滇东南中三叠统个旧组震积岩的发现及意义

THE DISCOVERY AND SIGNIFICANCE OF MIDDLE TRIASSIC GEJIU FORMATION SEISMITES IN SE YUNNAN

以往认为滇东南个旧地区中三叠统个旧组属台地相沉积,近期笔者在个旧组第三段中发现了大规模的震积岩,该震积岩分为脆性序列和液化序列,脆性序列震积岩主要由同沉积微断层、地裂缝、震碎角砾岩三种类型。同沉积微断层具有阶梯状、微地垒状、微地堑状构造样式组合特征。液化序列表现为形态、位态各异的手标本—露头尺度的顶厚翼薄褶曲。泥晶方解石脉、同沉积微断层伴随了个旧组第三段沉积的全过程。结合个旧组中发现夹有基性火山岩和滑塌角砾岩等,认为个旧组第三段震积岩是在强烈拉张构造背景下的产物。

In the past opinion, Middle Triassic Gejiu Formation in Gejiu area of SE Yunnan is the platform facies sediment. Recently, we have discovered the seismites on a large scale in Gejiu Formation 3 ^ rd Member. The seismites can be divided into the brittle series and the liquefaction series. The brittle series are mainly synsedimentary micro- fault, ground fracture and shatter breccias. The synsedimentary micro-fault is characterized by the assemblage feature of ladder, micro- horst, micro-graben structure pattern. The liquefaction series show different form, place thick top and thin limb fold on hand specimen-outcrop scale. The whole sedimentation of Gejiu Formation 3rd Member is in accompaniment of argillo-crystalline calcite vein, synsedimentary micro- fault. In combination with the discovery of basic volcanic rock and slump breccias in Gejiu Formation, we think the seismites in Ge-jiu Formation 3rd Member is formed under the intense tension tectonic background.