CAJ | 학술논문

宜昌砾石层上覆中更新世网纹红土,下伏白垩纪红层,共有22个岩性层组成,总厚超过100 m.通过对宜昌地区剖面出露砾石层的沉积相分析表明,善溪窑和云池剖面由下至上出现冲积扇扇中一扇根亚相:李家院剖面与上述两剖面间有沉积间断,由下至上出现冲积扇扇端一扇中亚相.粒度分析也证明了该砾石层中的砂体属冲积扇中的辫状水道沉积,与沉积相分析所得结论一致.研究认为,宜昌砾石层具有典型的冲积扇沉积环境特征,主要为冲积扇扇顶部分.该冲积扇在宜昌东南地区如此大规模的发育,显示其形成时具有强大的水动力条件,通过对其形成的地貌环境意义进行探讨,初步认为,该冲积扇为长江三峡贯通的产物.据前人研究推断,宜昌砾石层的形成时代应该在1.08～0.73 Ma B.P.,三峡贯通应在1.0 Ma B.P.之前.
의창력석층상복중경신세망문홍토,하복백성기홍층,공유22개암성층조성,총후초과100 m.통과대의창지구부면출로력석층적침적상분석표명,선계요화운지부면유하지상출현충적선선중일선근아상:리가원부면여상술량부면간유침적간단,유하지상출현충적선선단일선중아상.립도분석야증명료해력석층중적사체속충적선중적변상수도침적,여침적상분석소득결론일치.연구인위,의창력석층구유전형적충적선침적배경특정,주요위충적선선정부분.해충적선재의창동남지구여차대규모적발육,현시기형성시구유강대적수동력조건,통과대기형성적지모배경의의진행탐토,초보인위,해충적선위장강삼협관통적산물.거전인연구추단,의창력석층적형성시대응해재1.08～0.73 Ma B.P.,삼협관통응재1.0 Ma B.P.지전.
The gravel bed in Yichang is more than 100m thick and composed of 22 layers. It lies over Cretaceous red bed and covered wjth Middle Pleistocene plinthitic red earth. The authors analyzed the sedimentary fades of the gravel bed. The upper and middle fan subfacies of alluvial fan exist in Shanxiyao and Yunchi profiles from the bottom upward. There is a hiatus between Lijiayuan profile and the above two profiles. The middle and lower fan subfacies exist in Lijiayuan profile from the bottom upward. Grain size analysis also shows that the outcropped sand body has the characteristics of braided river and alluvial fan, which is consistent with the result of sedimentary fades analysis. It is thus concluded that the very thick gravel bed in Yichang is a typical alluvial fan and seems to be mainly the upper part of the fan. Such wide development of the alluvial fan can only occur under the condition of strong hydrodynamic action. Through a study of the geomorphology and environmental significance of the formation of the fan, the authors preliminarily consider that the outcropped gravel bed in Yichang was produced by the formation of the Three Gorges. Data available also show that the gravel bed was formed in 1.08-0.73 Ma B.P., whereas the Three Gorges were formed before 1.0Ma B.P.