Porters Landing Member, here named as the upper member of Parachucla Formation, is exposed along the Savannah River in southeast GA. The unit includes the combined Parachucla marl and Parachucla shale of Sloan (1908). Characterized by thick-bedded, vaguely stratified to massive, noncalcareous, nonfossiliferous fine- to medium-grained quartz sand and clay. Depositional environment is marine, inner to middle neritic continental shelf. Correlative strata is included in the Penney Farms Formation of FL by Scott (in prep). Unit is present beneath most of the eastern GA Coastal Plain. Probably underlies most of the Southeast GA Embayment area and the Gulf Trough. Southern limits are not known, but it does occur in outcrop on the upper Suwannee River at White Springs, northeastern FL. Overlies Tiger Leap Member (new name); underlies Marks Head Formation or Cypresshead Formation (new name). Exposed thickness at type locality is 20 ft (6 m). Reaches 48 ft (15 m) in the core Effingham 10, near the type area. Maximum recorded thickness of 229 ft (70 m) obtained from core Colquitt 3, Colquitt Co. Age is early Miocene (Aquitanian) based on planktonic Foraminifera.

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

Authors use 87Sr/86Sr isotopic analyses in an attempt to resolve age relations of fossiliferous marine units that contain the remains of terrestrial vertebrates. Nearly identical, latest Oligocene ages were calculated for samples from the Penney Farms Formation in Marion Co. (24.6 Ma) and the Parachucla Formation at White Springs in Hamilton Co. (24.4 Ma). The strata at White Springs has been correlated with the Porters Landing Member of the Parachucla, but a sample from the type locality of the Porters Landing in GA yielded a much younger age of 20.2 Ma.

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