早寒武世时大巴山、米仓山南缘属上扬子地台的北缘部分,处在碳酸盐台地边缘相带环境中。该区生物礁滩较发育,主要分布于陕西南郑、西乡、镇巴、紫阳等地和大巴山、米仓山南缘的四川南江一带;生物礁滩的类型有兰藻―古杯礁、凝块石灰泥丘、核形石生物层、生屑滩和鲕粒滩;造礁生物类型有古杯、兰藻细菌等,附礁生物除单体规则古杯外,还有三叶虫、腕足类、海百合、海绵骨针等。通过对寒武纪灰泥丘凝块石作生物标志化合物分析,证明了其有机质生源为菌藻类微生物。指出由于相对海平面升降和古地理环境的控制,使本区礁滩的发育具有明显的旋回性并控制了礁滩的发育类型和分布,礁滩层位自西向东有升高的趋势。

In the Early Cambrian, the southern margin of Daba Mt. and Micang Mt. located at the northern margin of Upper Yangze Platform. The reefs and banks whichdeveloped at the margin of carbonate platform, distributed in the area of Nanzheng,Xixiang, Zhengba, Ziyang of Sanxi province and nanjiang of Sichuan.The reefs and banks include cyanobacteria-Archaeocyathus reefs, thrombolite micrite mounds, oncolite biostromes and bioclasic & oolitic banks.The reef building organisms have Archaeocyathus, cyanobacteria. And the biomarks analyses are also proved that the microbial materials are in mud mounds.The reef living organisms have  brachiopoda, trilobite, crinoida, sponge. Because of the sea-level change and paleogeographic environment control, the reefs and banks show the cycle sequence, and migrate upper in sequence from the west to the east.