Stinky bubbles in Diamond Fork Canyon (Utah): A curious case of whodunit?
This paper presents the results of a scientific investigation into the cause of the stench in Diamond Fork Canyon, located in the Central Wasatch Front. This is an area with a rich cultural history that is also very popular for outdoor recreation. The stench was determined to be associated with bubbles (gas seeps) in thermal springs, based on the analysis of samples collected from the Diamond Fork and Fifth Water drainages. Bubbles were collected from the springs using an inverted funnel and transferred to appropriate containers for compositional and isotopic laboratory analysis. The results are consistent with the hypothesis that the stench is due to relatively high (1200-4300 ppm) concentrations of hydrogen sulfide (H2S) in the gas phase, concentrations sufficient to induce death if the collective bubbles are efficiently inhaled. The bubbles also contain a significant concentration of a very dry (i.e., mainly methane) thermogenic gas; approximately 90 percent by volume in the Fifth Water Hot Springs and 5 percent in the Diamond Fork area. Using the compositional and isotopic data, both of these components can be interpreted as originating from processes associated with thermal cracking of a hydrocarbon source rock and/or crude oil. The logical candidate for the genetic correlation is the Phosphoria Formation, which has circumstantial support from the drilling records of the Amoco Cottonwood Canyon #1 well in the study area. Water analyses in the two sample areas provide evidence for a fairly complex hydraulic system in Diamond Fork Canyon, with sampling localities classified as brackish and mildly alkaline waters, but the solute chemistry differs with the Fifth Water area being a mixed calcium sulfate type while the Diamond Fork area is a sodium bicarbonate type. The conspicuous blue color of the water that is occasionally reported in the thermal pools is consistent with the hypothesis of the presence of sulfur colloids in the water that can form as a partial oxidation by-product of the hydrogen sulfide that is present in the gas bubbles. An overall objective of this paper is to demonstrate that science can be interesting and fun (i.e., sleuth via geochemical forensics), a lesson we wish to share with our readers that have a passion for this popular recreation area.