[H-CG28] [EE] デルタ（三角州）：複雑系への学際的アプローチ

[HCG28-P07] Modern sediment accumulation and sedimentary structure of the modern Yellow River delta

ツオウ リャンヨン²、リュウ ジャン²、*斎藤 文紀^1,3、ガオ マオシェン²、ディアオ シャオボ²、チュウ ジャンドン²、ペイ シャオフェン² (1.国立研究開発法人産業技術総合研究所地質情報研究部門、2.中国地質調査局青島海洋地質研究所、3.島根大学汽水域研究センター)

キーワード：Yellow River (Huanghe), sedimentation rate, delta lobe

Since 1976 the Yellow River channel has been located on the east side of delta complex and has built out a broad sedimentary lobe. In 2012, extensive bathymetric and high resolution seismic profiles, vibrocores in the survey lines and surface sediments were collected off the Yellow River delta and in Laizhou Bay. This study examines the sedimentation and morphology in the modern Yellow River delta and in Laizhou Bay, based on analyses of radionuclides (¹³⁷Cs, ²¹⁰Pb, ¹³⁴Cs), sediment structure and texture, surface sediment distribution pattern, and the morphological change between 1976 and 2012. Bathymetric profiles, especially the S-N profiles, reveal the present morphology of the delta front which exceed previous estimated boundary, and this also validate on basis of analysis of ¹³⁷Cs in cores. The ¹³⁷Cs onset depths corresponding to the depths of lithological changes and morphological changes indicate that it can be a proxy to track the dispersal of Yellow River-derived sediments in the study area. Synthesis of bathymetry, seismic profiles, ¹³⁷Cs profiles and surface sediment pattern show that a depocenter occurs in the south frank of the Yellow River delta (morphologically a spit) in west of Laizhou Bay. The deposition probably results from the headland eddy that formed with the morphological change. ²¹⁰Pb profiles only in shelf area provide reliable accumulation rates, while ¹³⁷Cs profiles show the depositional thickness in the whole area. Morphological changes along with ¹³⁷Cs profiles of cores were used to establish the present sedimentary frame of the delta front slope and sediment dispersal in the west of Laizhou Bay.