31; Exploring the Paleontology
of Southernmost Georgia
By Thomas Thurman
Posted 20/July/2024
Our southernmost 11 counties are excellent research subjects for amateurs. Few professionals are looking at them. That’s unfortunate since Florida has done extensive research on their side of the border and published many vertebrate and invertebrate specimens in the scientific literature. These came from multiple quarries near the Florida/Georgia line.
This page (31) is an introduction to a new section on these counties, they will be explored in more detail as 31A, 31B, 31C…
The stratigraphic literature reveals an abundance of vertebrate fossils; teeth, scales & bones from Miocene deposits but no one has ever gone back and collected samples which could be identified and published. The stratigraphers were researching the environments in an attempt to understand contemporary climate changes, knowledge which would be applicable today. They weren’t looking at species populations and did not collect vertebrate material. Sediments with vertebrate fossils reported are highlighted in red.
Both marine and terrestrial vertebrates are known to occur.
This page (31) is an introduction to a new section on these counties, they will be explored in more detail as 31A, 31B, 31C…
The stratigraphic literature reveals an abundance of vertebrate fossils; teeth, scales & bones from Miocene deposits but no one has ever gone back and collected samples which could be identified and published. The stratigraphers were researching the environments in an attempt to understand contemporary climate changes, knowledge which would be applicable today. They weren’t looking at species populations and did not collect vertebrate material. Sediments with vertebrate fossils reported are highlighted in red.
Both marine and terrestrial vertebrates are known to occur.
But just collecting vertebrate fossils from these sites does not advance the science. Fossils must be reviewed and published in peer-reviewed publications to become part of Georgia’s fossil record!
Only in Statenville, Georgia has detailed research been done. In 1974 Michael Voorhies (UGA) collected some impressive vertebrate fossils. Sadly the university has since lost those fossils. This is especially distressing as a canid (dog-relative) sample was collected by Voorhies. It was housed in UGA vertebrate collection but has apparently been lost. It is very possible that this was an unknown species.
Voorhies 1974 finds from Statenvile Georgia (Section 18A of this website) include horse, rhinoceros, canid (small dog?), beaver, & shark, teeth. These were all from the Statenville Formation which Huddlestun considered sparsely fossiliferous (1988). There are other formations bearing fossils; vertebrate and invertebrate.
But just collecting vertebrate fossils from these sites does not advance the science. Fossils must be reviewed and published in peer-reviewed publications to become part of Georgia’s fossil record!
Only in Statenville, Georgia has detailed research been done. In 1974 Michael Voorhies (UGA) collected some impressive vertebrate fossils. Sadly the university has since lost those fossils. This is especially distressing as a canid (dog-relative) sample was collected by Voorhies. It was housed in UGA vertebrate collection but has apparently been lost. It is very possible that this was an unknown species.
Voorhies 1974 finds from Statenvile Georgia (Section 18A of this website) include horse, rhinoceros, canid (small dog?), beaver, & shark, teeth. These were all from the Statenville Formation which Huddlestun considered sparsely fossiliferous (1988). There are other formations bearing fossils; vertebrate and invertebrate.
Get out and have a look. Get your finds published. Even if it's the Georgia Journal of Science youir finds will become part of the literature and your name will be remembered.
Running west to east, these counties are;
- Seminole 31A
- Decatur 31B
- Grady 31C
- Thomas 31D
- Brooks 31E
- Lowndes 31F
- Echols 31G
- Clinch 31H
- Ware 31I
- Charlton 31J
- Camden 31K
The Florida & Georgia deposits are closely related, but often distinct. The Georgia sediments tend to be slightly older than the Florida fossil beds. Early Miocene sediments dominate in southernmost Georgia but older beds occur to the west and younger beds occur towards the coast.
As far as vertebrate species, there is little info on occurrences in Georgia though multiple reports exist about “abundant fossil bones” which are likely Miocene aged in two localities.
The Miocene is a long epoch that was generally warm like the Oligocene but saw a cooling phase towards the end which eventually resulted in the glacial cycles of the Pleistocene.
It began 23.03 million years ago and extended to 5.33 million years ago.
It’s followed by the Pliocene, 5.33 to 2.58 million years ago.
Then the Pleistocene, 2.58 million to 11,700 years ago.
In 1986 researchers from Florida Museum of Natural History recovered a nearly complete, Early Miocene (13.6 million year old) Metaxytherium calvertense, dugong (close relative to the manatee) from a fossil bed along the Suwannee River in Echols County, Georgia, just north of the Georgia/Florida line.
(See Section 18F of this website.)
As far as other vertebrates I’d quote the Florida Museum of Natural History; “Florida had giant tortoises, giant sloths, elephant-like proboscideans, tapirs, camels, horses, rhinos, and, of course, predators, like bear-dogs and saber-toothed false cats.”
Since most sediments are generally older, Georgia’s menagerie could be very different.
Several historic researchers looked at southern most Georgia;
- Professor Samuel McCallie in 1896 & 1908
- Otto Veatch and Lloyd Stephenson in 1911
- J. E. Brantly in 1916
- Wythe Cook in 1943
- Horace G. Richards in 1969
- Paul F. Huddlestun in 1988
- Daryl P, Domning in 1989
- Gary S. Morgan in 1989
These were all broad sweeps in research attempting to understand the stratigraphy and environments recorded. To my knowledge, except for Voorhies work in Staenville and the recovery of the 1986 recovery of the dugong by the Florida Museum of Natural Hitsory, (See Section 18F of this website) no work has been done on vertebrate remains in the area.
But this stratigraphy work is important! There was early confusion about the age of various fossil beds. The basic stratigraphy research confidently dates the beds and this gives us an environmental framework.
Stratigraphy
Southernmost Georgia is dominated by the Hawthorn Group, known by most of the early researchers as the Hawthorn Formation. Paul Huddlestun’s 1988 research showed that the traditional Hawthorn was actually multiple formations which shared a timeframe & environment. As a group, Hawthorn deposits have been expanded to include the Miocene, Pliocene and parts of the Pleistocene.
