Solid bitumen in deep fractures of the crystalline Precambrian basement of central Sweden – nature, origin and influence on the continental deep biosphere

• Applicant: Dr. Manuel Reinhardt
• Subject Area: Geology
• Term: since 2024
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 547262796

The continental deep biosphere contains estimated 2–19% of the Earth’s biomass. Considering this quantity, biological activity in deep continental subsurface environments should noticeably influence global element and energy cycles. However, limited access to this cryptic habitat, mainly restricted to boreholes and underground mines, leaves the deep continental biosphere and its biogeochemical cycling as yet widely unexplored. A comparably high density of traces for ancient and active microbial activity in the continental crust has been reported from the Precambrian basement of Sweden, especially central Sweden, making it an ideal study area for deep continental biosphere research. Biological activity in the deep continental subsurface of central Sweden may in parts be connected to solid bitumen occurrences in facture systems of the Precambrian crystalline basement. So far, the solid bitumen and its link to the local deep continental biosphere has not been investigated in great detail. The following open questions will be addressed in this study: (i) What is the solid bitumen composed of and does the composition vary between localities? (ii) What is the source of the solid bitumen? (iii) Is the solid bitumen used by organisms at depth as energy source? Answering these questions will help to understand the formation history of solid bitumen in the crystalline basement of central Sweden and to evaluate its importance for the deep continental biosphere. These investigations will consequently support the reconstruction of the deep continental carbon cycle.

• DFG Programme: Research Grants
• International Connection: Sweden
• Cooperation Partner: Dr. Henrik Drake