Provenance Study of Fe–Ti Oxide Minerals in the Quaternary Sediments in Yichang Area and Its Implication of Formation Time of the Yangtze Three Gorges, China

Abstract

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..

New evidence from heavy minerals and detrital zircons in Quaternary fluvial sediments for the evolution of the upper Yangtze River, South China

“…3). The electron spin resonance (ESR) age of the quartz grains from the sand interstitial material in the upper gravel layer is 0.75 Ma, which is comparable with the planation surface age of 0.8-0.75 Ma in the Yichang area (ESR age from Xiang et al [2005]).…”

“…The ESR ages of the sediments on the Yunmeng planation surface and terrace T 5 are ca. 0.75 Ma and 0.73-0.7 Ma, respectively (Xiang et al, 2005(Xiang et al, , 2020, so we believe that the paleo-Chuan River flowed westward before 0.75 Ma and reversed to flow eastward between 0.75 Ma and 0.73 Ma (Fig. 11a and b).…”

“…There are five main terraces (e.g., T 5 -T 1 , in descending order from oldest to youngest) below the Yunmeng planation surface along the slopes of the Yangtze River Gorges. Terraces T 5 and T 4 are mainly pedestal terraces, whereas terraces T 1 -T 3 are accumulation terraces (Tian et al, 1996;Xiang, 2004;Xiang et al, 2005). The detailed sedimentary characteristics of the terrace outcrops are discussed in the next section.…”

“…3). The ESR age of the gravel layer is between 0.73 and 0.7 Ma (Xiang et al, 2005(Xiang et al, , 2020. Sample TTL01 was collected from brownish-yellow interstitial sand materials (Fig.…”

“…Debate on the formation of the Three Gorges has continued. Most previous studies suggest that the formation age of the Three Gorges is 1.2 –0.7 Ma (Pleistocene) based on studies of terraces in the Three Gorges, Quaternary deposits in the Jianghan Basin, and continuous cores of boreholes in the Yangtze delta (Tang and Tao, 1997; Li et al, 2001; Yang et al, 2006; Wang et al, 2009; Xiang et al, 2011, 2018; Liu et al, 2018; Sun et al, 2018). Other studies, however, have indicated that the Three Gorges formed before the Pliocene, based on the fluvial deposition in the lower reaches of the Yangtze River, detrital zircons in the Yangtze delta, Nd and Pb isotopes in the sediments of the Hanoi Basin, and the Cenozoic sediments in the Jianghan Basin and offshore basins in East China (Clift et al, 2008; Jia et al, 2010; Zheng et al, 2013; Yang et al, 2019; Fu et al, 2021; Sun et al, 2021; Zhang et al, 2021).…”