A period of the Proterozoic eon that began 2050 Ma ago and ended 1800 Ma ago, both dates being fixed. The Orosirian followed the Rhyacian period and was followed by the Statherian period.
科学参考收录了60776条科技类词条，基本涵盖了常见科技类参考文献及英语词汇的翻译，是科学学习和研究的有利工具。