Geologic units in Charlton county, Georgia

Additional scientific data in this geographic area

Wicomico Shoreline Complex - marsh and lagoonal facies (Pleistocene) at surface, covers 44 % of this area

Wicomico Shoreline Complex - marsh and lagoonal facies

Wicomico Shoreline Complex - barrier island facies (Pleistocene) at surface, covers 30 % of this area

Wicomico Shoreline Complex - barrier island facies

Penholoway shoreline complex - marsh and lagoonal facies (Pleistocene) at surface, covers 11 % of this area

Penholoway shoreline complex - marsh and lagoonal facies

Penholoway shoreline complex - barrier island facies (Pleistocene) at surface, covers 9 % of this area

Penholoway shoreline complex - barrier island facies

Stream alluvium (Quaternary) at surface, covers 4 % of this area

Stream alluvium and undifferentiated terrace deposits

Charlton Formation and Duplin Marl (Pliocene) at surface, covers 2 % of this area

Charlton Formation and Duplin Marl

Pleistocene-Pliocene sands and gravels (Pleistocene-Pliocene) at surface, covers 0.9 % of this area

Includes, in part, Sunderland, Coharie, and Brandywine "Formations" of Cooke, 1939

Undifferentiated sediments (Pliocene/Pleistocene) at surface, covers < 0.1 % of this area

Undifferentiated Tertiary-Quaternary Sediments - These sediments are siliciclastics that are separated from undifferentiated Quaternary sediments solely on the basis of elevation. Based on the suggestion that the Pleistocene sea levels reached a maximum of approximately 100 feet (30 meters) msl (Colquhoun, 1969), these sediments, which occur above 100 feet (30 meters) msl, are predominantly older than Pleistocene but contain some sediments reworked during the Pleistocene. This unit may include fluvial and aeolian deposits. The undifferentiated Tertiary-Quaternary sediments occur in a band extending from the Georgia-Florida state line in Baker and Columbia Counties southward to Alachua County. These sediments are gray to blue green, unconsolidated to poorly consolidated, fine to coarse grained, clean to clayey, unfossiliferous sands, sandy clays and clays. Organic debris and disseminated organics are present in these sediments. The undifferentiated Tertiary-Quaternary sediments are part of the surficial aquifer system.

Cypresshead Formation (Pliocene) at surface, covers < 0.1 % of this area

The Cypresshead Formation named by Huddlestun (1988), is composed of siliciclastics and occurs only in the peninsula and eastern Georgia. It is at or near the surface from northern Nassau County southward to Highlands County forming the peninsular highlands. It appears that the Cypresshead Formation occurs in the subsurface southward from the outcrop region and similar sediments, the Long Key Formation, underlie the Florida Keys. The Cypresshead Formation is a shallow marine, near shore deposit equivalent to the Citronelle Formation deltaic sediments and the Miccosukee Formation prodeltaic sediments. The Cypresshead Formation consists of reddish brown to reddish orange, unconsolidated to poorly consolidated, fine to very coarse grained, clean to clayey sands. Cross bedded sands are common within the formation. Discoid quartzite pebbles and mica are often present. Clay beds are scattered and not areally extensive. In general, the Cypresshead Formation in exposure occurs above 100 feet (30 meters) above mean sea level (msl). Original fossil material is not present in the sediments although poorly preserved molds and casts of mollusks and burrow structures are occasionally present. The presence of these fossil "ghosts" and trace fossils documents marine influence on deposition of the Cypresshead sediments. The permeable sands of the Cypresshead Formation form part of the surficial aquifer system.

Hawthorn Group, Coosawhatchie Formation, Charlton Member (Miocene/Pliocene) at surface, covers < 0.1 % of this area

The Charlton Member (originally the Charlton formation, Veatch and Stevenson, 1911), crops out only in northern Nassau County near and along the St. Marys River. The Charlton Member in this area consists primarily of light gray to greenish gray, poorly to moderately consolidated, dolomitic to calcareous, silty, sandy, locally fossiliferous clays. Few carbonate beds occur.

Talbot shoreline complex - barrier island facies (Pleistocene) at surface, covers < 0.1 % of this area

Talbot shoreline complex - barrier island facies