Abstract
Basin models can simulate geological, geochemical and geophysical processes and potentially also the deep biosphere, starting from a burial curve, assuming a thermal history and utilizing other experimentally obtained data. Here, we apply basin modelling techniques to model cell abundances within the deep coalbed biosphere off Shimokita Peninsula, Japan, drilled during Integrated Ocean Drilling Program Expedition 337. Two approaches were used to simulate the deep coalbed biosphere: (a) In the first approach, the deep biosphere was modelled using a material balance approach that treats the deep biosphere as a carbon reservoir, in which fluxes are governed by temperature-controlled metabolic processes that retain carbon via cell-growth and cell-repair and pass it back via cell-damaging reactions. (b) In the second approach, the deep biosphere was modelled as a microbial community with a temperature-controlled growth ratio and carrying capacity (a limit on the size of the deep biosphere) modulated by diagenetic-processes. In all cases, the biosphere in the coalbeds and adjacent habitat are best modelled as a carbon-limited community undergoing starvation because labile sedimentary organic matter is no longer present and petroleum generation is yet to occur. This state of starvation was represented by the conversion of organic carbon to authigenic carbonate and the formation of kerogen. The potential for the biosphere to be stimulated by the generation of carbon-dioxide from the coal during its transition from brown to sub-bituminous coal was evaluated and a net thickness of 20 m of lignite was found sufficient to support an order of magnitude greater number of cells within a low-total organic carbon (TOC) horizon. By comparison, the stimulation of microbial populations in a coalbed or high-TOC horizon would be harder to detect because the increase in population size would be proportionally very small.
| Original language | English |
|---|---|
| Pages (from-to) | 804-829 |
| Number of pages | 26 |
| Journal | Basin Research |
| Volume | 32 |
| Issue number | 5 |
| Early online date | 4 Sept 2019 |
| DOIs | |
| Publication status | Published - Oct 2020 |
Bibliographical note
ACKNOWLEDGEMENTSThe authors are grateful to all crews, drilling team members, lab technicians and scientists on the drilling vessel Chikyu for supporting core sampling and on board measurements during the Chikyu shakedown cruise CK06‐06 and the Integrated Ocean Drilling Program (IODP) Expedition 337. This work was supported in part by the Japan Society for the Promotion of Science (JSPS) Strategic Fund for Strengthening Leading‐Edge Research and Development (to F.I. and JAMSTEC), the JSPS Funding Program for Next Generation World‐Leading Researchers (NEXT Program, no. GR102 to F.I.). All shipboard and shore‐based data presented in this manuscript are archived and publicly available on‐line in either the IODP Expedition 337 Proceedings through the J‐CORES (http://sio7.jamstec.go.jp/j-cores.data/337/C0020A/), the PANGAEA database (www.pangaea.de, doi.org/10.1594/PANGAEA.845984), or Inagaki et al., 2015, respectively. Petromod Basin Modelling software was provided by Schlumberger to the University of Aberdeen. This is a contribution to the Deep Carbon Observatory (DCO). SAB wishes to thank HSB for support preparing the manuscript.
DATA AVAILABILITY STATEMENT
All shipboard and shore‐based data presented in this manuscript are archived and publicly available on‐line in either the IODP Expedition 337 Proceedings through the J‐CORES (http://sio7.jamstec.go.jp/j-cores.data/337/C0020A/), the PANGAEA database (www.pangaea.de, https://doi.org/10.1594/PANGAEA.845984), or Inagaki et al., 2015, respectively.
Keywords
- basin modelling
- biodegredation
- deep biosphere
- Integrated Ocean Drilling Program
- IODP 337
- Shimokita coal
- subduction related basin
