Date of Graduation

5-2019

Document Type

Thesis

Degree Name

Master of Science in Geology (MS)

Degree Level

Graduate

Department

Geosciences

Advisor/Mentor

Hays, Phillip D.

Committee Member

Davis, Ralph K.

Second Committee Member

Brahana, John V.

Keywords

Carbon-14 age dating; Hot Springs National Park; Arkansas; Hydrogeochemistry; Mean Residence Time; NETPATH

Abstract

Mean water age for spring discharge in Hot Springs National Park was calculated as approximately 4,400 years by Bedinger et al (1978) using carbon-14. Their analysis indicated that the water was a mixture of a small portion of cold water that was less than twenty years old with a preponderance of hot water. However, this result includes some error due to Bedinger et al. using general isotopic values for soil dissolved inorganic carbon and mineral carbon instead of obtaining actual values from the study area. A more accurate age calculation for the springs has been made possible by additional geological and geochemical data collected (Bell and Hays, 2007; Kresse and Hays, 2009).An improved age model for the Hot Springs National Park was be developed using the USGS software NETPATH-WIN; this program models the isotopic compositions and net geochemical mass balance reactions along the flowpath. NETPATH-WIN is capable of calculating possible combinations of mass transfers. Rayleigh distillation calculations can also be applied to each model to predict carbon and radiocarbon dates at the end path. Seven different A0 models will be tested in conjunction with three different geochemical systems with mixing and non-mixing scenarios.

Geochemical, physical, and selected field parameters were collected from 10 cold-water springs, 30 cold-water wells, and 16 thermal springs, primarily by USGS personnel during three sampling events: 1) from January through September 1972; 2) from September 2007 to June 2008; and 3) during June 2018 by the author. Analysis from the 181 model runs that passed a QA/QC check determined that the most applicable most applicable geochemical system scenario and A0 model for the flow system is the Non-Mixing Alkaline-Earth geochemical system with the Mass Balance (1990) A0 model that produced a median mass residence time of 4,375 years.

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