| 摘要: |
| 牡蛎礁是具有重要生态功能的海岸带生境, 并且记录了丰富的环境演化信息。根据碳酸盐沉积层序模拟的方法, 提出了一个牡蛎礁演化模型, 由海平面波动过程、碎屑沉积物顶面高程、牡蛎礁垂直生长率、牡蛎礁顶部高程等四个模块所构成。垂向生长率函数的输入参数通过牡蛎礁沉积环境分析和古今地貌对比方法而确定。应用该模型探讨了江苏海岸小庙洪牡蛎礁的定殖、生长和最终被埋藏的演化历程。模拟结果显示, 牡蛎礁顶部水深和河口湾环境参数是牡蛎礁演化的两大限制因素, 小庙洪牡蛎礁的最大垂向生长率约为12 mm/a, 礁体发育初期以垂向增生为主, 大约910 年前礁体出露于平均低潮面后, 转向以侧向扩张为主。该礁体的出露规模在330 年前达到最大, 目前牡蛎礁的生长几乎停滞, 并将在250 年后被埋藏, 其时牡蛎礁的最大可能厚度达12 m。牡蛎礁演化模型显示牡蛎礁建造过程具有复杂性, 是海平面变化、地面沉降速率、碎屑沉积速率、盐度、悬沙浓度等诸多因素共同作用的结果。牡蛎礁顶板应看成是低于当时海平面的标志, 并不代表海平面高度。
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| 关键词: 牡蛎礁演化, 生长率函数, 沉积层序, 几何模型, 江苏海岸 |
| DOI：10.11693/hyhz201001001001 |
| 分类号: |
| 基金项目:国家973 计划前期研究专项-大型海岸沉积体系的航运、土地资源和生物能源潜力,2006CB708410 号。 |
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| A GEOMETRIC MODEL FOR OYSTER REEF EVOLUTION OFF SOUTHERN JIANGSU COAST, CHINA |
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CHEN Yun-Zhen, GAO Shu
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Key Laboratory of Coast & Island Development of Ministry of Education, Nanjing University
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| Abstract: |
| Oyster reefs are coastal habitats with important ecological benefits and record rich information in sedimentary history and environmental change. An oyster reef evolution model is proposed in the principle of carbonate sequence stratigraphy. The model contains four modules: sea level curve, top layer elevation of clastic sediments, reef vertical growth rate, and the elevation of the reef top. A carbonate production rate function is modified to calculate the oyster reef growth rate under specific conditions, and the input parameters are derived by sedimentary environment analysis and geomorphological comparison. The model was applied in the Xiaomiaohong oyster reef off the Jiangsu coast, China, and the colonization, development and burial of the reef were investigated. The model output shows that the water depth above the reef and the estuarine environment controlled the evolution of the reef, with a maximum vertical growth rate of about 13.5 mm/a. At the initial stage, the reef growth was dominated by straight up-building; after the reef emerged above the mean low tide on springs about 910 years ago, lateral expanding took place. 330 years ago, the area of the reef above the mean low tide on springs reached the maximum. At the present, the reef growth becomes extremely slow, and it will stop
growing in 250 years due to clastic accumulation. The model also shows that the evolution of the oyster reef was influenced by multiple factors, such as temperature, salinity, and sea level fluctuation, ground subsidence, clastic material deposition, and suspended sediment concentration. In terms of geology, the top layer of a reef should be an indicator of being below an ancient sea level, but the exact position of the sea level.
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| Key words: Oyster reef evolution, Growth rate function, Sedimentary sequence, Geometric model, Jiangsu coast |
