Three lenticular lithosomes identified in the subsurface of western FL and southern AL are here named the Perdido Key Formation. The largest marine-brackish Pliocene lens stretches beneath Perdido Key, Escambia Co., FL and extends eastward to Pensacola Naval Air Station. In the type core, unit is composed of very dense, moderately green to dark green, very fine sand, coarse silty, muddy and slightly granular sand. Formation is 30 ft (9 m) thick. Underlies Pleistocene Biloxi Formation; overlies Miocene Pensacola Formation or Miocene coarse clastics. Contains planktonic foraminifers, some of which are also present in the Jackson Bluff and Intracoastal Formations.

Source: GNU records (USGS DDS-6; Reston GNULEX).