20M: The Bone Bed,
Pleistocene, Coastal Georgia
By Thomas Thurman
Posted 21/Sept/2024
This page is dedicated to Ms. Ferris Flourney & Ms. Beth Carden of Darien, Georgia and their great little apartment I enjoy.
Darien, founded in 1736, is a delightful little town full of good folk, magnificent live oaks, Spanish moss, the shrimp fleet,
& the many ghosts
of Georgia’s early European settlement history.
But well before any humans arrived in our state, giant sloths, herds of horses, mammoths, & mastodons, walked Coastal Georgia
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In 1943 Wythe Cooke, working for the USGS, published his survey of Georgia’s Coastal Plain. At the end of that paper he placed his 5 page report on the coastal Bone Beds of Georgia's Pliestocene Epoch sediments...
On Skidaway Island, Chatham County, bones of the giant ground sloth, Eremotherium laurillardi, were found in 1823. The bed containing them was called the "inland swamp formation" by J. Hamilton Couper, whose description of the occurrence is included in a pamphlet by Hodgson published in 1846. |
Dr. Robert McAffee, an Associate Professor of Anatomy and Paleontologist specializing in sloths, once reminded me that there is no anatomical reason to think the giant sloths were as slow moving like their modern relatives. These very large animals were living in a predator rich environment. As large or larger than a mammoth, it probably wasn’t quick, but its unlikely it was as slow moving as a modern sloth.
McAffee teaches at the Philadelphia College of Osteopathic Medicine in Suwannee, Georgia.
McAffee teaches at the Philadelphia College of Osteopathic Medicine in Suwannee, Georgia.
The Pliestocene Epoch spands from 2.58 million to 11,700 years ago, but the sediments of the Bone Bed that Wythe Cooke is discussing here are perhaps less that 25,000 years ago. The animals discussed on this page may have lived while native Americans were present in Georgia. That has yet to be fully investigated.
Ocmulgee National Monument in Macon, Georgia states that the site has been continuouslly inhabited for "more than" 12,000 years.
Columbian mammoths and giant sloths survived to at least 12,000 year ago.
Ocmulgee National Monument in Macon, Georgia states that the site has been continuouslly inhabited for "more than" 12,000 years.
Columbian mammoths and giant sloths survived to at least 12,000 year ago.
Eremotherium herds?
Eremotherium laurillardi is the largest known ground sloth and is well known from Georgia.
Eremotherium fossils frequently occur in clusters representing multiple individuals. This has happened in several sites in Georgia, sites in Mexico, Ecuador, and Brazil. In several cases sites produced multiple adult and juvenile specimens in a single horizon.
Eremotherium laurillardi is the largest known ground sloth and is well known from Georgia.
Eremotherium fossils frequently occur in clusters representing multiple individuals. This has happened in several sites in Georgia, sites in Mexico, Ecuador, and Brazil. In several cases sites produced multiple adult and juvenile specimens in a single horizon.
In Georgia, the most I’m aware of in 3 individuals from a single site (See below, Sir Charles Lyell 1855). But only small scale, short term, excavations (with very limited funding) have been done. Wikipedia reports that one site in Mexico produced 4 individuals. One site in Ecuador produced 15 and another site produced 22 individuals. A sinkhole site in Brazil produced 19 individuals.
Parts of South Georgia have many sinkholes, most are unexplored by researchers.
Parts of South Georgia have many sinkholes, most are unexplored by researchers.
These numbers suggests that giant ground sloths possibly lived in small herds. Additionally, these were very large animals requiring a great deal of food.
A modern adult Indian elephant weighs 4 to 6 tons and consumes 350 to 450lbs of food daily. A large, modern African elephant bull comes in at 7 tons. It’s thought that an adult Eremotherium laurillardi weighed 5 to 7 tons.
Eremotherium laurillardi
A modern adult Indian elephant weighs 4 to 6 tons and consumes 350 to 450lbs of food daily. A large, modern African elephant bull comes in at 7 tons. It’s thought that an adult Eremotherium laurillardi weighed 5 to 7 tons.
