A multidisciplinary project on an archaeological site on the Mitchell River, which feeds into Choctawhatchee Bay on the Florida panhandle, was designed to understand human adaptations to a dynamic hydrological environment during the Middle and Late Archaic period (ca. 8000–3000 B.P.). Now in a freshwater environment, on a sandy terrace above the Mitchell River floodplain, the Mitchell River 1 archaeological site contains an oyster-shell midden and other features indicating human exploitation of an estuarine environment. Estuarine exploitation at the site occurred over a long span of time, from around 7300 to 3400 2cal B.P., although the site was abandoned two or three times over the millennia. The site was more permanently abandoned after 3400 B.P.
Because estuarine shellfish, such as oysters, are low trophic level species, they have been considered marginal resources, and archaeologists modeling collector strategies assume that people will not travel far to obtain them. Under an optimal foraging model, estuarine resources should have been closer to the site than at present. A multidisciplinary team was assembled to address whether a mid-Holocene sea-level highstand had produced estuarine conditions in the Mitchell River floodplain during the Archaic. Using microfossils and stratigraphy from a dated core taken in the floodplain due south of the site, the project members attempted to correlate the changing paleoenvironment with human occupation and abandonment of the area. Results indicate that, at ca. 7300 cal B.P., when the Mitchell River 1 site was first inhabited, the floodplain was a shallow, open, sedge marsh. The site inhabitants must have traveled some distance to gather the oysters and other estuarine species that were discarded on the site. The earliest occupation was brief, but the site was reoccupied between 5900 and 5300 cal B.P., when the floodplain had become a Taxodium/Nyssa swamp. Site deposits indicate intensive exploitation of oyster and to a lesser extent Rangia, which may have been closer to the site than at 7300 B.P. but still would have required some travel. At some point, the mouth of the Mitchell River was forced eastward, and the bayhead delta, recognized as a 2-meter-deep wedge of sand in the core, was located adjacent to the site. By 4700 cal B.P., brackish water conditions prevailed, although direct evidence of oyster beds in the immediate area is lacking. Unfortunately, scouring of the core sediments sometime after 4700 cal B.P. destroyed the paleoenvironmental record for the last part of the Archaic occupation of the site. However, some evidence in Core 1, along with research elsewhere on the Florida panhandle, suggests that catastrophic storms may have played a part in the more permanent abandonment of the site after 3400 B.P.