Compaction of Muddy Sediment and Its Significance to Groundwater Chemistry

Muddy sediment is one of the most common aquitards. During the burial compaction of mud, the pressure and temperature of strata increased with depth, in which some complex physical, chemical and biological reactions occurred. Meanwhile, a large amount of porewater, which interacts with microbes, organic matter and minerals in mud, would be discharged into adjacent aquifers. Numerous previous efforts by geologists have put forward some evidences, indicating that a portion of components (such as ions and nutrient) in groundwater are from muddy sediments. This paper provides a brief overview of efforts on different reactions in pore water in which environments change from oxidation to reduction and interfaces between the aquitard and the aquifer. Then, in the view of geological evolution, an idea is proposed that mud provided not only water but also material source for adjacent aquifer during its compaction and burial. In order to further understand the genesis of natural groundwater, especially natural inferior groundwater and brine, the diagenetic reaction and mineralization, water-rock interaction during the compaction of sediment should be considered, which will be of great significance in hydrogeology.