二叠纪古板块再造与岩相古地理特征分析

Characteristics of the reconstruction of Permian paleoplate and lithofacies paleogeography

依据古地磁方法,对二叠纪全球古板块进行再造,并在此基础上,结合区域地质资料,编制了二叠系全球古板块再造图、全球岩相及烃源岩分布图和全球古地理图。二叠纪板块格局以泛大陆和泛大洋为主,大陆内部裂谷系(如劳亚板块内部北海—北大西洋裂谷系和非洲大陆内部裂谷系)持续发育,最终导致了泛大陆的裂解。二叠纪冰期持续发育,又由于干旱带广泛发育的古气候条件,造成全球海平面在晚二叠世达到整个显生宙的最低值。浅海广泛发育的古地理环境造成古、新特提斯洋周缘和劳亚大陆整体以浅海碳酸盐岩和海相碎屑岩沉积为主。冈瓦纳大陆内部以河湖相碎屑岩沉积为主。二叠系烃源岩不发育,主要层系是下二叠统泥页岩,分布集中在劳亚大陆北缘、特提斯洋周缘以及冈瓦纳大陆内部和澳大利亚东部,以海陆过渡相沉积环境为主。泛大陆形成过程中,洋壳消减与不同陆块之间的拼合,最终造成了二叠纪末气候的剧变,形成了晚古生代末超大规模的冰期。板块运动所产生的壳幔物质循环造成二叠纪全球二氧化碳含量剧烈升高,最终导致了二叠纪生物灭绝程度最大。

Basing on paleomagnetic methods, the authors reconstructed the location of Permian paleoplate, And combination with regional geological information, compiled the Permian global paleoplate map, global lithofacies paleogeography map and distribution map of hydrocarbon source rocks in Permian. Pangea and Panthalassa around were the main continental pattern. Rift systems were well developed, such as the North Sea- North Atlantic rift system in Laurasia and the rift system in African. The continuous development of the rift systems eventually led to the breakup of Pangaea. Meanwhile, Due to the continuous development of glaciation in Permian and the widespread drought environment, global sea levels in the late Permian reached thelowest in Phanerozoic. Shallow seas were wildly spread around Neo- Tethys and Paleo- Tethys. These paleogeographic environments caused the deposition of shallow marine carbonate and clastic sediments in the whole Neo- Tethys periphery and Laurasia. Lacustrine clastic sediments were deposited internally in Gondwana. Source rocks in Permian were not widely developed,the main layer system was Lower Permian shale, which was mainly concentrated in the northern margin of Laurasia, Tethys periphery and interior of Gondwana as well as eastern margin of Australia, dominated by transitional facies depositional environment.