Methanogenesis dominates organic matter mineralization in ferruginous sediments
Abstract
Organic matter mineralization and diagenesis in ferruginous (Fe-rich) sediments played a key role in biogeochemical cycling during the Archaean and Proterozoic eons. Knowledge of organic matter mineralization in ferruginous sediments, however, remains almost entirely conceptual, as analogous modern sediments are extremely rare and largely unstudied. We used several biogeochemical analyses to assess rates and pathways of organic matter mineralization in modern ferruginous sediments from Lake Towuti, Indonesia, as an analogue to the Archaean and Proterozoic Ocean. We used a suite of biogeochemical analyses as well as modeling to assess rates and pathways of organic matter mineralization. Despite an abundance of ferric iron minerals known to support microbial respiration in laboratory experiment, organic matter degradation proceeds predominantly through methanogenesis. Co-existence of abundant methane and ferric iron throughout the sediment further suggests negligible anaerobic methane oxidation coupled to iron respiration. This tendency towards methanogenesis, without anaerobic methane oxidation, implies that methanogenesis would have been important to organic matter mineralization in Precambrian times, leading to high atmospheric CH4 concentrations, and playing a key role regulating Earth's early climate.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFM.B22B..08K
- Keywords:
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- 0414 Biogeochemical cycles;
- processes;
- and modeling;
- BIOGEOSCIENCES;
- 0426 Biosphere/atmosphere interactions;
- BIOGEOSCIENCES;
- 0448 Geomicrobiology;
- BIOGEOSCIENCES;
- 0473 Paleoclimatology and paleoceanography;
- BIOGEOSCIENCES