兰州-民和盆地河口群层序地层格架特征及盆地演化

兰州-民和盆地河口群形成于早白垩世，其间充填了巨厚的陆源碎屑物，碎屑物的组合内容和方式反映了冲积扇相，扇三角洲相，湖泊相沉积体系占主导，盆地地层层序具有退积型。加积型，进积型叠置的变化旋回，显示了全韵律的特点。代表了构造旋回幕的产物。根据盆地的发展演化特征和层序界面的确定，初步建立了盆地的层序地层格架，同时阐述了盆地的演化过程。

Sequence stratigraphic framework of the Hekou Group and evolution of the Lanzhou-Minhe Basin

The Hekou Group in the Lanzhou-Minhe Basin formed during the Early Cretaceous consists primarily of the tremendous terrigenous clastics composed of alluvial fan, fan-delta and lacustrine depositional systems. The stratigraphic sequences in the basin are involved in the retrogradational, aggradational and progradational cycles that represent the tectonic cyclic episodic products. The sequence stratigraphic framework of the Hekou Group is made up, on the basis of sequence features and lithofacies changes, of the lake transgressive (LTST), lake flooding (LFST) and lake regressive (LRST) systems tracts. The basin went, by and large, through the initial rifting and subsiding during the Jurassic, spreading and expansion during the middle Early Cretaceous, and collapse during the late Early Cretaceous.