Lanzhou-Minhe basin is a typical intracontinental rift basin in northwest Gansu formed in the Early Cretaceous. The Hek-ou Group in Lanzhou-Minhe basin is characterized by purplish red clastic sediments with a variety of grain sizes. On the basis of previous researches, the authors conducted field sedimentary investigations and studies of sedimentary fades, provenance and palaeocurrent of the Hekou Group along different stratigraphic sections such as Hekou, Yanguoxia and Zhongpu. The results indicate that the Hekou Group experienced an evolution of sedimentary faices from alluvial fan through fan delta and lacustrine/fluvial facies to deltaic sedimentary facies. Provenance and palaeocurrents suggest that the uplifted Qilian Mountain around the basin was the main material source of sediments during the Early Cretaceous. It is also shown that the previous Datonghe Formation belonged to the Late Jurassic-Early Cretaceous period and the Heko Group was deposited since the earlier Early Cretaceous. In addition, dinosaur fossils and pollen assemblages in the Heko Group and their environmental implications were described as well. Finally, a reconstruction model for palaeogeography of Lanzhou-Minhe basin in the Early Cretaceous was established.%兰州-民和盆是早白量世时期中国西部典型的陆内断陷沉积盆地,该时期主要发育的河口群是一套红褐色碎屑岩地层.在前人研究的基础上,对河口、盐锅峡、兰州中铺等地河口群进行野外地质调查,以盆地分析方法为手段,从地层、沉积相、物源和古水流等方面对盆地内的河口群进行研究分析认为,河口群在沉积相序上经历了冲积扇相-扇三角洲相-湖相/河流相-三角洲相的演化过程.在对大通河组与河口群综合研究的基础上,认为大通河组的时代宜划归为晚侏罗世-早白垩世,且河口群地层包括了早白垩世早期的沉积.结合河口群砾石成分、砂岩组分和古水流等的分析,认为早白垩世盆地周缘的祁连山隆起区为主要的物源供给区,早白垩世时期河口群在不同地区呈现出不同的沉积特点,并以此进一步建立了兰州-民和盆地早白垩世古地理格局.
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