滇东南地区新发现中三叠统关岭组典型台缘生物礁和斜坡滑塌灰岩

The new discovery of the Mid-Triassic typical platform-marginal reefs and slump limestone in southeastern Yunnan,China

2012年底在云南省泸西县东山镇地区中三叠统关岭组中发现大规模典型台地边缘鲕粒浅滩和生物礁,同时在向阳乡方摆村附近发现典型台地前缘斜坡相泥晶灰岩,滑塌构造发育。台缘生物礁垂向3分结构明显,礁基为浅滩相鲕粒灰岩、豆粒灰岩;礁核为粘结海绵-水螅骨架岩,蓝绿藻粘结结构和亮晶栉壳状胶结结构发育;礁盖为台缘斜坡相深灰色薄层泥晶灰岩和泥质灰岩。生物礁横向展布也具有3个明显特征:礁后为碳酸盐台地相灰岩,礁核为粘结海绵-水螅骨架岩,礁前为台缘斜坡相薄层灰岩和泥岩,局部发育滑塌构造和滑塌角砾岩。该发现可为滇东南地区继续寻找油气资源开辟新的勘探方向。

The huge typical platform-marginal oolitic shoal and reefal limestone have been firstly discovered that distributed in the mid-Triassic Guanling Formation, the Dongshan area of the Luxi County, Yunnan Province, during the end of 2012. At the same time, the thin-bedded micritic limestones and slump structures of platform fore-marginal slope are also developed in the Fangbai vil- lage, Xiangyang town. There are apparent vertical tripartite frameworks in the platform marginal reefs： the reefal-base subfacies com- posed of the shoal oolitic and pisolitic limestones; the reefal-core subfacies composed of the boundstone and sponge-hydroid frame- workstone, especially development of bluegreen algae bound-textures and sparry pectinate cement-textures; and the reefal-cap subffa- cies composed of the dark-gray thin-bedded micrite and muddy limestone of the platform fore-marginal slope. In the horizontal dis- tribution, the reefs model developed three obvious properties： the back-reef subfacies consisted of the platforms limestones; the reefal- core subfacies consisted of the boundstone and sponge-hydroid frameworkstone; the front-reef subfacies consisted of the thin-bedded micrite and shale of platform fore-marginal slope with local development of the slump structure and slump breccias that are composed of the reeFal limestone, oolitic and pisolitic grainstones.