摘要
由于地质历史时期环境多变,同一深度带生境未必均一,加之生物自身对各环境因素的适应能力各不相同,因而各底栖组合的界线应有一定限度的变化范围。在正常情况下,每个底栖组合一般都有明确的岩性、岩相和生物群标志。研究者可以通过综合研究群落的组成、特征、埋藏特点和围岩特点等,确定每个群落所属的底栖生态位。生境的含氧性和构造环境等因素也可使底栖组合的正常分布受到干扰。
The benthic assemblage was suggested by Boucot (1975) to be based on five depth-relatedcommunities as described by Zigler in 1965 from Silurian rocks in the Welsh Borederland and Wales.The following questions are discussed in this paper. 1. The boundary of two neihgbouring benthic assemblages is not always constant. There is a limit-ed narrow band of overlap which depends on the pelaeogeographical, palaeoenvironmental conditionsand the pettern of faunal distribution at the given time and locality. 2. Scope of each benthic assemblage: There is a definite area in which each benthic assemblage canbe correlated with facies belts of sedimentation generally. Of course, some facies belts can overlap. 3. Some kinds of sedimentary rocks, structures, texture and communities fauna even genera can beused as markers for assigning a community to the benthic assemblage, such as: Colites, shellbeds, reef,various body and trace fossils. 4. The normal depth gradient of marine faunas can be obscured by oxygenation level of the bot-tom water. Of course, it is true that the deeper the water, the lower the oxygenation level. But in plat-form areas, the oxygenation level of bottom water should be normal for all benthic fauna in general.Thus, more attention must be paid to some benthic communities inhabiting the shallow water,dysaero-bic even anerobic environments. There are actually some deepwater basins on shore or in shelf areas caused by geologic structureconditions. At least BA4 may be occasionally placed in the shelf platform, or behind the barrier islandzone.
基金
国家自然科学基金
关键词
地层
底栖生物
古环境
古生物学
community
benthic assemblage
ecostratigraphy
palaeontology and palaeoenvironment
