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The aerobic diagenesis of Mesoproterozoic organic matter

Wang, Xiaomei ; Zhao, Wenzhi ; Zhang, Shuichang ; Wang, Huajian ; Su, Jin ; Canfield, Donald E and Hammarlund, Emma U LU (2018) In Scientific Reports 8(1). p.1-10
Abstract

The Xiamaling Formation in the North China Block contains a well-preserved 1400 Ma sedimentary sequence with a low degree of thermal maturity. Previous studies have confirmed the dynamic and complex nature of this evolving marine setting, including the existence of an oxygen-minimum zone, using multi-proxy approaches, including iron speciation, trace metal dynamics, and organic geochemistry. Here, we investigate the prevailing redox conditions during diagenesis via the biomarkers of rearranged hopanes from the finely laminated sediments of the organic-rich black shales in Units 2 and 3 of the Xiamaling Formation. We find that rearranged hopanes are prominent in the biomarker composition of the oxygen-minimum zone sediment, which is... (More)

The Xiamaling Formation in the North China Block contains a well-preserved 1400 Ma sedimentary sequence with a low degree of thermal maturity. Previous studies have confirmed the dynamic and complex nature of this evolving marine setting, including the existence of an oxygen-minimum zone, using multi-proxy approaches, including iron speciation, trace metal dynamics, and organic geochemistry. Here, we investigate the prevailing redox conditions during diagenesis via the biomarkers of rearranged hopanes from the finely laminated sediments of the organic-rich black shales in Units 2 and 3 of the Xiamaling Formation. We find that rearranged hopanes are prominent in the biomarker composition of the oxygen-minimum zone sediment, which is completely different from that of the sediment in the overlying anoxic strata. Since the transition process from hopanes to rearranged hopanes requires oxygen via oxidation at the C-l6 alkyl position of 17α(H)-hopanes, we infer that dissolved oxygen led to the transformation of hopane precursors into rearranged hopanes during the early stages of diagenesis. The use of hopanoid hydrocarbons as biomarkers of marine redox conditions has rarely been previously reported, and the hydrocarbon signatures point towards oxic bottom waters during the deposition of Unit 3 of the Xiamaling Formation, which is consistent with the earlier oxygen-minimum zone environmental interpretation of this Unit.

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author
publishing date
type
Contribution to journal
publication status
published
in
Scientific Reports
volume
8
issue
1
article number
13324
pages
1 - 10
publisher
Nature Publishing Group
external identifiers
  • scopus:85052949202
  • pmid:30190572
ISSN
2045-2322
DOI
10.1038/s41598-018-31378-6
language
English
LU publication?
no
id
dc9010b4-8ad9-4285-a37a-e928ad21e050
date added to LUP
2019-04-10 16:20:38
date last changed
2020-03-29 07:36:44
@article{dc9010b4-8ad9-4285-a37a-e928ad21e050,
  abstract     = {<p>The Xiamaling Formation in the North China Block contains a well-preserved 1400 Ma sedimentary sequence with a low degree of thermal maturity. Previous studies have confirmed the dynamic and complex nature of this evolving marine setting, including the existence of an oxygen-minimum zone, using multi-proxy approaches, including iron speciation, trace metal dynamics, and organic geochemistry. Here, we investigate the prevailing redox conditions during diagenesis via the biomarkers of rearranged hopanes from the finely laminated sediments of the organic-rich black shales in Units 2 and 3 of the Xiamaling Formation. We find that rearranged hopanes are prominent in the biomarker composition of the oxygen-minimum zone sediment, which is completely different from that of the sediment in the overlying anoxic strata. Since the transition process from hopanes to rearranged hopanes requires oxygen via oxidation at the C-l6 alkyl position of 17α(H)-hopanes, we infer that dissolved oxygen led to the transformation of hopane precursors into rearranged hopanes during the early stages of diagenesis. The use of hopanoid hydrocarbons as biomarkers of marine redox conditions has rarely been previously reported, and the hydrocarbon signatures point towards oxic bottom waters during the deposition of Unit 3 of the Xiamaling Formation, which is consistent with the earlier oxygen-minimum zone environmental interpretation of this Unit.</p>},
  author       = {Wang, Xiaomei and Zhao, Wenzhi and Zhang, Shuichang and Wang, Huajian and Su, Jin and Canfield, Donald E and Hammarlund, Emma U},
  issn         = {2045-2322},
  language     = {eng},
  month        = {09},
  number       = {1},
  pages        = {1--10},
  publisher    = {Nature Publishing Group},
  series       = {Scientific Reports},
  title        = {The aerobic diagenesis of Mesoproterozoic organic matter},
  url          = {http://dx.doi.org/10.1038/s41598-018-31378-6},
  doi          = {10.1038/s41598-018-31378-6},
  volume       = {8},
  year         = {2018},
}