31B: Decatur County
Fossils & Natural History
By Thomas Thurman
25/Aug/2024
There are geological & paleontological reports about Decatur County going back to Professor Samuel McCallie in 1896.
The Paleobiology Database shows a wealth of fossils reported from Decatur County. We looked at Gastropod Gulch and the roughly 21-million-year-old, Miocene sea snail shell fossils reported by Julia Gardner starting in 1926. (See Section 18G of this website.) Her research revealed new species previously unknown to science. Further down in the stratigraphy we find a wealth of 30+ million-year-old Oligocene corals also present in Decatur County, with as many as 21 species reported by T.W. Vaughan in 1919. This includes more new species previously unknown to science.
The Paleobiology Database shows a wealth of fossils reported from Decatur County. We looked at Gastropod Gulch and the roughly 21-million-year-old, Miocene sea snail shell fossils reported by Julia Gardner starting in 1926. (See Section 18G of this website.) Her research revealed new species previously unknown to science. Further down in the stratigraphy we find a wealth of 30+ million-year-old Oligocene corals also present in Decatur County, with as many as 21 species reported by T.W. Vaughan in 1919. This includes more new species previously unknown to science.
Decatur County is fertile hunting ground for paleontologists, but as far as I can tell it’s been many decades since any serious field research has been done in the county.
Vaughan’s 1919 report included large boulders of chert containing many species of corals at Hales Landing, 6.25 miles southwest of the highway bridge at Bainbridge. We’ll look at these in some detail.
Vaughan’s 1919 report included large boulders of chert containing many species of corals at Hales Landing, 6.25 miles southwest of the highway bridge at Bainbridge. We’ll look at these in some detail.
The area is geographically complex, the Doughtery Plain, Pelham Escarpment, and Tifton Upland all meet in Decatur County. The local bedrock is a limestone karst, meaning much of the bedded limestone has been dissolved away in spots by acidic groundwater, creating caves, caverns and sinkholes. This allows underground rivers to flow.
This limestone is evidence of multiple seas which covered the area from 20 to 15 million years ago. We’ll look at some of these in detail.
This limestone is evidence of multiple seas which covered the area from 20 to 15 million years ago. We’ll look at some of these in detail.
Those weren’t the only times the area was beneath a subtropical sea. At 14,500 years ago the Bølling-Allerød (Late Glacial Interstadial) warming began abruptly triggering the onset of rapid glacial retreat & sea level rise. Levels quickly rose by more than 100 meters or 328 feet. Most of Decatur County is below 300 feet in elevation.
An Interstadial is a warming event. There is a rough global rhythm of Glacial (Cold) Events & Interstadial (Warm) Events.
At about this same time (14,500 years ago) humans are in the Southeast, confirmed in Florida.
An Interstadial is a warming event. There is a rough global rhythm of Glacial (Cold) Events & Interstadial (Warm) Events.
At about this same time (14,500 years ago) humans are in the Southeast, confirmed in Florida.
The Pelham Escarpment
The Pelham Escarpment is a long, deeply weathered cliff on the eastern flank of the Dougherty Plain which formed when it and the Tifton Upland weathered at different rates. It is a cuesta, defined in Wikipedia as a hill or ridge with a gentle slope on one side, and a steep slope on the other. In geology, the term is more specifically applied to a ridge where a harder sedimentary rock overlies a softer layer, the whole being tilted somewhat from the horizontal.
The escarpment extends from the vicinity of Wilcox County, Georgia, southwestward to southwestern Decatur County, Georgia, where it merges into the eastern valley wall of the Flint River (Lake Seminole). Between the vicinities of Bristol and Chattahoochee, Florida, the Pelham Escarpment also forms the eastern wall of the Apalachicola River Valley, and large bluffs are formed where the river flows against the Pelham Escarpment.
