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多元统计及物源分析支持的北部湾东部海域沉积物输运趋势
Sediment transport patterns in Eastern Beibu Gulf based on grain-size multivariate statistics and provenance analysis
投稿时间:2009-04-13  修订日期:2009-11-25
DOI:
中文关键词:  粒度  重矿物  多元统计  粒径趋势分析  北部湾
英文关键词:grain size  heavy mineral  multivariate statistics  grain size trend analysis  Beibu Gulf
基金项目:
作者单位邮编
徐志伟* 南京大学 210093
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中文摘要:
      通过对北部湾东部海域表层底质样的粒度和重矿物分析,获得了其粒度参数与矿物组成特征。对粒度信息进行多元统计分析,其中聚类分析结果反映了沉积物粒度特征差异,将研究区底质分为7种沉积物类型,可用于该海域沉积物的底质类型分区;因子分析获得4个主控因子,分别代表了4种粒级区间(2.5~3.75和5.75~7.75、8.5~11.5、4.25~5.25),反映的粒度变化范围清晰并且因子得分的空间分布可指示沉积环境(物源特征、水动力条件)的空间分异特征。在使用粒径趋势分析模型获取沉积物净输运方向时,不能忽略物源差异对沉积物粒径趋势的影响,特别是在空间尺度较大、物源复杂的沉积环境下。重矿物分析结果表明,北部湾东部海域表层沉积物的物质来源可划为4个分区;分别对四个物源分区使用粒径趋势分析模型,合并后可获得整个研究区的更符合实际情况的趋势矢量,其中海湾北部沉积物输运汇聚中心的位置与余环流的中心位置基本一致。通过对表层沉积物粒度信息的多元统计和重矿物分析,可发现有的海区存在多物源混合的情形,其空间粒度分布的差异也可形成特定的粒径趋势,而这种趋势是否指示真实的沉积物净输运方向是有疑问的,尚需其他证据的进一步支持。因此,综合考虑水动力环境、物质来源和粒径趋势获得的沉积物净输运概图可更好地反映大尺度沉积系统的物质输运特征。
英文摘要:
      Sediment samples were collected from Beibu Gulf in July and Augest, 2006, and then analyzed in the laboratory to obtain grain size distributions and mineral components. Multi-variable analysis on grain size shows that Q-clustering results can distinguish the diversity of grain size characteristics and can be used to show the distribution pattern of sediment types. Four main control factors are obtained clearly by using factor analysis, which represent 4 grain-size fractions(2.5~3.75&5.75~7.75,8.5~11.5, 4.25~5.25). Score distribution of each factor is related with sedimentary environment (provenance character and dynamic condition). Sediment source character and dynamic condition of sedimentary system should be both included when using grain-size data to indicate sedimentary environment. Mixing of materials from different sources makes responsible for the formation of grain-size trends. Thus, grain size trend vector should be used carefully to define sediment transport pathways when multi-sources are present. Especially in a large dimension area, grain size trends reveal a cumulate impression that responses to long time period of sediment transport and deposit processes, which contains complex superposition information of sediment provenance and sedimentary dynamic condition. Then, the whole area are seprated into 4 sub-area due to the sediment sources on the basis of heavy mineral analysis. The grain size trend analysis model are used for the 4 sub-areas to obtain the whole sediment transport pattern in the bay. It shows that in the northern gulf there is a converge center of sediment transport, which is well agreement with the geomorphological structure, large scale of ocean circulation current and sediment provenance. Accumulation of muddy sediment here is the result of sedimentary dynamic condition and sediment source. The formation of grain-size trend vectors in the area west to Hainan Island may result from sedimentary dynamic selective transport combined with mixing of material derived from different sources. It is uncertainty on the sediment transport pattern in this area; further study are required in the futrue. Hence, sketch map based on general consideration of dynamic condition, sediment provenance and grain size trends may produce a reasonable sediment transport patterns.
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