| 摘要: |
| 为了查明闽江口外海域晚第四纪地震地层特征，进行了高分辨率浅地震剖面调查，穿透的沉积物厚度最大约90m，划分为6个地震层序，自上向下为U1-U6。U1为全新世（海洋同位素阶段（marine isotope stage，MIS）1期）海相沉积单元，U3为MIS 3期的滨浅海-河口相，U5为MIS 5期的滨浅海与河流交互相，在MIS 5.2和5.4亚期海平面下降超过15m，发育了河流沉积；U2和U4分别为MIS 2和MIS 4期的河流充填相，而U6为MIS 6期的陆相沉积单元。根据地震层序关系研究了埋藏古河道的断面和分布特征、发育年代、演变及原因等。在全新世初期（11.5ka BP）之前，古闽江呈SE向经研究区南部和海坛岛东面流入东海（台湾海峡北口），随着研究区上游地势不断淤高，在11.5ka BP之后发育了NE向经北部向海到达西引岛附近的古河流，至约9.2ka BP海平面上升到约-30m高度时，全部河流消失于海面之下，闽江最后一次退出研究区。在闽江口东面，埋藏古丘陵的中南部高于现海面下50m（-50m），受其阻挡未能发育向东直接入海的闽江古河道。本文的研究结果提供了研究区自MIS 6末期以来古河流发育和演变等方面的新认识和证据。 |
| 关键词: 地震层序 晚第四纪 古河道 演变 闽江口 |
| DOI：10.11693/hyhz20180400087 |
| 分类号:P539.1 |
| 基金项目:我国近海海洋综合调查与评价专项，908-01-QC20号。 |
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| SEISMIC SEQUENCES AND EVOLUTION OF PALEO-RIVER CHANNELS OF LATE QUATERNARY OFF MINJIANG RIVER ESTUARY, SOUTHEAST CHINA |
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LIU A-Cheng1,2,3, TANG Jian-Zhong1,2, WU Wei1,2, ZHANG Jie1,2
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1.Shanghai East Sea Marine Engineering Survey and Design Institute, Shanghai 200137, China;2.East Sea Marine Survey and Prospect Center of State Oceanic Administration, Shanghai 200137, China;3.East Sea Information Center of State Oceanic Administration, Shanghai 200136, China
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| Abstract: |
| High-resolution shallow-seismic surveys were carried out off the Minjiang River estuary in Southeast China in May-July 2005 and October 2008 to March 2009. The maximum sediment penetration was about 90 m. Six seismic units, i.e., U1-U6, were identified. They formed a serial sedimentary marine-littoral-alluvial sequence deposited during the MIS 1 to MS 6, respectively, of which between subphases MIS 5.2 and 5.4 was a sea level regression when sea level dropped for over 15 m. Based on seismographic interpretation, the distribution, evolution, and formation of the sequences were analyzed. Results revealed paleo-river channels that developed during MIS 2, 4, 5.2 and 5.4, respectively. In detail, before the Early Holocene (11.5 ka BP), the paleo-Minjiang River flew southeastward through the southern part of the study area and the east of the Haitan Island into the East China Sea (the north entry of the Taiwan Strait). Later, as the upstream of the study area was silted up by alluvial deposition, NE-directed paleo-rivers were developed reaching the Xiyin Island across the northern part of the study area. At about 9.2 ka BP when sea level raised to 30m below present sea level (BPSL), all paleo-rivers in the study area submerged under the sea, and the Minjiang River retreated from the study area for the last time, and no eastward paleo-rivers into the sea had ever developed due to the barriers of buried paleo-hills (-50 m BPSL) to the east. |
| Key words: seismic sequences Late Quaternary paleo-river channels evolution Minjiang River estuary |
