96-14 Out of the Salt Pan, into the Diapir – Survival in the Salty Deep Biosphere

Session: Twenty-Seven Years of Advances in Understanding Salt-Sediment Interaction: A Legacy of Katherine A. Giles

Presenting Author:

Alexa Couroux

Authors:

Couroux, Alexa M.¹, Martinez, Valeria², Gannaway Dalton, Cora Evelyn³, Brunner, Benjamin⁴

(1) Department of Earth, Environmental and Resource Sciences, The University of Texas at El Paso, El Paso, TX, USA, (2) Department of Earth, Environmental and Resource Sciences,, The University of Texas at El Paso, El Paso, TX, USA, (3) Geosciences, Utah State University, Price, UT, USA, (4) Department of Earth, Environmental and Resource Sciences, University of Texas at El Paso, El Paso, TX, USA,

Abstract:

Salt diapirs play a significant role in the oil and gas industry, by influencing hydrocarbon movement and reservoir development, acting mostly as barriers, but occasionally as migration pathways. Salt diapirs are also promising targets for the storage of hydrogen gas (H₂) as carbon-free fuel. Subsurface microbial activity can alter the porosity and permeability of rocks, mediating genesis of secondary porosity as well as occluding porosity by cementation. Moreover, microbes can cause oil souring by hydrogen sulfide production and consume stored fuels. From a geomicrobiology perspective, it is unclear whether microbes involved in such processes are introduced by drilling or if they are native to the subsurface environment, and in the latter case, how they got there. The fact that salt tectonic processes can bring deeply buried strata into near-surface environments opens the intriguing question of whether microbes thriving in evaporite basins can first be incorporated within layered evaporite deposits (‘salt’) and later be exhumed during salt diapirism. With our study, we assess 1) what types of microbes or what consortium of microbes is best suited to survive burial within the salt, followed by exhumation as the diapir rises, and 2) how the unique physical properties of salt may benefit or be detrimental to survival. We find that, compared to a burial in an open-marine sedimentary environment, salt diapirs may provide unique advantages. Layered evaporite sequences often host not just evaporite rocks but also non-evaporitic rocks, a combination of lithologies that offers consortia of micro-organisms ample metabolic opportunities, as well as a means to dispose of their waste products. Unlike typical marine burial settings, where high pressures and temperatures threaten microbial viability, the high thermal conductivity of salt creates a chimney effect, allowing microbes to persist at greater depths. Additionally, salt can act as a seal, preserving porosity in encased rock units and maintaining microbial habitats. Given microbes’ 3.5-billion-year history, evolution had numerous opportunities to optimize resilience to burial and exhumation in salt bodies. This research integrates salt tectonics, petroleum geoscience, microbial ecology, petrophysics, and geochemistry, offering insights into both applied and fundamental Earth system science.

Geological Society of America Abstracts with Program. Vol. 57, No. 6, 2025

doi: 10.1130/abs/2025AM-4828

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