Eremotherium laurillardi
- Largest giant sloth
- Overall adult length of 20ft
- 6.6ft tall on all fours
- 13 ft raised on hind legs to feed on trees
- Adult weight of 5 to 7 tons
- Overall adult length of 20ft
Columbian Mammoth
Columbian Mammoths Named From a Georgia Tooth
It is well known that herds of mammoths and mastodons once wandered across Georgia. One of the largest of the elephant-clan to ever walk the Earth the Columbian mammoth (Mammuthus columbi) a species was named from a Georgia fossil found by Hamilton Cooper during the construction of the Brunswick Canal in 1838 to 1839. (Brunswick was originally settled in 1738.) He put it in the hands of Sir Charles Lyell during one of the famous geologist’s visits to North America and Georgia. Lyell passed the fossil to Hugh Falconer, who founded the species.
It is well known that herds of mammoths and mastodons once wandered across Georgia. One of the largest of the elephant-clan to ever walk the Earth the Columbian mammoth (Mammuthus columbi) a species was named from a Georgia fossil found by Hamilton Cooper during the construction of the Brunswick Canal in 1838 to 1839. (Brunswick was originally settled in 1738.) He put it in the hands of Sir Charles Lyell during one of the famous geologist’s visits to North America and Georgia. Lyell passed the fossil to Hugh Falconer, who founded the species.
Wikipedia’s description of the event
The Columbian mammoth was first scientifically described in 1857 by naturalist Hugh Falconer, who named the species Elephas columbi after the explorer Christopher Columbus. The animal was brought to Falconer's attention in 1846 by Sir Charles Lyell, who sent him molar fragments found during the 1838 excavation of the Brunswick–Altamaha Canal in Georgia, in the southeastern United States.
No mention is made of Hamilton Cooper by Wikipedia.
The Columbian mammoth was first scientifically described in 1857 by naturalist Hugh Falconer, who named the species Elephas columbi after the explorer Christopher Columbus. The animal was brought to Falconer's attention in 1846 by Sir Charles Lyell, who sent him molar fragments found during the 1838 excavation of the Brunswick–Altamaha Canal in Georgia, in the southeastern United States.
No mention is made of Hamilton Cooper by Wikipedia.
Columbian Mammoth (Mammuthus columbi)
- Size estimates
- Length 12.2 ft to 13.8ft (3.72 m–4.2 m)
- Average shoulder height of 12.3 ft (3.75 m)
- Average weight 9 to 13 tons
Why would the United States Geological Survey (USGS) be interested in Georgia’s Coastal Plain and send Cook to investigate it? Because our Coastal Plain distinct in the Southeast, the surface beds are completely different that those of the surrounding states. This difference was well-known but unexplained in 1943. Sadly there is much still to learn and little to no active research being done.
Cooke was an excellent field researcher. He was a trained and published invertebrate paleontologist and stratigrapher, but he didn’t unravel the mystery of why Georgia’s Coastal Plain is distinct. That would have to wait for J. P. Ranker and Burt (B.D.) Carter’s field work published in 1987, they discovered and described a powerful current which crossed the state for tens of millions of years, whenevr seal levels were higer, altering the sediments of Georgia’s Coastal Plain forever. (See Section 8: The Suwannee Current, of this website.)
8: Suwannee Current, Gulf Trough, & Bridgeboro Limestone - Celebrating 10 Years Online! (georgiasfossils.com)
8: Suwannee Current, Gulf Trough, & Bridgeboro Limestone - Celebrating 10 Years Online! (georgiasfossils.com)
Cooke’s primary goal was to understand our Coastal Plains sediments. Cooke would go on to create and published a very important field report on the occurrence of Cenozoic echinoids (sand dollar and sea urchin) fossils in the Eastern United States. This report often allows researchers to date sediments based on what echinoid fossils they find. Our friend Burt Carter, an expert in echinoids, has greatly expanded Cooke’s work.
The Georgia reports from Cooke's 1959 paper on echinoids is covered in Section 29 of this website (29: Echinoids of Georgia, Cenozoic Era (Sand Dollars & Urchins) - Celebrating 10 Years Online! (georgiasfossils.com)), the actual 5 pages of Cooke's 1943 report on the Bone Bed are below.
The Georgia reports from Cooke's 1959 paper on echinoids is covered in Section 29 of this website (29: Echinoids of Georgia, Cenozoic Era (Sand Dollars & Urchins) - Celebrating 10 Years Online! (georgiasfossils.com)), the actual 5 pages of Cooke's 1943 report on the Bone Bed are below.