The Pelham Escarpment is a long, deeply weathered cliff on the eastern flank of the Dougherty Plain which formed when it and the Tifton Upland weathered at different rates. It is a cuesta, defined in Wikipedia as a hill or ridge with a gentle slope on one side, and a steep slope on the other. In geology, the term is more specifically applied to a ridge where a harder sedimentary rock overlies a softer layer, the whole being tilted somewhat from the horizontal.
The escarpment extends from the vicinity of Wilcox County, Georgia, southwestward to southwestern Decatur County, Georgia, where it merges into the eastern valley wall of the Flint River (Lake Seminole). Between the vicinities of Bristol and Chattahoochee, Florida, the Pelham Escarpment also forms the eastern wall of the Apalachicola River Valley, and large bluffs are formed where the river flows against the Pelham Escarpment.
Various formations are present in the face of the Pelham Escarpment along its length. At Alum Bluff on the Apalachicola River, near Bristol, Florida, the lower Miocene Chipola Formation is overlain by the upper Pliocene Jackson Bluff Formation in the face of the escarpment, and the upper Pliocene Citronelle Formation caps the escarpment. The geologic section exposed in the face of the Pelham Escarpment rises northward into southwestern Georgia, exposing older formations. From Aspalaga Bluff in Gadsden County, Florida, northward into Decatur County, Georgia, the sections exposed in the bluffs of the Apalachicola and lower Flint Rivers consist of Chattahoochee Formation, overlain by Torreya Formation, and capped by Citronelle or Miccosukee Formations. From northeastern Mitchell County to its termination in Wilcox County, Oligocene limestones, or residuum thereof, occur at the base of the escarpment, and Altamaha Formation caps the escarpment.
For more information on Decatur County fossils reported from the face of the Pelham Escarpment see this website section 18G: Gastropod Gulch, Julia Gardner, & Miocene Invertebrates In Decatur County - Exploring Georgia's Natural History (georgiasfossils.com)
For more information on Decatur County fossils reported from the face of the Pelham Escarpment see this website section 18G: Gastropod Gulch, Julia Gardner, & Miocene Invertebrates In Decatur County - Exploring Georgia's Natural History (georgiasfossils.com)
Decatur County
Stratigraphy
In 1988 Huddlestun recognized the following stratigraphy in Decatur County, he only reported vertebrate material in the clay-rich Dogtown Member of the Torreya Formation.
Hawthorn Group
Coosawatchee Formation
Meigs Member
The age of the Meigs Member is early-middle Miocene, Langhian Stage, roughly 15 million years old.
Torreya Formation
Sopchoppy Member
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.
Dogtown Member
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
Only a small part of the Dogtown Clay Member contains a commercial grade fuller's earth. In places where the commercial fuller's earth beds are separated into lower and upper beds, the intervening deposits are mainly sand, calcareous sand, limestone, dolomitic clay, and clayey dolostone.
Minor components include quartz sand, calcite, dolomite, phosphate, mica, K-feldspar, pyrite, heavy minerals, rare fossil bones and rare and scattered petrified wood.
Parachula Formation
The Parachucla Formation is Early Miocene (Aquitanian) 20-23 million years old.
The 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.
Stratigraphy
In 1988 Huddlestun recognized the following stratigraphy in Decatur County, he only reported vertebrate material in the clay-rich Dogtown Member of the Torreya Formation.
Hawthorn Group
Coosawatchee Formation
Meigs Member
The age of the Meigs Member is early-middle Miocene, Langhian Stage, roughly 15 million years old.
Torreya Formation
Sopchoppy Member
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.
Dogtown Member
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
Only a small part of the Dogtown Clay Member contains a commercial grade fuller's earth. In places where the commercial fuller's earth beds are separated into lower and upper beds, the intervening deposits are mainly sand, calcareous sand, limestone, dolomitic clay, and clayey dolostone.
Minor components include quartz sand, calcite, dolomite, phosphate, mica, K-feldspar, pyrite, heavy minerals, rare fossil bones and rare and scattered petrified wood.
Parachula Formation
The Parachucla Formation is Early Miocene (Aquitanian) 20-23 million years old.
