【摘要】 河流自山区流至下游盆地过程中，当所搬运的碎屑物在磨损和分选作用下逐步变细至中粗卵砾尺度时，河床沉积在一段相对短的距离内从砾石迅速转变为砂，这一粒度陡变的河段被称为砾-砂过渡带(Gravel-sand Transition, GST)。河流砾-砂过渡带现象具有时间和空间的普遍性。砾-砂过渡带被埋藏在地层中成为砾岩-砂岩过渡带，沉积盆地充填碎屑中的砾岩-砂岩过渡带的位置变化所反映的砾-砂过渡带时空演化历史对区域构造与气候变化有明确的指示意义。基于已有文献，对地质演化时间尺度下砾-砂过渡带的位置变化控制因素及其地质指示意义进行梳理和展望。对世界范围沉积盆地内砾-砂过渡带时空演化历史的重建表明，盆地沉降速率、沉积物供给量与供给沉积物初始粒度分布是控制砾-砂过渡带在盆地内相对位置的主要因素，且不同盆山关系下砾-砂过渡带空间变化具有不同的地质意义。盆山相对位置固定背景下，盆地沉积序列内砾-砂过渡带在垂直造山带方向上的水平迁移反映山脉隆升等构造活动或气候变化引起的盆地沉降速率、沉积物供给量变化；盆山相对汇聚背景下，前陆盆地内砾-砂过渡带向前陆方向的持续迁移反映盆地基底与造山带之间的汇聚过程，砾-砂过渡带迁移速率是约束地壳缩短速率的有效指标。更多还原

【Abstract】 Sediments from the mountain are transported downstream and accumulate in basins by river systems. Sediments routing through the network of rivers display downstream grain size fining due to sorting and abrasion. The riverbed sediments rapidly change from gravel to sand over a short downstream distance, the grain size transition from gravel to sand along rivers is termed the gravel-sand transition(GST). GST is preserved in the stratigraphy as the conglomerate-sandstone transition. Previous studies demonstrate that GST is a universal sedimentary facies symbol in spatial and temporal evolution of sedimentary basins, and it has tectonic and climatic implications. The controlling factors of the positions of GST and their geological implications from the existing related studies were summarized and reviewed. The reconstruction of the spatial and temporal evolutionary history of GST within the sedimentary basins reflects that the position of GST in a sedimentary basin succession is determined by basin subsidence rate, sediment supply flux, and grain size distribution of sediment supply, and the geological implications of GST in different basin-mountain backgrounds are entirely different. The horizontal migration of GST relative to the basin reflects the changes in basin subsidence rate or sediment supply flux decided by tectonic or climate changes, when the basin is fixed relative to the mountain. The migrations of GST within the convergent foreland basin-orogen systems reveal the convergence processes between the basins and orogens, and the migration rates of GST provide a potential proxy for long-term crustal shortening rates in the systems.更多还原