中国中奥陶世岩相古地理

本文是中国早、中、晚寒武世和早奥陶世岩相古地理诸文的继续。在笔者等的华北地区、华南地区和西北地区寒武纪和奥陶纪定量岩相古地理研究及编图成果的基础上,结合其他地区（主要是蒙兴地区、昆仑秦岭地区、西藏地区、海南岛地区和台湾地区）的地质资料,编制出了中国中奥陶世岩相古地理图,并撰写出本文。华北地区、华南地区和西北地区的研究程度较高,其岩相古地理图和文字论述都是定量的。其他地区的研究程度较低,其岩相古地理图和相应的文字论述则是定性的和概略性的。中国中奥陶世岩相古地理的基本格局仍和早奥陶世的一样为“两槽和三台相间分布”。两槽即天山北山蒙辽吉槽地和昆仑秦岭槽地,三台即准噶尔蒙兴台地、塔里木柴达木华北台地和西藏华南台地。但是这些古地理单元及其次级古地理单元的特征却与早奥陶世的有所不同或大不相同。

LITHOFACIES PALAEOGEOGRAPHY OF THE MIDDLE ORDOVICIAN IN CHINA

This paper is a continuation from a series of papers on lithofacies palaeogeography of the Early,Middle and Late Cambrian and Early Ordovician in China. It is based on the present writers' achievements of study and mapping of quantitative lithofacies palaeogeography of the Cambrian and Ordovician in North China,South China and Northwest China. On such a basis,in combination with the geological data of other areas,mainly Mongolia-Xinganling,Kunlun-Qinling,Tibet,Hainan Island and Taiwan areas,through comprehensive analysis and judgment,the lithofacies palaeogeography map of the Middle Ordovician in China is compiled and this paper is completed. In this paper,the lithofacies palaeogeography in North China,South China and Northwest China is quantitative and the description is in detail,while the lithofacies palaeogeography in other areas is qualitative and the description is general. In the Middle Ordovician,the lithofacies palaeogeography framework of two troughs alternating with three platformsin the Early,Middle and Late Cambrian and Early Ordovician was unchanged. The two troughs are Tianshan-Beishan-Mongolia-Liaoning-Jilin Trough and Kunlun-Qinling Trough. The three platforms are Junggar-Mongolia-Xinganling Platform,Tarim-Qaidam-North China Platform and Tibet-South China Platform. The scopes of these palaeogeographic units in the Middle Ordovician are basically the same as those in the Early,Middle and Late Cambrian and Early Ordovician,but the characteristics of their second-rank palaeogeographic units are different from those.