The 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.
Dr. Burt Carter
Paleontology Professor Emeritus, Georgia Southwestern
September, 2024
Text Message Concerning Decatur County Chert Boulders
(These observations should be viewed with a high degree of certainty. Burt is a friend and advisor of the author and deeply knowledgeable and experienced with SW Georgia stratigraphy.)
There are a lot of chert boulders in Decatur County.
Between the Escarpment and the (Flint) river they are mostly obviously Bridgeboro (Limestone). Rhodoliths are obvioius. (See Section 8 of this website.) Very close to the riverthere aren't rhodoliths that I have seen, but no good fossils either, so could be uppermost Ocala.
Middle Ocala in the Flint, undifferentiated (Oligocene Resdiuum), from Albany to the lake. West of the river near ichway the chert has upper Ocala fossils.
(There is a large pile of chert boulders)of GA311 and Deese Rd a few miles north of Bainbridge. Should be obvious on Satellite.
Paleontology Professor Emeritus, Georgia Southwestern
September, 2024
Text Message Concerning Decatur County Chert Boulders
(These observations should be viewed with a high degree of certainty. Burt is a friend and advisor of the author and deeply knowledgeable and experienced with SW Georgia stratigraphy.)
There are a lot of chert boulders in Decatur County.
Between the Escarpment and the (Flint) river they are mostly obviously Bridgeboro (Limestone). Rhodoliths are obvioius. (See Section 8 of this website.) Very close to the riverthere aren't rhodoliths that I have seen, but no good fossils either, so could be uppermost Ocala.
Middle Ocala in the Flint, undifferentiated (Oligocene Resdiuum), from Albany to the lake. West of the river near ichway the chert has upper Ocala fossils.
(There is a large pile of chert boulders)of GA311 and Deese Rd a few miles north of Bainbridge. Should be obvious on Satellite.
In 1943 Cooke made the following observations
Decatur County
On Flint River, the lowest known exposure of the Flint River Formation (Early Oligocene Residuum) is at Wyley Landing, which is on the south bank 3 miles above the mouth of Spring Creek. (Still accessible?) Near the water level is a white limestone containing many reef corals (details below), and other fossils.
The limestone, which varies in texture from loose and granular to hard, massive, and crystalline, is overlain by sticky greenish clay. Still higher is hard conglomeratic limestone supposed to be basal Tampa. (Huddlestun formally abandoned the Tampa Limestone in Georgia, divide and reassigned it as the Chattahoochee Formation and Parachula Formation.)
Chattahoochee Formation
Dolomitic limestone
Early Miocene (Aquitanian) 20-23 million years old.
Parachula Formation
Phosphatic, clay-rich, carbonate sandy clay
Early Miocene (Aquitanian) 20-23 million years old.
Huddlestun shows that both the Chattahoochee and Parachula Formation occur on the Tifton Upland and are equal in age. The Chattahoochee is roughly more western, being against & below the Pelham Escarpment. The Parachula occurs in the more eastern part of the county.
To continue with Cooke’s description…
About 3 feet of hard crystalline limestone, was noted in 1914 at the lower end of Fort Scott Bluff, on the right bank of Flint River 1.5 miles below Hutchenson’s Ferry.
At Hutchenson’s Ferry, 7.25 miles east-northeast of the mouth of Spring Creek, huge lumps of chert of the Early Oligocene residuum (?) rise almost 15 feet above water level.
Five feet of hard pinkish-white limestone containing obscure corals crops out on the east bank 5.25 miles northeast of Hutchenson’s Ferry. This place is 3 miles below Hales Landing. Additionally, Rhyncolampus gouldii was noted in 1914 in large masses of chert 2 miles below Hales Landing.
About 3 feet of hard crystalline limestone, was noted in 1914 at the lower end of Fort Scott Bluff, on the right bank of Flint River 1.5 miles below Hutchenson’s Ferry.
