Provenances of Cenozoic sediments in the Jianghan Basin and implications for the formation of the Three Gorges

ABSTRACT

The formation of the Three Gorges (TG), the most important capture point along the Yangtze River, has been debated since the last century. Most of hypotheses on its formation are based on the timing of unconformities detected in the sedimentary basins along the riverbed. These unconformities may mark periods of tectonic activity and enhanced hydrodynamic condition. Herein, we detail the Cenozoic sedimentary provenance of the Jianghan Basin through LA-ICP-MS zircon U-Pb geochronology and heavy mineral analyses. The obtained data suggest that during Palaeocene-Oligocene time, the Jianghan Basin was supplied by sediments from the nearby mountain belts. However, the occurrence of zircons with ages <32 Ma above the unconformity at ~24.6 Ma indicates a provenance from Cenozoic igneous rocks which are exposed only in the Qiangtang Block and the Songpan-Ganzi Orogen. We propose therefore that the TG formed between the late Oligocene and the early Miocene and that the ~24.6 Ma unconformity in the Jianghan Basin represents the best dating of the TG formation.

KEYWORDS:

• Detrital geochronology
• heavy minerals
• sedimentary provenance
• Three Gorges
• Jianghan Basin

Acknowledgments

We are very grateful to Professor Lothar Ratschbacher for polishing the English; Dr. Zhao Yang for their kind help with CL analysis; and Dr. Lulu Wu for their sample collections. This work was supported by the National Natural Science Foundation of China (No. 41672140, 41372140), the Outstanding Youth Funding of Natural Science Foundation of Hubei Province (No. 2016CFA055), the Program of Introducing Talents of Discipline to Universities (No. B14031), the Wuhan Science and Technology Project (No. 2016070204010145), Fundamental Research Fund for the Central Universities, China University of Geosciences (Wuhan) (CUGCJ1820), and the China scholarship Council (201806410013).

Disclosure statement

No potential conflict of interest was reported by the authors.

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Funding

This work was supported by the National Natural Science Foundation of China [41372140,41672140]; Outstanding Youth Funding of Natural Science Foundation of Hubei Province [2016CFA055]; the Fundamental Research Fund for the Central Universities, China University of Geosciences (Wuhan); [CUGCJ1820]; Wuhan Science and Technology Project [2016070204010145]; the China Scholarship Council [201806410013]; and Program of Introducing Talents of Discipline to Universities [B14031].