Early Holocene mud-ridge formation in the Yangtze offshore, China: a tidal-controlled estuarine pattern and sea-level implications
Early Holocene mud-ridge formation in the Yangtze offshore, China: a tidal-controlled estuarine pattern and sea-level implications
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DOI：
10.1016/s0025-3227(03)00119-1
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发表时间：
2003-07
期刊：
影响因子：
2.9
通讯作者：
Zhongyuan Chen;Y. Saito;K. Hori;Yiwen Zhao;A. Kitamura
中科院分区：
文献类型：
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作者：
Zhongyuan Chen;Y. Saito;K. Hori;Yiwen Zhao;A. Kitamura
研究了长江口泥脊系统的地形演化和沉积特征。地震剖面显示，宽2-3公里，长5-8公里，厚达15米的泥脊，相隔5-10公里，向东南方向延伸，大致平行于现代潮汐的涨潮和落潮方向。一些泥脊直接位于更新世末的陆地沉积物之上，暴露于现今海底，而另一些则被向陆增厚的全新世三角洲沉积物所掩埋。一个11米长的振动岩心从一个泥脊回收揭示均匀和斑驳的粉质粘土和粘土质粉砂，有孔虫丰富，这表明河口环境的沉积。年代地层对比结合声学相分析表明，泥脊主要形成于10-7 ka，对应于全球海平面上升的减速期。该泥脊下覆有厚的晚更新世河流至海岸细砂至中砂，顶部为不整合面，上覆有现代三角洲沉积物，其间为侵蚀面。我们认为，泥脊沉积在潮汐控制的河口条件下，在全新世早期海平面上升减速。研究区全新世海侵与泥脊沉积几乎同期，三角洲沉积发生在泥脊形成之后。这些海脊后来主要由于强大的潮汐流而被改造。
The purpose of the present study is to examine the topographic evolution and sedimentary characteristics of a mud-ridge system in the Yangtze offshore region. As revealed by seismic profiling, 2–3-km-wide, 5–8-km-long, up-to-15-m-thick mud ridges, situated 5–10 km apart, extend here in a southeasterly direction, approximately parallel to the direction of the ebb and flood flow of the modern tide. Directly resting upon the latest Pleistocene terrestrial sediments, some mud ridges are exposed on the present seafloor, while others are buried by landward-thickening Holocene deltaic sediments. An 11-m-long vibrocore recovered from one mud ridge reveals homogenous and mottled silty clay and clayey silt, rich in foraminifera, suggesting an estuarine environment of deposition. Chronostratigraphic correlation in association with acoustic facies indicate that the mud ridge was formed primarily during ∼10–7 ka, corresponding to a period of global decelerating rise in sea level. This mud ridge is underlain by thick, late Pleistocene fluvial to coastal fine to medium sands with an unconformity surface on top, and it is overlain by modern deltaic sediments with an erosional surface in between. We propose that the mud ridges were deposited under tidal-controlled estuarine conditions during the early Holocene deceleration of the rise in sea level. The Holocene transgression in the study area was nearly coeval with the mud ridge deposition, and the deltaic sedimentation occurred after the mud ridges formed. The ridges were subsequently reworked, largely by strong tidal currents.