对中国第四系中统划分方案的回顾与讨论

国内地层规范中规定第四系划分为两个统，即全新统和更新统，后者又分为下、中、上３个阶。这３个阶大部分第四纪地质工作者习惯称为下、中、上更新统。本文仍暂用此名。下、中更新统的界线一般以Ｂ／Ｍ为界，年龄为０．７８ＭａＢ．Ｐ，但从泥河湾组、午城组顶界看，可能要到１００～１．２０ＭａＢ．Ｐ．；中、上更新统界线，一般以０．１２８ＭａＢ，Ｐ为界，代表末次冰期的开始，但从黄土高原Ｓ１底界、萨拉乌苏组底界和小渡口组顶界看，其年龄为０．１２８ＭａＢ，Ｐ，或０．１４ＭａＢ Ｐ或０．２０ＭａＢ，Ｐ．；上更新统与全新统的界线，其年龄基本上集中在０．０１０～０．０１１ＭａＢ，Ｐ，代表冰期结束，温暖期开始。

DISCUSSION ON PLANS OF DIVIDING QUATERNARY TO SERIES IN CHINA

Quaternary was divided into Pleistocene and Holocene according to standard in China. The former was divided into three stages. Most geologists treaded them as three series. Quaternary is four-division. We present following advice. (l) Quaternary is generally divided into two series-Pleistocene and Holocene in the world. Quaternary researchers of China are used to divide Pleistocene into Lower-Pleistocene, Middle-Pleistocene, Upper-Pleistocene. Considering of the status quo of Quaternary research, national economic construction and study on global changes, we suggest that it is more suitable to consider rather 'Lower-Pleistocene', 'Middle-Pleistocene', 'Upper-Pleistocene' as series than stages. However, the division of series and the stages is global tendency, and the division of Quaternary still needs to be discussed further. (2) According to chronostratigraphy, the boundary between Lower-Pleistocene and Middle-Pleistocene is located at B/M boundary (0.78MaB.P.); on the basis of petrostra- tigraphy and biostratigraphy of Nihewan Formation and Wucheng Formation, the Q2/Q1 boundary is dated at l.00-l.20MaB. P. (3) According to chronostratigraphy, the boundary between Middle-Pleistocene and Upper-Pleistocene is located at 0.128MaB.P., which stands for the beginning of last interglacial, according to petfostratigraphy and biostratigraphy of paleosol S1 at Loess Plateau, Salawusu Formation and Xiaodukou Formation, the Q3 / Q2 boundary may be alternative in 0.128MaB.P. or 0.14MaB.P. or 0.20MaB.P. (4) The boundary between Upper-Pleistocene and Holocene is mainly about 0.010-0.011MaB. P., which represents the end of glacial and the beginning of thermomer.