Shale interfaces as heterotrophic hotspots in the deep subsurface Michael J. Wilkins School of Earth Sciences Ohio State University

Shale formations are relevant at the global scale

Do shale interfaces act as hotspots for microbial activity in the subsurface?

Krumholz et al., Nature, 1998 SRB and acetogenic microorganisms were isolated from these materials

Key questions 1.Can we support the shale interface ‘hotspot’ hypothesis in older, deeper shale? (DCO carbon/life interactions) 2.What are potential limits to life with regard to pore sizes in shale rock? (DCO environmental limits) 3.Have populations with shale formations been isolated since deposition? (DCO define diversity/distribution) 4.What is the extent of phylogenetic and functional diversity within these environments, given the heterogeneous nature of the carbon substrates (DCO define diversity/distribution) 5.How do microbially catalyzed processes in DSIs impact hydrocarbon resources across the Appalachian Basin (e.g., hydrocarbon oxidation, methane cycling) (ICDP societal needs)

Potential sites for drilling? Marcellus shale is shallower (500-2,300 m) Utica shale (1,400-4,000 m) Utica in Ohio is thought to be rich in oil, condensate, and natural gas liquids

Shale stratigraphy in eastern Ohio

Potential sites for drilling?

Pre-existing site characterization

Geophysical downhole gamma ray logs N S

Microbiological data to date Analyses and results have been focused on hydraulically fractured flow- back fluids However, results indicate that halophilic indigenous biomass is present, and active Evidence for a strong viral signal Taken from Cluff et al., ES&T, 2014

Since the last study on DSIs… The advancement of several new techniques/technologies will enable new questions to be asked Omics approaches – shotgun community genomics, single cell genomics? Noble gas measurements Cryo-electron microscopy Carbon turnover times via racemization measurements?

Other benefits of sites in Ohio 1.Extensive drilling expertise in this region due to energy extraction activities 2.Land owned by Ohio State University --> long-term access to wells 3.Complementary site characterization via NETL project? (USEEL laboratory funded to work at the EAR) 4.Shale has global relevance 5.Opportunity to study effects of temperature/depth across formations