While there’s been several papers touching on fossils from the Bone Bed, it still has not been fully explored. Section 20A of this website (20A; Clark Quarry's Mammoths & Bison - Celebrating 10 Years Online! (georgiasfossils.com)) describes finds reported by Dr. Al Mead at Georgia College in Milledgeville from Clark Quarry in Brunswick. These finds came from the Bone Bed as described by Cooke in 1943.
In 1971 Dr. Michael Voorhies (of Nebraska Ashfall Fossil Beds fame), was the Professor of Paleontology at the University of Georgia. He reported partial skeletons from one juvenile and two adult Eremotherium giant ground sloths from Watkins quarry in Glynn County, near Brunswick. See Section 20J of this website for details (20J; Watkins Quarry Pleistocene Vertebrates, Glynn County, GA - Celebrating 10 Years Online! (georgiasfossils.com)). These are also from the Bone Bed Cooke described by Cooke in 1943.
Section 20K of this website (20K: Pleistocene Vertebrates from Coastal Georgia - Celebrating 10 Years Online! (georgiasfossils.com)) is a research project by Dr. Richard Hulbert and Anne Pratt published in 1998 and looks at fossils in Chatham & Glynn County. In that paper Hulbert and Pratt speculate on the dominance of Eremotherium laurillardi in the sediments and how that might relate to dating the deposits…
“There is an additional factor which may provide some chronologic information. Eremotherium laurillardi (Giant ground sloth) is the numerically dominant ground sloth in the Savannah region and other coastal sites in Georgia. Florida has a much greater number of Pleistocene vertebrate sites than Georgia, with better chronologic control, thus allowing more precise resolution of the distribution of certain taxa. Eremotherium was common in Florida up through the last interglacial 75,000 years ago, but thereafter became very rare and is generally absent at most sites. Megalonyx (large ground sloth) is the typical latest Pleistocene ground sloth in Florida. Assuming that this was also the case in Georgia, abundant Eremotherium at sites would suggest a minimum age of about 75,000 for these localities.”
However, the material collected by Georgia College (Section 20A of this website) showed a different age in radio carbon dating of the giant bison remains, those provided a date of 21,000 years ago. Clearly more work needs to be done to understand the history of these sediments.
I’m aware of no fossils from Bryan, Liberty, McIntosh and Camden Counties which also share the coast with Chatham and Glynn Counties. Darien is actually in McIntosh County, and some of the canal fossils could be from McIntosh, but the record says Glynn.
A search of the Paleobiology Database, which admittedly has omissions and errors, shows no further coastal locations as appearing in the published record.
To Continue with Cooke
Distribution.-Though reported at only a few places in Georgia, the bone bed is probably represented by many widely scattered patches, some of which may be concealed by Recent deposits. Besides Skidaway Island, the bed has been reported on the nearby mainland at Hainers Bridge (could not locate, also spelled as Hayners) and in Glynn County. It is probably equivalent to the Melbourne bone bed which has been thoroughly explored at several places in Florida.
A search of the Paleobiology Database, which admittedly has omissions and errors, shows no further coastal locations as appearing in the published record.
To Continue with Cooke
Distribution.-Though reported at only a few places in Georgia, the bone bed is probably represented by many widely scattered patches, some of which may be concealed by Recent deposits. Besides Skidaway Island, the bed has been reported on the nearby mainland at Hainers Bridge (could not locate, also spelled as Hayners) and in Glynn County. It is probably equivalent to the Melbourne bone bed which has been thoroughly explored at several places in Florida.
Cooke shares J. Hamilton Couper’s 1846 description of the sediments.
***This is a good guide for in the field observations.***
Thickness and lithologic character
Couper describes the "inland swamp formation" as follows:
This formation consists, usually, of a surface stratum of loam 1 or 2 feet deep, resting on a compact clay destitute of vegetable matter. The stratum of clay varies in depth but is generally from 5 to 10 feet deep and is of various colors but is more commonly blue or yellow. It frequently contains beds of marl, calcareous and siliceous gravel, petrified wood, bog iron ore, and in most instances exhibits traces of lime and iron. In some localities it assumes the appearance of green marl and contains grains of proto-phosphate of iron. It rests, in every instance, at a greater or less depth on a sandy, newer Pliocene formation. No fossil shells have hitherto been noticed in it; but, as has been observed, all the fossil bones of the terrestrial Mammalia discovered on the seacoast of Georgia have been found at the bottom of it and embedded in it, but resting on the newer Pliocene sand.
