Lithofacies Paleogeography of the Carboniferous in the  East of North Qilian Mountains

Key words: 
• East of North Qilian /
• Carboniferous /
• lithofacies palaeogeography

Abstract: The characteristics of Carboniferous lithofacies palaeogeography in the east of North Qilian Mountains have been discussed based on the analysis on outcrop sedimentary facies, clastic composition, particle size, rock texture and structure, paleontology, paleoecology. Shoreshallow marine facies, lagoon facies, delta facies and eleven sedimentary subfacies have been identified. In the early period of early Carboniferous，the marine water invaded the area from Qinling through the TianshuiJingning strait，resulting in a gulf surrounded by Alashan, Ordos, Longxi oldlands, mainly with salted lagoon facies and shoreshallow facies. In the late period of early Carboniferous, the transgression area became progressively extended, mainly with clastic rock and carbonate rock of shoreshallow marine facies. In the period of late Carboniferous, the transgression became high frequency, with several transgression and regressive cycle. In the period of Taiyuan Formation sediment, the North Qilian sea water conjoined with Ordos sea water to expand epicontinental sea. The chain shape uplift and below water uplift distribute into the Qilian marine basin. Palaeotopography is characteristic of high west and north, low east and south. 