Regional Geochemical and Hydrogeological Study of the Great Plains Aquifer System and the Western Interior Plains Aquifer System in the Mid-Continent, United States
The Great Plains (GP) aquifer system and the Western Interior Plains (WIP) aquifer system exhibit a wide range of chemical and isotopic variability that reflect a range of fluid mixing processes. Chemical variability exists within the two aquifers as evidenced by the salinity ranging from 300 mg/l to 74,000 mg/l in the GP and from 20,000 mg/l to 200,000 mg/l in the WIP. The study area in the mid-continent extends a 1000 km east to west, from the Colorado Front Range to Central Missouri.
Previous work in the WIP identified three geochemical endmembers of distinct origin: Endmember 1 originating in the Ozark Mountains of western Missouri, Endmember 2 originating somewhere west of southeast Kansas, and Endmember 3 originating in the Anadarko Basin in Oklahoma. Geochemical modeling suggests that the geochemistry of the GP and the WIP in the study area is, in part, controlled by geographically specific inputs of fluid. Oxygen, hydrogen, strontium and chlorine isotopic analyses together with major element and trace element analysis are used to characterize sources of dissolved constituents, recharge areas, chemical endmembers and flow directions.
Musgrove and Banner (1993) showed that hydrogen and oxygen isotopes are good tools to distinguish groundwater recharge areas. In this investigation, oxygen and hydrogen isotopes are used to determine the origin or recharge area of the groundwater, (i.e. meteoric, glacial, high altitude or colder climate conditions). Stable isotopes are also used to determine if diffusion is a significant process for generating salinity. Strontium is used to determine the extent of fluid rock interaction and the origin of salinity while chlorine will be used to provide an age range of the groundwaters and identify flow paths.
This is the research of Ph.D. candidate Rosario Vasquez Scheerhorn.