***This is a good guide for in the field observations.***
Thickness and lithologic character
Couper describes the "inland swamp formation" as follows:
This formation consists, usually, of a surface stratum of loam 1 or 2 feet deep, resting on a compact clay destitute of vegetable matter. The stratum of clay varies in depth but is generally from 5 to 10 feet deep and is of various colors but is more commonly blue or yellow. It frequently contains beds of marl, calcareous and siliceous gravel, petrified wood, bog iron ore, and in most instances exhibits traces of lime and iron. In some localities it assumes the appearance of green marl and contains grains of proto-phosphate of iron. It rests, in every instance, at a greater or less depth on a sandy, newer Pliocene formation. No fossil shells have hitherto been noticed in it; but, as has been observed, all the fossil bones of the terrestrial Mammalia discovered on the seacoast of Georgia have been found at the bottom of it and embedded in it, but resting on the newer Pliocene sand.
Fossil vertebrates Cooke reports from near Brunswick
Fossil vertebrates Cooke reports from near Brunswick
- Castoroides ohioensis.
- Giant beaver, 6’ to 7’ long, 200lbs to 275lbs
- No evidence of a paddle-shaped tail exist
- Elephas columbi
- Reassigned as Mammuthus columbi
- Largest known member of the elephant family
- Widespread in North Amercia
- Orginally described from a Georgia fossil (tooth) found near Brunswick.
- Sir Charles Lyell, the father of modern geology, was involved in the discovery and reporting of this species.
- Mammut americanum
- American Mastodon
- Widespread in Georgia & North America
- Bison sp. indet.
- Both modern and extinct giant bison occur in Georgia’s fossil record
- Cervus? sp.
- Elk and related
- Tapirus haysii
- an extinct species of tapir
- Equus complicates
- Horse
- Equus leidyi
- Horse
- Equus littoralis
- Horse
- Eremotherium laurillardi
- Largest giant sloth
- Mylodon harlani
- Giant sloth
- Chelonia (?) couperi
- Originally identified as a sea turtle, the fossil was later reassessed and ID’s as belonging to a giant sloth.
- Crocodylus sp. indet.
- Crocodile or alligator
- Lamna sp
- Shark tooth
- Galeocerdo sp
- Shark tooth
- Carcharodon sp
- Shark tooth
- Dasyatis sp
- Stingray
As seen above three species of horse were reported in 1943, but the evolution of horses in North America and Georgia is complex. A great deal of work has been done since 1943 and apparently all three of the species have been reassigned. I couldn’t find clear paths to modern nomenclature. The teeth probably need to be re-examined, there are experts on this very subject at the Florida Museum of Natural History.
Cooke continues….
Several of these species and the box tortoise Terrapene canalioulata are listed by Hay from near Savannah. The species thus far discovered in the bone bed represent only a small part of the contemporaneous fauna. They are merely accidental finds, not the result of systematic exploration. The probably contemporaneous Melbourne bone 'bed of Florida has yielded 66 species, including human remains.
Notice that Cooke labels these finds as accidental discoveries “…not the results of systematic exploration” At the time he published this, 1943, there was a war going on. Now, 80+ years later there has still been no systematic exploration, only further accidental finds.
Our current Georgia Governor Brian Kemp (2024) enjoys a budget surplus, turning this towards systematic exploration of our natural resources and natural history, and spending some of it with institutions which actively investigate Georgia’s natural history (Tellus, Columbus State University & Georgia College come to mind) would do much to increase our education standards and establish new business opportunities.
Several of these species and the box tortoise Terrapene canalioulata are listed by Hay from near Savannah. The species thus far discovered in the bone bed represent only a small part of the contemporaneous fauna. They are merely accidental finds, not the result of systematic exploration. The probably contemporaneous Melbourne bone 'bed of Florida has yielded 66 species, including human remains.
