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前寒武纪地层分会,包括在1982年有12名正式成员和30名通讯成员参加的最后正式会议的时候在内,已经为制定可接受的前寒武纪划分积极工作了十年以上,为主要前寒武纪地盾作出了综合年代一岩石图,并对若干和全部具有共同性的格局和事件的复合记录进行了分析。地质年代划分方案也逐渐形成,反映了地球历史主要事件格局,与此同时还识别出那些事件从一个地区到另一地区其强度和时间的的选择是典型地多变的。时间单位界线已被选定,因而可用来圈定或划出沉积、造山和岩浆等作用的边界,但这些界线以年龄确定,对任何岩体毫无专门参考价值。通过间隔2—4年召开正式会议相继发展的和在地质刊物发表的要求评论和批判的若干推荐建议如下: (1)重申推荐建立两大宙级时间单位—太古宙和元古宙,其时间界线为25亿年。 (2)临时性推荐把元古宙再划分为三个代级单位,进一步确定暂时以元古Ⅰ、元古Ⅱ和元古Ⅲ表示,其时间界线分别为25、16、9和约5.7亿年。 (3)把元古宙进一步划分为八个纪级时间单位,但迄今尚未命名,暂时推荐其时间界线分别为25、21、18、16、14、12、9、7和约5.7亿年。分会评议的性质和发展的指导方针将在本文叙述。征求的评论和批判意见拟按程序和推荐本身加以说明。
The Precambrian strata, including the final official meeting of 12 full members and 30 communications members in 1982, have worked actively for more than a decade to develop an acceptable Precambrian distinction The main Precambrian shields have made a comprehensive rock-and-stone picture and have analyzed composite records of several and all patterns and events that share commonalities. The geo-dating program also evolved to reflect the pattern of major events in Earth’s history while at the same time identifying the choices of intensity and timing of those events from one region to another that are typically variable. The boundaries of time units have been selected and therefore can be used to delineate or demarcate the boundaries of sedimentation, orogenies and magmas, but these boundaries are determined by age and have no specific reference to any rock mass. A number of recommended recommendations that have been reviewed and critiqued in successive posts and published in geologic journals at regular 2-4 year intervals are as follows: (1) Reiterate the recommendation to establish two major universe time units, Archean and Proterozoic, whose time Boundary of 2.5 billion years. (2) Provisional recommendation to divide the Proterozoic into three subordinate units, and further to be temporarily identified by Proterozoic I, Proterozoic II and Proterozoic III with time boundaries of 25, 16, 9 and about 570 million years respectively . (3) The Proterozoic is further divided into eight class time units, but so far it has not yet been named. Temporarily recommended time lines are 25, 21, 18, 16, 14, 12, 9 and 7 and about 570 million years respectively. The nature of the subcommittee’s comments and the guidelines for development will be described in this article. Comments and critical comments sought are to be explained in terms of procedures and recommendations.