265-6 Factors Influencing Ambient Gas Concentrations in South-Central Kentucky Karst

Session: New Frontiers in Cave and Karst Science (Posters)

Poster Booth No.: 105

Presenting Author:

Madison High

Authors:

High, Madison¹, Washburn, Rachel², Washburn, Alex Matthew³, Zierer, Deron⁴, Walton, Zach⁵, Hawksley, Andrew⁶

(1) Kentucky Geological Survey, Lexington, KY, USA, (2) Kentucky Geological Survey, Lexington, KY, USA; University of Kentucky, Lexington, KY, USA, (3) Kentucky Geological Survey, Lexington, KY, USA, (4) Kentucky Geological Survey, Lexington, KY, USA; University of Kentucky, Lexington, KY, USA, (5) Kentucky Geological Survey, Lexington, KY, USA, (6) Kentucky Geological Survey, Lexington, KY, USA,

Abstract:

South-central Kentucky is home to over five thousand caves formed in Mississippian-aged limestones. In addition to being well-known for its karst features, south-central Kentucky also has numerous orphaned oil and gas wells, with at least one drilled directly through a cave. Karstic systems could be acting as pathways for methane and other gases emitted from these wells. This research investigates spatial and temporal variations in methane (CH4), carbon dioxide (CO2), and water vapor (H2O) concentrations across both commercial and wild caves to assess the influence of human activity and legacy oil and gas infrastructure on cave atmosphere dynamics. 

The project is ongoing and will include investigation of a minimum of ten caves throughout the study area that vary in proximity to orphaned oil and gas wells, levels of tourist activity, and morphology. Gas concentrations are collected via walkthrough surveys using a LI-COR LI-7810 trace gas analyzer, which provides real-time readings of CH4 (ppb), CO2 (ppm), and H2O (ppm). Cave temperature, barometric pressure, and time of day are also recorded at each site. Caves are revisited over time to evaluate how environmental factors such as temperature and barometric pressure, anthropogenic activity, and legacy infrastructure affect these gases on both diurnal and seasonal timescales. 

We hypothesize that elevated methane concentrations in karst features could be associated with proximity to leaking orphaned hydrocarbon wells, while caves unaffected by legacy infrastructure may exhibit concentrations of methane below that of the atmosphere. Preliminary results from one commercially visited cave show a sharp decline in CH4 from atmospheric levels (~2,000 ppb) at the entrance to less than 100 ppb deeper in the cave, despite active ventilation with outside air. This suggests the cave may be acting as a methane sink—a finding that will be further evaluated through upcoming surveys. 

This research can be used as a basis for future investigations into how cave gas composition may have broader impacts within karst systems, including altered rates of speleogenesis, mineral precipitation, and growth and development of microbial communities. Understanding these relationships is essential not only for evaluating the long-term evolution of karst systems but also for assessing the ecological impacts of emissions from leaking oil and gas wells on sensitive cave environments and the potential impacts of tourism in commercial caves. 

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

doi: 10.1130/abs/2025AM-8674

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