Notice that Cooke labels these finds as accidental discoveries “…not the results of systematic exploration” At the time he published this, 1943, there was a war going on. Now, 80+ years later there has still been no systematic exploration, only further accidental finds.
Our current Georgia Governor Brian Kemp (2024) enjoys a budget surplus, turning this towards systematic exploration of our natural resources and natural history, and spending some of it with institutions which actively investigate Georgia’s natural history (Tellus, Columbus State University & Georgia College come to mind) would do much to increase our education standards and establish new business opportunities.
Stratigraphic relations and origin
The bone bed is said to fill hollows in the underlying shell bed, which may represent the Talbot formation. It is being eroded today (1943), and Recent sediments are being deposited unconformably on it. The writer (Cooke) has not seen any fresh exposures of the bone bed in Georgia, but as it appears to be very much like the Melbourne bone bed, he offers the following hypothesis of its origin, based on his observations of the Melbourne bone bed.
During the latter part of the Pamlico epoch, while the sea still stood at the 25-foot level, a series of low barrier islands fringed the Atlantic coast and offered habitat to many living creatures. Between the islands and the mainland were tidal marshes, shallow lagoons, and deeper channels. From time to time, bones of land animals and teeth of sharks and other fishes were buried in the watercourses by sand blown from the islands or mud dropped by the turbid water of the Savannah, Ogeechee, and Altamaha Rivers.
Accumulation of the bed ceased at the end of the Pamlico epoch, when sea level fell to the low level of the late Wisconsin glacial stage, and the bed was trenched by rapid streams. Melting of the Wisconsin ice sheet at the beginning of Recent time raised the level of the ocean and flooded the newly carved valleys and the older lagoons to the height of present sea level. If this interpretation is correct, the bone bed is of late Pamlico age or in terms of glacial chronology, it marks the end of the mid-Wisconsin interglacial stage.
The bone bed is said to fill hollows in the underlying shell bed, which may represent the Talbot formation. It is being eroded today (1943), and Recent sediments are being deposited unconformably on it. The writer (Cooke) has not seen any fresh exposures of the bone bed in Georgia, but as it appears to be very much like the Melbourne bone bed, he offers the following hypothesis of its origin, based on his observations of the Melbourne bone bed.
During the latter part of the Pamlico epoch, while the sea still stood at the 25-foot level, a series of low barrier islands fringed the Atlantic coast and offered habitat to many living creatures. Between the islands and the mainland were tidal marshes, shallow lagoons, and deeper channels. From time to time, bones of land animals and teeth of sharks and other fishes were buried in the watercourses by sand blown from the islands or mud dropped by the turbid water of the Savannah, Ogeechee, and Altamaha Rivers.
Accumulation of the bed ceased at the end of the Pamlico epoch, when sea level fell to the low level of the late Wisconsin glacial stage, and the bed was trenched by rapid streams. Melting of the Wisconsin ice sheet at the beginning of Recent time raised the level of the ocean and flooded the newly carved valleys and the older lagoons to the height of present sea level. If this interpretation is correct, the bone bed is of late Pamlico age or in terms of glacial chronology, it marks the end of the mid-Wisconsin interglacial stage.
Economic Significance
So far as known the bone bed has no intrinsic value. The bones in it, however, have much scientific interest, and have some market value if properly described and identified. In many cases skeletons, or partial skeletons, have been recovered and have marketable value to collectors and museums.
There is also the economic benefit Georgia would enjoy by becoming a leader in environmental science education and tourism, Imagine a Coastal Georgia Natural History Museum featuring locally collected fossils.
So far as known the bone bed has no intrinsic value. The bones in it, however, have much scientific interest, and have some market value if properly described and identified. In many cases skeletons, or partial skeletons, have been recovered and have marketable value to collectors and museums.
There is also the economic benefit Georgia would enjoy by becoming a leader in environmental science education and tourism, Imagine a Coastal Georgia Natural History Museum featuring locally collected fossils.
Local Occurrence
Chatham County (Charles Lyell 1855)
A bluff where the tidal currents of Burnside and Back Rivers scour against the shore of Skidaway Island, 4 miles south of the village of Isle of Hope, is the type locality of the. Bone bed. Here, according to (Charles) Lyell. Sir Charles Lyell is the Father of Modern Geology, friend and a mentor to Charles Darwin. He visited the Brunswick/Darien area.
