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分布于扬子区西北缘宁强—广元地区志留系宁强组以约三千米厚的浅水相泥页岩、海相红层夹灰岩为特征 ,部分灰岩层段中发育生物礁。通过对礁灰岩的微相分析表明 ,菌藻类可通过四种方式参与造礁过程 :1)叠层石 ;2 )凝块岩 ;3)核形石 ;4 )钙藻碎屑堆积。其中以叠层石和凝块岩最为常见 ,它们对灰泥基质起显著的粘结作用。而核形石和钙藻相对较少。有的叠层石出现于礁顶相并作为后生动物骨架岩造礁衰减的标志
Located in the northwestern margin of the Yangtze area, the Ningqiang-Guangyuan area of the Silurian Ningqiang Formation is characterized by shallow-water shale and marine red-bedded limestone of about three kilometers in thickness, and some reefs are developed in some limestone intervals. Microfacies analysis of reef limestone shows that bacteria and algae can participate in the reefing process through four ways: 1) strata; 2) clinker; 3) nucleus; 4) accumulation of calcium algal debris. Among them, strata and clinker are most common, and they play a significant role in binding the stucco matrix. The stone and calcium algae relatively less. Some of the strata appear in the top of the reef and serve as markers for the attenuation of metazoan skeleton rocks