At Hutchenson’s Ferry, 7.25 miles east-northeast of the mouth of Spring Creek, huge lumps of chert of the Early Oligocene residuum (?) rise almost 15 feet above water level.
Five feet of hard pinkish-white limestone containing obscure corals crops out on the east bank 5.25 miles northeast of Hutchenson’s Ferry. This place is 3 miles below Hales Landing. Additionally, Rhyncolampus gouldii was noted in 1914 in large masses of chert 2 miles below Hales Landing.
At Hales Landing, 6.25 miles southwest of the highway bridge at Bainbridge, large blocks of chert contain many silicified fossils including, according to T.W. Vaughan (1911) about 21 species of corals.
Corals are also present at Little Horseshoe Bend, Blue Spring, and Cherry Chute, 3 to 4 miles below Bainbridge.
At Red Bluff, on Flint River 6 miles north of Bainbridge, pinnacles of Ocala limestone, crested with limonite, rise 20 feet above the water.
Corals are also present at Little Horseshoe Bend, Blue Spring, and Cherry Chute, 3 to 4 miles below Bainbridge.
At Red Bluff, on Flint River 6 miles north of Bainbridge, pinnacles of Ocala limestone, crested with limonite, rise 20 feet above the water.
The Early Oligocene residuum (Flint River Formation), which overlies it unconformably, contains much gravel throughout. Much of it may have been originally calcareous sandstone-an algal reef-but all the lime has been leached out. The formation now consists of fine cohesive sand and gravel in which are embedded lumps of fossiliferous chert. The colors are light yellows and grays.
In the late 1800s adventuresome Georgia geologist Professor Samuel W. McCallie explored the Coastal Plain for water resources and spent some time in our southernmost counties, he published 2 reports, and 1896 paper on phosphates and marls, and a 1908 report on ground water.
In the late 1800s adventuresome Georgia geologist Professor Samuel W. McCallie explored the Coastal Plain for water resources and spent some time in our southernmost counties, he published 2 reports, and 1896 paper on phosphates and marls, and a 1908 report on ground water.
McCallie is a favorite of mine, a natural explorer and scientist. From 1908 to 1933 he stood as the Georgia State Geologist. In 1896 published field research with W. S. Yeates and F. P. King reporting gold ore from Cherokee, Lumpkin (Dahlonega), Dawson, Union, & White Counties in North Georgia.
Dahlonega Georgia is, of course, famous for one of the USA’s earliest gold rushes, starting in 1829.
McCallie also acquired and described several meteorites, some of which were Georgia finds. Famously, the Cedartown, Polk County Meteorite came into McCallie’s possession around 1898. It was a 9” x 11” hexahedrite weighing 25.5lbs. McCallie studied it closely. Meteorites in Georgia reports that it was on the second floor of his Atlanta two story, 8 room, home when the residence tragically burned to the ground within an hour. McCallie, ever the scientist, recovered the meteorite from the ashes and studied it further to see if the fire had affected it in any way. He reported that neither the Neumann lines, nor any of the meteorites other diagnostic features, were harmed.
Dahlonega Georgia is, of course, famous for one of the USA’s earliest gold rushes, starting in 1829.
McCallie also acquired and described several meteorites, some of which were Georgia finds. Famously, the Cedartown, Polk County Meteorite came into McCallie’s possession around 1898. It was a 9” x 11” hexahedrite weighing 25.5lbs. McCallie studied it closely. Meteorites in Georgia reports that it was on the second floor of his Atlanta two story, 8 room, home when the residence tragically burned to the ground within an hour. McCallie, ever the scientist, recovered the meteorite from the ashes and studied it further to see if the fire had affected it in any way. He reported that neither the Neumann lines, nor any of the meteorites other diagnostic features, were harmed.