“…no less than three skeletons of the huge Megatherium have been dug up, besides the remains of the Mylodon, Elaphas primigenius, Mastodon giganteus, and a species of the ox tribe. The bones occur in a dark, peaty soil of marsh mud, above which is a stratum three or four feet thick of sand charged with oxide of iron, and below them and beneath the sea level occurs sand containing a great number of marine fossil shells, all belonging to species which still inhabit the neighboring coast.”
Similar conditions exist at Hayners Bridge, 2.5 miles west of Isle of Hope, where Mammut americanum (American mastodon) and Mylodon harlani (Giant sloth) were found below high tide level in White Bluff River overlying a shell bed.
Chatham County (Charles Lyell 1855)
A bluff where the tidal currents of Burnside and Back Rivers scour against the shore of Skidaway Island, 4 miles south of the village of Isle of Hope, is the type locality of the. Bone bed. Here, according to (Charles) Lyell. Sir Charles Lyell is the Father of Modern Geology, friend and a mentor to Charles Darwin. He visited the Brunswick/Darien area.
“…no less than three skeletons of the huge Megatherium have been dug up, besides the remains of the Mylodon, Elaphas primigenius, Mastodon giganteus, and a species of the ox tribe. The bones occur in a dark, peaty soil of marsh mud, above which is a stratum three or four feet thick of sand charged with oxide of iron, and below them and beneath the sea level occurs sand containing a great number of marine fossil shells, all belonging to species which still inhabit the neighboring coast.”
Similar conditions exist at Hayners Bridge, 2.5 miles west of Isle of Hope, where Mammut americanum (American mastodon) and Mylodon harlani (Giant sloth) were found below high tide level in White Bluff River overlying a shell bed.
Glynn County &
The Brunswick Canal
These beds were recognized during the construction of the Brunswick-Darien canal, here is Wikipedia’s description (edited);
The Brunswick Canal was 12 miles long and built to connect Darien’s Altamaha River to the Turtle River of Brunswick, to transport goods farther north and inland. It included locks on both ends. It was originally proposed in 1798. Construction was started in 1836 by Thomas Butler King. The canal was completed and opened in 1854. However, railroads made the canal immediately obsolete. The canal was closed by 1860. Importantly, the Columbian mammoth was discovered, described, and named during the construction of the canal. Brunswick, Darien, and the canal’s place in history is secured through paleontology and a link to Sir Charles Lyell.
The Brunswick Canal
These beds were recognized during the construction of the Brunswick-Darien canal, here is Wikipedia’s description (edited);
The Brunswick Canal was 12 miles long and built to connect Darien’s Altamaha River to the Turtle River of Brunswick, to transport goods farther north and inland. It included locks on both ends. It was originally proposed in 1798. Construction was started in 1836 by Thomas Butler King. The canal was completed and opened in 1854. However, railroads made the canal immediately obsolete. The canal was closed by 1860. Importantly, the Columbian mammoth was discovered, described, and named during the construction of the canal. Brunswick, Darien, and the canal’s place in history is secured through paleontology and a link to Sir Charles Lyell.
Most of the bones found near Brunswick were discovered during canal construction. The occurrence is described by Couper (1846) as follows:
The Brunswick Canal, from which the fossil terrestrial and marine bones and fossil marine shells were taken during the years 1838 and 1839, is intended, when finished, to connect the Altamaha and Turtle Rivers. It lies about 9 miles from the ocean and 2 from the eastern edge of the mainland, to which its general course is parallel, and is excavated, in part, through the sandy newer Pliocene which forms this part of the continent and, in part, through a narrow inland swamp, called the Six-Mile Swamp.
This swamp is connected by creeks with the Altamaha and Turtle Rivers at its opposite ends, and at either extremity the sandy land closes in between the swamp and the rivers and leaves only small shallow channels for the discharge of its waters. It presents, therefore, the appearance of a small shallow lake, which has been gradually filled up by alluvial deposits to within a few feet of the surrounding sandy plain.
