Hydrogeological Characteristics and Lithofacies Palaeogeography of Cretaceous Artesian Basin, Ordos

Key words: 
• Ordos /
• artesian basin /
• Cretaceous /
• palaeogeographic groundwater /

Abstract: Ordos basin is only the largest artesian basin in China during Cretaceous. Characteristics of early Cretaceous lithofacies palaeogeographic are significant factors that influence distributing features, aquosity and quality change of three waterbearing Formations, Luohe, HuanheHuachi and Luohandong Formation. Through analyzing palaeotectonic, palaeogeographic, sedimentary environment and lithofeature, sedimentary facies types of mainly waterbearing formation are divided in this article, and relationships between sedimentary facies with aquosity and distributing rule of waterbearing formation have been discussed further.It is considered that waterbearing formations lain in the margin of basin, composed of alluvial fans, rive facies and distributary channel of delta plain, have characteristics of different episode of sedimentary granulite superposition, thicker waterbearing layers, less waterresisting layers of mudstones, optimum circle system of groundwater and low mineralization degree; and there are two types in the inside of basin, windbearing facies sandstones of Luohe Formation and Luohandong Formation are the best of waterbearing formation with charateristics of stabile occurrence, high maturation in component and structure, low solube component and reasonably spatial matching relation of roof and floor lithology and boundary isolated barrier lithology; on the other hand, waterbearing sand boies of HuanheHuachi Formation, composed of feldsparquartz finesand of bar and lakefront, occurs isolated lens and has charateristics of poor aquosity, complex porethroat texture, strong corrosion and high mineralization degree. Asymmetrical lakebasin structure of Ordos basin in EW way, formed in early Cretaceous, not only control development and distribution of main waterbearing bed, but also is the basis of structure forming of artesian basin nowadays.