title: Long term geological record of a global deep subsurface microbial habitat in sand injection complexes.
abstract: There is extensive evidence from drilling into continental margins for microbial colonization of a deep biosphere. However it is difficult to prove deep biosphere activity in the geological record, where evidence for life is dominated by the remains of organic matter buried after deposition at the surface. Nevertheless we propose that natural injections of sand into muddy strata at continental margins represent an excellent habitat opportunity for deep microbial activity down to several kilometres' present day depth. Sulphur isotope data for iron sulphides precipitated soon after injection indicate consistent microbial sulphate reduction through the geological record. The complexes are favourable sites for colonization, because high permeability and extensive sand/mud interface allow ready availability of electron donors and nutrients. The measured examples of iron sulphide in injected sands extend back to the Proterozoic, and show that injected sand complexes have been a long-term environment for deep subsurface microbial colonization.
authors.affiliation: School of Geosciences, University of Aberdeen, Aberdeen AB24 3UE, United Kingdom. j.parnell@abdn.ac.uk
authors.forename: John
authors.initials: J
authors.lastname: Parnell
authors.forename: Adrian J
authors.initials: AJ
authors.lastname: Boyce
authors.forename: Andrew
authors.initials: A
authors.lastname: Hurst
authors.forename: Brett
authors.initials: B
authors.lastname: Davidheiser-Kroll
authors.forename: Joanna
authors.initials: J
authors.lastname: Ponicka
mesh_terms: D001419:Bacteria / Q000378:metabolism*; D017753:Ecosystem; D004777:Environment; D019015:Geologic Sediments / Q000382:microbiology*; D007501:Iron / Q000737:chemistry*; D008855:Microscopy, Electron, Scanning; D012822:Silicon Dioxide / Q000737:chemistry*; D013440:Sulfides / Q000737:chemistry*; D013460:Sulfur Isotopes / Q000032:analysis
chemical_list: D013440:Sulfides; D013460:Sulfur Isotopes; C011342:pyrite; D012822:Silicon Dioxide; D007501:Iron