The proposed Deep Underground Science and Engineering Laboratory (DUSEL) provides a unique opportunity to study deep subsurface ecosystems, an endeavor that could fundamentally change the way we view the origin and early evolution of life on Earth, the search for novel materials, or the generation of energy to sustain future generations. We are guided by the over-arching question: What controls the distribution and evolution of subsurface life? Our hypothesis is that these controls are dominated by processes related to geology, geochemistry, geomechanics, and hydrology. Themes of scaling and the development of facies, or zones of similar characteristics, cut across all the processes. This project responds to the DUSEL S4 solicitation and has the ultimate goal to prepare a Preliminary Design Report describing experiments that will be developed as part of the DUSEL facility. Project planning activities include 1) refinement of the ecohydrological facies model using extensive Homestake data, 2) a workshop to refine goals, experimental designs, infrastructure, and education and outreach activities, and 3) writing the Preliminary Design Report and Work Breakdown Structure.
What we know about subsurface life has come from only a few studies of a few boreholes and deep mines. We are planning the first detailed study of a deep ecosystem in the context of the hydrology, geochemistry, and rock system state that sustain it at the former Homestake gold mine in the Black Hills of South Dakota where DUSEL has been proposed. The development of a long-term deep geosciences observatory at the Homestake DUSEL will revolutionize the field of deep subsurface ecohydrology. The opportunities for young scientists and international participation in such a facility will be tremendous. Results from the work will have wide ranging implications as 20% of the current earth's surface consists of a similar geologic setting. DUSEL also will facilitate experiential learning for K-12 through graduate school students working alongside world-class geoscientists. Current activities will focus in particular on South Dakota-based target audiences and programs.
The deep subsurface continental biosphere has recently been recognized as containing functioning ecosystems that could profoundly influence the way we view the importance of microorganisms to deep crustal processes, the origin and early evolution of life on Earth, our search for novel life forms and enzymes, and our approaches to future energy production. Despite the fact that the deep subsurface comprises a significant fraction of the living carbon on our planet, it is poorly understood. This work developed a framework for understanding the development of fluid pathways through crystalline fractured rocks. We also examined a set of factors contributing to permeability distribution at the DUSEL site with a specific focus on: 1) refining permeability-depth models for fractured rock to include the influence of both normal and shear fracture deformation on permeability-depth trends, 2) promote the development and testing of a stress-path fracture permeability hypothesis to examine space-time fracture permeability evolution at various depths, and 3) evaluate factors necessary to create and sustain isolated fracture clusters that could be targets for studies of ecohydrology. We produced a detailed understanding of the competing roles of deformation in fractured rock and how that could influence the connectivity of pathways. This physically-based understanding of the hydrology of fractured rocks is of relevance to many societal problems including: hydraulic fracturing, fresh water supplies in aquifers, and deep waste disposal and injection.