Miocene
- Chattahoochee Formation
- Parachucla Formation
- Tiger Leap Member
- Porters Landing Member
- Marks Head Formation
- Torreya Formation
- Unnamed dolostone & clay (Does not occur in GA)
- Coosawhatchie Formation
- Berryville Clay Member
- Ebenezer Member
- Tybee Phosphate Member
- Charlton Member
- Meigs Member
- Statenville Formation
- Wabasso Beds
- Altamaha Formation
- Screven Member
- Cypresshead Formation
- Miccosukee Formation
- Nashua Formation
- Satilla Formation
- Undifferentiated alluvial deposits
- Undifferentiated lacustrine and paludal deposits
- Undifferentiated surficial sand
Additionally, there are marine terraces.
Chattahoochee Formation
Chattahoochee Formation is early Miocene (Aquitanian) in age or 20-23 million years old.
The dominant and characteristic of the Chattahoochee Formation is dolostone (from limestone). Subordinate components include quartz sand, clay, calcite, limestone, chert, mica, heavy minerals, phosphate, and fossils. The dolostone of the Chattahoochee Formation, commonly reported as limestone in the past, is typically yellowish gray in color, uniform in texture, chalky to granular, rarely pelletal and foraminiferal, fine- to medium-grained, compact, prominently but rudely bedded, and poorly to moderately consolidated and recrystallized.
Limestone and calcite occur only rarely in the Chattahoochee Formation in Georgia, but are more common and widespread farther to the south and southwest in Florida. The dolomite in the Chattahoochee Formation appears to be secondary because the fossils that were once calcareous are now present only as molds and casts in the dolostone. Fine-grained, well-sorted quartz sand and silt are characteristic of the Chattahoochee Formation. Typically the sand is evenly distributed throughout the dolostone, but it also occurs in medium to thick beds with variable admixtures of clay and dolomite. In some sections, significant proportions of the formation consist of fine-grained sand and clay and, in general, sand and clay appear to constitute a more significant component of the formation near the northern and eastern limits of the formation.
Fossiliferous intervals are generally present but not common in the Chattahoochee Formation at any given site in Georgia the frequency of occurrence of macrofossils in the Chattahoochee Formation in Georgia ranges from rare, scattered, fossil molds in the dolostone, to rich concentrations of fossil molds in scattered, thin to thick beds of dolostone. Most microfossils have been obliterated by dolomitization, but the benthic foraminifera Sorites and Archaias are locally common as molds and casts. The Chattahoochee Formation is more generally fossiliferous to the south in Florida where extensive faunal lists' have been published from the type area.
Chattahoochee Formation is early Miocene (Aquitanian) in age or 20-23 million years old.
The dominant and characteristic of the Chattahoochee Formation is dolostone (from limestone). Subordinate components include quartz sand, clay, calcite, limestone, chert, mica, heavy minerals, phosphate, and fossils. The dolostone of the Chattahoochee Formation, commonly reported as limestone in the past, is typically yellowish gray in color, uniform in texture, chalky to granular, rarely pelletal and foraminiferal, fine- to medium-grained, compact, prominently but rudely bedded, and poorly to moderately consolidated and recrystallized.
Limestone and calcite occur only rarely in the Chattahoochee Formation in Georgia, but are more common and widespread farther to the south and southwest in Florida. The dolomite in the Chattahoochee Formation appears to be secondary because the fossils that were once calcareous are now present only as molds and casts in the dolostone. Fine-grained, well-sorted quartz sand and silt are characteristic of the Chattahoochee Formation. Typically the sand is evenly distributed throughout the dolostone, but it also occurs in medium to thick beds with variable admixtures of clay and dolomite. In some sections, significant proportions of the formation consist of fine-grained sand and clay and, in general, sand and clay appear to constitute a more significant component of the formation near the northern and eastern limits of the formation.
Fossiliferous intervals are generally present but not common in the Chattahoochee Formation at any given site in Georgia the frequency of occurrence of macrofossils in the Chattahoochee Formation in Georgia ranges from rare, scattered, fossil molds in the dolostone, to rich concentrations of fossil molds in scattered, thin to thick beds of dolostone. Most microfossils have been obliterated by dolomitization, but the benthic foraminifera Sorites and Archaias are locally common as molds and casts. The Chattahoochee Formation is more generally fossiliferous to the south in Florida where extensive faunal lists' have been published from the type area.
Hawthorn Group
Dominantly sand and clay, Subordinate components include dolomite, calcite, limestone, phosphorite, silicified claystone (opal-cristobalite), chert, & silicified microfossils. Locally, or in beds or lenses, all of the above can occur. Clay occurs in all proportions, beds or lenses of relatively pure sand are rare.
Parachucla Formation
Age
The Parachucla Formation is early Miocene (Aquitanian) 20-23 million years old.
Lithology
The Parachucla Formation consists of sand, clay, calcite, and dolomite in varying admixtures. Sand is the primary lithic component of the formation, but limestone or dolostone can locally dominate the lithology of the formation. Clay, although prominent, is not known to dominate the lithology of the formation at any site. Other lithic components of the Parachucla Formation include fossil shells (both calcitic and aragonitic), phosphate, siliceous claystone and chert, mica, feldspar, zeolite, and lignitic flecks. Petrified wood occurs rarely in the type area.
Tiger Leap Member
Of the Parachucla Formation
Age
The Tiger Leap Member is early Miocene (early Aquitanian) about 22 million years old.
Lithology
In its type area in southern Screven and northern Effingham Counties, Georgia the Tiger Leap Member consists of limestone; calcareous shelly sand (shell bed); calcareous, micro-fossiliferous sand; noncalcareous, argillaceous (clay) sand; and noncalcareous, pebbly, prominently bedded, feldspathic sand. In addition to the above, lithologies that have been observed in the Tiger Leap Member elsewhere in the state includes dolostone and phosphatic sand and sandstone. Clay-rich, fine-grained, well-sorted sand that is variably phosphatic, micaceous, calcareous, dolomitic, and fossiliferous is the basic lithology of the Tiger Leap Member.
