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### 基于GPR图像的河北昌黎海岸横向沙脊北段沉积构造及其成因

1. 1. 福建师范大学地理科学学院,福州 350007
2. 福建师范大学地理研究所,福州 350007
3. 湿润亚热带生态地理过程省部共建教育部重点实验室,福州 350007
• 出版日期:2015-08-25 发布日期:2015-08-20
• 作者简介:

作者简介：史本林（1967- ）,男,河南柘城人,教授,主要从事区域环境变化方面研究。E-mail: shibenlin@163.com

### The sedimentary structure and genesis of the northern transverse dune on the coast of Changli county, Hebei province from ground penetrating radar

Feng JIANG1,3, Zhizhong LI1,2,3, Jianhui JIN1,2,3, Tao DENG1,3, Xianli WANG1,3, Jing XIA1,3

1. 1. College of Geographical Sciences, Fujian Normal University, Fuzhou 350007, China
2. Institute of Geography, Fujian Normal University, Fuzhou 350007, China
3. Key Laboratory of Humid Subtropical Eco-geographical Process, Ministry of Education, Fuzhou 350007, China
• Online:2015-08-25 Published:2015-08-20

Abstract:

The sedimentary structure of dune systems provides available information about the development of dunes. Along the coast of Changli County, Hebei Province, China, a high large transverse coastal dune has been formed. This place is a typical coastal sand dune field in China, where the highest point of the dune reaches up to 40 m above sea level. The transverse dune runs NNE-SSW and the dominant wind direction is NE or NNE in the study area. In order to gain more detailed data of the sedimentary structure and to understand its formation better, we performed a study to detect the inner structure of the transverse dune using ground-penetrating radar (GPR) and to analyze the grain-size characteristics. GPR is a non-invasive technique that allows the study of the structure of dune systems when outcrops are limited. The images of sedimentary structure at a depth of 0-20 m obtained from the GPR reveal dip direction, dip angle and distribution of the bedding. There is a strong reflector at about 6 m depth inside the dune. Above the reflector, high-angle cross bedding is generally found; the dip direction of the bedding is SWW and the dip angle ranges from 30° to 32°. The high-angle cross bedding formed by onshore wind is a kind of foreset beds. We can also find some reactivation or erosion surfaces on the windward slope which are influenced by the secondary changes of wind. On the top of the transverse dune, trough cross-bedding caused by the seasonal variation of wind direction is developed. Below the surface, cross-lamination shaped by the wave action is found. The cross-lamination develops both in landward and seaward slopes, where it dips landwards and seawards respectively. The results of grain-size analysis indicate that the sediment is well-stored medium sand. But the grain size at the base of the dune is coarser than that at the top of the dune. The sediment at the base deposited under the action of wave, while the sediment at the top deposited under the action of wind. Therefore, based on the characteristics of sedimentary structure and grain size, we conclude that the strong reflector is the interface of an old beach barrier and aeolian dune. Integrating previous studies on the changes of the coastline since late Holocene in the study area, around 2000 years ago suggest that the beach barrier controlled by wave action exposed above sea water and the Qilihai Lagoon formed on the landward side. The transverse dune developed based on the beach barrier outside the Qilihai Lagoon since 2000 aBP and it was eroded by wave, at the beginning of the formation of the aeolian dune. The high large transverse dune is the result of steady accretion under the action of wind for a long time.