Geochemistry of the alginite and amorphous organic matter from type II-S kerogens

B. Artur Stankiewicz, Michael A. Kruge, Maria Mastalerz, Gary L. Salmon

Research output: Contribution to journalArticle

34 Scopus citations

Abstract

Maceral fractions of the Type II-S kerogens from the Monterey Formation (Miocene. California. U.S.A.) and Duwi Formation (Campanian/Maastrichtian, Egypt) were separated by density gradient centrifugation. The Monterey Fm. kerogen sample was comprised chiefly of light red-fluorescing amorphous organic matter (AOM), the flash pyrolyzate of which was characterized by a predominance of alkylbenzenes, alkylthiophenes and alkylpyrroles. In contrast, the pyrolyzates of its alginite concentrate showed a highly aliphatic character, typical of this maceral, with the series of n-alkenes and n-alkanes (C6- C26) predominating. The pyrolyzate of the dominant light brown-fluorescing AOM of the Duwi Fm. kerogen had a relatively high concentration of alkylbenzenes and alkylthiophenes, while its elginite concentrate showed a more aliphatic character upon pyrolysis. There was a marked enrichment of thiophenic sulfur in the light-colored AOM of both samples (and also pyrrolic nitrogen in the case of the Monterey) relative to the alginite. The results support a bacterially-mediated, degradative origin for Type II-S amorphous organic matter, with algal remains as the primary source of the kerogen.

Original languageEnglish
Pages (from-to)495-509
Number of pages15
JournalOrganic Geochemistry
Volume24
Issue number5
DOIs
StatePublished - May 1996

Keywords

  • alginite
  • alkylpyrroles
  • alkylthiophenes
  • amorphous organic matter
  • density gradient centrifugation
  • kerogen
  • maceral
  • pyrolysis gas chromatography mass spectrometry

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