Late Pleistocene baldcypress ( <i>Taxodium distichum</i> ) forest deposit on the continental shelf of the northern Gulf of Mexico

Approximately 13 km south of Gulf Shores, Alabama (United States), divers found in situ baldcypress (Taxodium distichum) stumps 18 m below the ocean surface. These trees could have only lived when sea level fell during Pleistocene subaerially exposing tectonically stable continental shelf. Here we investigate geophysical properties along with microfossil and stratigraphical analyses sediment cores to understand factors that lead this wood’s preservation. The are exposed an elongated depression (~100 long, ~1 deep) nested a trough northwest–southeast trending Holocene sand ridges troughs 2–5 vertical relief ~0.5 wavelength. Radiocarbon ages wood were infinite thus optically stimulated luminescence (OSL) dating was used constrain site’s age. Below sands (~0.1–4 thick), separated by regional erosional unconformity, Late mud-peat (72±8 ka OSL), mud-sand (63±5, 73±6 palaeosol (56±5 OSL) facies grade laterally from west east, respectively. Foraminiferal analysis reveals location terrestrial-marine transitional layer above interbedded mud (3940±30 (1?) 14C BP), which is part lower shoreface or marine-dominated estuarine environment. occurrence swamp broadly similar elevation suggests glacial landscape possessed topographic allowed wood, peats be preserved for ~50 subaerial exposure before transitioning modern marine We hypothesize rapid sea-level rise occurring ~60 ~40 ago provided opportunities local flood-plain aggradation bury preserving other sites may exist northern Mexico