Status: this preprint is open for discussion and under review for Biogeosciences (BG).
Microbial Interactions with Dissolved Organic Matter (DOM) from Immature Cretaceous Marine Black Shale: Implications for subsurface carbon flux and geothermal energy systems
Muhammad Sabiu Jibrinand Abdulhamid Dahiru
Editorial note: the list of co-authors is currently part of an investigation and could change.
Abstract. Microbial transformation of dissolved organic matter (DOM) is a central process in subsurface carbon cycling, yet its long-term dynamics in shale environments remain poorly constrained. We conducted an 810‑day incubation experiment using DOM leached from immature Cretaceous marine black shale to investigate fluid–rock–microbe interactions and their role in climate‑active gas generation. Liquid chromatography–organic carbon detection (LC‑OCD) revealed progressive microbial degradation of labile DOM pools and the accumulation of recalcitrant fractions, accompanied by sustained CO₂ and CH₄ release. These findings demonstrate that shale DOM can fuel persistent microbial metabolism, restructure DOM composition, and contribute to subsurface carbon fluxes over extended timescales. Our results highlight the ecological significance of shale DOM biodegradation in unlocking deep carbon reservoirs and provide new insights into the microbial mediation of subsurface biogeochemical cycles.
Received: 18 May 2026 – Discussion started: 04 Jun 2026
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Department of Pure and Industrial Chemistry, Bayero University, Kano, 700241, Nigeria
Lyell Centre, Heriot-Watt University, EH14 4AS, UK
Abdulhamid Dahiru
Lipid Technology Laboratory, School of Bioresources and Technology, King Mongkut's University of Technology Thonburi, Bangkhunthian, Bangkok, 10150, Thailand
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We studied how microbes interact with organic matter released from ancient shale rock over more than two years. We found that this material can fuel microbial activity and lead to continuous production of carbon dioxide and methane. These results show that deep rocks are not inert but can influence climate and energy systems, highlighting the need to understand subsurface processes when developing geothermal energy.
We studied how microbes interact with organic matter released from ancient shale rock over more...
