https://scholars.lib.ntu.edu.tw/handle/123456789/45127
標題: | 台灣西南部化石珊瑚礁的發育和衰退過程及其古海洋環境的研究(2/2) | 作者: | 戴昌鳳 | 關鍵字: | Cold seep carbonates;coral reef;foreland basin;lucinids;dolomites | 公開日期: | 2003 | 出版社: | 臺北市:國立臺灣大學海洋研究所 | 摘要: | Pleistocene scleractinian reefs in SW Taiwan developed on several local structural highs that were closely associated with anticlines and faults in a Plio-Pleistocene foreland basin. Lithological successions of these fossil reefs are characterized by rapid facies changes from the underlying mudstone foundations upward into fossiliferous mudstones, then into reef limestone lithofacies. This study investigated how these coral reefs were able to establish in an environment dominated by fine-grained siliciclastics. Detailed studies of 3 quarry outcrops and 44 borehole cores reveal 5 types of local pioneering sedimentation at or near the base of the carbonates: (1) mound-like dolomitic mudstones, (2) dolomitic lithoclasts, (3) dolomitic conglomerates, (4) chimney-like dolomitic tubes, and (5) plume-like dolomitic mudstones. Abundant in situ lucinid bivalves were found from one of the mound-like dolomitic mudstones, with the tops encrusted with coralline algae, then overlaid by bioclastic limestone. In addition, four types of facies changes from underlying mudstone upward into the bottom of the reefal limestone were recognized. These successions suggest that the mudstone substrates at many locations were firm ground or hardground before the development of coral reefs, and served as the substrate on which sessile organisms were able to colonize in a muddy environment. According to the co-occurrences of dolomitic mudstones and fossil lucinids, as well as the tectonic setting of the study area, it is suggested that cold seep carbonates developed during shallowing of the structural highs in SW Taiwan, and served as the hardground and carbonate factories for the initial development of coral reefs in the siliciclastic environment. The occurrences of dolomitic lithoclasts, muddy conglomerate, and scouring of the upper most mudstones mark an erosional event occurred on these structural highs. It suggests that these lithologies were formed and deposited as the result of gas hydrate degassing, which was possibly triggered by the impulsion of tectonic activities such as earthquakes. |
URI: | http://ntur.lib.ntu.edu.tw//handle/246246/14832 | 其他識別: | 912611M002022 | Rights: | 國立臺灣大學海洋研究所 |
顯示於: | 海洋研究所 |
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912611M002022.pdf | 274.82 kB | Adobe PDF | 檢視/開啟 |
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