晋中南地区上石炭统-下二叠统太原组碳酸盐岩中遗迹组构及其沉积环境

晋中南地区上石炭统-下二叠统太原组是一套海陆交互相含煤地层,其中碳酸盐岩中发育丰富的遗迹化石。通过对山西太原西山和陵川附城一带露头剖面遗迹化石的详细观察、鉴定与分析,共识别出10个遗迹属、14个遗迹种,其生态类型包括进食迹10种、觅食迹和居住迹各2种。基于各灰岩层中遗迹化石的组成、产状、大小、潜穴充填物的成分及颜色、宿主岩的岩性等特征,建立了4种遗迹组构及其沉积环境分布模式:类型A:大型Zoophycos-Thalassinoides遗迹组构,出现于海湾(潟湖)及潮坪沉积环境;类型B:大型Zoophycos-Planolites遗迹组构,发育在海平面至正常天气浪基面附近区域的浅海上部沉积环境或水体浅且较平静的局限碳酸盐岩台地环境;类型C:中型Zoophycos-Teichichnus遗迹组构,主要产生在正常天气浪基面之下、风暴浪基面之上的浅海中部沉积环境;类型D:小型Zoophycos-Chondrites遗迹组构,形成于风暴浪基面之下、水体较深且贫氧的浅海下部沉积环境。这一成果可以为精细研究本区太原组的沉积环境变迁史提供重要的生物学信息,也可为煤与煤层气的生成环境提供生物学记录方面的科学依据。

Ichnofabrics and Their Sedimentary Environments in Carbonate Rocks of the Upper Carboniferous-Lower Permian Taiyuan Formation in Middle South Shanxi Province

The Upper Carboniferous-Lower Permian Taiyuan Formation in the middle-south Shanxi province is a set of coal-bearing formation with marine-terrigenous facies. Abundant ichnofossils are discovered in carbonate rocks of this formation.10 ichnogena and 14 ichnospecies has been recognized and described from the observation of the outcrop sections in Xishan area of Taiyuan city and near Fucheng of Lingchuan county, which include Fodinichnia(10 ichnospecies), Pascichnia(2 ichnospecies) and Domichnia(2 ichnospecies) according to the ethological classification. Based on the composition, occurrence and size of ichnofossils as well as the components and color of burrow filling, and combined with lithologic characteristics of host rock, four types of ichnofabrics and their sedimentary environment model can be established, i.e., Type A, the large-sized Zoophycos-Thalassinoides ichnofabric, which is formed in restricted bay or lagoon sedimentary environment; Type B, the large-sized Zoophycos-Planolites ichnofabric, which occurrs in the upper shallow marine environment between sea level and fair-weather wave base or restricted carbonate platform environment with shallow and relatively calm water body; Type C, medium-sized Zoophycos-Teichichnus ichnofabric, which is generated in middle shallow sea between fair-weather wave base and storm wave base; Type D, small sized Zoophycos-Chondrites ichnofabric, which is developed in the lower zone of shallow sea below the storm wave base, showing the low oxygen and deeper water environment. The result will provide biologic information in order for the detailed studies on sedimentary environmental evolution of the Taiyuan Formation and can also provide scientific evidence for the study of coal and coalbed gas formation palaeoenvironment in this area.