南海珊瑚砂砾屑灰岩磷质胶结物的数字影像分析及其环境意义  

DIGITAL IMAGE ANALYSIS OF PHOSPHATIC CEMENTATION OF CORAL CALCARRENITE IN THE SOUTH CHINA SEA AND ITS ENVIRONMENTAL IMPLICATIONS

作　　者：赵三平[1] 袁仁民[1] 孙立广[1] 刘晓东[1] 谢周清[1] 刘克新[2] 吴小红[3] 

机构地区：[1]中国科学技术大学地球与空间科学学院,合肥230026 [2]北京大学重离子物理教育部重点实验室,北京100871 [3]北京大学考古文博学院第四纪年代测定实验室,北京100871

出　　处：《海洋地质与第四纪地质》2007年第1期147-153,共7页Marine Geology & Quaternary Geology

基　　金：国家自然科学基金项目(40231002)

摘　　要：应用计算机数字影像学原理，建立了对磷质胶结微细纹层研究的数值化方法，研究了西沙东岛珊瑚砂砾屑灰岩磷质胶结物的胶结结构和微纹层特征，定量地刻画了微条纹的宽度和颜色变化信息。东岛珊瑚砂砾屑灰岩磷质胶结物的形成以沉淀胶结为主，不同时期形成的胶结物微条纹系列，由于受到气候、生态因素的影响，具有不同的宽度、明暗度组合；对3个层次磷质胶结物的分析表明，在2900～5700aBP西沙群岛东岛存在至少3次鸟类和植物的繁盛期；不同时期微纹层的气候、生态记录对比发现，相对稳定的气候条件有利于岛屿海鸟数量的扩大；提供了一种新的方法来探索岛屿鸟粪磷质胶结物的结构和生态环境意义。A digitization method was established using the principles of digital image to study the microlaminae and textures of the guano phosphatic cementation of coral calcarrenite. By this high-resolution method, some characters of the microlaminaes such as width, brightness and color were described and analyzed quantificationally. The results showed that the deposition of guano-derived phosphate onto the surface of carbonate bioclasts layer by layer might have been controlled by the cementation process of the coral calcarrenite. The digital characteristics for the phosphatic cements of three sedimentation layers indicated that the cemented time of coral calcarrenite was obviously different, and at least three episodes could be distinguished. Since the phosphate cementation on the surface of coral calcarrenite was closely associated with the superficial coating of avian guano on this island, the cementation processes with different times implied that there were at least three flourish periods of seabird population and vegetation distribution on the Dongdao Island between 2 900 and 5 700 aBP. Furthermore, the phosphate cements formed at different stages had different digital character assemblages of microlaminae width and brightness which might have recorded the continuous information of historical climate and ecology change. Comparing the change curves of seabird population and the climate on Dongdao Island at three stages of 2 900 aBP, 5 000 aBP and 5 700 aBP, we can find that the relatively stable climate condition might be advantageous for the increase of seabird population. This paper provides a new approach to studying the texture characteristics of guano phosphate cements found in numerous islands of tropical regions and their eco-environmental implications.

关 键 词：磷质胶结 微纹层 数字影像学 西沙群岛东岛 

分 类 号：P585[天文地球—岩石学]