摘要
滇西昌宁－孟连带地质构造特征及构造环境分析王义昭（云南地矿局区调所）该带由于地质构造复杂，基础地质研究难度较大，８０年代以来，一直成为“三江”地区争议的热点，故此，本文拟对其进行较详细的讨论。一、概况自１∶２０万景洪幅（１９７９）在澜沧岩群中发现蓝闪...
The Carboniferous Permian strata in the Changning Menglian zone,Yunnan may be divided,at least,into eastern and western parts.The eastern part is represented by the Carboniferous Nanduan Group and Permian Laba Group,the former of which consists mainly of thickly massive lithic quartz sandstones and siltstones interbedded with mudstones/shales.The quartz sand ubiquitous in the sandstones is well rounded,poor sorted and different in grain size.The rocks are characterized by higher compositional maturity and lower textural maturity.The Nanduan Group is overlain unconformably upon the Huimin Formation of the Lancang Group of Middle Proterozoic age,and conformable with the overlying Laba Group.From the base upwards,the lithology and lithofacies display remarkable changes in the Laba Group,where the sediments were laid down in a relatively deep environment,and there are plenty of fine grained clastic and siliceous sediments.Furthermore,the intercalations of gravel bearing marls composed of limestone debris are also identified in the middle part of the Laba Group.The fusulinid fossils are often found in the limestone debris to be of Carboniferous to Early Permian age.The Late Permian radiolarias occur in the siliceous rocks,and the contemporaneous lamellibranches and ammonites appear in the associated fine grained clastic sediments,indicating that the siliceous rocks are Late Permian in age. The oldest strata of Devonian in age crop out in the western part of the study area.These strata significantly comprise graptolites shales,fine sandstones,siltstones,shales and siliceous rocks,covered by Lower Carboniferous basic volcanic rocks which,in turn,are conformable with the overlying Middle Carboniferous to Early Permian platform carbonate rocks.The lithology and lithofacies and fossils at the uppermost of the strata in this area may be compared with those of the Maokouian limestones which are overlain pseudoconformably by the clastic sediments interbedded with siliceous rocks in the Late Permian Nanpihe Formation.It
出处
《沉积与特提斯地质》
CAS
CSCD
1997年第21期33-57,共21页
Sedimentary Geology and Tethyan Geology
