泥质对志留系礁滩生长的抑制作用:黔北桐梓韩家店组的例证  

EMBRYONIC PATCHY REEFS FROM THE SILURIAN OF GUIZHOU——AN EXAMPLE OF MUDDY SEDIMENTS CONSTRAINING REEF-BANK GROWTH

作　　者：李启剑[1] 王媛媛[1] 李越[1] 马俊业[1] 张园园[1] 邓小杰[1] 蔡习尧[2] 

机构地区：[1]中国科学院南京地质古生物研究所,南京210008 [2]中国石油化工股份有限公司石油勘探开发研究院,北京100083

出　　处：《古生物学报》2012年第1期127-136,共10页Acta Palaeontologica Sinica

基　　金：中国科学院资源环境领域知识创新工程方向性项目(KZCX2-YW-Q05-01;KZCX2-YW-122);国家重点基础研究发展规划项目(2006CB806402);国家自然科学基金(41072002)联合资助

摘　　要：黔北桐梓的戴家沟剖面和狮溪剖面志留系兰多维列统特列奇阶下部的韩家店组出露完好,该组泥岩、粉砂岩中夹有厚度1—3m、直径4—7m的小型点礁。礁核相多具典型的障积格架岩特征,但生长时限短暂,群落分异度低,仅见床板珊瑚、单体四射珊瑚、苔藓虫和海百合茎,礁间为珊瑚、苔藓虫和海百合茎碎片堆积的滩相,伴生丰富的遗迹化石。在陆源碎屑快速沉积的背景下,浑浊海水频繁的富营养化过程限制了礁体纵横向生长和朝高分异度群落发展的可能性。During the Early Silurian the Yangtze Platform of the South China Block was mainly covered by terrigenous sediments derived from the surrounding land, which was then being uplifted. The palaeogeographic setting of the Hanchiatien Formation （lower Telychian, Llandovery, Lower Silurian） indicates a seaward ramp oriented northwards, with a nearby shoal belt spanning northern Guizhou and southern Sichuan. The unit was dominated lithologically by muddy and silty sediments. A sporadic supply of siliciclastic debris enhanced turbidity, resulting in an environment unsuitable for development of a large scale carbonate plat- form. However, a benthic assemblage of the brachiopods Nalivkinia and Striispirifer indicates a palaeodepth （BA2） which was above the fair weather base and was favourable for reef and bank formation; and the shallow marine red beds of the lower member of the formation further indicate a suitably warm palaeoclimate for reef development. Constrained mainly only by the high clastic input, small scale embryonic patch reefs therefore formed and are known from the Hanchiatien Formation at Daijiagou and Shixi, in Tongzi County of northern Guizhou. Generally they are one to three metres thick, four to seven metres in diameter, and are knoll-shaped in morphology. The reef bases and tops have sharp lithological boundaries with the underlying and overlying mudstones, so the growth margins are clearly defined in the field. The reef＇s biotic diversity is low but is high in skeletal density of tabulate and rugose corals, bryozoans, and crinoid fragments. Massive tabulate corals such as Favosites, Heliolites, Subalveolites, Halysites were crucial for differentiating frameworks. Bryozoan frameworks are richly occurred from the reef cores in Shixi. Dense aggregations of coarse crinoid fragments are partly stacked as grainstones. Stromatoporoidal taxa, which are mostly stenotypic and more sensitive to turbid water, have not been found as a component of these reefs. The inter-reef facies （reef banks） were h

关 键 词：生物礁滩 泥质沉积物 韩家店组 志留系 桐梓 黔北 

分 类 号：Q911[天文地球—古生物学与地层学]