四川米易二滩地区的二滩组

四川盐边凹路、力马、红果及米易二滩、金龙山等地的二滩组上、下部均为细砂岩、粉砂岩、铁铝质粘土岩夹赤铁矿和铝土矿透镜体,底部常见砾岩,顶部为灰黑色碳质页岩夹劣质煤透镜体,中部为微晶生物灰岩夹粗粒白云质钙质石英砂岩。以富含腕足化石为特色,还可见珊瑚、虫筵、非虫筵有孔虫、介形虫、三叶虫、苔藓虫、腹足类等生物化石。沉积二滩组时期,研究区处于泥坪、混合坪、不稳定碳酸盐台地及潮坪沼泽等环境,代表一次较大的海进海退过程。二滩组与梁山组、树河组在岩性特征、所含生物面貌及时间跨度等方面存在显著差异。新建二滩组相当于研究区原石炭系与原梁山组之和,其时代为早二叠世栖霞期至茅口早期

ERTAN FORMATION OF THE ERTAN REGION, MIYI, SICHUAN

The Ertan Formation extends from Aolu, Lima and Honggou in Yanbian County to Ertan, Jinlongshan in Miyi County etc.. The Upper and Lower parts of the Ertan Formation consist predominantly of fine grained sandstone, siltstone and iron aluminous claystone interbedded with lenticular bodies of hematite and bauxite. The dominant lithologies of the middle part are microcrystalline bioclastic limstone interbedded with coarse grained dolomitic and calcareous quartzose sandstone. There are generally thick bedded conglomerate at the base. The dominant lithologies of the top are gray dark carbonaceous shale interbedded with lenticular bodies of coal smit. The formation is characterized by an abundance of Brachiopoda, and still corals, Fusulinida, Ostracoda, Trilobita, bryozoan and gastropda etc.. The Ertan Formation represents depositional environment of mudflat, mixed flat, unstable carbonate platform and supratidal marsh. They represents a relatively large transgression regression depositional sequence. The Ertan Formation is different from the Liangshan Formation or Shuhe Formation in their lithological characteristics,fossil assemblages and time range etc.. This Formation is equivalent to the Carboniferous and Liangshan Formation in the past here, and its age is Qixia Age to early Maokou Age.