Organomineral nanocomposite carbon burial during oceanic anoxic event 2

S. C. Löhr*, M. J. Kennedy

*Corresponding author for this work

Research output: Contribution to journalArticle

15 Citations (Scopus)
10 Downloads (Pure)

Abstract

Organic carbon (OC) enrichment in sediments deposited during Oceanic Anoxic Events (OAEs) is commonly attributed to elevated productivity and marine anoxia. We find that OC enrichment in the late Cenomanian aged OAE 2 at the Demerara Rise was controlled by the co-occurrence of anoxic bottom water, sufficient productivity to saturate available mineral surfaces, and variable deposition of high surface area detrital smectite clay. Redox indicators show consistently oxygen-depleted conditions, while a strong correlation between OC concentration and sediment mineral surface area (R2Combining double low line 0.92) occurs across a range of total organic carbon (TOC) values from 9 to 33%. X-ray diffraction data indicate the intercalation of OC in smectite interlayers, while electron, synchrotron infrared and X-ray microscopy show an intimate association between clay minerals and OC, consistent with preservation of OC as organomineral nanocomposites and aggregates rather than discrete, Î1/4m-scale pelagic detritus. Since the consistent ratio between TOC and mineral surface area suggests that excess OC relative to surface area is lost, we propose that it is the varying supply of smectite that best explains variable organic enrichment against a backdrop of continuous anoxia, which is conducive to generally high TOC during OAE 2 at the Demerara Rise. Smectitic clays are unique in their ability to form stable organomineral nanocomposites and aggregates that preserve organic matter, and are common weathering products of continental volcanic deposits. An increased flux of smectite coinciding with high carbon burial is consistent with evidence for widespread volcanism during OAE 2, so that organomineral carbon burial may represent a potential feedback to volcanic degassing of CO2.

Original languageEnglish
Pages (from-to)4971-4983
Number of pages13
JournalBiogeosciences
Volume11
Issue number18
DOIs
Publication statusPublished - 18 Sep 2014
Externally publishedYes

Bibliographical note

Copyright the Author(s) 2014. Version archived for private and non-commercial use with the permission of the author/s and according to publisher conditions. For further rights please contact the publisher.

Fingerprint Dive into the research topics of 'Organomineral nanocomposite carbon burial during oceanic anoxic event 2'. Together they form a unique fingerprint.

  • Cite this