中国晚泥盆世晚期“阶”和“亚阶”的划分与对比

On the subdivision and correlation of late Upper Devonian Stages and Substages in China

简要回顾了中国晚泥盆世晚期地层"阶"和"亚阶"划分的历史沿革,阐述了划分的基本原则,即在全球性或大区域性关键地质事件和生物进化事件研究的基础上,"阶"和"亚阶"的底界应置于地质事件之后某一或某些主导生物门类谱系演化的分支点上,且以主导生物门类的某一新分子在谱系中首次出现来定义。根据地层的分布和发育特征,拟将中国晚泥盆世晚期地层分为2阶:锡矿山阶和邵东阶。锡矿山阶可分为冷水江亚阶(亚阶I)和新化亚阶(亚阶II),邵东阶又可分为邵阳亚阶(亚阶III)和新邵亚阶(亚阶IV)。冷水江亚阶的底界与锡矿山阶的底界相一致,也与国际上法门阶的底界相一致,以牙形类Palmatolepis triangularis的首次出现为标志;新化亚阶的底界以牙形类Palmatolepis rhomboidea的首次出现为标志;邵阳亚阶的底界与锡矿山阶的顶界和邵东阶的底界相一致,以牙形类Palmatolepis rugosa trachytera的首次出现为标志;新邵亚阶的底界以牙形类Bispathodus aculeatus的首次出现为标志,顶界与邵东阶的顶界相一致,也与国际泥盆系—石炭系界线一致,以牙形类Siphonodella sulcata的首次出现为标志。

This paper introduces the research history of late Late Devonian stages and substages in China and the basic principles of their subdivision. On the basis of the studies on global and regional critical geo- and bio-events, the basal boundaries should be placed at the stratigraphic levels above the event beds and defined by the first appearance of new elements within the phylogenetic lineages of one or some leading taxa. The stratigraphic development and distribution of Upper Devonian in China suggest that, the late Upper Devo- nian in China can be divided into two stages： the Xikuangshanian Stage （lower） and the Shaodongian Stage （upper）. The Xikuangs- hanian Stage can be subdivided into two substages： the Lengshuijiangian Substage and the Xinhuaian Substage, and the Shaodongian Stage can be subdivided into two substages ： the Shaoyangian Substage and the Xinshaoian Substage. The lower boundary of the Leng- shuijiangian Substage corresponds to that of the Xikuangshanian Stage, and also agrees with the lower boundary of the intemational Fa- mennian Stage, which is defined by the first appearance of Palmatolepis triangularis （conodonts）. The lower boundary of the Xinhuaian Substage is marked by the first appearance of Palmatolepis rhomboidea （conodonts）. The lower boundary of the Shaoyangian Substage corresponds to the upper boundary of the Xikuangshanian Stage and the basal boundary of the Shaodongian Stage, and is characterized by the first appearance of Palmatolepis rugosa trachytera （conodonts）. The lower boundary of the Xinshaoian Substage is recognized by the first appearance of Bispathodus aculeatus （conodonts）, and its upper boundary corresponding to that of the Shaodongian Stage, also consistent with the international Devonian-Carboniferous boundary, is defined by the first appearance of Sihonodella sulcata （conodonts）.