- Geobiology of modern and ancient cold seep ecosystems
- Trace and rare earth element geochemistry of authigenic minerals
- Low temperature geochemical modeling of biogeochemical processes
Trace elements in pyrite - A new proxy for modes of sulfate reduction and fluid composition at hydrocarbon seeps?
The key biogeochemical process at cold seeps today is the sulfate-driven anaerobic oxidation of methane (AOM), which triggers the formation of authigenic minerals within shallow sediments. These minerals are are excellent archives of biological and geochemical processes operating through geologic time. Aside from authigenic carbonates, pyrite is the other common solid phase product of AOM at seeps, and represents an understudied archive of geochemical and microbiological processes. This project aims to put pyrite in the spotlight as a prime target for elucidating previously unconstrained parameters that govern environmental conditions in these chemosynthesis-based settings. Using trace element geochemistry, two questions are tackled:
(1) Is authigenic pyrite a reliable archive for fluid chemistry at seeps?
(2) Does pyrite record different sulfate reduction pathways at seeps?
Daniel Smrzka, Gerhard Bohrmann, Yiting Tseng, Wolfgang Bach, Patrick Monien, Thomas Pichler, Henning Fröllje (FB 5), Marta Torres (Oregon State University, USA), Jörn Peckmann, Zhiyong Lin (University of Hamburg)
Putative fossilized sulfur oxidizing bacteria from Devonian cold seeps, Morocco
The colorless sulfide-oxidizing bacteria are important agents in themarine sulfur cycle, and may have been so since the Precambrian. The genera Thiomargerita, Thioploca, and Beggiatoa are all members of the colorless sulfur-oxidizing bacteria, and are among the largest unicellular organisms known on Earth.
Today, these bacteria inhabit shallow seafloor sediments where their metabolism couples the carbon, sulfur and nitrogen cycles. At modern cold methane seeps, where hydrocarbon compounds are emitted from deeper organic-rich sediments to bottom waters, sulfur oxidizing bacteria form large microbial mats that utilize dissolved reduced sulfide and oxidize it to elemental sulfur and sulfate using molecular oxygen derived from seawater. This process has a profound impact on the distribution of dissolved chemical species, microbial ecology, and the stability of authigenic carbonate minerals.
This project investigates putative Devonian microfossils of sulfur oxidizing bacteria from an ancient cold seep site from Morocco.
Daniel Smrzka (FB 5), Jennifer Zwicker (University of Vienna), Jörn Peckmann (University of Hamburg)
Phosphatic stromatolites within black shales from the Devonian - Carboniferous boundary. Rheinisches Schiefergebirge, Germany
Phosphatic stromatolites are unusual microbial fossils in the rock record. These fossil microbiota are known from the Proterozoic to the Phanerozoic, and occur in multitudes of morphologies such as oncoid, cone-like stromatolites, domal stromatolites, and microstromatolites.
A yet unknown occurrence of these unique fossils is currently under investigation from the Lower Alum Black Shale deposited during the Devonian – Carboniferous transition in Central Germany.
These microbial fossils possibly mediated one of several types of metabolisms that coupled the geomicrobiological cycles of sulfur, iron, and phosphorus.
It is the goal of this project to establish the mechanisms of phosphorite formation, as well as to elucidate possible microbial metabolisms that were active.
Jennifer Zwicker (University of Vienna), Daniel Smrzka (FB 5), Jörn Peckmann (University of Hamburg)