月球地质年代学研究方法及月面历史划分

The methods of lunar geochronology study and the subdivisions of lunar geologic history

介绍了确定月球地层单元相对年龄和绝对年龄的方法。建立相对年龄的方法主要有4种:地层叠置法、撞击坑大小-频率分布统计法、撞击坑形态法和月壤成熟度法;研究绝对年龄的方法有两种:样品的同位素测年法和月球成坑计年法。回顾了现用月球层序划分的形成及发展过程,在此基础上,提出了改善月球年代划分的建议,分别用冥月宙、古月宙和新月宙表示月球内动力地质作用为主的时期、内外动力地质作用共同作用的时期和外动力地质作用为主的时期。推荐以南极艾肯盆地的形成为界线,将前酒海纪划分为前艾肯纪和艾肯纪,分别表示月球内动力地质作用为主的演化期和内外动力地质作用并重的演化初期。这种改进后的"三宙六纪"的月球年代划分既可以形成逻辑上更符合月球动力学演化过程的月球年代划分,同时又有助于开展在月球背面的地质研究。

The dating methods of relative age and absolute age of lunar stratigraphic units are summarized.There are four ways to establish the relative age：the geological law of superposition,crater size-frequency distribution,crater morphology as degradation,and soil maturity,whereas the absolute age can be determined only by isotopic geochronology or lunar cratering chronology.To better know about the lunar stratigraphic subdivisions presently used,the formation and evolution of the stratigraphic units are reviewed here.Based on the analysis of the established lunar stratigraphic subdivisions and lunar evolution theory,we suggest that use the term Eolunarisian Eon for representation of the lunar history when endogenic process dominated,that use the term Paleolunarisian Eon for the lunar history when endogenic process and exogenic process were both weighty,and that use the term Neolunarisian Eon for the lunar history when exogenic process dominated.And we propose that the pre-Nectarian Period could be substituted by pre-Aitkenian Period and Aitkenian Period,and the two periods are divided by the impact event forming south pole-aitken basin.The pre-Aitkenian Period was included in Eolunarisian Eon,while the Aitken Period represents the early stage of Paleolunarisian Eon,during which the impact event was the most typical geologic process.This kind of modified subdivisions not only corresponds to the lunar dynamic evolvement rule,but also provides convenience for the study of lunar farside.