台灣南灣地區微孔珊瑚微構造之應用

Abstract

Coral has been one of the best materials to study climate change. Researchers use the variations of trace elements and stable isotopes in coral skeletons to reconstruct environment at the time of its deposition. However, the coral growth is not always in the same direction due to environmental changes or unknown reasons. It, thus, has problem for climatic changes by slicing coral samples along the major axis of growth. That is why we need to check the micro-structure of coral skeletons for further study. In this study, we collected Porites sp. coral which has completed slicing subsamples along the major axis of growth from the Nanwan bay, Taiwan. Then, we use the scanning electron microscope (SEM) to get secondary electron (SE) and backscattered electron (BSE) images. Comparing the images of X-ray, SE and BSE, we found that the growth direction of coral is quite different to the major axis of growth. It means that there were some problems in the samples sliced along the major axis of growth currently. On the other hand, we found low density bands in the X-ray and BSE images, and it is well correlated to anomalous Ba/Ca ratios. Accordingly, low density bands in Porites sp. coral from the Nanwan bay seems to be likely originated by coral mass spawning. Therefore, we use those low density bands to construct age model in advance. Further, we use dissepiments which are the skeletal structure in coral to push time resolution scale to monthly. Therefore, using the micro-structures of coral can avoid the problem which growth direction of coral change, and can construct age model more accurately.