An Alluvial Fan to Coastal Transition: A case study of Mesoproterozoic Bingmagou Formation, southern margin of the North China Craton

Key words: 
• Binmagou Formation /
• alluvial fan /
• coastal /
• Proterozoic /
• southern margin of the North China Craton

Abstract: The Precambrian sedimentary strata in the southern margin of the North China Craton are well developed, and widely exposed, it has a high value to study further. But no unambiguous biogenic criteria exist to discriminate Precambrian ancient sedimentary strata, the judgement of sedimentary environment is often based on the tectonic background, geographical environment, rock types and sedimentary structure, resulting in previous research have some controversies. This paper takes Bingmagou Formation in the Ruyang Group in the southern margin of the north China craton as an example, through the analysis of rock features, paleocurrent and sedimentary facies, combined with the regional comparison of relevant strata and the reconstruction of ancient landform, to explain the depositional genesis and the environmental transition of Bingmagou Formation. The sedimentary strata of the Ruyang Group unconformably onlaps Archean crystalline basement or Proterozoic Xionger Group, the Bingmagou Formation as the bottom unit of the Ruyang Group, obviously controlled by topography and fracture, accepted the rich fragment deposition, was a very particular "bilayer superimposition" sedimentary strata, represented an alluvial fan to coastal transition, and it also was the beginning of marine deposition in the southern margin of the North China Craton.