滇东南个旧地区必需分解的三叠系中统个旧组顶部层序——暨莫贾组建立的意义 The Top Sequence of the Middle Triassic Series Gejiu Formation Would Be Essentially Decomposed in Gejiu Area of Southeast Yunnan—The Establishment Significance of Mojia Formation
滇东南个旧地区以往划分的整合于三叠系中上统法郎组灰岩之下的三叠系中统个旧组顶部地层层序经区域地质调查证实，为浅灰、灰黄色薄层状泥晶灰岩、浅灰–深灰色钙质泥岩、泥(质板)岩夹中基性火山岩的地层层序，且分布广泛、厚度稳定。本文将其从个旧组中分解出来，新建莫贾组，其分别与下伏个旧组灰岩、上覆法朗组灰岩呈整合接触，含双壳类Costatoria glodfussi manssuyi-Adonella paradaxica组合，时代为中三叠世Anisian期。莫贾组与上下地层之间物性界面显著，底以泥岩的出现、顶以泥岩的消失作为划分莫贾组的标志。发育薄层状粉砂质泥岩–泥岩、薄层状灰岩–钙质泥岩组成的韵律，灰岩中发育震积岩和系列的滑塌褶曲，以夹基性火山(熔)岩区别于上下地层，具有显著的活动性沉积建造特征，沉积环境为裂谷型盆地。因此，建立三叠系中统莫贾组为研究个旧裂谷的发展演化和建立地层层序具有非常重要的现实意义。
The previous partion top sequence of the Middle Triassic Series Gejiu Formation integrated under the Mid-Upper Triassic Series Falang Formation limestone from Gejiu area in southeast Yunnan that was confirmed by the regional geological survey to the stratigraphic sequence: Its lower part was grey, grey-yellow and light grey-dark grey calcareous mudstone, dark grey argillite that in-terbedded with grey green and yellow green compact basalt and altered andesite basalt. The li-thology of the upper part was grey black-dark grey mudstone, silty mudstone and thin-bedded micrite that they alternatively outcropped and interbedded with unstable intermediate basic vol-canic rock, and it is widely distributed and has stable thickness. This paper holds that the strati-graphic sequence disagrees with the definition of Gejiu Formation. Therefore, it is necessary to decompose out from Gejiu Formation and establish a new lithostratigraphic unit—Mojia Formation. This set of strata has a conformable contact with the underlying Gejiu Formation limestone of great thickness and overlying Falang Formation limestone. This set of strata contains bivalve Costatoria glodfussi manssuyi-Adonella paradaxica combination and its age is Middle Triassic Anisian. These have met the conditions of Formation of establishment. The material interfaces of Mojia Formation with the upper and lower strata were significant. At the bottom of Mojia formation appeared mudstone and at the top of the disappearance of mudstone as the dividing indexes of Mojia formation. The rhythm of flaggy silty mudstone-mudstone and flaggy limestone-calcareous mud-stone grew in Mojia formation. And the seismites and slump folds developed in the limestone. On the basis of interbedding with basic volcanic rock in Mojia Formation is different from the overlying strata and the underlying strata that it has significant active sedimentary formation characteristics. The sedimentary environment is the rift basin. Therefore, the establishment of Middle Triassic Mojia Formation has important practical significance for the study of the Triassic
