元谋盆地晚新生代地质研究的新进展

NEW DEVELOPMENT IN RESEARCH OF LATE CENOZOIC STRATIGRAPHY IN YUANMOU BASIN

“川滇南北构造带中段晚新生代地质研究”项目，从选择最佳地质剖面入手，对元谋盆地茂易─马头山剖面进行了详细的地质测量、编录和多学科综合研究。作者对剖面的岩石地层学、生物地层学、磁性地层学、重矿物和岩相古地理的主要特征进行了简要的总结；并对第四纪下限（Ｎ／Ｑ界限）的各种标志进行了讨论。在此基础上确定了元谋盆地第四纪下限为２．４８ＭａＢ．Ｐ．左右，并对该盆地第四纪地层进行了划分。作者认为过去对元谋盆地第四纪地层划分的所谓“元谋组”，实际上是一套跨第三纪晚期和第四纪早期的地层。作者根据不同级别岩石地层单元划分方案和命名原则，将这套河湖相地层按地层规范定为元谋群，其中的下部地层沿用周明镇最早提议的名称“沙沟组”，上部地层称为“元马组”。

Detailed geological records and multidisciplinary researches ofMaoyi-Matoushanprofile of Yuanmou Basin have been taken to select best geological profile in the projectof“research on Late Cenozoic geology of middle range of south─north tectonic zone inSichuan─Yunnan”.We have briefly surnmed up main characteristics of the lithostrati-graphy,biostratigraphy,magnetic stratigraphy,heavy minerals,lithofacies and paleo-geography.And we studied many indicators of the lower boundary of Quaternary. Basedon these,the lower boundary of Quaternary has been established and Quaternary stratig-raphy in Yuanmou Basin divided.The pervious“Yuanmou Formation”,in fact,is a seriesof strata located in upper Tertiary through lower Quaternary in Yuanmou Basin。Wenamed the series of fluvio-lacustrine sediments “Yuanmou Group”,according to divisionand nomenclature of stratigraphic units in different orders,The lower part of it is called“Shagou Formation”by Zhou Mingzhen,and the upper part is“Yuanmou Formation”。