Paleoenvironmental and geomorphological changes in an ancient baldcypress swamp preserved on the Northern continental shelf in the Gulf of Mexico

Wave action and seafloor scouring, likely from Hurricane Ivan, exposed an area of baldcypress (Taxoidum distichum) stumps, still in growth position and rooted in terrestrial soil, on the northern continental shelf of the Gulf of Mexico.  This site, known as the Underwater Forest, is located roughly 10 km off the coast of Gulf Shores, Alabama, USA, in approximately 18m of water.  Radiocarbon and optically stimulated luminescence dates from the mud/peat sections of the cores suggest a baldcypress swamp existed between approximately 70-40 ka BP (MIS 3-4) during the Würm glaciation.  Multiproxy analysis of sediments suggests significant geomorphological changes occurred to this backswamp environment overtime, which significantly impacted vegetation assemblage of the area.  Pollen evidence shows a clear transition from a baldcypress/tupelo gum (Nyssa aquatica) community to an alder (Alnus) dominated bar community.  This change suggests a transition to a braided river system, though it remains unclear whether these geomorphological changes resulted from terrestrial sources, marine transgression, or a combination of both.  The final vegetation change is to a more open, marsh environment resulting from sea-level rise.  Tree-ring analysis of the stumps suggest a synchronous death event, likely by burial, which may have also preserved the site.