太古宇的建系:前寒武纪年代地层划分大胆的尝试和重要的进展  

SYSTEM-LEVEL DIVISION OF THE ARCHEAN EONOTHEM:AN IMPORTANT ADVANCEMENT AND A BOLD PROPOSAL OF PRECAMBRIAN CHRONOSTRATIGRAPHICAL DIVISION

作　　者：梅冥相[1] 

机构地区：[1]中国地质大学北京地球科学与资源学院,北京100083

出　　处：《地层学杂志》2016年第2期186-208,共23页Journal of Stratigraphy

基　　金：国家自然科学基金会项目(No.41472090,40472065,49802012)

摘　　要：前寒武系,虽然不是一个正式的地层单位,但是,却简单明了地代表了形成于寒武纪开始(显生宙起始时)之前的所有岩石,因而就囊括了可以追索到地球形成的所有时间阶段的物质记录。遵循现代地层学的概念体系,要建立一个更加精确的前寒武纪地质年代表将面临着很多挑战。与寒武纪以来的显生宙相对应,前寒武纪曾经被称为"隐生宙"。随着研究的深入,尤其是地质学家在前寒武纪地层中发现了许多生命活动的痕迹,被称为"隐生宙"的前寒武纪就进一步划分为冥古宙、太古宙和元古宙,这代表了前寒武纪地层学研究的第一次概念进步。现行的前寒武纪年代地层划分,主要基于不同克拉通上的可对比的地质事件,而且基于合适的计时性(大致为整数的)时间界限来划分前寒武系,这个划分方案已经服务地球科学界三十余年,尤其是基于大范围的构造活动与沉积特征尝试性地建立了元古宙的纪(埃迪卡拉纪除外),代表了前寒武纪年代地层划分的第二次概念进步。随着对地球前寒武纪演变历史的深入研究而识别出许多不同时代的重要事件,以及更为重要的是从岩石记录的背景变化中识别出造成这些事件的成因,这不但导致了对前寒武纪地球的更加深入的了解,而且为今天重新修订一个新的前寒武纪地质年代表提供了一个难得的机会,从而产生了前寒武纪年代地层划分的第三次概念进步。在新修订的前寒武纪地质年代表中,表现出以下重要的进展:1)运用现代地层学的理念,重新定义了冥古宙、太古宙和元古宙;2)明确了具有特殊地质学涵义的太古宙的底界;3)明确并修订了太古宙-元古宙界线;4)尝试性地进行太古宇的建系。一个修订了的太古宙,可以定义为前寒武纪历史进程中具有以下特征的时间段,即地表上保存的最古老岩石的首次出现(4030 Ma的Acasta片麻岩)、大致在2420 The Precambrian system is not a formal stratigraphic unit, but it refers tO all rocks that formed prior to the beginning of the Cambrian Period （base of Phanerozoic） and by this very nature therefore in- cludes the full period of time back to the formation of the Earth. According to the conceptual system of the modern stratigraphy, the establishment of a chronostratigraphic time scale for the Precambrian will be fa- cing significant challenges. Contrasting with the Phanerozoic Eon （from the Cambrian to the Quaternary）, the Precambrian is also named as the Cryptozoic Eon. Further researche has shown that there are traces of biological activities in the Precambrian, which led to the subdivision of the Precambrian into three Eons, i. e. the Hadean, the Archean and the Proterozoic Eon~ this is an important conceptual advancement in Pre- cambrian stratigraphy. The current time scale of the Precambrian is based on numerical ages that approxi- mate the time of major geological changes, and Proterozoic periods are chosen to reflect large-scale tectonic or sedimentary features （except for the Ediacaran Period）. This scheme has served the geosciences commu- nity over the past 30 years, and it represents another important advancement in the study of Precambrian stratigraphy. With further investigation of the evolutionary history of the Precambrian Earth, a number of significant changes over time have been recognized. This has led to a more thorough understanding of Pre- cambrian Earth and offers an opportunity to establish and to revise the chronostratigraphic division of the Precambrian. A revised time scale of the Precambrian is proposed, including： 1） the redefinition of theHadean, Archean, and Proterzoic Eon on the basis of modern stratigraphic concepts; 2） the geological meaning of the lower boundary of the Arehean Eon; 3） a revised definition of the Archean-Proterozoic boundary; 4） a tentative system-level subdivision scheme for the Archean Eonothem. The revised Archean Eon can be defined as the

关 键 词：年代地层学 建系 重要进展 太古宇 前寒武纪 全球 

分 类 号：P534.2[天文地球—古生物学与地层学]