New Centers Emerge (Phase 4)
Phase 4, the final phase of occupation at Crystal River and Roberts Island, started sometime between around AD 780 and 870 and ended between 900 and 980, spanning the transition between the Late Woodland period and Mississippian period, and the beginning of the Medieval Warm period. Occupation at the former site waned during this interval, while Roberts Island emerged as a major ceremonial center that included three small platform mounds tightly clustered around a small plaza. The pattern is reminiscent of earlier spatial layouts at Crystal River, but other features--such as linear ridges of shell and a water court--suggest greater influence from the Caloosahatchee tradition to the south. Isotopic studies of oyster shells from Roberts Island display less variability in habitat relative to those from earlier contexts, perhaps consistent with ownership of particular resource locations. Possibly, larger corporate groups (such as matrilineages) began working cooperatively to target specific resource locales that they owned and managed for themselves, to the exclusion of other such groups.