The Caloosahatchee Formation consists of Plio-Pleistocene fossiliferous quartz sand with variable amounts of carbonate matrix interbedded with variable sandy, shelly limestones. Mollusks are typically the predominant fossils, along with corals, bryozoans, echinoids, and vertebrates. Fresh water limestones are commonly present within this unit. Classic exposures of the formation occur along the Caloosahatchee River in Lee and Charlotte Counties.