Finely sandy limestone and dolostone that are variably fossiliferous, argillaceous, and phosphatic are other prominent lithology types of the Tiger Leap. Locally, limestone, dolostone, or both are the principal lithologies of the Tiger Leap Member.
Subordinate components of the member include clay, shells (both calcitic and aragonitic), phosphate, siliceous claystone, feldspar, mica, zeolite, and lignitic (brown coal) flecks.
Porters Landing Member
of the Parachucla Formation
Age
The Porters Landing Member is early Miocene (Aquitanian) 20-23 million years old and overlies the Tiger Leap Member.
Lithology
The Porters Landing Member consists predominantly of quartz sand and clay. Other lithiccomponents include calcite, limestone, dolomite, dolostone, mica, phosphate, siliceous claystone, zeolite, shells (only calcitic shells are known), and lignitic flecks and fragments. Characteristically in the type area in northern Effingham County, the Porters Landing Member is a thick-bedded, vaguely stratified to massive, noncalcareous, nonfossiliferous fine-to medium-grained sand and clay. Although quartz sand appears to be the dominant component of the member, clay is the characteristic component that serves to distinguish the member lithologically from the underlying Tiger Leap Member. Clay in the Porters Landing Member occurs both in discrete beds and interstitally in the sand. The bedded clay is typically medium to dark bluish-gray or dark greenish-gray, indistinctly layered and blocky, tough, bioturbated, and massive (as at the type locality), noncalcareous, and finely sandy to silty.
Marks Head Formation
Age
The Marks Head Formation is late early Miocene (Burdigalian) about 17 million years old.
Lithology
The Marks Head Formation consists of slightly dolomitic (rarely calcareous), phosphatic, argillaceous sand and sandy clay with scattered beds of dolostone, limestone, and siliceous claystone. In general, quartz sand appears to be the dominant lithic component of the formation, whereas clay is both a major and characteristic component. The sand-clay distribution of the Marks Head Formation reflects the tendency for grain sizes in the formation to become finer in a seaward direction. In outcrop in horthen1 Effingham County, the Marks Head Formation consists predominantly of argillaceous sand, whereas in central Effingham County, the formation consists of inter layered finely sandy clay and argillaceous fine sand. In the subsurface in southern Effingham County and Chatham County, the Marks Head Formation consists predominantly of finely sandy clay with minor argillaceous (clay-rich) sand. Subordinate lithic components include dolomite, dolostone, calcite, limestone; phosphate, mica, zeolite, feldspar, siliceous claystone, shells, and rare, scattered, vertebrate bone debris. The clay component of the Marks Head Formation occurs in discrete clay beds and interstitially in the quartz sand. The stratified clay occurs in laminae or streaks, thin beds, and thick beds, or as massive, finely sandy clay that constitutes the entire formation.
Phosphate and fine, vertebrate debris and fish-scales are commonly concentrated on bedding planes in the Berryville Clay
Torreya Formation
Age
The age of the Torreya Formation is early to middle Burdigalian, approximately in the middle part of the early Miocene or roughly 18 million years old.
Lithology
The Torreya lithology is typically an argillaceous fine grained sand/finely sandy clay that is variably calcareous and dolomitic. In outcrop, the carbonate component is generally absent due to leaching, and the physical appearance of the Torreya Formation is that of an indistinctly layered, pale green, clayey, fine-grained sand to sandy clay. The quartz sand, clay, and carbonate are generally present together m varying proportions. Only a few clay beds in the Dogtown Clay Member and a few limestone intervals in the lower part of the formation contain relatively few impurities.
Subordinate lithic components of the Torreya Formation include chert (opal-cristobalite) phosphate, heavy minerals (zircon, tourmaline, rutile, apatite, staurolite, kyanite, sillimanite, and opaques, mica, feldspar, pyrite, wad, invertebrate macrofossils of various kinds (mostly molds and casts), petrified wood, fossil bone material, and rare calcareous and siliceous microfossils.
Sopchoppy Member
of the Torreya Formation
Age
The Sopchoppy Member of the Torrey a Formation is assigned the same age as the rest of the formation, and is believed to be early Miocene (early to middle Burdigalian) about 20 to 18 million years old.
Lithology
The Sopchoppy Member was originally called a limestone by Dall (1892): It is my observation, however, that the Sopchoppy Member consists of several lithofacies along the Sopchoppy River. The two dominant lithofacies include a sandy, fossiliferous limestone (the original concept of the unit) and a tough, phosphatic, dolomitic sand. The two lithofacies are not completely exclusive.
of the Torreya Formation
Age
The Sopchoppy Member of the Torrey a Formation is assigned the same age as the rest of the formation, and is believed to be early Miocene (early to middle Burdigalian) about 20 to 18 million years old.
Lithology
The Sopchoppy Member was originally called a limestone by Dall (1892): It is my observation, however, that the Sopchoppy Member consists of several lithofacies along the Sopchoppy River. The two dominant lithofacies include a sandy, fossiliferous limestone (the original concept of the unit) and a tough, phosphatic, dolomitic sand. The two lithofacies are not completely exclusive.
No Published Map
Dogtown Member
of the Torreya Formation
Age
The Dogtown Clay Member of the Torreya Formation is assumed to be early Miocene (early to middle Burdigalian) about 20 to 18 million years old.
Lithology
The Dogtown Clay Member of the Torreya Formation is primarily clay. Palygorskite is the characteristic clay mineral of the member, but in specific beds montmorillonite may dominate the clay mineral suite. Sepiolite and illite are subordinate Clay mineral components. In addition, the relative portions of the clay minerals fluctuate from bed to bed. Other subordinate lithic components include quartz sand, calcite, dolomite, phosphate, mica, K-feldspar, pyrite, heavy minerals, rare fossil bones and rare and scattered petrified wood.
Locally, quartz sand, limestone or dolostone are the dominant lithologies present in specific beds. Clay beds, especially in the upper fullers earth bed, may grade laterally into sandy clay or argillaceous sand. The purity of the clay in the Dogtown Clay Member is variable. Relatively pure, palygorskite-rich fuller's earth is not present everywhere, however, and even minor amounts of quartz sand or carbonate render it noncommercial.
of the Torreya Formation
Age
The Dogtown Clay Member of the Torreya Formation is assumed to be early Miocene (early to middle Burdigalian) about 20 to 18 million years old.
