GSA Connects 2021 in Portland, Oregon

Paper No. 50-5
Presentation Time: 2:45 PM


CLARY, Renee M., Department of Geosciences, Mississippi State University, 101D Hilburn Hall, Mississippi State, MS 39762 and DOCKERY III, David T., Mississippi Office of Geology, Mississippi Department of Environmental Quality, P.O. Box 2279, Jackson, MS 39225-2279

In the mid-nineteenth century, Charles Lyell (1797-1875) traveled with his wife, Mary, to the United States Gulf Coastal Plain to investigate Tertiary strata on the other side of the Atlantic Ocean. In early 1846, in Alabama, the Lyells collected Cretaceous fossils, visited Albert Koch’s site where his “sea serpent” Zeuglodon (now Basilosaurus) had been excavated, and observed that Nummulitic Limestone rested on top of the fossil whale beds. The Lyells’ excursion next took them from Alabama to New Orleans, and on to Natchez and Vicksburg in Mississippi, where Lyell left Mary and trekked eastward to Jackson. Upon his arrival in the capital city, Lyell visited the local pharmacist, who introduced him to Dr. Gist, a resident collector familiar with Lyell’s Principles of Geology. Gist brought Lyell to collect fossils at the Town Creek locale, where a stream exposed fossiliferous beds. Lyell concluded that Town Creek fossils were older than those at Vicksburg, and that strata dipped westward from Jackson. In the 1850s, Mississippi’s state geologist Eugene Hilgard (1833-1916) identified this fossiliferous stratum at the base of the Yazoo Clay and recognized the first volcanic doming evidence; he correctly concluded that a “local upheaval” had lifted the Jackson, MS area. Later research revealed an extinct volcano as the source of the Jackson Dome, explaining the strata dip and Lyell’s observation that Eocene fossils at Jackson were older than those collected at Vicksburg. The Vicksburg fossils were subsequently identified as Oligocene. The Jackson fossiliferous stratum, known today as Moodys Branch, was threatened when a 2003 proposed flood control project would have flooded LeFleur’s Bluff State Park and the Town Creek locale. Several scientists, including Mississippi geologist David Dockery, III, and Oxford University’s Jim Kennedy, rallied for the preservation of the geologically and historically important site. The Town Creek locality survived the challenge and remains available to scientists and the interested public, with state historical markers interpreting the local geology.