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G.L. Salmon

Publications and source records attributed to G.L. Salmon.

3 recordsLinked to original sources
USGS1996

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

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.

Organic Geochemistry↗
USGS1994

Density gradient centrifugation: Application to the separation of macerals of type I, II, and III sedimentary organic matter

Samples of organic matter from nine well-known geological units (Green River Fm., Tasmanian Tasmanite, Lower Toarcian Sh. of the Paris Basin, Duwi Fm., New Albany Sh., Monterey Fm., Herrin No. 6 coal, Eocene coal, and Miocene lignite from Kalimantan) were processed by density gradient centrifugation (DGC) to isolate the constituent macerals. Optimal separation, as well as the liberation of microcrystalline pyrite from the organic matter, was obtained by particle size minimization prior to DGC by treatment with liquid N2 and micronization in a fluid energy mill. The resulting small particle size limits the use of optical microscopy, thus microfluorimetry and analytical pyrolysis were also employed to assess the quality and purity of the fractions. Each of the samples exhibits one dominant DGC peak (corresponding to alginite in the Green River Fm., amorphinite in the Lower Toarcian Sh., vitrinite in the Herrin No. 6, etc.) which shifts from 1.05 g mL-1 for the Type I kerogens to between 1.18 and 1.23 g mL-1 for Type II and II-S. The characteristic densities for Type III organic matter are greater still, being 1.27 g mL-1 for the hydrogen-rich Eocene coal, 1.29 g mL-1 for the Carboniferous coal and 1.43 g mL-1 for the oxygen-rich Miocene lignite. Among Type II kerogens, the DGC profile represents a compositional continuum from undegraded alginite through (bacterial) degraded amorphinite; therefore chemical and optical properties change gradually with increasing density. The separation of useful quantities of macerals that occur in only minor amounts is difficult. Such separations require large amounts of starting material and require multiple processing steps. Complete maceral separation for some samples using present methods seems remote. Samples containing macerals with significant density differences due to heteroatom diversity (e.g., preferential sulfur or oxygen concentration in the one maceral), on the other hand, may be successfully separated (e.g., coals and Monterey kerogen). ?? 1994 American Chemical Society.

Conference Paper↗