【作者】 刘治帅；

【导师】 汪亚平；

【作者基本信息】 南京大学 ， 海洋地质， 2012， 硕士

【摘要】 本文以厦门海域的沉积物空间分布特征以及对沉积环境的响应为研究目标,通过分析表层沉积物的粒度来探讨空间分布特征以及与沉积环境之间的关系,对沉积物进行了沉积物的类型以及输运趋势和物质来源的综合分析；采用沉积学以及210Pb测年方法,对沉积物的柱状样品进行粒度、敏感组分、沉积速率分析,结合潮周期尺度的沉积动力学现场观测,进一步探讨了物质来源以及海洋沉积环境的互相作用,为沉积环境的判别提供依据。结合前人及本文的研究发现,研究区域表层沉积物种类较多,以粉砂质砂以及砂质粉砂为主,九龙江口海域颗粒较粗,同安湾颗粒较细,翔安南部以及厦门岛东部海域介于前两者之间,而大、小金门岛的沉积物种类较多、分布格局比较复杂。其中较粗的(<0.65φ)、分选较好的(<2)的沉积物主要分布于九龙江口内。运用Gao-Collins模型计算研究区的沉积物净输运趋势,发现九龙江口的海底沉积物向东南净输运,大金门南侧海域沉积物有向九龙江口输运的趋势,厦门湾的沉积物则和来自外海(台湾海峡)的物质在厦门西南侧汇集。同安湾沉积物由海岸向湾中央输运,厦门东部海域有向北的输运趋势,翔安南部海域沉积物输运方向向同安湾口以及澳头岸边输移。对九龙江区域进行潮周期的水动力观测数据表明,区域属于正规半日潮,往复流,落潮流速大于涨潮流速,观测期间,水深变化范围5.87m-11.52m,温度变化范围16℃-17.95℃,盐度变化范围21-28,悬沙浓度随流速的增大而增大,再悬浮现象较为显著。对九龙江地区获取的柱状样作沉积物粒度敏感组分分析,其结果显示了标准偏差随粒级组分变化的规律曲线呈现出“双峰分布”,其峰值分别对应于两个环境敏感粒度组分,分布范围分别在5.0～10.2gm和136.8～193.4μm之间,其最大值分别为7.18,162.67μm,前者为粘土质粉砂,代表悬移质组份,来源可能包括了流域来沙和外海输入；后者为粉砂质砂,代表推移质组份,主要来自于上游流域。对柱状岩心进行放射性同位素210Pb测年分析,九龙江附近的柱状样测得沉积速率为2.62cm/a。综合前人的研究结果发现,研究区域的沉积速率近年来有增大的趋势。此外,九龙江区域整体的沉积速率要高于同安湾,厦门外港总体上要高于九龙江口附近。研究区的物源主要来自于九龙江流域,前述粗颗粒敏感组份即代表此物源。此外,还有来自台湾海峡的物质,主要以悬移质为主。上述物源的推断与沉积物净输运趋势的空间格局相一致。此外,潮汐,波浪以及风暴潮导致研究区沉积物空间分布格局进行再分配、调整,从而对沉积环境的变化产生重要影响。更多还原

【Abstract】 The present study investigated spatial distribution characteristics of sediment and the response to the depositional environment in the Xiamen sea. Particle size analysis of surface sediments were used to establishthe relationship between the spatial distribution characteristics and depositional environment.Thus, a variety of analyses wereused to obtain the type of sediment distribution pattern, net sediment transport trends and thesources.We also collectedthe coresamples to obtain thesediment grain size, sensitive components and deposition rate,according to the sediment dynamics and210Pb dating. Further, the interaction of the material sources and marine sedimentary environments are explored by the observation of tidal-cycle hydrodynamic process atthe study area.The previous and presentstudy suggestthatthe sediments of the study area are consist of various types, mainly silty sand and sandy silt. The sediment at Jiulong River Estuary isconsist of coarse particles,and that is medium grain size at the southernXiang’an and the eastern Xiamen Island area. The sediment around the Kinmen Island is muchcomplex. The coarse (<0.65φ) andwellsortedsediment (<2) is mainly observedin the Jiulong River Estuary.The Gao-Collins grain size model was applied to estimate the net sediment transport pathways in the study area. It suggests that the sediment transport southeastward in the Jiulong River Estuary, and towards this estuary from Dajinmen area. Marine sediments of Xiamen Bay transport from the ocean currents from the Taiwan Strait in the southwest of Xiamen. In addition, the sediment transport offshore to the central bay in Tonganwan area. The sediments transport towards north in the eastern Xiamen sea, and towards the mouth of Tonganwan and onshore of Aotou.The tidal-cycle hydrodynamicsmeasured atJiulong River Estuary show thatthe study area is regular semidiumaltide and reciprocating flow. The ebb is dominant during a tidal cycle.The water depth varied from5.87cm toll.52cm,temperature range is16℃-17.95℃,salinity varied from21to28,suspended sediment concentration increased with increasing velocity.Sensitive component of the sediment particle size is derived from the core samples collected at the Jiulong River Estuary. It shows that standard deviation curve of the grain size fraction has a bimodal distribution pattern. It represents two environmentally sensitive components,with the ranges5.0～10.2μm and136.8～193.4μm, and the peaks7.18μm and162.67μm, respectively. The former is clayey silt, representative suspended quality components, the sources may include the input of the basin to sand and offshore,while the latter is silty sand, on behalf of the bedload component, mainly from the upper basin.The sediment core was analyzed by using210Pb dating method, and showed that the deposition rate was2.62cm/a in the Jiulong River Estuary. Thereis an increasing trend in deposition rate in recent. In addition,the deposition rate atthe Jiulong River Estuaryas a whole is higher than that at Tongan Bay,while theXiamen is higher than the Jiulong River Estuary. The sedimentin the study area comesmainlyfrom the Jiulong River watershed, and also from the Taiwan Strait,which is consistent with the net sediment transport trends.Additionally,Tidal, wave and storm surge leada complex distribution pattern of sediments in the study area, and thus induceimpacts on the depositional environment.更多还原