McCallie, 1908
Decatur County had several large springs, only two of which have been visited by the author. One of the springs, here referred to, is located in the southwestern part of the county, near the mouth of Spring Creek, about 20 miles south of Bainbridge. This spring, which furnishes several millions of gallons of water per day, is in the form of a nearly circular basin, many rods in circumference (Rod, old English term, one rod equals 11 cubits, 16.5 feet, or 5.029 meters) and is 10 to 30 feet deep. The spring is noted for the transparency of its waters and its large flow.
Decatur County had several large springs, only two of which have been visited by the author. One of the springs, here referred to, is located in the southwestern part of the county, near the mouth of Spring Creek, about 20 miles south of Bainbridge. This spring, which furnishes several millions of gallons of water per day, is in the form of a nearly circular basin, many rods in circumference (Rod, old English term, one rod equals 11 cubits, 16.5 feet, or 5.029 meters) and is 10 to 30 feet deep. The spring is noted for the transparency of its waters and its large flow.
So remarkably transparent is the water of these springs, that, when on them in a boat, one feels as though the boat were suspended in mid-air. Fish, at a depth of 15 feet or more, are distinctly seen, and their specific markings can be studied almost as perfectly, as if they were in an aquarium. The transparency of the water of these springs would seem to indicate that they come up from considerable depth, and have no direct surface connection with the numerous lime sinks often met with throughout the county.
In addition to the large springs of Decatur County, it is also fairly well supplied with small springs, which furnish ample water for domestic purposes. The water of some of these small springs carries iron, hydrogen sulphide, etc., and is regarded locally as possessing medicinal properties of value.
Decatur county, owing to its being underlain by rather porous Eocene limestone (likely Miocene), is noted for its many lime sinks and underground streams. A good example of these subterranean streams may be seen at what is known as Forest Falls, seven miles north of Whigham. (In 1896 Whigham was part of Decatur County, it is now in Grady County. Grady County was created in 1905 from both Decatur and Thomas Counties.)
Decatur county, owing to its being underlain by rather porous Eocene limestone (likely Miocene), is noted for its many lime sinks and underground streams. A good example of these subterranean streams may be seen at what is known as Forest Falls, seven miles north of Whigham. (In 1896 Whigham was part of Decatur County, it is now in Grady County. Grady County was created in 1905 from both Decatur and Thomas Counties.)
At Forest Falls, a brook of sufficient size to run a mill, disappears underground in a lime sink after a perpendicular descent of 80 feet. A few miles further to the north, at what is called the "Water Falls," a second stream disappears underground in like manner. At the bottom of some of the deeper lime sinks, east of the Flint River, are occasionally seen rapidly flowing underground streams. More generally, however, the sinks are partially filled with water, and form beautiful ponds, well stocked with fish. During the dry season many of these ponds are drawn off by the underground streams, with which they seem to be invariably connected.
(Forest Falls is problematical. The location McCallie gives is now Grady County. This will be discussed in more detail in the Grady County section {31C}. There are confusing reports of the location and current condition of this remarkable waterfall, the author {Thurman 2024} suspects it still exist on private property but could not confirm or get much from Grady County offices.)
McCallie, 1896
One of the most extensive rocks exposures on Decatur County’s Spring Creek was seen 4 miles north of Brinson. (1896, W.D. Lane property, Lot 234, 27th District) The exposure extends over a number of acres in the piney woods near the creek. It consists of flint boulders, many weighing several tons, and all well filled with fossil oysters, pectens, sea urchins and small gastropods. Similar outcroppings were observed one mile west of Brinson and several other points along Spring Creek as far south as its junction with the Flint River.
One of the most extensive rocks exposures on Decatur County’s Spring Creek was seen 4 miles north of Brinson. (1896, W.D. Lane property, Lot 234, 27th District) The exposure extends over a number of acres in the piney woods near the creek. It consists of flint boulders, many weighing several tons, and all well filled with fossil oysters, pectens, sea urchins and small gastropods. Similar outcroppings were observed one mile west of Brinson and several other points along Spring Creek as far south as its junction with the Flint River.
