Theses and Dissertations

Issuing Body

Mississippi State University


Kirkland, L. Brenda

Committee Member

Dewey, P. Christopher

Committee Member

Schmitz, W. Darrel

Date of Degree


Document Type

Graduate Thesis - Open Access



Degree Name

Master of Science (M.S.)


College of Arts and Sciences


Department of Geosciences


The Lower Permian Laborcita Formation, Sacramento Mountains, New Mexico crops out along a narrow, 27 km strip, and is 240 m at its thickest. The objective of this study was to document ham-shaped microbial deposits through petrography and scanning electron microscopy. The study concluded that the hams began as microbial oncoids, and only the third growth zone exhibited in situ growth giving the deposit its shank-like shape. They are believed to have originated as oncoids on the presence of irregular, concentric, biogenic micritic laminae surrounding a nucleus. A microbial origin is based upon the presence of irregular laminations, fenestral fabrics, peloids, and fossil bacteria seen in SEM. The results are significant because they document enigmatic carbonate precipitation in a dominantly siliciclastic, ecologically stressful setting. By improving the understanding of organic matter in calcium carbonate precipitation, the results of this study will potentially benefit applications in medical, industrial, and academic fields.