摘要： 鄂尔多斯盆地奥陶纪华北海与祁连海演变关系是多年来研究中的一大难题。本文依据古生态演化的不可逆性及地理分区, 并结合盆地中东部、西部和南部奥陶纪地层的系统对比,深入探讨了奥陶纪牙形刺动物群在不同沉积分区的演化特征及其与华北海和祁连海之间的关系。并在此基础上, 将祁连海侵漫到盆地西缘地区的时间, 确定在华北海马家沟四期最大海侵的晚期, 侵漫范围尚末过中央古隆起带的鄂6井到定探1井一线。中央古隆起在马家沟四期沉积后, 对华北海和祁连海具有明显的分隔作用。根据牙形刺动物群的面貌及不同阶段的地理分区, 结合古构造格局及岩石、岩相标志, 系统分析了奥陶纪不同阶段的沉积特征,再现了各期岩相古地理面貌, 为鄂尔多斯奥陶系天然气勘探奠定了地质基础。

关键词: 鄂尔多斯盆地, 奥陶纪, 华北海, 祁连海, 古生物分区, 岩相古地理

Abstract: The evolution between North China Sea and Qilian Sea of the Ordovician in Ordos Basin has been remained one of the problems for many years. The evolution characteristics of conodont fauna in Ordovician and its relationships with North China Sea and Qilian Sea have been highly discussed in this article on the basis of the irreversibility of ecology evolution and palaeontologic subareas, and the systematic stratigraphic correlation of Ordovician in the central east, west and south part of the basin It has been decided that the late period of the greatest transgression of Majiagou Age 4 was the time when Qilian Sea invaded into the west part of the basin, and the invaded range did not exceed beyond the west line from Well E 6 to Well Dintan 1 on the central paleo-uplit. The central paleo-uplift had played a role in dividing the North China Sea and Qilian Sea after the sedimentation of Majiagou Age 4 In the light of the features of conodont fauma and the geographic distribution of different stages, combined with the ancient structures and the lithofacies marks, the characteristics of lithofacies palaeogeography of different ages have been reconstructed. This research will establish a geological foundation for natural gas exploration in the Ordovician.

Key words: Ordos Basin, Ordovician, North China Sea, Qilian Sea, palaeontologic subareas, lithofacies palaeogeography

中图分类号: 

• F531