T.W. Vaughan, 1919
The greatly developed Oligocene (Age?) coral reefs of Antigua (Isle of Antigua, West Indies) are to be correlated with the reefs of Bainbridge.
The Oligocene coral reef along Flint River near Bainbridge, Georgia, rests on the eroded surface of an upper Eocene limestone now designated the Ocala limestone.
The greatly developed Oligocene (Age?) coral reefs of Antigua (Isle of Antigua, West Indies) are to be correlated with the reefs of Bainbridge.
The Oligocene coral reef along Flint River near Bainbridge, Georgia, rests on the eroded surface of an upper Eocene limestone now designated the Ocala limestone.
The localities at which the specimens of fossil corals were obtained are at Blue or Russell Springs on Flint River about 4 miles below Bainbridge, and at other localities along Flint River to Hale’s Landing, about 7 miles below Bainbridge.
Burt Carter, an old fossil-friend, was quick to remind me that these two sites are extinct. Drowned beneath Lake Seminole. Jim Woodruff Lock and Dam was completed in 1952, submerging the sites. Hales landing stite exist and has been developed into a capsite, but it isn't in the same spot. Lake Seminole claimed that location.
The coral faunas are not the same, and there is at least a species of one genus at Tampa of stratigraphically later affinities than any species in the vicinity of Bainbridge.
The following are the species from near Bainbridge mentioned in this paper.
The following are the species from near Bainbridge mentioned in this paper.
Fossil corals Vaughan placed in Chattahoochee formation
Near Bainbridge, Georgia.
Near Bainbridge, Georgia.
- Stylophora minutissima
- Described by Vaughan, new species known only from Georgia (1919)
- Stylocoenia pumpellyi
- Described by Vaughan, new species from Georgia
- Also reported on the Island of Antigua & West Indies
- Astrocoenia decaturensis
- Described by Vaughan, new Georgia Species in 1919
- Also observed on Island of Antigua & Cuba.
- Orbicella bainbridgensis
- New species described by Vaughan & named for Bainbridge.
- Also observed by Vaughan in Saint Domingo, of the Dominican Republic & Puerto Rico.
- Antiguastrea cellulosa
- Also observed on the Iland of Antigua, & Tampa area.
- Antiguastrea silecensis
- New species described by Vaughan from Georgia Specimen
- Also observed by Vaughan on the Island of Antigua.
- Favites polygonalis
- Also observed on the Island of Antigua.
- Siderastrea silecensis
- New species described by Vaughan
- Also observed in the Tampa area.
- Diploastrea crassolamellata
- Also observed on the Island of Antigua.
- Diploastrea magnifica
- Also observed on the Island of Antigua.
- Astreopora antiguensis
- New species described by Vaughan.
- Also observed on the Island of Antigua.
- Actinacis alabamiensis
- New species described by Vaughan.
- Also observed on the Island of Antigua and Salt Mountain, Alabama.
- Goniopora decaturensis
- New species described by Vaughan
- Also observed in Cuba.
Of the 13 species and varieties listed above, 9 are common to Antigua, and Goniopora decaturensis occurs in Cuba in association with species of corals abundant in Antigua; of the 3 remaining species, Stylophora minutissima has so far been positively identified only at Bainbridge, but it is very near a species common in Antigua; 2 of the 13 forms are known from the ‘‘silex’’ bed of Tampa.
The coral fauna near Bainbridge is a moderately rich one.
The coral fauna near Bainbridge is a moderately rich one.
In addition to those listed above, Vaughan also reported the following genera from the Bainbridge area.
- Stylophora
- Astrocoenia
- Antillia
- Astrangia or Rhizangia
- Mesomorpha
- Astreopora
- Actinacis
- Goniopora
- Alveopora
Age of the Boulders Containing Corals.
So where does this put us?
The reported fossils in the boulders date to the early Rupelian Stage of the Oligocene Epoch, or between 34 to 30 million years old.
