The 1-2 million year old Frasassi cave system (Italy) is a dark sulfuretum that has been studied for more than a decade for it’s dynamic and conspicuous lithoautotrophic biota. Active sulfur transformations in the system include (1) sulfate reduction and pyrite/marcasite precipitation in the anoxic aquifer zone, (2) sulfide oxidation, sulfur disproportionation, and sulfide degassing in the microoxic aquifer zone, and (3) sulfide oxidation and gypsum precipitation in the oxic vadose zone. Recent studies attempt to constrain rates of sulfur transformations by integrating hydrogeology, geochemistry and microbiology. On time scale of 105 – 106 yrs, the sulfuretum is powered by ancient organic matter and tectonics, and acts like an evaporite “lift” that moves CaSO4 against gravity to elevations up to a km or more higher than the source. Microbial involvement in this tectonic “lift” leaves a signature in the form of light S isotopes in gypsum. On timescales of 101 – 103 yrs, microorganisms and the modern organic matter they produce in situ influence S transformation rates and mineral forms of S in the system, including the stabilization of unexpected mineral phases such as marcasite and beta-S8.

Biogeochemical rates in a dark sulfuretum

255th National Meeting (2018)

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.