The dry mountain ranges of the western United States contain rocks dating back 440 to 510 million years, to the Ordovicianperiod, and teeming with evidence of tropical marine life.
美国西部干燥的山脉包含了距今4.4亿至5.1亿年前的奥陶纪岩石,其中充斥着热带海洋生物生存的迹象。
2
At the end of OrdovicianPeriod, a differential elevation occurred in the central Shanganning Basin due to the Caledonian Movement.
陕甘宁盆地中部气田的主要储气层段为奥陶系马五段的古岩溶层。
3
Eurypterid: any of various large segmented aquatic arthropods of the order eurypterida that existed from the ordovicianperiod to the Permian period.