Vaughan was indecisive in his dates. I consulted with Dr. Burt Carter, Paleontology Professor Emeritus from Georgia Southwestern. Burt knows the sediments and literature of SW Georgia; he’s explored both widely. He referred me back to Wythe Cooke’s 1943 review and reminded me that Cooke was also paying close attention to both stratigraphy and literature.
Cooke cites a 1914 report of the echinoid (urchin) Rhyncolampus gouldii from chert boulders 2 miles below Hales Landing. Rhyncolampus gouldii is an Early Oligocene index fossil.
So where does this put us?
The reported fossils in the boulders date to the early Rupelian Stage of the Oligocene Epoch, or between 34 to 30 million years old.
Vaughan was indecisive in his dates. I consulted with Dr. Burt Carter, Paleontology Professor Emeritus from Georgia Southwestern. Burt knows the sediments and literature of SW Georgia; he’s explored both widely. He referred me back to Wythe Cooke’s 1943 review and reminded me that Cooke was also paying close attention to both stratigraphy and literature.
Cooke cites a 1914 report of the echinoid (urchin) Rhyncolampus gouldii from chert boulders 2 miles below Hales Landing. Rhyncolampus gouldii is an Early Oligocene index fossil.
Cooke referred to these chert boulders as the Flint River Formation, which Huddlestun reassigned as Early Oligocene Residuum. (A reassignment which might need revisiting.) This is the same material which reaches up into Houston County and shows what was once a widespread sea.
Interestingly, if all of this does indeed represent the same Early Oligocene sea, the “Flint River Formation” fossils further north on the Coastal Plain tend to have high populations with very low diversity. In 1970 Sam Pickering only counted 18 species, mostly small clams, as occurring in the Flint River Formation of Houston & Pulaski County, including only one coral from the genus Trochocyathus. Here in Decatur County, as many as 21 species of coral occur. This suggests a distinct shift in conditions and available food supplies in this lost sea.
Interestingly, if all of this does indeed represent the same Early Oligocene sea, the “Flint River Formation” fossils further north on the Coastal Plain tend to have high populations with very low diversity. In 1970 Sam Pickering only counted 18 species, mostly small clams, as occurring in the Flint River Formation of Houston & Pulaski County, including only one coral from the genus Trochocyathus. Here in Decatur County, as many as 21 species of coral occur. This suggests a distinct shift in conditions and available food supplies in this lost sea.
To continue with Cooke’s description…
Rhyncolampus gouldii was noted in 1914 in large masses of chert 2 miles below Hales Landing. At Hales Landing, 6.25 miles southwest of the highway bridge a Bainpridge. large blocks of chert contain many silicified fossils including, according to Vaughan, about 21 species of corals. Corals are also present at Little Horseshoe Bend, Blue Spring, and Cherry Chute, 3 to 4 miles below Bainbridge.
Rhyncolampus gouldii was noted in 1914 in large masses of chert 2 miles below Hales Landing. At Hales Landing, 6.25 miles southwest of the highway bridge a Bainpridge. large blocks of chert contain many silicified fossils including, according to Vaughan, about 21 species of corals. Corals are also present at Little Horseshoe Bend, Blue Spring, and Cherry Chute, 3 to 4 miles below Bainbridge.
At Red Bluff, on Flint River 6 miles north of Bainbridge, pinnacles of Ocala limestone, crested with limonite, rise 20 feet above the water. The Flint River formation, which overlies it unconformably, contains much gravel throughout. Much of it may have been originally calcareous sandstone-an algal reef-but all the lime has been leached out. The formation now consists of fine cohesive sand and gravel, in which are embedded lumps of fossiliferous chert. The colors are light yellows and grays.
Furthermore, in 1959 Wythe Cook published an extensive report on echinoids occurring in the eastern United States, below are his observations for Decatur County, Georgia. Cooke’s reports are augmented, below, by the fieldwork of Dr. Burt Carter, retired, from Georgia Southwestern.
