Secular fluctuations in reef ecosystems during the Middle Palaeozoic to earliest Mesozoic interval : integration of metazoan and microbial reefal changes

点击翻译按钮获取中文摘要

1.Firstly, this research project has focused on lithofacies, depositional facies, and biofacies of Permian and Triassic transitional beds, as well as lowest Triassic (the Hindeodus parvus Zone) beds, along the southern periphery of the Yangtze Platform. Chief results are as follows :(1)The Permian/Triassic boundary is unconformable, based on detailed lithologic and biostratigraphic evidence.(2)The lowest Triassic is characterized by intercalations of thrombolites that exhibit characteristic microscopic to megascopic features. Irrespective of the region studied, variations in mesoscopic texture and macroscopic structure are common in thrombolites.(3)The initiation and cessation of thrombolite formation show a common pattern in the individual sections measured. This pattern is especially marked with respect to : 1)the nature of the Permian/Triassic stratigraphic contact ; 2)variations in texture and structure of thrombolites ; and 3)modes of occurrence of thrombolites, together with fluc … More tuations in ocean conditions after the end-Permian collapse of metazoan reef ecosystems.2.Secondly, the genesis of Lower Devonian metazoan and microbial reefs in N.S.W., Australia, was elucidated in terms of the infilling patterns of microbialites within microenvironments that were created during specific stages of stromatoporoid growth. Continuously modified cryptic spaces are utilized by a variety of microbial communities and their growth products.3.Thirdly, growth plasticity in the Rugosa, one of the most important Palaeozoic metazoan groups, was considered in relation to the regularity of asexual reproduction and the flexibility of growth modes.In order to decipher the true nature of reef ecosystems during the Middle Palaeozoic to earliest Mesozoic interval, special attention should be paid to the geobiological interrelationships between individual metazoans and microbes, as well as to their modifications through time.Some of the results noted above have been presented in academic journals and at meetings of the Geological Society of Japan, the Palaeontological Society of Japan, and others. Less