空分布样式  

FLUVIAL TERRACES AND RIVER INCISION RATES IN ACTIVE OROGEN AND THEIR SPATIAL AND TEMPORAL PATTERN

作　　者：张金玉[1] 刘静[1] 王伟[1] 唐茂云 李占飞 

机构地区：[1]中国地震局地质研究所地震动力学国家重点实验室,北京100029 [2]重庆地震局,重庆401147 [3]北京地震局,北京100080

出　　处：《第四纪研究》2018年第1期204-219,共16页Quaternary Sciences

基　　金：国家自然科学基金项目（批准号：41502188和41225010）、中国地震局地质研究所地震动力学国家重点实验室自主项目（批准号：LED2016A02）和国家重点研发计划项目（批准号：2016YFC0600310）共同资助

摘　　要：河流下切带动区域地貌的演化，因此河流下切速率及其时空分布样式是解析构造、地表过程和气候变化之间广泛相互作用的关键切入点之一。根据阶地的保存状况，利用河流阶地的累积下切量和下切时间可以直接测得千年到百万年时间尺度的下切速率。鉴于此河流下切速率是链接不同时间和空间尺度上地貌侵蚀速率的关键所在，并具有较精细的时空分辨率。计算河流下切速率时，累积下切量上限是阶地基座的拔河高度，下界最优选择是低级阶地基座，而累积下切时间的最佳约束是尽量靠近阶地基座的冲洪积物的沉积时间；运用河流下切速率获得岩石抬升速率和区域构造变形量时，通常假定区域地貌处于均衡状态，河流下切速率代表着岩石抬升速率。但是由于气候变化，河流下切过程具有较强的时空不稳定性，导致这些假设经常失效。此外，河流加积和下切的转换与第四纪冰期一间冰期的变化并不一定存在时间上的一一对应关系，这可能是由于河流裂点的溯源迁移以及河流对气候变化的响应方式与强度存在差异。因此，实际工作中需要多方面获得不同时空尺度和分辨率的构造变形、气候变化以及地表过程的基本信息，借助地貌数值模拟程序，定量解析构造、气候和地表过程之间的广泛而复杂的相互作用。River incision is generally believed to have driven the evolution of regional landscape, and therefore the rates and spatio-temporal pattern act as the starting point to explore the interactions between tectonic, surface processes, and climate. Depending on the preservation conditions of fluvial terrace, the river incision rate can be calculated directly by the cumulative incision amount and temporal duration, and ranges at the time scale of thousands and several million years. Therefore, river incision rate is the key component linking erosion rates at various time scales, and possesses fine resolution in terms of spatio-temporal scales. When calculating river incision rate, the upper bound of cumulative incision amount is the bedrock strath of the target higher terrace, while the lower bound is preferred to be that of the lower dated terrace. In addition, the cumulative incision timing is better constrained by the burial ages of alluvial sediments as close to the bedrock strath as possible. When using river incision rates to derive tectonic deformation rates, it is generally assumed that the regional landscape is in an equilibrium state, and correspondingly river incision rates are believed to equal to rock uplift induced by tectonic uplift. This assumption generally fails due to the instability of river incision behavior, which might result from differential hydrologic response in time and space to the Quaternary climate fluctuations. Furthermore, the transition timing from river aggradation to incision does not agree well with the glacial-interglacial shift timing. This might be due to upstream migration of the knickpoint, or various ways or magnitudes of fluvial response to climate variations. Consequently, multiple methods should be utilized to capture the fundamental data of tectonic deformation, climate change, and surface processes on a series of time and space scales, which contribute to quantify the widespread and complex interactions among tectonic, climate and surface processes via landscape numerica

关 键 词：河流阶地 下切速率 时空展布 构造与气候 瞬时性 

分 类 号：P542[天文地球—构造地质学] P931.1[天文地球—地质学]