兰州-民和盆地下白垩统河口群沉积序列及沉积相研究

兰州—民和盆地下白垩统河口群是一套厚度巨大的陆相碎屑岩沉积，根据岩性组合和沉积旋回，自下而上将河口群划分为8个非正式的组级单位。通过对河口群基本层序的分析和沉积序列及沉积相的研究，可以识别出冲积扇相、三角洲相和滨浅湖相3类相环境，细分为13种微相。沉积相的演变从整体上反映了整个盆地的演化过程。河口群的沉积环境由冲积扇相→三角洲相→滨浅湖相→三角洲平原相演变，形成了一个完整的序列，反映了盆地从开裂→扩张→萎缩→消亡的不同发展阶段。

STUDY ON THE SEDIMENTARY SEQUENCE AND SEDIMENTARY FACIES OF THE EARLY CRETACEOUS HEKOU GROUP IN LANZHOU-MINHE BASIN

The Early Cretaceous Hekou Group in Lanzhou-Minhe Basin is composed of terrestrial sediments with great thickness, and can be subdivided into eight informal formations.According to the lithologic combination and sedimentary cycles,the alluvial fan facies,delta facies and the shallow lacus facies as well as thirteen kinds of subfacies are identified in Hekou Group.The evolution of the sedimentary facies reflected whole development of the basin.In a word,the Lanzhou-Minhe Basin Cretaceous has experienced three phases :the alluvial fan facies;delta facies,the shallow lacus facies, and the delta-fluvial facies-delta facies, reflecting the different phases the basin experienced.