湖北崇阳二叠纪-三叠纪之交钙质微生物岩的时代及基本特征

湖北崇阳钙质微生物岩产在二叠纪末礁相绝灭界线之上, 绝灭界线之下即为晚二叠世长兴期的海绵礁灰岩、棘屑灰岩及藻有孔虫生物碎屑灰岩.微生物岩基本上由中粗晶-微晶方解石组成, 主要沉积构造有“花斑状构造”及藻叠层构造.目前微生物岩中发现的化石主要有球状菌藻类化石、介形虫、微型腹足、双壳、鱼牙及分类位置尚无法确定的棒状微型化石.微生物岩中已发现有牙形石化石: Hindeodusparvus, H.typicalis和H.latidentatus, 从牙形石的类型及产出层位分析, 崇阳钙质微生物岩的下部属于晚二叠世长兴期, 上部为早三叠世.崇阳微生物岩在沉积特征、生物组成及牙形石带上均基本可与华南其他地区已发现的微生物岩进行对比. 

Age and General Characteristics of Calcimicrobialite near the Permian-Triassic Boundary in Chongyang, Hubei Province

The microbialites of Chongyang in Hubei Province occur above the mass extinction line in the Late Permian reef facies. Below the boundary are the sponge reef limestone, crinoid limestone and alga-foraminifer bioclastic limestone of the Changxing Formation. The microbialites are generally composed of mid-coarse grains and microlite calcite with a structure of "graniphyic fabric" and stromatolite. The fossils discovered in the microbialites include globular cynobacteria, ostracods, micro-gastropods, bivalves, fish teeth and some problematical micro-fossils. Conodont fossils of Hindeodus parvus, H. typicalis and H. latidentatus were also found. According to the conodonts, microbialites spanned the Late Permian and Early Triassic in Chongyang. The upper part above the first occurrence of Hindeodus parvus should be attributed to the Early Triassic, and the low part to Changxingian. The sedimentary structure, fossil composition and conodont zonation of the Chongyang microbialites can be well correlated with the microbialites found in other areas of South China.