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日本四国南部所记录的连续地震剖面,揭示了土佐阶地、大陆坡、南海海槽和四国盆地附近的浅部构造。土佐阶地至少包括1.5公里厚的、由外部构造堤接受的陆源水平层状沉积物。沉积作用可能始于晚第三纪早期。这些沉积物不整合地复盖在第三纪早期的沉积物之上,后者的上部出露面显得截断。大陆坡的变形的沉积岩和火成岩基底已经断裂成上覆近代沉积物堆积的海坪(beaches)和出露基底的陡崖。在四国盆地内出现平均将近600米的浊流和远洋沉积物的互层。南海海槽内沉积物的厚度平均为1公里。海丘周围的壕沟表明浊流沉积物是从七岛一硫黄岛脊外海搬运到四国盆地来的。南海海槽内已有近代浊流沉积,而且在靠近陆坡处,它们遭受褶皱作用。该现象及陆坡脚下插进的基底表明海底扩张。
The continuous seismic profiles recorded in southern Japan, Shikoku, reveal the shallow structures near the Tuso terrace, the continental slope, the South China Sea trough and the Shikoku basin. The Tuso terraces include at least 1.5 km of terrestrial horizontal bed sediments that are accepted by the external structural dike. Sedimentation may begin early in the late Tertiary. These sediments unconformably overlie sediments earlier in the Tertiary period, the upper exposed surface of the latter appears to be cut off. Deformable sediments and igneous rocks on the continental slope have been broken into beaches that cover recent modern sediments and steeply exposed basal cliffs. In the Shikoku basin an average of nearly 600 meters of turbidity and oceanic sediments interbed. The thickness of sediments in the South China Sea trough is 1 km on average. The trenches around the seashore show that the turbidity sediment was transported from the islet to the Shikoku basin on the outskirts of the island. In the South China Sea trough, there are modern turbidite sediments, and near the slope, they suffer from folds. This phenomenon and the basement inserted at the foot of the slope indicate the expansion of the seabed.