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根据沉积背景和岩石学特征分析,塔中地区奥陶系良里塔格组中可划分出3类礁建造:格架礁、礁丘和灰泥丘,其中化石丰富,具有承前启后的重要作用。造礁生物有菌藻、钙藻、珊瑚、海绵、苔藓虫和层孔虫等,附礁生物有介形类、腹足类、腕足类和棘皮类等。在生物礁的演化阶段上,发育完整的造礁生物生长序列,出现拓殖期—泛殖期—衰亡期的阶段演化;礁的生长过程中,生物属种、含量和组合特征均表现出明显的演替。通过分析认为,塔中地区生物礁单个礁体厚度大、发育旋回多,多期礁滩组合规模大,礁体微相发育完善,沿台地边缘成群、成带分布。生物礁和粒屑滩组合发育形成大型的礁滩复合体,为形成大型礁滩型油气藏奠定了良好的基础。
According to the analysis of sedimentary background and petrological characteristics, three types of reefs can be divided into three types in the Ordovician Lianglitage Formation in the Tazhong area: grid reefs, reef mounds and stucco mounds, of which the fossils are abundant and have an important bearing on the past. Reef organisms have bacteria and algae, algae, algae, corals, sponges, bryozoans and stomatal insects, reef creatures with mesoids, gastropods, brachiopods and echinoderms. In the evolutionary stage of reefs, the complete sequence of reef-making biological growth appears during the stages of colonization-pan-colonization-decay; in the process of reef growth, the species, content and combination features of the reefs show obvious succession. According to the analysis, the individual reefs in the Tazhong area are large in thickness, more in development, more in reef-shoal assemblages, and well-developed reef microfacies. They are clustered and distributed along the edge of the platform. The combination of reefs and litter banks formed a large reef-beach complex, which laid a good foundation for the formation of large-scale reef-shoal reservoirs.