--> ABSTRACT: Programmed Pyrolysis and Fluorescent Light Microscopy of Kerogen: Sparta Formation, South-Central Louisiana, by Elizabeth W. Chinn, William Gregory, and Roger Sassen; #91022 (1989)

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Programmed Pyrolysis and Fluorescent Light Microscopy of Kerogen: Sparta Formation, South-Central Louisiana

Elizabeth W. Chinn, William Gregory, Roger Sassen

Kerogen of middle Eocene Sparta Formation mudstones of Pointe Coupee Parish, Louisiana, was characterized using programmed pyrolysis of core samples and transmitted-light and fluorescent-light microscopy of isolated kerogen. Results indicate that kerogen fluorescence better indicates source potential, as measured by programmed pyrolysis, than visual examination using transmitted light alone. Stratigraphic interpretation of cores suggests that the mudstones were deposited in lagoon and marine shelf environments associated with a prograding barrier island system. Pyrolysis hydrogen index (HI) of Sparta Formation lagoonal mudstones averages 160 mg HC/gm rock; marine shelf mudstones have an average HI of 341 mg HC/gm rock. Transmitted-light microscopic characterization of ker gen isolates using Hart's 1986 method indicates that amorphous kerogen of mixed terrestral and marine origin dominates samples from both depositional environments. However, a poor correlation is found between the amount of amorphous kerogen of marine origin and HI. Microscopic examination under fluorescent light indicates that much of the amorphous kerogen, including terrestrially derived kerogen, fluoresces to some degree. A relative fluorescence scale was devised based on observations of Sparta kerogen. HI values show a positive correlation with the total number of fluorescing particles in the isolate, as well as relative fluorescent levels. As the HI increases, moderately fluorescent particles increase in abundance and weakly fluorescent particles become less abundant. The results sug est that the use of fluorescence in conjunction with standard transmitted-light analysis of kerogen is crucial in determining the source potential of terrestrially dominated kerogen assemblages.

AAPG Search and Discovery Article #91022©1989 AAPG Annual Convention, April 23-26, 1989, San Antonio, Texas.