QUANTIFYING THE IMPACT OF AEOLIAN DUST ON THE COMPOSITION OF YELLOWSTONE WATERS AND THEIR PRECIPITATES

An important unanswered question in our understanding of Yellowstone hydrothermal systems is- how much do aeolian components impact the chemistry of hot spring fluids and their precipitates? Answering this question has implications for our understanding of: a) water-rock interaction; b) U-series dating of the precipitate deposits; and, c) what nutrient components are available for chemotrophic life.

To answer this question we looked at anion, cation and trace-element abundances and Sr, Nd, Hf and Pb isotopic composition of the fluids and sinter deposits of Steep Cone Spring, Sentinel Meadows, Lower Geyser Basin in Yellowstone National Park. We chose Steep Cone for two reasons. First, undercutting by Sentinel Creek has recently caused a section of the cone to collapse, providing an unprecedented temporal record of its structural and chemical evolution. Second, Steep Cone is perched high above its surroundings, allowing us to examine the impact of wind-blown dust on compositional measurements without disturbances from local fauna or major surface processes.

Our results show that wind-blown dust has a significant influence on both Steep Cones sinter deposits and modern waters. This influence is variable across time. Our calculations show that the chemical and isotopic data are influenced by a mixture of dust coming from the Columbia River basalts (Stefano et al., 2019; Chem Geo 513) and more regional components coming from across the western US (Aarons et al., 2017; GCA 215; Monroe et al., 2019; Aeolian Res. 38). Identifying sources of contamination is critical for accurately determining uranium-series ages, which are an important potential chronometer for determining the timescales of Steep Cone’s formation. Additionally, understanding the extent and composition of wind-blown dust in Yellowstone’s hydrothermal waters provides insight into the availability of nutrient sources for chemotrophic biota.