南海北部滨珊瑚微结构的SEM分析及其对气候记录重建的意义

造礁珊瑚是重建高分辨率的古气候变化记录的理想载体,而珊瑚骨骼的微结构反映珊瑚的生长特征,了解珊瑚的微结构有助于更好地理解珊瑚的古气候记录。利用扫描电镜分析了南海北部三亚和北海一些中全新世及现代滨珊瑚的微结构。在低放大倍数下(<1000倍)观察到珊瑚单体、隔壁、隔壁齿、孔洞、隔膜、共骨、横梁等结构。在高放大倍数下(≥ 1000倍)观察到具有鹅卵石状、蔟状、柱状及针状4种文石晶体的基本类型及文石晶体组成的钙化中心、隔膜等结构。根据这些基本微结构变化特征,可以清楚分辨出珊瑚死亡一恢复生长界线,并可观察到珊瑚的文石晶体是否受到后期蚀变的影响,例如充填、重结晶等。在所分析的三亚、北海滨珊瑚样品中,冬季最冷及夏季最热时期均没有发现死亡一恢复生长界线,指示持续生长的方式。经过测量,珊瑚隔膜横向延展形成的纹层生长时间约为一个月,这对于利用微区分析建立精细的超过月分辨率的气候记录具有重要意义。微结构显示北海地区的老珊瑚暗层具有较多的杂质充填,结合氧同位素地球化学记录的变化特征,可以发现这些暗层形成于夏季,受高温以及海水强烈扰动而导致生长速率减缓所致。

SEM STUDIES ON THE MICROSTRUCTURE OF PORITES CORAL FROM THE NORTHERN SOUTH CHINA SEA:IMPLICATIONS FOR PALEOCLIMATE RECORD RECONSTRUCTION

Reef corals are perfect materials for reconstructing high-resolution paleoclimate records. The microstructures of reef coral provide detail information of their growth, and are very important for us to understand the paleoclimate records reconstructed on corals. In this paper, we analyze the microstructures of some modern and mid-Holocene Porites corals from Beihai and Sanya in the northern South China Sea using Scanning Electron Microscope (SEM) method, and seek for microstructures that can be used for paleoclimate reconstructi septa, spine, pore, di types of aragonite crys on. The microstructures observed at ssepiment, coenosteum and synapticu tals(shingle, cluster, pillar and needle low magnification (Porites corals may grow continuously through the whole year in these two regions. However, several death-growth recovering boundaries were found and recovery events for Porites extremes may account for them. and measuring distance between in some modern Porites corals from Beihai, indicating several extinction corals in recent years in this region. Some other factors rather than SST By counting on the numbers of dissepiments within annual growth bands dissepiments, we found that the time for concreting materials between two dissepiments was about one month. Therefore, the dissepiments in Porites may indicate monthly bands, which is valuable for reconstructing paleoclimate records of higher-resolution. Extraneous materials were found to fill in the dark bands of some fossil Porites corals from Beihai. Coupled with the X-ray microstructures and oxygen isotopes, the high-density bands.