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Sediment Dynamics and Morphodynamics of River-Sea Sediment Dispersal Systems through Space and Time: A Source-to-Sink Perspective
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Possible geological evidence for historical storm events from Dongshan Bay, southern China
P-G1-01-S
Chengcheng Gao* , State Key Laboratory of Marine Environmental Science, Xiamen University, Xiamen, China
Fengling Yu, State Key Laboratory of Marine Environmental Science, Xiamen University, Xiamen, China
Tian Xia, State Key Laboratory of Marine Environmental Science, Xiamen University, Xiamen, China
Hui Zhang, Lanzhou University, Lanzhou, China
Liangrong Zou, State Key Laboratory of Marine Environmental Science, Xiamen University, Xiamen, China
Zhangyu Cheng, State Key Laboratory of Marine Environmental Science, Xiamen University, Xiamen, China
Presenter Email: 1512998201@qq.com |
| Every year, typhoon storm surges cause huge casualties and property losses in China. The prospective and accuracy of existing storm surge warning and forecasting methods is not enough to meet the requirements of disaster prevention. The occurrence law of ancient storm surges can be retrieved by geological records, which provides a scientific basis for the prevention and treatment of storm surges at a larger time and space scale. This study aims to reconstruct palaeo-typhoon/storm events using geological records from Dongshan Bay, Fujian Province, southern China.
In 2018, a total of 12 surface sediments from the inner bay (near Zhangjiang Estuary) to the outer bay mouth, and one gravity core, 55cm in length, were collected. All samples were analyzed for particle size through Malvern Mastersizer 3000, and the core was scanned by XRF core scanner for elemental composition in Xiamen University.
Results of the surface samples show that sediments from the inner bay are well-sorted clay and silt, with the maximum grain size of 500 microns, mostly 7 microns. Sediments become coarser from the inner bay to the outer bay. At the bay mouth region near the Gulei Penisula, the coarse particles increased significantly, and the gravel composition could account for 21.87% of the surface sediments. These coarse gravel components are most likely transported during recent storms from the Gulei Peninsula and/or Dongshan Island.
The results of the particle size of the core show that core sediments are dominantly silt, between 10-50 microns, deposited under a low-energy condition. Results also show that the 55 cm core contains multiple coarse-grained interlayers (0-8cm,22-23cm,40-41cm and 51-55cm) with maximum particle sizes exceeding 3 mm, indicating at least two strong-energy events, such as typhoon-induced storm. Furthermore, the results of the elemental analysis show that these coarse layers contains higher contents of Cu, Zn, Ga, Br and Rb than the rest part of the core.
The above preliminary results show that the grain size and element analysis of surface sediments and core samples in Dongshan Bay, will provide a reliable geological basis for the reconstruction of palaeo-storm events and for the estimation of their reoccurrence period. More analyses on geochemistry and chronology are under process.
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