| Popis: |
The Song Hong (Red River) delta, which is located on the western coast of the Gulf of Bac Bo (Gulf of Tonkin) in the South China Sea is characterized by three morphological systems that are clearly distinguished spatially: fluvial-, tidal-, and wave-dominated. We obtained a 70-m-long core of sediments (the Nam Dinh-1 core) from the central part of the delta in 1999. This paper presents the first detailed description of sedimentary facies with high-resolution radiocarbon dating for the latest Pleistocene–Holocene sediments of the Song Hong delta. The core sediments were divided into three units on the basis of the sediment facies: in ascending order, Unit 1, fluvial sediments consisting of fining-upward gravels to clay; Unit 2, coarsening-upward marine clay to shelly sand; and Unit 3, coarsening-upward marine clay and laminated sand. Twenty-one radiocarbon dates showed that the core succession was deposited after the Last Glacial Maximum (LGM); the ages were 15–11 cal. kyr bp for Unit 1, 11–9 cal. kyr bp for Unit 2, and 8–0 cal. kyr bp for Unit 3. These data indicate that sediments were deposited in transgressive fluvial/estuarine to regressive deltaic environments formed in the central delta plain of the Song Hong after the LGM in response to sea-level changes. |
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