Lithology
The Dogtown Clay Member of the Torreya Formation is primarily clay. Palygorskite is the characteristic clay mineral of the member, but in specific beds montmorillonite may dominate the clay mineral suite. Sepiolite and illite are subordinate Clay mineral components. In addition, the relative portions of the clay minerals fluctuate from bed to bed. Other subordinate lithic components include quartz sand, calcite, dolomite, phosphate, mica, K-feldspar, pyrite, heavy minerals, rare fossil bones and rare and scattered petrified wood.
Locally, quartz sand, limestone or dolostone are the dominant lithologies present in specific beds. Clay beds, especially in the upper fullers earth bed, may grade laterally into sandy clay or argillaceous sand. The purity of the clay in the Dogtown Clay Member is variable. Relatively pure, palygorskite-rich fuller's earth is not present everywhere, however, and even minor amounts of quartz sand or carbonate render it noncommercial.
Coosawhatchie Formation
Age
The Coosawhatchie Formation is middle Miocene (early Serravallian) or about 14 million years in age.
Lithology
The Coosawhatchie Formation is predominantly a phosphatic clay, sandy clay, argillaceous sand, and phosphorite that originally was called the Coosawhatchie member of the Hawthorne Formation
The Coosawhatchie is a lithologically mixed formation that consists dominantly of clay and sand. Clay appears to be the dominant and characteristic lithic component of the formation, but sand is also important and locally dominates the lithology. Significant minor lithic components include phosphate, phosphorite, dolostone, limestone, and calcite. Other subordinate lithic components include dolomite, mica, siliceous claystone and chert, siliceous microfossils, zeolite, and scattered vertebrate debris.
Berryville Clay Member
Of the Coosawhatchie Formation
Age
The age of the Berryville Clay Member is middle Miocene (early Serravallian), about 12 million years.
Lithology
The Berryvillle Clay Member of the Coosawhatchie Formation consists principally of yellowish gray to light olive gray, silty, phosphatic, calcareous in some areas, variably siliceous clay. Clay is the dominant lithic component of the member, whereas minor components of the lithology include quartz sand and silt, mica, phosphate, calcite, limestone, dolomite, lignitic flecks, scattered fine vertebrate debris, siliceous claystone and opaline cristobolite, traces of feldspar, zeolite, calcareous and siliceous microfossils, and rare shelly material in the type area (especially barnacle scutes). On casual inspection, the Berryville Clay appears to be massive, very thick bedded, and blocky. However, on close inspection, the clay is commonly thin-bedded to laminated, with dustings of silt, mica, phosphate, and fine vertebrate debris (especially fossil fish scales) along partings or bedding planes.
The olive-gray to olive-black color of the Berryville Clay, the common occurrence or abundance of small and delicate vertebrate bone debris and fish-scales along bedding planes, the characteristic thin bedding and lamination rather than bioturbation or homogenization of the sediments (due to an infauna), and the local occurrence of sulphosalts on outcrops of the clay are all indicative of an anaerobic, stagnant environment inimical to a bottom dwelling fauna.
Ebenezer Member
Of the Coosawhatchie Formation
Age
Other than scattered fine vertebrate debris, the only known fossils in the Ebenezer Member are molds and casts of mollusks in the central part of the Southeast Georgia embayment. Because the Ebenezer Member is gradational with the Berryville Clay Member, both down section and laterally, it is assumed here that the Ebenezer is the same age as the Berryville Clay, middle Miocene (early Serravallian), about 14 million years.
Lithology
The Ebenezer Member of the Coosawhatchie Formation is typically a gray to olive-gray, slightly phosphatic, micaceous, argillaceous sand. Sand is the dominant lithic component of the member, whereas subordinate components are clay, mica, calcite, limestone, dolomite, dolostone, phosphate, siliceous claystone, feldspar, zeolite, and fine vertebrate debris. Typically, the sand is fine- to medium-grained, rarely medium- to coarse-grained; moderately to well sorted, rarely poorly sorted; thinly and distinctly to indistinctly bedded rarely to bioturbated or structureless; and argillaceous. In the coarser grained lithofacies in the central part of the Southeast Georgia Embayment, the Ebenezer Member is more commonly medium- to coarse-grained, moderately to poorly sorted, thick- to medium-bedded, commonly massive and structureless, pebbly, feldspathic, and not conspicuously argillaceous.
Tybee Phosphate Member
Of the Coosawhatchie Formation
Age
The age of the Tybee Phosphorite Member is inferred to be Middle Miocene, early Serravallian, about 13 million years old.
Lithology
The Tybee Phosphorite Member of the Coosawhatchie Formation principally consists of quartz sand and phosphate with minor clay and dolomite. The phosphate, which commonly is the dominant lithic component, typically consists of round to irregularly rounded, black to brown to amber-colored grains of apatite that range in size from about I mm to less than 0. I mm. The phosphate is generally associated with abundant fine vertebrate debris (fish teeth, miscellaneous small bones, vertebrae, fish scales, etc.). Subordinate lithic components include quartz sand, clay, dolomite, dolostone, and mica. Scattered small quartz pebbles occur locally in the basal phosphorite, and scattered thin layers of sand, clay, or dolostone occur locally within the member. The dolostone layers in places contain molds and impressions of mollusks. The clay mineral suite consists of palygorskite and smectite, in approximately equal proportions, with some illite and minor sepiolite and kaolinite.
The environment of deposition of the Tybee Phosphorite Member of the Coosawhatchie Formation was marine, probably shallow-water but far-offshore, continental shelf. The bioturbation to complete homogenization of the sediments indicates an active infauna during sedimentation Scattered thin dolostone beds with molluscan molds also indicate the local presence of a meager fauna living upon the substrate. As a result, it is concluded that the environment of deposition of the Tybee Phosphorite was not anaerobic and stagnant as the adjacent Berryville Clay. However, the abundance of small vertebrate (presumably fish), fossil bone debris indicates that the overlying water-mass must have been highly productive in terms of marine life, and the abundance of the debris would suggest that the bottom environment could have been locally or periodically stagnant with putrifying material.
