陆相流域盆地沉积通量模拟及古地貌意义——以西藏尼玛地区为例

青藏高原新生代的地貌演变一直是国际地球科学研究的前沿领域和热点问题。目前对于高原中部新生代地貌演变及其动力学机制的认识仍旧存在较大的争议，并且通过不同研究手段得到的结论也存在较大不同。流域盆地内的沉积物不仅记录了其沉积场所的大地构造背景、古气候和古环境特征等重要信息，同时也记录了源区的剥露历史，以及整个流域盆地的时空展布、地貌演变、风化强度和沉积通量变化等重要的地表过程。高原中部至少在早中新世就已形成的内流水系为进一步认识高原地貌演化提供了可能。基于源—汇系统质量平衡原则，以高原中部新生代尼玛盆地及其物源区构成的陆相盆地源—汇系统为研究对象，以沉积通量数值模拟（BQART-MCS）为研究方法，尝试重建高原中部新生代晚期的地貌格局。模拟结果表明:只有在年均气温为2 ℃~10 ℃、最大地势为1~3 km、干旱—半干旱的地貌条件下，源区产生的碎屑物质总量才可以与汇区沉积物总量达到平衡。本项研究是深时沉积通量数值模拟方法（BQART-MCS）在青藏高原的首次尝试，为在陆相盆山源—汇系统开展沉积物定量研究提供了新的思路。

Sediment Flux Simulation Paleogeomorphological Implications in the Terrestrial Source-to-Sink System:A case study in Nima area,central Tibet

The Cenozoic paleogeomorphology of the central Qinghai-Tibetan Plateau has been controversial and has always been a major research area. The inner drainage system that existed in the central plateau， at least in the early Miocene， seems to provide a new perspective for solving the paleogeomorphological problems in the central plateau. In order to reconstruct the Cenozoic paleomorphic pattern of the central plateau， this study selected the terrestrial source-to-sink system in the Nima area as the research object using the sedimentary flux numerical simulation model （BQART-MCS） to test the views of previous studies. The simulation results indicate that the total amount of sediment produced in the source area equals the total amount of sediment in the sink area only in the case of an average annual temperature of 2 ℃?10 ℃， a maximum terrain elevation of 1?3 km， and arid to semi-arid climatic conditions. Sedimentological and geochemical considerations have tended to confirm that the geomorphology during the Oligocene?Pliocene period was typical of a cool， dry climate at an elevation of about 2?4 km and an annual temperature less than 10 ℃. This was the first application of the BQART-MCS model in the terrestrial source-to-sink system of the Tibetan Plateau， and effectively modeled the total amount of sedimentary material in the deep-time source-to-sink system. It suggests a new approach to the quantitative study of source-to-sink systems.