讨论三峡和宜昌地区第四纪古气候的演化过程及青藏高原隆升对古气候演化的影响。以三峡及宜昌地区第四纪沉积物为主要研究对象,在沉积剖面研究的基础上,对低夷平面、阶地及冲积扇和湖相沉积物进行地球化学元素分析,依据地球化学元素的变化曲线及沉积特征,认为三峡及宜昌地区第四纪古气候的演化趋势相似,经历了早更新世晚期及中更新世暖湿气候到晚更新世干冷气候的转变。结合全球气候背景、青藏高原隆升过程对气候影响等方面的资料,认为150 ka B.P.之后青藏高原隆升至4 km时,青藏高原对三峡及宜昌地区的古气候产生了较大影响。
The Three Gorges are considered to be critical to understand the formation of Yangtze River. Recent research results suggest that the Yangtze Three Gorges was created during the Quaternary but the exact time is debatable. Fe–Ti oxide minerals are seldom used to study sediment provenance, expecially using scanning electron microscopy(SEM), and energy dispersive spectrometer(EDS). In this study, the provenance of Quaternary sediments in Yichang area, which is located to the east of the Yangtze Three Gorges, was investigated by using SEM and EDS to research Fe–Ti oxides. The Panzhihua vanadium titanomagnetite and Emeishan basalt outcrop are located to the west of the Three Gorges. Further, the materials from them are observed in the Quaternary sediments of Yichang area. Fe–Ti oxide minerals from the Huangling granite are observed in the Yunchi and Shanxiyao Formations, which were formed before 0.75 Ma B.P., whereas Fe–Ti oxide minerals from the Huangling granite, Panzhihua vanadium titanomagnetite, and Emeishan basalt are observed in the riverbed and fifth-terrace sediments of the Yangtze River, which were formed after 0.73 Ma B.P.. Thus, we can infer that the Three Gorges formed after the deposition of the Shanxi Formation and before the fifth-terrace; i.e., 0.75–0.73 Ma B.P..