To the author’s knowledge (Thurman July/2024) no vertebrate species have ever been reported in peer reviewed literature from the Tybee Phosphate though shark teeth have been collected recently from the southern type of Tybee Island and reported to this author through Facebook. (Which is not peer-reviewed publication) This author encouraged the finder to report the material. Georgia’s record of Miocene vertebrates is very thin despite an appearance abundance of available material.
Charlton Member
Of the Coosawhatchie Formation
Age
Huddlestun provisionally assigned the same age as the rest of the Coosawhatchie, middle Miocene, early Serravallian or about 13 million years old… However, coastal deposits are complex and often mixed due to repeated sea level change and coastal flooding due to climate change. In 1988 Huddlestun described the age of the Charlton Member thusly.
Veatch and Stephenson (1911, p. 392-400) provisionally placed the Charlton in the Pliocene on the basis of a few molluscan and ostracod species. Cooke (1943, 1945) concurred with this appraisal. The fossils that would have indicated a Pliocene age for Charlton include Pecten gibbus, Rangia cuneata, Chione cancellata, and Mulinia lateralis. The fossil then identified as P. gibbus, a Pleistocene and Holocene species, was subsequently renamed P. charltonius by Mansfield (1936) and transferred to Argopecten charltonius by Waller (1969). The only known geographic occurrence of A. charltonius is within the Charlton Member and A. charltonius is, therefore, of little value in biostratigraphic correlation. Waller ( 1969}, however, suggested that the Charlton is late Miocene based on the general similarity between A. charltonius and A. choctawhatcheensis of the Area Zone of the upper Miocene Choctawhatchee Formation of western Florida. Supporting Waller's (1969) suggestion of an older age for the Charlton Member, I recently (1988) examined the fossil collections from the Charlton in the U.S. National Museum in Washington, D.C., and could find no Pleistocene or Pliocene species as described by Veatch and Stephenson (1911) and by Cooke (1943, 1945)(i.e., Rangia cuneata, Chione cancellata, and Mulinia laterais). I have also not found these species in the Charlton, either in outcrops or cores. Therefore, there is no existing paleontological evidence, known to this author, for a post-Miocene age for the Charlton Member. Because the physical stratigraphic relationships indicate that the Charlton is a lithofacies of the upper part of the Coosawhatchie Formation, the Charlton Member is here provisionally assigned the same age as the rest of the Coosawhatchie, (i.e., middle Miocene. early Serravallian. This report does not exclude a late Miocene age for the Charlton Member, as suggested by Waller ( 1969). Other than the similarity between Argopecten charltonius and A. choctawhatcheensis noted by Waller. however, no paleontological or physical evidence exists to suggest or support a late Miocene age for the Charlton member. On the other hand, no evidence, other than the appearance of gradational contacts between the Charlton and Ebenezer Members, exists to deny a younger Miocene or late Miocene age for the Charlton or Ebenezer Members.
Lithology
Typical Charlton Member consists of clay, dolostone, and limestone. Clay appears to be the dominant lithic component. However, dolostone and limestone are more conspicuous in outcrop, probably because they are more resistant to erosion and persist longer in outcrop. Also, the clay, dolomite, and calcite commonly occur in varying combinations. Other subordinate lithic components of the Charlton Member include quartz sand, phosphate, and shells.
Meigs Member
Of the Coosawhatchie Formation
Age
The age of the Meigs Member is early- middle Miocene, Langhian Stage, roughly 15 million years old.
Lithology
Available information indicates that the Meigs Member of the Coosawhatchie Formation is a lithologically heterogeneous unit. Well-sorted, fine-grained sand is the dominant lithic component of the unit, but clay is prominent and is the characteristic lithic component of the unit. Other subordinate lithic components include mica, chert, silica-cemented sandstone, wad (hydrated Mn02), minor feldspar, heavy minerals, siliceous microfossils, and minor phosphate. The quartz sand is typically fine-grained and well-sorted, but minor fine- to medium-grained sand has been observed. The sand beds are generally thin to thick, vaguely and rudely bedded to massive and structureless. Scattered small-scale crossbedding has been observed in fine-grained sand sections. Relatively pure quartz sand is not known in the Meigs Member, and the sand is always argillaceous to some degree with minor to abundant interstitial clay.
Statenville Formation
(See Section 18E of this website)
Age
The Statenville Formation contains a Barstovian land mammal fauna, micro-faunce confirms this and places it in the early Serravallian, middle Miocene, 14 million years old.
The Statenville Formation is very sparsely fossiliferous. Molds and casts of mollusks occur locally in moderate frequency in the dolomitic beds. Fossils with calcitic shells such as scallops, oysters, and barnacles are very rare. Voorhis (1974b) reported a meager assemblage of vertebrate fossils from the type locality of the formation. Vertebrate fossil debris, such as small fish teeth and bones, is not rare in the phosphatic beds of the formation, and the trace fossil Ophiomorpha nodosa is locally common in sand beds on both the Alapaha and Suwannee Rivers.
Lithology
The Statenville Formation is a prominently cross-bedded, undulatory-bedded, to horizontal bedded, dolomitic, phosphatic, argillaceous sand with scattered beds or lenses of clay and dolostone. Quartz sand is the dominant lithic component, whereas clay, dolomite, dolostone, phosphate, and mica are subordinate lithic components. The grain-size of the quartz sand ranges from fine to coarse, and the sorting ranges from well-sorted to poorly sorted. Quartz pebbles occur in the coarser beds or lenses of the formation, and flat pebbles have been observed among the quartz pebbles. The coarser, pebbly sand phases of the formation generally are the more poorly sorted. Dolomite is characteristically conspicuous in the formation and is present both interstitially and in discrete, thin beds. Dolostone beds may be relatively pure (as, in beds at the type locality) or sandy, argillaceous, and phosphatic. The bedded dolostone is typically buff to tan, fine-grained, saccharoidal, hard, and resistant to erosion. In outcrop, the dolostone beds produce prominent ledges in contrast to the soft, nonindurated sand layers. Some beds consist of a dolostone conglomerate or breccia cemented by dolomite of similar lithology and appearance. Phosphate is characteristic of and is commonly conspicuous in the Statenville Formation. The phosphate grains range from the typical small, black, brown, to amber colored, rounded, sand-size apatite grains or pellets to irregularly shaped, rounded, black, shiny, sand size grains or small pebbles; to black, brown, orange, or buff-colored, irregularly shaped pebbles ranging from 1 to 5 cm in diameter.
