辽宁本溪牛毛岭石炭系本溪组腕足动物群落及其古环境意义

Brachiopod communities from the Benxi Formation of Carboniferous at Niumaoling in Benxi City of Liaoning Province and their palaeoenvironmental significance

通过对本溪牛毛岭石炭系本溪组底栖生物群落的组成结构和个体生态研究,详细探讨了各群落的古环境意义;结合剖面沉积相和沉积旋回分析,探讨了相对海平面变化对群落取代的影响。本溪组上、下段沉积时期主要受潮汐作用影响,而中段沉积时期河流作用明显。辽宁本溪地区本溪期底栖生物群落的生态位主要集中在BA1—BA3之间,即潮间、潮上带到潮下浅海环境,沉积最大水深一般不超过60 m。古水深是控制各环境因素变化的重要原因,也是控制群落取代的根本原因。在水深变化不大的情况下,底质环境、海水含盐度、水动力强度等对群落的内部演替和群落之间的相互取代都具有重要影响。底栖生物群落生态位变化和剖面沉积相分析所揭示的海水深度的垂向变化规律,显示该区石炭纪本溪期经历了4次明显的三级相对海平面变化旋回。与华北其他地区相比,本区本溪期多了一次海平面变化旋回,显示该区本溪期海侵较早,该区下部旋回发育时,华北其他地区尚未接受沉积。

According to the section measured and fossils collected for the Benxi Formation of Carboniferous at the Niumaoling site of Benxi city of Liaoning Province, the autoecology and the textures of the benthic communities are analyzed in detail and the palaeoenvironmental significance of the communities is discussed. Meanwhile, combined with the analyses of sedimentary facies and depositional cycles of the section, the influence of the relative sea level changes to the replacement of the communities has also been studied. The results show that （ 1 ） The lower and upper members of the Benxi Formation were mainly controlled by tidal action while they were deposited, but the middle member was influenced mainly by river action; （2）The ecological positions of the benthic communities of the Benxi Formation were mainly distributed between BA1 to BA3, which were located in the eulittoral zone with the water depth being not more than 60 meters; （3） The water depth played a very important role in the change of environmental factors, and it controlled the replacement of the communities. In the case of little change in water depth, the substratum, water salinity and hydropower conditions played a key role in the internal succession within a community and the replacement between two communities; （4） During four cycles of relative sea level changes could be community palaeoecology. There was one more cycl indicates that the transgression of Carboniferous in the deposition of the Benxi Formation of Carboniferous, identified based on the study of sedimentary facies and e than that found in the other part of North China, which the study area occurred earlier.