Gulf Islands National Seashore: Paleontological resource inventory (public version)

Clinton, John; Visaggi, Christy; Tweet, Justin; Santucci, Vincent; Irick, Kelly

doi:10.36967/2299352

Gulf Islands National Seashore (GUIS) encompasses areas of the mainland as well as eight main offshore barrier island areas over the Florida and Mississippi coasts. Mainland areas of GUIS include the Pensacola Naval Air Station and Naval Live Oaks in Florida, and Davis Bayou in Mississippi. Floridian barrier islands include Santa Rosa Island and the eastern end of Perdido Key. Mississippian barrier islands include East and West Petit Bois Islands, Horn Island, Ship Island, and Cat Island. The lands at GUIS are composed primarily of Pliocene, Pleistocene, and some Holocene sediments which have been deposited over the previous 5.3 million years (Schupp 2019). The barrier islands within the boundaries of the park are younger, having been formed over the past 5,000 years. The islands and mainland coastlines of GUIS are constantly changing due to interactions with natural coastal processes such as storms, waves, tides, sediment transport, inlet dynamics and sea level change (Schupp 2019). Additionally, GUIS is being altered by more recent anthropogenic activities including inlet dredging and shoreline engineering which have disturbed the Quaternary sediments within the park. Known paleontological resources at GUIS were previously limited to mollusks and microfossils including foraminifera (“amoebas with shells”) identified in drill cores taken at a few islands in the park (Schupp 2019). As of the most recent Paleontological Resource Inventory and Monitoring summary report for the Gulf Coast Inventory & Monitoring Network (Kenworthy et al. 2007), no documented surficial fossils had been found on land managed by GUIS. The only known fossil specimens in the GUIS collections included several specimens collected outside of park boundaries in the 1940s. Recent anecdotal information by park staff and visitors pointed to the presence of additional fossil resources at GUIS not previously documented. During the synthesis of this inventory, new paleontological resources were officially documented and new localities were identified. These new finds consisted primarily of shark teeth found on island beaches. The discovery of these new resources also brought with it many questions. One of the more pressing questions explored in this inventory is the potential source sediments and geologic formations of the newly discovered fossils at GUIS. Additionally, suggestions are made for how GUIS can more effectively manage and educate about these fossil resources to ensure they can be protected and appreciated for generations to come. The hundreds of chondrichthyan (shark and ray) fossils collected at GUIS throughout 2021 and 2022 and described within this inventory hold special significance. There is a noted gap in scholarly knowledge relating to chondrichthyan fossil assemblages of any age from the coastal units managed by GUIS. Apart from ancillary studies such as those conducted at Dauphin Island, Alabama (Ebersole et al. 2017), there is no mention in the literature of chondrichthyan fossils from the western panhandle of Florida or the Mississippi–Alabama barrier islands. Most, if not all, of the fossil chondrichthyan specimens at GUIS are presumed to have been inadvertently placed there through anthropogenic means. The localities with the greatest fossil abundance at GUIS are all areas that have been subject to beach renourishment using dredged ocean sediment which is very likely to be pre-Holocene and fossiliferous. While GUIS should take the necessary steps to ensure proper management of these newly discovered fossils, the national seashore may also want to investigate avenues of preserving and sharing this resource’s significance with the scientific community.

Gulf Islands National Seashore: Paleontological resource inventory (public version)

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