Modern sediment characteristics and accumulation rates from the delta front to prodelta of the Yellow River (Huanghe) |
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| Authors: | Liangyong Zhou Jian Liu Yoshiki Saito Maosheng Gao Shaobo Diao Jiandong Qiu Shaofeng Pei |
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| Institution: | 1.Key Laboratory of Marine Hydrocarbon Resources and Environment Geology, Qingdao Institute of Marine Geology,China Geological Survey,Qingdao,China;2.Laboratory for Marine Geology,National Laboratory for Marine Science and Technology,Qingdao,China;3.Geological Survey of Japan,Tsukuba,Japan;4.Department of Natural Environmental Studies, Graduate School of Frontier Sciences,University of Tokyo,Kashiwa,Japan;5.Key Laboratory of Coastal Wetland Biogeosciences, China Geological Survey,Qingdao Institute of Marine Geology,Qingdao,China |
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| Abstract: | Since 1976, the main channel of the Yellow River (Huanghe) has been on the east side of the delta complex, and the river has prograded a broad new delta lobe in Laizhou Bay of the Bohai Sea. In 2012, extensive bathymetric and high-resolution seismic profiles were conducted and sediment cores were collected off the new delta lobe. This study examined delta sedimentation and morphology along a profile across the modern subaqueous Yellow River delta and into Laizhou Bay, by analyzing sediment radionuclides (137Cs, 210Pb and 7Be), sedimentary structure, grain-size composition, organic carbon content, and morphological changes between 1976 and 2012. The change in the bathymetric profile, longitudinal to the river’s course, reveals subaqueous delta progradation during this period. The subbottom boundary between the new delta lobe sediment and the older seafloor sediment (before the 1976 course shift) was identified in terms of lithology and radionuclide distributions, and recognized as a downlap surface in the seismic record. The accumulation rate of the new delta lobe sediment is estimated to be 5–18.6 cm year–1 on the delta front slope, 2 cm year–1 at the toe of the slope, and 1–2 cm year–1 in the shelf areas of Laizhou Bay. Sediment facies also change offshore, from alternations of gray and brown sediment in the proximal area to gray bioturbated fine sediment in the distal area. Based on 7Be distribution, the shorter-term deposition rate was at least 20 cm year–1 in the delta front. |
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