Study On Geological Structural Characteristics And The Controlling Functions On Groundwater In Dawen River Basin

The shortage of water resources has always been a major problem faced by the bedrock mountain area.This paper studies the geological structure characteristics of Dawen River Basin and its control effect on groundwater.The results can provide certain theoretical basis and practical experience for the water exploration work in the bedrock mountain area in the future.The Da Wen River Basin originates from the county of the northern part of the province.The structure consists of four rift basins,Taylor,Tun,Da Wen and Yang.Based on the regional geological structure pattern,this paper analyses the structural distribution of the Dawen River Basin,and focuses on the formation and evolution of the Tailai Basin in the region by using the balanced section method.Then,the hydrogeological significance of geological structure is studied from the aspects of water bearing rock group distribution,magmatic intrusion,and Paleogene water abundance.Combined with the characteristics of the rich water block,the groundwater enrichment pattern is summarized.1.The development of faults is the main structural feature of Dawen River Basin.There are four types of faults in this area,namely,NW,NEW,NE and torsional faults.The tectonic evolution of the Tailai Basin,a key basin in the basin,was analyzed by using the method of balanced profiling,which experienced five stages of development:pre-Paleozoic depression,late Jurassic-early Cretaceous fault depression,Paleogene fault depression,Late Oligocene compression and Neogene thermal return.2.Tectonic evolution controls the distribution of geomorphology,stratigraphic lithology and aquifer formations,and determines the occurrence of groundwater and the characteristics of aquifer system.Based on the geological structure conditions,the Da Wen River Basin is divided into four relatively independent groundwater aquifer systems:Tai Lai,Wei,Da Wen and chi.Geological structure constitutes the boundary of aquifer system,and the occurrence,enrichment and movement of groundwater in each aquifer system are controlled by folds and faults.3.Examples show that tectonics controls groundwater enrichment:magma intrudes along tectonics to form water-resisting structures,and karstification forms karst fissures in the contact zone with carbonate rocks,thus enriching groundwater to form water-rich blocks.Semi-consolidated Paleogene glutenite strata are usually poorly water-rich,but in the northwestern margin of the Tailai Basin,the formation is well water-rich,which is controlled by the old and new structures.The typical water-rich groundwater blocks in the basin are analyzed,and the groundwater enrichment model is summarized.