| 珠江三角洲西缘晚第四纪沉积演化和最大海侵古岸线的重建 |
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| 引用本文： | 周良,王洋,杜学斌,卜建军,吴俊,吕万军,刘秀娟.珠江三角洲西缘晚第四纪沉积演化和最大海侵古岸线的重建[J].沉积学报,2022,40(1):119-135. |
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| 作者姓名： | 周良 王洋 杜学斌 卜建军 吴俊 吕万军 刘秀娟 |
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| 作者单位： | 1.中国地质调查局海口海洋地质调查中心, 海口 570100 |
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| 基金项目： | 中国地质调查局项目（DD20160064,DD20208013）~~； |
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| 摘 要： | 第四纪以来，受全球气候和海平面变化影响，海岸带地区发生了一系列强烈的海陆相互作用和海侵—海退等地质事件，包含了丰富的沉积环境演化和海平面变化等信息。选用珠江三角洲西缘台山地区的30个地质钻孔，通过14C、光释光、地球化学特征、底栖有孔虫、磁化率数据，建立了晚更新世以来的地层框架，重建了最大海侵古岸线的位置。研究结果表明:1）研究区自下而上划分为4个沉积单元（石排组、西南镇组、三角组、横栏组），经历了晚更新世中晚期的河流—海相交替沉积环境、末次冰期的海退暴露环境以及全新世滨海、浅海沉积环境。MIS3和MIS1的高海面时期发生了2次主要的海侵事件。2）依据钻孔圈定的晚更新世和全新世最大海侵界线最远向陆延伸分别为15.4 km和16.3 km，两条最大海侵线距离接近，走势相同。这与当时实际海平面高度之间的显著差异不符，可能是由于构造抬升作用导致晚更新世海侵时古地势较低。两期海侵沉积物的高程和年代资料揭示了研究区晚更新世以来整体处于构造抬升状态，抬升速率为+0.51 mm/a，而全新世以来整体处于沉降状态，沉降速率为-0.61 mm/a，重建的MIS3和MIS1时期最大海侵古岸线分别与研究区当前2.8 m和3 m等高线相符。此外，中国沿海不同地区由于新构造背景不同，晚第四纪海侵发生次数和最大范围在空间上整体具有“北强南弱”的特点，同一地区不同时期之间海侵强度差异并未完全遵循“早弱晚强”的特征，主要原因是除不同构造单元存在着构造差异外，海平面高度和沉积物供给变化同样对海侵强度有着一定的影响。
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| 关 键 词： | 珠三角西缘 晚第四纪 沉积演化 最大海侵古岸线 新构造运动 |
| 收稿时间： | 2020-06-23 |
Sedimentary Evolution and Reconstruction of Maximum Coastline Transgression During the Late Quaternary at the Western Margin of the Pearl River Delta |
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| ZHOU Liang,WANG Yang,DU XueBin,BU JianJun,WU Jun,Lü WanJun,LIU XiuJuan.Sedimentary Evolution and Reconstruction of Maximum Coastline Transgression During the Late Quaternary at the Western Margin of the Pearl River Delta[J].Acta Sedimentologica Sinica,2022,40(1):119-135. |
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| Authors: | ZHOU Liang WANG Yang DU XueBin BU JianJun WU Jun Lü WanJun LIU XiuJuan |
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| Institution: | 1.Haikou Marine Geological Survey Center, China Geological Survey, Haikou 570100, China2.Hubei Key Laboratory of Marine Geological Resources, China University of Geosciences, Wuhan 430074, China3.Wuhan Center, China Geological Survey, Wuhan 430200, China |
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| Abstract: | A series of intense sea?land interactions and transgression/regression geological events occurred in coastal areas from the beginning of the Quaternary， influenced by global climate and sea-level changes. These have left rich information about the sedimentary environment evolution in the transgression records. Based on 30 new drilled holes at the western margin of the Pearl River Delta， combined with 14C and OSL dating， geochemistry， micropaleontology and magnetic susceptibility， sedimentary evolution and the reconstruction of the maximum transgression coastline was completed. This study found the following:（1） The study area is divided into four sedimentary units from bottom to top: consecutive fluvial?marine alternating sedimentary environments in the middle to late Pleistocene； a regressive exposed environment in the Last Glacial Period； and coastal and shallow marine sedimentary environments in the Holocene. Two major marine transgression events occurred during the MIS3 and MIS1 high sea-level periods.（2） The maximum landward positions of the transgressions inland from the present shoreline were about 15.4 km in the Late Pleistoceneand 16.3 km in the Holocene. This similarity in distance and trend， which is inconsistent with the global pattern of sea-level change， was probably caused by tectonic uplift in addition to global climate fluctuation. The elevation and age data of the two-stage transgression sediments reveals that from the Late Pleistocene the whole area was experiencing tectonic uplift at a rate of +0.51 mm/a. The whole area has been in a tectonic subsidence state at a rate of -0.61 mm/a since the Holocene. The reconstructed maximum transgressions of the MIS3 and MIS1 coastlines are consistent with the current 2.8 m and 3 m contour lines in the research area. In addition， due to neotectonic movement， the transgression frequency and maximum range in the Late Quaternary may be summarized as “north powerful and south weak” in China’s coastal regions. Transgressive intensity differences in the same area at different times were not fully consistent with “early weak， later powerful” characteristics， the main reason being that， besides the tectonic differences in different tectonic units， the changes in sea level and sediment supply influenced the intensity of transgression to a certain extent. |
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| Keywords: | western margin of the Pearl River Delta Late Quaternary sedimentary evolution maximum transgression coastline neotectonic movement |
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