Study On Archaeocyaths From The Shuijingtuo Formation (Series2), Lower Cambrian Of The Three Gorges Area, Hubei Province

The horizon of Precambrian-Cambrian in Yichang, Hubei Province, is well developed and well-exposed, the classic section of the domestic and international Ediacaran-Cambrian located on this area. The study on Small Shelly Fossils of Yanjiahe Formation, Meishucunian (or the same period) in the area were on higher level. However, the research of fossil in the overlying strata is very weak. During graduate school the auther have measured seven Precambrian-Cambrian sections in Changyang and Yichang of Hubei Province, and sampling from these sections several times. These samples were acid digested indoor. After that, we found many shelly fossils from upper part of Shuijingtuo Formation in the Aijiahe section. Of particular importance is that we collected several exquisitely preserved body fossils of archaeocyatha among these shelly fossils. which with the style to save the beautiful ancient cup fossils found in these shell fossils. Preliminary study can be classified these archaeocyathas as2genera and2indeterminate species (Robustocyathellus. Sp. and Rotundocyathus.sp.). On the basis of the advisors earlier work in the area, auther chose the arcaeocyatha to be the research object of master’s thesis.The early study showed that the oldest archaeocyatha fossils in Yichang were in the upper part of the Tianheban Formation of lower Cambrian. Therefore, the discovery of archaeocyatha fossils in Shuijingtuo Formation not only makes the first appearance of archaeocyatha in Yichang much earlier, but also composed the evolutionary sequence with the archaeocyatha from the Tianheban Formation. It is worth mentioning is that the technidues of study on archaeocyatha was different from the traditional thin sectioning. We collected many three-dimensional preservation scleritome of archaeocyatha. These fossils provied special material can make us get a chance to multi-angle know the animal’s internal anatomy, and obtain new information to understand the life style and structure and secretion of skeleton of archaeocyatha.The primary content of the thesis gave an detailed discreption of the archaeocyatha fossils, and try to give a comprehensive and objective characteristic of them, to provide material for further classification and structure research of archaeocyatha.The traditional view that the fundamental skeleton of archaeocyatha is innerwall,outerwall and septum, the central cavity and intersept are hollow. The skeleton structure of archaeocyatha that author collected from Shuijingtuo Formation were different from the traditional view. After the scanning electron microscope imaging, we found:the intersept and central cavity were solid, the spaces between two intersept and the spaces between central cavity and innerwall were hollow. The gap of these spaces were20μm. Energy spectrum analysis on these fossils showed that the composition of these fossils is siliceous calcium phosphate, the siliceous content of substance in the central cavity and in the intersept were higher than that of the outerwall and septa. The intersept and central cavity were filling By Silicon matieral, and metasomatosis occurred during the process of preservation.During the research on archaeocyatha, the auther found many microborings on the surface of skeleton of archaeocyatha, some of these microborings were with microbes in it. I also study on these microborings and microbes.