中国南方中及晚奥陶世岩相古地理

LITHOFACIES PALAEOGEOGRAPHY OF THE MIDDLE AND LATE ORDOVICIAN IN SOUTH CHINA

中国南方是指西至金沙江—元江断裂、西北至龙门山断裂、北至城口—房县—襄樊—广济断裂、东北至郯城—庐江断裂、东至黄海和东海、南至南海的中国南方的广大地区 ,面积约 2 0 0万km2 。在露头剖面和钻井剖面的地层学和岩石学研究所取得的各种定量及定性资料的基础上 ,采用单因素分析综合作图法 ,编制出了中国南方中奥陶统胡乐阶 (庙坡阶 )和江阶 (宝塔阶 )以及上奥陶统石口阶 (临湘阶 )和五峰阶的各种单因素图以及相应的各世的岩相古地理图。在这些古地理图中 ,有 7个主要的古地理单元 ,即滇西台地、康滇陆、扬子台地、斜坡、江南盆地、东南台地和华夏陆。前 5个古地理单元属康滇古地理体系 ,后两个古地理单元属华夏古地理体系。这些古地理图的最大特征是定量 ,即每个古地理单元的划分和确定都有确切的定量的单因素图和数据为依据。这种定量的岩相古地理图在我国南方中及晚奥陶世还是首次出现。这种定量岩相古地理图在古地理学中是个重大的进展 ,对石油、天然气以及其他沉积矿产的预测和勘探有重要的指导作用。最后 ,对两个古地理体系和 7个主要古地理单元在整个寒武纪和奥陶纪各期或世的历史演化进行了较详细的探讨。

The South China in this paper refers to the broad region bounded on the west by the Jinshajiang River-Yuanjiang River Fracture, on the northwest by the Longmenshan Fracture, on the north by the Chengkou-Fangxian-Xiangfan-Guangji Fracture, on the northeast by the Tancheng-Lujiang Fracture, on the east by the Huanghai Sea and Donghai Sea, and on the south by the Nanhai Sea. The area is about 2 000 000 km 2. Based on the quantitative and qualitative data from the study of stratigraphy and petrography of outcrop and well sections,according to the single factor analysis and comprehensive mapping method, the single factor maps of the Hule(Miaopo) Stage and Hanjiang(Baota) Stage of the Middle Ordovician, and the Shikou(Linxiang) Stage and Wufeng Stage of the Upper Ordovician, and the lithofacies palaeogeography maps of the Hule(Miaopo) Age and Hanjiang(Baota) Age of the Middle Ordovician and the Shikou(Linxiang) Age and the Wufeng Age of the Late Ordovician in South China are compiled. In these lithofacies palaeogeography maps, there are 7 principal palaeogeographic units, i.e. Dianxi Platform, Kangdian Land, Yangtze Platform, Slope, Jiangnan Basin, Sotheast Platform and Cathaysian Land. The former 5 units belong to the Kangdian Palaeogeography System, and the latter 2 units belong to the Cathaysian Palaeogeography System. The most important character of these lithofacies palaeogeography maps is quantification. Quantification means that the determination of each palaeogeographic unit is based on the accurate quantitative data and single factor map. This is the first time in the study and mapping of the Middle and Late Ordovician in South China. These quantitative lithofacies palaeogeography maps are important development in palaeogeography, and are the guide to the prediction and exploration of oil, gas and other sedimentary mineral resources. In conclusion, the two palaeogeographic systems and the evolutionary history of the 7 principal palaeogeographic units in the whole Cambrian and Ordovician are discussed in detail.