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Paleoecological research on Carboniferous corals from the Akiyoshi Limestone

秋吉石灰岩石炭纪珊瑚的古生态学研究

基本信息

批准号：
06640604
负责人：
SUGIYAMA Tetsuo
金额：
$ 1.22万
依托单位：
Fukuoka University
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (C)
财政年份：
1994
资助国家：
日本
起止时间：
1994 至 1995
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-06640604/
关键词：
Akiyoshi Limestone Carboniferous Coral fauna Paleoecology Growth form Organic reef complex Framework 古環境

项目摘要

The investigators carried out field researches in the Maruyama Quarry and the Minami-dai Quarry in the Nishino-dai area of the Akiyoshi Limestone. About 700 thin sections of limestones and coral materials and 30 sheets of limestone slabs have been prepared and analyzed for the investigations on paleoecology and growth forms of reef building organisms. The results are as below :1. Well-preserved reef facies zonation : lagoon facies zone, reef core facies zone, and fore reef slope facies zone, was recognized in the lower Upper Carboniferous part of the Minamidai area, based on distribution of the limestone rock types, the size and density of the reef frameworks, and growth forms of the frame-builders. The reef core facies zone was divided into five subfacies zones.2. Among the subfacies zones, the reef front subfacies zone is characterized by the highest density of the reef-building organisms which have various growth forms. The relationships between basal planes of discoidal coral colonies and geopetal planes were confirmed that the reef slope was inclined about 30 to 40 degrees from the sea level.3. The main reef builders in the early Late Carboniferous limestones fo the Akiyoshi Organic Reef Complex are rugose corals, Chaetetes, calcareous blue-green algae, tabulate corals, bryozoans, and encrusting foraminifers. Their distributions and various assemblages in the organic reef complex are discriminated. They have different growth forms and functional roles in the reef frameworks of the diffrent micro-environments, even in organisms belonging to the same taxon.4. The Carboniferous part of the Akiyoshi Limestone includes paleokarst deposits, providing evidence of aerial exposure during regressive events. Some of transitional intervals between coral faunas coincide with these regressive events.

调查人员在秋吉石灰岩西野代地区的丸山采石场和南代采石场进行了实地研究。为研究造礁生物的古生态和生长形式，制备和分析了石灰岩和珊瑚材料的薄片约700片，石灰岩板片约30片。结果如下：1。根据灰岩类型的分布、礁格架的大小和密度以及礁格架构建物的生长形式，在米米代地区上石炭统下段确定了保存完好的礁湖相带、礁核相带和礁前斜坡相带。礁核相带划分为5个亚相带。在各亚相带中，礁前亚相带的造礁生物密度最高，生长形式多样。盘状珊瑚群基面与顶面的关系证实了礁坡与海平面的倾斜度约为30 ~ 40度。秋吉有机礁杂群晚石炭世早期灰岩中主要的造礁生物是褶皱珊瑚、毛纲、钙质蓝绿藻、表状珊瑚、苔藓虫和包壳有孔虫。区分了它们在生物礁复合体中的分布和各种组合。它们在不同微环境的礁架中具有不同的生长形式和功能作用，即使在属于同一分类的生物中也是如此。秋吉灰岩石炭纪部分包括古岩溶矿床，提供了在退变事件期间空气暴露的证据。珊瑚群之间的一些过渡间隔与这些退化事件相吻合。