Vicksburg National Military Park: Paleontological resource inventory (sensitive version)

Abstract

Vicksburg National Military Park (VICK) was established for its historical significance as a one of the principle military sieges resulting in a turning point during the American Civil War. The steep terrain around the city of Vicksburg was integral in the military siege, providing high vantage points and a substrate that was easy to entrench for the armies, but unknown to many is the fossil content, particularly a diversity of fossil mollusks. These fossils at VICK are important paleontological resources which have yet to receive focused attention from park staff, visitors, and researchers. The park’s geology is dominated by windblown silt from the last Ice Age which overlays river-transported gravels and bedrock of the late Oligocene–early Miocene-age Catahoula Formation or early Oligocene Vicksburg Group. The park is home to the type section (a geological reference locality upon which a formation is based) for the Mint Spring Formation, one of the most fossiliferous formations in this group (Henderson et al. 2022). Beginning roughly 32 million years ago (Dockery 2019), the early Oligocene deposits of the Vicksburg Group were deposited as the sea level along the Gulf Coast shore repeatedly rose and fell. The eponymously named Vicksburg Group is comprised of, from oldest to youngest, the Forest Hill, Mint Spring, Marianna Limestone, Glendon Limestone, Byram, and Bucatunna Formations. Each of these formations are within VICK’s boundaries, in addition to outcrops of the younger Catahoula Formation. Paleozoic fossils transported by the ancestral Mississippi River have also been redeposited within VICK as pre-loess stream gravels. Overlying these layers is the Quaternary-age silt which composes the loess found throughout VICK, meaning the park’s fossils span the entire Phanerozoic Eon. The fossils of VICK consist mostly of near-shore marine Oligocene invertebrates including corals, bryozoans, bivalves, gastropods, scaphopods, ostracods, and more, though terrestrial and freshwater snails of the loess, microfossils, plant fossils, occasional vertebrates, and others can also be found in the park. Notable historical figures such as Charles Alexandre Lesueur, Charles Lyell, and John Wesley Powell all collected fossils or studied geology in the Vicksburg area. The Vicksburg Group is culturally relevant as well, as the Glendon Limestone Formation has been identified by its embedded fossils as a source rock for Native American effigy pipes. This paleontological resource inventory is the first of its kind for VICK. Although Vicksburg fossils have most recently been studied as part of the Gulf Coast Inventory & Monitoring Network (Kenworthy et al. 2007), the park has never received a comprehensive, dedicated fossil inventory before this report. At least 27 fossil species, listed in Appendix B, have been named and described from specimens collected from within VICK’s lands, and VICK fossils can be found at six or more non-NPS museum repositories. Beginning in January 2022, field surveys were undertaken at VICK, covering nearly all the park’s wooded areas, streams, and other portions beyond the preserved trenches and tour road. Fossils were collected or observed at 72 localities. These specimens will be added into VICK’s museum collections, which previously contained no paleontological resources. Considering the minimal attention dedicated to these resources in the past, these newly acquired fossil specimens may be used in the future for educational, interpretive, or research purposes. Future park construction needs should take into account the protection of these resources by avoiding important localities or allowing collection efforts before localities become inaccessible or lost.