松滋刘家场地区Tremadocian早期Pelmatozoan生物礁的发现

首次在刘家场地区早奥陶世Tremadocian早期地层（南津关组下部）中发现Pelmatozoan生物礁， Pelmatozoan不仅单独形成障积礁，而且和低等微生物菌藻类一起联合形成微生物岩礁--障积礁和粘结礁。障积礁可分为Pelmatozoan障积礁和有柄棘皮类包壳状蓝细菌粘结障积礁，粘结礁可分为硅化海绵有柄棘皮类蓝细菌障积粘结礁和有柄棘皮类蓝细菌障积粘结礁。相应地，可以划分为4个生物群落，即Pelmatozoan群落、有柄棘皮类包壳状蓝细菌群落、硅化海绵有柄棘皮类蓝细菌群落和有柄棘皮类蓝细菌群落。在对研究区Pelmatozoan与叠层石纹层破坏的关系讨论中，笔者认为Pelmatozoan障积作用而阻断部分纹层的生长可能是主要原因，Pelmatozoan滤食可能是次要原因。生物礁发现表明，有柄棘皮动物在全球最早建礁的时间是Tremadocian早期，更重要的是该发现提供了中寒武世古杯点礁衰亡之后后生动物第一次恢复造礁的证据。因此，Tremadocian早期Pelmatozoan生物礁的发现不仅对于有柄棘皮动物生物礁和奥陶纪生物礁的演化史研究具有重要理论意义，而且对江汉平原油气评价等经济领域具有一定的实际意义。

Discovery of Pelmatozoan reefs of Early Tremadocian at Liujiachang in Songzi Area

It is the first time that Pelmatozoan reefs was discovered from early Tremadocian strata (lower Nanjinguan Formation) of early Ordovician at Liujiachang in Songzi area of Hubei Province. Pelmatozoan not only forms individually bafflestone reef, but also combines together with low microbial algae to form microbial reefs, namely baffling and binding reefs. Baffling reefs can be divided into Pelmatozoan bafflestone reefs and stalked echinodermsconcentric circles cyanobacteriabinding baffling reef, Binding reefs can be divided into the siliconized spongestalked echinodermscyanobacteria bafflingbinding reef and stalked echinodermscyanobacteria binding reef. Accordingly, it can be divided into 4 biomes, namely, Pelmatozoan community, stalked echinodermsconcentric circles cyanobacteria community, siliconized spongestalked echinodermscyanobacteria community and stalked echinodermscyanobacteria community. Composition, structure, function and ecologic environment of each community are expounded and analysed. In the reefs discovered, the diameter of pelmatozoan is much smaller than that of pelmatozoan during late Tremadocian, this phenomena shows the evolution rule of organism from small to large during geological time. In the baffling reefs found, the content of pelmatozoan is lesser than that of late Tremadocian pelmatozoan, this phenomena reveals that reproductive ability and reef building function of organism is weaker during early geological time. In the discussion of the relationship between filter feeding of pelmatozoan and destruction of the stromatolites lamina in the study area, this paper argues that the baffling of pelmatozoan may be the main reason blocking off part of the lamina growth of stromatolites, while filter feeding of pelmatozoan may be secondary reason, As the pelmatozoan is not a wandering animal or boring animal, the predation and disturbing ability may be poorer than that of other boring animals. The discovery of organic reefs demonstrates that the earliest reef building age of stalked echinoderms in the world is early Tremadocian in the study area, at the same time, it also confirmed that early Tremadocian is also the earliest reef building age during Ordovician. Therefore, the discovery of early Tremadocian Pelmatozoan reefs is not only of important significance theoretically for the evolution studying of stalked echinoderms reefs and Ordovician reef, but also of certain practical significance for the evaluation of oil and gas for Jianghan Plain and other fields of the economy.