| Titre | Molecular and isotopic evaluation of the maturation history of the organic matter in an Ordovician aquiclude (Michigan Basin): Evidence for late diagenetic biodegradation |
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| Auteur | Jautzy, J J ;
Ahad, J M E; Jensen, M; Clark, I D |
| Source | Organic Geochemistry vol. 125, 2018 p. 129-141, https://doi.org/10.1016/j.orggeochem.2018.09.007 |
| Image |  |
| Année | 2018 |
| Séries alt. | Ressources naturelles Canada, Contribution externe 20200263 |
| Éditeur | Pergamon-Elsevier Science Ltd |
| Document | publication en série |
| Lang. | anglais |
| DOI | https://doi.org/10.1016/j.orggeochem.2018.09.007 |
| Media | papier; en ligne; numérique |
| Formats | pdf |
| Province | Ontario |
| SNRC | 41A/03; 41A/04; 41A/05; 41A/06 |
| Région | Bruce Nuclear site |
| Lat/Long OENS | -82.0000 -81.0000 44.5000 44.0000 |
| Sujets | maturité organique; géochimie organique; diagenèse; biodégradation; isotopes de carbone; isotopes d'hydrogène; études des isotopes stables; Bassin de Michigan ; géochimie; Nature et environnement;
Sciences et technologie; pédologie; Ordovicien |
| Illustrations | profils; cartes de localisation; échelles stratigraphiques; graphiques |
| Diffusé | 2018 09 08 |
| Résumé | (disponible en anglais seulement)
Previous characterization of a low permeability (10 (16) <= K-h <= 10 (12) m s (1)) and high salinity (> 5 Mof Cl , > 10 x seawater salinity) aquiclude, in
Upper Ordovician-aged sediments situated on the eastern flank of the Michigan Basin, where a deep geological repository for low and intermediate level nuclear waste is proposed, suggested a microbial origin for CH4 and CO2 based on their stable
isotope values. CH4 is believed to have been produced and trapped during the Paleozoic in a relatively discrete and high organic matter (OM) horizon at the shale/carbonate transition. To further investigate the efficiency of confinement of this
aquiclude, here we present detailed isotopic and geochemical stratigraphic profiles of OM and biomarkers, with the objective of understanding the origin of CH4 and its relative timing of confinement. Classical diagnostic ratios of polycyclic aromatic
hydrocarbons, relative abundances of hopanes and degraded hopanes coupled to dual compound-specific isotopic analysis of n-alkanes, as well as delta C-13 analysis on different fractions of OM were measured. A partitioning of the Ordovician
sedimentary succession into two systems is observed with an upper system that is self-sourced and confined, hosting the microbially derived CH4 with evidence of late diagenetic OM biodegradation and a lower system that reveals later secondary oil
migration which has overprinted the organic geochemical record. We propose a conceptual model that would explain the generation and preservation of this paleo-bioreactor over time using the maturation history reconstruction derived from this dataset.
This work not only provides essential field empirical evidence of a relationship between methanogenesis and late diagenetic biodegradation, but also shows the power of dual-compound-specific isotope analyses in deciphering between different
maturation processes affecting OM in natural subsurface settings. |
| GEOSCAN ID | 326675 |
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