Furthermore, in 1959 Wythe Cook published an extensive report on echinoids occurring in the eastern United States, below are his observations for Decatur County, Georgia. Cooke’s reports are augmented, below, by the fieldwork of Dr. Burt Carter, retired, from Georgia Southwestern.
Age of Other Sediments Occurring in Decatur County
The following echinoids (urchins and sand dollars) are reported from Decatur County, echinoids are good indicators for the age of their matrix.
The following echinoids (urchins and sand dollars) are reported from Decatur County, echinoids are good indicators for the age of their matrix.
- Agassizia clevei
- Late Eocene (B. Carter)
- Brissus bridgeboroensis
- Early Oligocene (B. Carter)
- Clypeaster rogersi
- Throughout Oligocene (B. Carter & others)
- Eupatagus ocalanus
- Late Eocene (B. Carter 1987)
- Fibularia vaughani
- Late Eocene (B. Carter 1987)
- Lytechinus floralanus
- Late Eocene (B. Carter 1987)
- Oligopygus wetherbyi
- Late Eocene (B. Carter 1987)
- Phyllacanthus mortoni
- Middle to Late Eocene
- Plagiobrissus curvus
- Late Eocene (B. Carter 1987)
- Rhyncholampas conradi
- Late Eocene (B. Carter 1987)
- Rhyncholampas georgiensis
- Late Eocene (B. Carter 1987)
- Rhyncholampas gouldii
- Early Oligocene
- Salenia palmyra
- Early Paleocene
- Weisbordella johnsoni
- Late Eocene
Lastly, Dr. Burt Carter, Professor Emeritus, Georgia Southwestern did a large research project on the Bridgeboro Limestone which also occurs in Decatur County. See Section 8 of this website. The Bridgeboro Limestone reveals that the Suwannee Current carved the Gulf Trough across our state. Though it is richly fossiliferous, diversity is limited to primarily algae rhodoliths.
References
- Cooke, C. Wythe; Geology of the Coastal Plain of Georgia, United States Geological Survey (USGS), Bulletin 941, 1943
- 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
- McCallie, Samuel W.; A Preliminary Report on the Underground Waters of Georgia; Bulletin 15, Georgia Geologic Survey, 1908
- Henderson, E.P.; Furcron A.S.; Meteorites in Georgia, Georgia Dept of Mines, Mining & Geology, Atlanta, 1966.
- McCallie, Samuel W.; A Preliminary Report Phosphates and Marls of Georgia, Bulletin# 5-A, Georgia Geologic Survey, 1896
- 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
- The Paleobiology Database; PBDB Navigator (paleobiodb.org)
- Vaughan, Thomas Wayland; Fossil Corals From Central America, Cuba, Porto Rico, With an Account of the American Tertiary, Pleistocene and Recent Coral Reefs; Smithsonian Institution, United State National Museum, Bulletin 103, 1919
- Cooke, C. Wythe; Cenozoic Echinoids of the Eastern United States, Geologic Survey Professional Paper 321, U.S. Dept of Interior, USGS, 1959
- Florida Museum of Natural History, Collection Directory, Invertebrate Paleontology; Web Portal (ufl.edu)
- Carter, Burchard D. & McKinney, Michael L.; Eocene Echinoids of the Suwannee Strait, and Biogeographic Taphonomy, Paleobiology 18 (3), Pg 299-325, 1992
- Carter, Burchard D.; Paleogene Echinoid Distributions in the Atlantic and Gulf Coastal Plains; Palaios, 1987, v.2, pgs. 390-404, The Society of Economic Paleontologists and Geologists
- Carter, Burchard D.; McKinney, Michael L.; Eocene Echinoids, The Suwannee Strait, and biogeographic taphonomy; Paleobiology, 183(2), 1992, pp. 299-325
- Pickering, Sam M.; Stratigraphy, Paleontology, and Economic Geology of Portions of Perry and Cochran Quadrangles. The Geological Survey of Georgia, Department of Mines, Mining and Geology, Bulletin 81. 1970.
