BIOGEOCHEMICAL AND PLANETARY IMPLICATIONS OF SALINE LAKE BRINES (Invited Presentation)

Saline lake brines are agents of planetary change. On Earth, Mars, and likely elsewhere in our solar system, they drive landscape evolution, deposit novel minerals, and build unique rock formations. These brines, minerals, and rocks are participants in, witness to, and records of biogeochemical evolution. Importantly, the unique properties of these brines – they are denser, more viscous, saltier, and chemically dissimilar from the ground and lake waters with which we are more familiar and from which they evolve – lead to unique flow and reaction processes in saline lake environments. Here, we will present results of shallow geophysical (Electrical Resistivity Tomography, Apparent Conductivity, and Seismic refraction) surveys, hydrogeologic monitoring, and lake water, pore water, and ground water analyses in the Cariboo Plateau of British Columbia, Western Canada. The chemical and electrical analyses clearly demonstrate highly conductive brines in the subsurface below all surveyed lakes. At the same time, they also show sharp interfaces with dilute, resistive fluids – regional ground waters – that suggest density-driven flow via Rayleigh-Taylor instabilities. The vigor of these instabilities depends on a number of parameters, including the geometry of the basin, the composition of the brine, and the regional groundwater flux. Ultimately, the movement and mixing of these waters dictates the biological habitability of these saline lake systems, the minerals they deposit, and the chemical and isotopic signals they record. We will conclude by presenting a series of reactive transport simulations designed to investigate the spectrum of fluid flow behavior in these unique geologic systems and their implications for biogeochemical and planetary proceses.