Date of Award

Fall 12-2018

Degree Type


Degree Name

Master of Science - Geology



First Advisor

Dr. LaRell Nielson

Second Advisor

Dr. Wesley Brown

Third Advisor

Dr. Melinda Faulkner

Fourth Advisor

Dr. Robert Friedfeld


Fresh Weches Formation (Middle Eocene) exposures found in aggregate quarries in Sabine County, Texas, were sampled, measured, and logged with gamma-ray spectrometry (GRS). Sedimentology and petrology characteristics of Weches samples were analyzed through thin section, scanning electron microscopy, energy-dispersive spectroscopy, X-ray diffraction, and GRS Th/K ratios analyses. The source rock quality of the Weches was evaluated with geochemical techniques involving total organic carbon (TOC), Rock-Eval pyrolysis, and GRS Th/U ratios.

The Weches, in the study area, is 27.4 meters thick, and delineated into three major stratigraphic facies: an upper marginal marine prodeltaic facies (Therrill Member) comprised of silty claystones and two lower marginal marine to inner-shelf facies (Viesca and Tyus Members) of primarily pelleted, fossiliferous claystones and pelleted, fossiliferous packstones that form a stacked condensed section. The Viesca and Tyus Members are comprised of predominantly iron-rich serpentine and kaolinite clays. Conversely, the Therrill Member contains mostly smectite clays. The Viesca and Tyus Members had TOC values < 0.50 weight % and Th/U ratios > 7 ppm, indicating no hydrocarbon generative potential and an oxic environment. Whereas the Therrill Member had TOC values ranging from 0.46–2.85 weight % and Th/U ratios between 2 and 7 ppm, indicating some hydrocarbon generative potential and an intermittent suboxic to oxic environment. Rock-Eval pyrolysis analysis for the Therrill Member identified Type III kerogens (dry gas prone) but poor source rock quality based on S1 values < 0.5 and S2 values < 2.5.

Results from this study indicate that all three members of the Weches would be poor candidates to target as an unconventional resource. However, the Therrill Member may warrant further investigation in other regions where it may have more desirable unconventional resource characteristics.

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