Tertiary sedimentary features and environment of the Lanzhou-Minhe basin

On the basis of the field regional geological surveys and through studies of the lithology, sedimentary structures, paleocurrent direction, vertical sequence and three dimensional shape and association of sedimentary units and grain size analysis and scanning electron microscope analysis, the delta facies, delta plain facies, fluvial facies, lacustrine facies, alluvial facies and eolian sand dunes are distinguished in Tertiary strata of the Lanzhou Minhe basin. The authors made a systematic study of the vertical infilling sequence of the basin. Moreover, the corresponding environmental evolution is discussed in detail.