Wabasso Beds
Age
Ample foraminifera samples provide clear dating of the Wabasso Beds to the Early Pliocene, Zanclean age, at 5.3 to 3.6 million years.
The Wabasso beds is an informal name applied here to lower Pliocene, phosphatic, calcareous and micro-fossiliferous. variably argillaceous, silty, fine-grained to very fine grained sand in the subsurface of the coastal area of Georgia.
Lithology
Typically, the Wabasso beds consist of silty, fine- to very fine-grained sand that is variably phosphatic, calcareous, micro-fossiliferous, and argillaceous. Limited information suggests that clay, both interstitially and in discrete beds, is a minor component of the unit. In the core Phred 1 (W -13958) from Indian River County, Florida, the Wabasso beds consist of thinly layered to laminated, well-sorted, phosphatic sand with clay partings. The unit is calcareous on the upper part and weakly to noncalcareous in the lower part.
Altamaha Formation
Age
The Altamaha Formation is nonfossiliferous so its age must be inferred, it is roughly time-equivalent to the Coosawhatchie Formation and is probably middle Miocene (Serravallian) or 13.8 to 11.6 million years of age.
Lithology
The Altamaha Formation consists of thin to thick bedded or crossbedded, well-sorted to very poorly sorted, variably feldspathic, sporadically pebbly or gravelly, clay rich sand, sandstone, sandy clay, clay, and claystone. Often darkly stained with iron-oxide. Quartz sand is the dominant lithic component of the Altamaha Formation, but clay is also significant and dominates the lithology of the formation at some sites. The sand ranges in size from fine through very coarse, with coarser quartz ranging from granule to cobble size. The quartz gravel of the Altamaha is subangular to well-rounded and is characteristically coarser than the gravel in ·the older Cretaceous and Lower Tertiary deposits in Georgia. Quartz cobbles up to 7 inches (18 em) in diameter along the major axis have been observed in Washington County, Georgia, and Aiken County, South Carolina. Generally, the finer the upper limit of the sand-size present, the better the sorting; and conversely, the coarser the upper limit of the sand-size present, the poorer the sorting. Poorly sorted, clayey, gravelly sands are characteristic of the Altamaha Formation in the updip areas. Commonly, the coarser beds in the Altamaha are conspicuously feldspathic, and lath-shaped feldspar pebbles within the gravelly beds have been reported by Veatch and Stephenson.
Generally, in the Altamaha Formation, the sand and clay occur in varying states of admixture, with lithologies ranging from argillaceous sand to sandy clay. Beds or lenses of relatively pure sand occur locally but are exceptional. Relatively pure clay or claystone, however, is commonly encountered only in the lower Miocene component of the Altamaha Formation.
Altamaha Formation
Age
The Altamaha Formation is nonfossiliferous so its age must be inferred, it is roughly time-equivalent to the Coosawhatchie Formation and is probably middle Miocene (Serravallian) or 13.8 to 11.6 million years of age.
Lithology
The Altamaha Formation consists of thin to thick bedded or crossbedded, well-sorted to very poorly sorted, variably feldspathic, sporadically pebbly or gravelly, clay rich sand, sandstone, sandy clay, clay, and claystone. Often darkly stained with iron-oxide. Quartz sand is the dominant lithic component of the Altamaha Formation, but clay is also significant and dominates the lithology of the formation at some sites. The sand ranges in size from fine through very coarse, with coarser quartz ranging from granule to cobble size. The quartz gravel of the Altamaha is subangular to well-rounded and is characteristically coarser than the gravel in ·the older Cretaceous and Lower Tertiary deposits in Georgia. Quartz cobbles up to 7 inches (18 em) in diameter along the major axis have been observed in Washington County, Georgia, and Aiken County, South Carolina. Generally, the finer the upper limit of the sand-size present, the better the sorting; and conversely, the coarser the upper limit of the sand-size present, the poorer the sorting. Poorly sorted, clayey, gravelly sands are characteristic of the Altamaha Formation in the updip areas. Commonly, the coarser beds in the Altamaha are conspicuously feldspathic, and lath-shaped feldspar pebbles within the gravelly beds have been reported by Veatch and Stephenson.
Generally, in the Altamaha Formation, the sand and clay occur in varying states of admixture, with lithologies ranging from argillaceous sand to sandy clay. Beds or lenses of relatively pure sand occur locally but are exceptional. Relatively pure clay or claystone, however, is commonly encountered only in the lower Miocene component of the Altamaha Formation.
Screven Member
Of the Altamaha Formation
Age (?)
The Screven Member of the Altamaha Formation is barren of fossils and trace fossils. Therefore, the age of the member must be inferred from stratigraphic position and physical correlation. This becomes complex and requires further research. Reviewing Huddlestun’s 1988 research (Bulletin 104), and keeping in mind that large scale erosion occurred on the Coastal Plain, the Screven Member grades into Middle Miocene deposits (Serravallian 13.8-11.6 million years ago) in some areas and earliest Miocene (Aquitanian 23.0 to 20.4 million years ago) in other areas.
Lithology
The Screven Member of the Altamaha Formation consists of a maze of fluvial channel, cut-and-fill structures, and typical Screven sediments are channel-fill deposits in the cut-and-fill structures. The Screven channel-fill deposits consist of planar and trough cross-bedded, variably micaceous and feldspathic, argillaceous, pebbly to gravelly sands with clay clasts, and scattered lenses of clay channel-fill. The sand phase of the Screven Member is the dominant and characteristic lithofacies of the member. Screven-Member sands are typically poorly sorted and coarse-grained. As with the rest of the Altamaha Formation, the sorting of the sand component deteriorates as the upper limit of the sand size increases. However, it is only in the southeastern-most occurrences of the Screven Member, in Pierce and Ware Counties, that I (Huddlestun) have observed fine to medium grained, moderately well sorted sand in the Screven Member.
