37-12 Microfossils Analysis for Provenance of Carbonate Gravels in the Ogallala Formation, Texas

Session: Geoscience Research Poster Showcase by 2YC and 4YCU Undergraduate Students

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Abstract:

I am researching the Miocene cobbles and gravels of the Ogallala Formation in the southern high plains. The samples contain diagnostic microfossil assemblages that provide important evidence for the provenance of the Paleozoic carbonate source rocks from which they were derived. Brachiopod shell pieces in varying conditions and sizes are present in all samples examined and represent one of the most consistently occurring fossil groups. Diagenesis is evident in both fossil pieces and matrices varying across all samples. The assemblages are dominated by echinoderm fossils, including both transverse and longitudinal skeletal fragments. Lunate fossil pieces interpreted as crinoid arm elements are also common. Crinoids and brachiopods constitute the most abundant microfossil allochems in the samples, indicating derivation from shallow marine carbonate depositional environments. Less abundant fossil groups include bryozoans, foraminifera, and non-crinoid echinoderms, although their relative abundance varies among samples.

The observed microfossil assemblages strongly suggest derivation from Pennsylvanian carbonate formations exposed in eastern New Mexico, particularly the Sandia, Gray Mesa, and Atrasado formations, as well as the Sangre de Cristo and Manzano mountain ranges of the Madera Limestone Group of northern New Mexico. This interpretation is supported by the depositional environments, fossil assemblages, and regional correlations of these formations.

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