黔北凤岗硐卡拉奥陶系湄潭组中灰岩:典型的暖水相  

"MIDDLE MEMBER LIMESTONE" OF THE ORDOVICIAN MEITAN FORMATION IN DONGKALA,FENGGANG,NORTHERN GUIZHOU,SW CHINA:TYPICAL WARM MARINE FACIES

作　　者：李启剑[1] 李越[1] Steve KERSHAW 张园园[1] 邓小杰[1] 

机构地区：[1]中国科学院南京地质古生物研究所,南京210008 [2]Institute for the Environment,Brunel University,Uxbridge,Middlesex

出　　处：《微体古生物学报》2010年第2期150-158,共9页Acta Micropalaeontologica Sinica

基　　金：中国科学院创新工程方向性项目(KZCX2-YW-Q05-01;KZCX2-YW-122);科技部973项目(2006CB806402);国家自然科学基金项目(40572069和40532009)的共同资助

摘　　要：黔北凤岗硐卡拉剖面下—中奥陶统湄潭组泥岩、粉砂岩中夹含一套47.5m的连续灰岩建造,是区内迄今所测得厚度最大的"中灰岩"段。中灰岩的岩石学特征显示其成分多为分异度很高的生屑、鲕粒(豆粒)和核形石等,颗粒破碎程度偏高,丰度高时可达颗粒支撑,灰泥基质和亮晶方解石胶结均有。这些颗粒堆积形成中—高能带生屑、内碎屑浅滩,纵向上略显旋回,亦见两层较薄含瓶筐石格架的生物层。这些特征皆属浅海带暖水型沉积的标志,将该剖面的湄潭组中灰岩与之同期的大湾组和紫台组中的灰岩相比较,后者形成于偏深的相带,灰泥和泥级、粉砂级陆源碎屑含量高,也缺乏典型的暖水成因标志,故可推知扬子区陆表海的灰岩沉积相存在深度控制的海水温差分异现象。The ＂Middle Member Limestone＂ of the Meitan Formation in Dongkala,Fenggang,northern Guizhou,is considered as the indicator of a regression during the Early-Middle Ordovician interval.This sequence is up to 47.5 m in thickness,which is the maximum data comparing to its surrounding outcrops.There are kinds of shallow bank facies composed of rich oolitic,oncolitic intraclastics as well as high diverse bioclastics.The richness of the grain commonly reaches to support grade and are cemented by micritic or spar.Deposition of these grains formed intra-or/and bio-clastic banks from shallow mid-high energy settings and shows as somewhat recycles.Two thin bedded biostromal units were formed by Calathium as bafflestone frameworks together with other debris.These sedimentary as well as biological features indicate a warm and shallow marine background.Coeval limestone units of the Dawan and Zitai formations from deeper belts of the Yangtze Platform are composed of richer limemud,terrigenous mud and silts lacking index warm marine facts.Therefore,the temperature differentiation of the marine water controlled by the depth zonation did exist in the Yangtze Sea.

关 键 词：瓶筐石生物层 浅滩 中灰岩 湄潭组 下—中奥陶统 硐卡拉 凤岗 黔北 

分 类 号：P585[天文地球—岩石学]