Cypresshead Formation
Age Pliocene to Pleistocene
The Cypresshead Formation has few fossils useful for dating, but such forams as could be recovered from multiple locations (See Bulletin 104, Huddlestun, 1988) places the age span of the formation from Early Late Pliocene (Piacenzian) to early Pleistocene (Calabrian) spanning 3,600,000 to 770,000 years old. Huddlestun speculates that the true likely age, is Late Pliocene (Piacenzian) 3.6 to 2.8 million years ago.
Lithology
The Cypresshead Formation is dominantly a quartz sand. In some downdip areas, clay beds are prominent or may even dominate the Cypresshead section. Other subordinate lithic components include pebbles and gravel, heavy minerals, mica, trace fossils, and rarely, phosphatic pebbles, calcite, shells, calcareous microfossils, and siliceous microfossils. The Cypress head Formation is a coastal, beach/ sound type of deposit and, therefore, is lithologically variable over short distances. However, two gross lithofacies types can be distinguished in the formation in outcrop and in the shallow subsurface: one typically developed in the updip area and near the large rivers (Savannah and Altamaha Rivers), the other typically developed between the large rivers and in downdip areas. The updip lithofacies is coarse-grained, and the sand-size ranges from fine to coarse and pebbly with scattered gravel stringers. Sorting ranges from well-sorted to poorly sorted in the coarser facies. Bedding is typically prominent with bed thickness ranging from thin to thick and bedding definition ranging from vague to distinct. Cross-bedding is conspicuous in this lithofacies, and the scale is variable with the largest scale cross-bedding associated with the coarsest and most poorly sorted sands. Ophiomorpha nodosa, a trace fossil, is locally common in this lithofacies and is especially characteristic of the massive. structureless, medium to coarse sands. Similarly, there arc scattered occurrences of bioturbated and burrowed beds. This coarse-grained sand lithofacies is reminiscent of the time-equivalent Citronelle Formation of western Florida. The downdip lithofacies of the Cypresshead Formation consists of fine-grained sand and clay. This is the more distinctive lithology of the formation. It is characterized by thinly-bedded, fine-grained, well-sorted sand with thin layers, laminae, or partings of clay dispersed through the sand.
The sand is typically weathered to a moderate reddish-brown or orange, and the clay layers and laminae are white, producing a dramatic color contrast that highlights the bedding of the formation.
In some scattered areas, the bulk of the formation consists of massive, argillaceous, fine-grained sand that is devoid of any primary sedimentary or biogenic structures. The sediment in this type of deposit is interpreted as being completely mixed and homogenized by burrowing organisms.
Miccosukee Formation
Age
The Miccosukee Formation is non-fossiliferous and therefore can only be dated by stratigraphic correlation, but the evidence suggests an early Late Pliocene age or roughly 3 million years old.
Lithology
The lithology of the-Miccosukee Formation is dominated by sand, although in some areas, and in some parts of the section, clay is a significant or dominant component of the lithology. Other known subordinate lithic components include mica, heavy minerals, feldspar, and rarely, wad or Mn02 dendrites. Limonite is locally present as a weathering product. The clay mineral components consist of montmorillonite, kaolinite, and illite. Several lithology types or lithofacies can be identified in the Miccosukee Formation. The most characteristic lithology type is a thinly bedded to laminated, well-sorted, fine-to medium-grained sand with scattered layers or laminae of clay. Where the clay layers are absent, the sand generally remains distinctly and thinly layered, fine- to very fine grained and well-sorted. Medium- and, rarely, coarse grained sand beds are associated with· the thinly layered, fine-grained sand lithologies. The clay layers typically range in thickness from 1 foot (30 cm) to 1/16 inch (1 mm). Thicker beds of clay are rare. Also associated with clay beds are thin beds of intra-clastic or intraformational clay breccia. Some beds or stratigraphic intervals in this lithofacies are bioturbated with incomplete mixing of the sediments. In outcrop, the Miccosukee Formation is moderately to deeply weathered, and the sands typically are orange to moderate reddish brown. The clay layers or laminae are
white, and the resulting color contrast imparts a dramatic and characteristic appearance to the formation (identical to the analagous lithofacies of the equivalent Cypresshead Formation). Pebbly to gravelly, coarse-grained sand lenses are present locally in the Miccosukee Formation and represent tidal channel scour-and-fill structures. These deposits are conspicuously cross-bedded, and the sorting commonly is poor. Gravel occurs in stringers. Lithologies intermediate to the thinly bedded, fine-grained sand lithofacies and the pebbly, cross-bedded sand also exist, indicating a wide spectrum of energy levels in the paleo-environment.
Miccosukee Formation Vertebrate Fossils in Florida
In 1988 Huddlestun reports…
J.W. Yon (1966) identified the vertebrate fossil bed exposed on highway S-146 in northern Jefferson County, Florida as being Miccosukee Formation. He dated the site to Late Miocene age on the basis of molars from the horse Merychippus sp. and the rhinoceros Diceratherium sp. It’s now believed (1984), however, that those Jefferson County (FL) fossils are of middle Miocene age (late Barstovian, NALMA, 16.3 to 13.6 million years old). They would correlate with the Statenville Formation (Statenville local fauna) at Statenville, Georgia. (See Section 18E of this website.)
Nashua Formation
Age
The molluscan fauna of the Nashua Formation and its age implications have been discussed at some length in the literature. The foraminifera evidence in northeastern Florida supports an age range for the Nashua from late Pliocene (Piacenzian), to early Pleistocene (Calabrian), this spans 3,600,000 to 770,000 years ago.
