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许多冲积扇沉积中的层序、大层序和盆地充填层序常具渐变特征。通过研究,提供了沉积过程(层序)、短期扇形成过程(层序)、长期扇形成过程(大层序)和沉积盆地背景(盆地充填层序)的证据。这些层序的出现和识别主要取决于整个扇的沉积物特征、沉积过程、沉积物的分布、活动扇沉积区的改变和迁移,沉积事件的规律性以及不受后期洪水再改造。“扇形成的首要条件是具有高地和低地毗邻的地形背景” (Denny,1967)。如果冲积扇只依赖于初始断层崖或侵蚀地形而发育,那么就会形成分布有限的、粒度逐渐变细的薄层冲积扇,如果冲积扇是由于断层连续运动所形成,那么就会形成地理上分布较广、厚度较大的冲积扇,即层序和大层序多次叠加而成的冲积扇盆地充填层序。
Many alluvial fan sedimentary sequences, large sequences and basin filling sequence often have gradual changes. Through the research, there is evidence of sedimentary process (sequence), short-term fan formation process (sequence), long-term fan formation process (large sequence) and sedimentary basin background (basin fill sequence). The appearance and identification of these sequences depend mainly on the sediment characteristics of the entire fan, the deposition process, the distribution of sediments, the alteration and migration of depositional zones in the active fan, the regularity of sedimentary events, and the reengineering of later floods. “The first condition for fan formation is the terrain with high and low contiguous terrain” (Denny, 1967). If the alluvial fan relies solely on the initial fault cliffs or eroded terrain, a finitely distributed, thin grain alluvial fan will develop, and if the alluvial fan is formed by the continuous motion of the fault, it will be geographically The alluvial fans, which are widely distributed and large in thickness, are filled with alluvial fan basins, which are superimposed by sequences and large sequences.