Lithology
The type locality of the Nashua Formation, by original designation, is "one fourth mile south of Nashua, Putnam County", Florida. Mansfield (1924) noted that the type locality is on the "riverbank." There are, however, low bluffs with scattered, poorly exposed outcrops along the St. Johns River for approximately 2 miles (3.2 km) on the east side of the river at Nashua. Cooke and Mossom (1929) were unable to find the specific site of the type locality designated by Matson and Clapp (1909); therefore, the precise location of the type locality of the Nashua Formation is not clear. According to the information supplied by the above authors, however, the type locality must be on the east bank of the St. Johns River, approximately 3 miles (4.8 km) southwest of the community of Satsuma, and approximately 10 miles (16 km) south of the town of Palatka, Florida. The type section (unit strato-type) of the Nashua Formation is that section of Nashua exposed at the type locality. The exposures of the Nashua Formation in the bluffs at the type locality are all low. No more than about 3 feet (1m) of section is currently exposed, and neither lower nor upper contacts can be seen.
Satilla Formation
Age
The Satilia Formation is of late Pleistocene and Holocene age. Late Pleistocene planktonic foraminifera were recovered from the Satilla Formation in Chatham County, GA. Say less than 100,000 years old.
Lithology
The Satilla Formation is a lithologically heterogeneous unit and consists variably of sand and clay. Sand appears to be the dominant lithic component, at least in the barrier island lithofacies, and is most conspicuous at the type locality and reference localities. Other subordinate lithic components include calcite, shells and other fossils, heavy minerals, mica, humate, scattered carbonaceous material, and, locally, fossil vertebrate remains.
The sand generally is fine to medium grained and well sorted. Coarser grained sand, where present, generally is more poorly sorted. Bedding in the dominantly sand lithofacies includes well-stratified sands with well-defined horizontal-bedding and various kinds of crossbedding; vaguely bedded sands; and massive-bedded sand devoid of primary sedimentary structures. Bioturbated argillaceous sand is present in the more marine, inner shelf phases of the formation. Locally, as at Reids Bluff, channel cut-and-fill structures are conspicuous. Humate-cemented sandstone is also locally prominent, with large boulders of humate sandstone littering the bases of bluffs.
The Satilla Formation exhibits two types of clay deposits: variably bedded, variably calcareous and fossiliferous, silty to sandy clay of inner continental shelf origin; and massive bedded, blocky to hackly clay of marsh origin with local concentrations of the oyster Crassostrea virginica. Based on limited core and outcrop control, it would appear that much of the Pamlico terrace complex is underlain by marsh-type clay in the area south of the Altamaha River(Logan, 1968). Clay containing Crassostrea virginica is exposed at Reids Bluff and at Orange Bluff on the St. Marys River in Nassau County, Florida. No stratigraphic information is available for the area north of the Altamaha River.
Satilla Formation
Age
The Satilia Formation is of late Pleistocene and Holocene age. Late Pleistocene planktonic foraminifera were recovered from the Satilla Formation in Chatham County, GA. Say less than 100,000 years old.
Lithology
The Satilla Formation is a lithologically heterogeneous unit and consists variably of sand and clay. Sand appears to be the dominant lithic component, at least in the barrier island lithofacies, and is most conspicuous at the type locality and reference localities. Other subordinate lithic components include calcite, shells and other fossils, heavy minerals, mica, humate, scattered carbonaceous material, and, locally, fossil vertebrate remains.
The sand generally is fine to medium grained and well sorted. Coarser grained sand, where present, generally is more poorly sorted. Bedding in the dominantly sand lithofacies includes well-stratified sands with well-defined horizontal-bedding and various kinds of crossbedding; vaguely bedded sands; and massive-bedded sand devoid of primary sedimentary structures. Bioturbated argillaceous sand is present in the more marine, inner shelf phases of the formation. Locally, as at Reids Bluff, channel cut-and-fill structures are conspicuous. Humate-cemented sandstone is also locally prominent, with large boulders of humate sandstone littering the bases of bluffs.
The Satilla Formation exhibits two types of clay deposits: variably bedded, variably calcareous and fossiliferous, silty to sandy clay of inner continental shelf origin; and massive bedded, blocky to hackly clay of marsh origin with local concentrations of the oyster Crassostrea virginica. Based on limited core and outcrop control, it would appear that much of the Pamlico terrace complex is underlain by marsh-type clay in the area south of the Altamaha River(Logan, 1968). Clay containing Crassostrea virginica is exposed at Reids Bluff and at Orange Bluff on the St. Marys River in Nassau County, Florida. No stratigraphic information is available for the area north of the Altamaha River.
References
- Brantly, J.E.; A Report on the Limestones and Marls of the Coastal Plain of Georgia, Bulletin 21, Georgia Geological Survey, 1916
- Veatch, Otto; Stephenson, Lloyd William; Preliminary Report on the Geology of the Coastal Plain of Georgia; US Geological Survey, Georgia Geological Survey, Bulletin 26, 1911
- Cooke, C. Wythe; Geology of the Coastal Plain of Georgia, United States Geological Survey (USGS), Bulletin 941, 1943
- McCallie, Samuel W.; A Preliminary Report Phosphates and Marls of Georgia, Bulletin# 5-A, Georgia Geologic Survey, 1896
- McCallie, Samuel W.; A Preliminary Report on the Underground Waters of Georgia; Bulletin 15, Georgia Geologic Survey, 1908
- Richards, Horace G.; Illustrated Fossils of the Georgia Coastal Plain, Georgia Dept of Mines, Mining & Geology, Georgia Mineral Newsletter, 1969
- Morgan, Gary S; Miocene Vertebrate Faunas From The Suwannee River Basin Of North Florida and South Georgia; Miocene Paleontology and Stratigraphy of the Suwannee River Basin of North Florida and South Georgia; Southeastern Geological Society, Guidebook Number 30, Annual Field Trip, 07/Oct/1989
- Huddlestun, Paul F.; The Miocene Through the Holocene, A Revision of the Lithostratigraphic Units of the Coastal Plain of Georgia, Bulletin 104, Georgia Geologic Survey, 1988
- Miocene Epoch in Florida – For Educators (ufl.edu)
- Yon, J.W. Jr., 1965: The stratigraphic significance of an upper Miocene fossil discovery in Jefferson County, Florida, Southeastern Geology, v. 6, no. 3, p. 167-176.