This alluvium consists of a hard, compact clay, generally of a yellow color, much impregnated with iron, and contains thin strata of a soft chalky marl and numerous fragments of calcareous petrified wood. It is covered by a thin stratum of vegetable and sandy loam and rests, at an average depth of 5 or 6 feet, on a yellow sand varying in coarseness but always of well-rounded grains. The surface of the swamp is about 11 feet at its ends and 16 in the center above the line of high water at spring tides and forms an inclined plane sloping off to the two rivers.
The Brunswick Canal, from which the fossil terrestrial and marine bones and fossil marine shells were taken during the years 1838 and 1839, is intended, when finished, to connect the Altamaha and Turtle Rivers. It lies about 9 miles from the ocean and 2 from the eastern edge of the mainland, to which its general course is parallel, and is excavated, in part, through the sandy newer Pliocene which forms this part of the continent and, in part, through a narrow inland swamp, called the Six-Mile Swamp.
This swamp is connected by creeks with the Altamaha and Turtle Rivers at its opposite ends, and at either extremity the sandy land closes in between the swamp and the rivers and leaves only small shallow channels for the discharge of its waters. It presents, therefore, the appearance of a small shallow lake, which has been gradually filled up by alluvial deposits to within a few feet of the surrounding sandy plain.
This alluvium consists of a hard, compact clay, generally of a yellow color, much impregnated with iron, and contains thin strata of a soft chalky marl and numerous fragments of calcareous petrified wood. It is covered by a thin stratum of vegetable and sandy loam and rests, at an average depth of 5 or 6 feet, on a yellow sand varying in coarseness but always of well-rounded grains. The surface of the swamp is about 11 feet at its ends and 16 in the center above the line of high water at spring tides and forms an inclined plane sloping off to the two rivers.
The fossil bones of the terrestrial Mammalia were discovered during the excavation of the canal at the southern end of the swamp at six different points, extending for three miles from its junction with the salt marsh.
In every instance they were found at the bottom of the alluvial formation, between 4 and 6 feet below the surface, embedded in clay but resting on yellow sand. This yellow sand stratum is, at these points, about 5 feet above the line of high tides. Five feet below its surface, or at the height of high water, it changes from a yellow to a white color and assumes a quicksand character, which it retains for 1 or 2 feet. It is then succeeded by a coarser and sharper sand with occasional thin strata of a fetid black mud. Marine fossil shells of the same species as those now existing along the adjoining coast are found in small masses in a slightly inclined or horizontal position scattered at intervals throughout the whole length of the canal and at depths extending from the surface of the sand to 5 feet below the line of high water-which is the greatest depth to which the excavation has extended.
The same species, particularly the Mulinia lateralis (dwarf surf clam), are generally found grouped together; and as several of them, such as the Dosinia concentrica and Tellina alternata (tellin shell), are so perfect as still to retain their epidermis, it is obvious that they originally grew on or near to the spot in which they are now found.
In every instance they were found at the bottom of the alluvial formation, between 4 and 6 feet below the surface, embedded in clay but resting on yellow sand. This yellow sand stratum is, at these points, about 5 feet above the line of high tides. Five feet below its surface, or at the height of high water, it changes from a yellow to a white color and assumes a quicksand character, which it retains for 1 or 2 feet. It is then succeeded by a coarser and sharper sand with occasional thin strata of a fetid black mud. Marine fossil shells of the same species as those now existing along the adjoining coast are found in small masses in a slightly inclined or horizontal position scattered at intervals throughout the whole length of the canal and at depths extending from the surface of the sand to 5 feet below the line of high water-which is the greatest depth to which the excavation has extended.
The same species, particularly the Mulinia lateralis (dwarf surf clam), are generally found grouped together; and as several of them, such as the Dosinia concentrica and Tellina alternata (tellin shell), are so perfect as still to retain their epidermis, it is obvious that they originally grew on or near to the spot in which they are now found.
The bones of the different species of Mammalia occurred together in groups, and in some cases the greater part of the bones of the same skeleton were found in immediate juxtaposition. They were generally unbroken when first uncovered but, being soft and tender, fell to pieces if roughly handled.
Many of the specimens were quite perfect and beautifully fossilized, and in no instance, except when they had been washed out into a salt-water creek, was there any abrasion of the surface or incrustation of marine shells. (The reported condition of the fossils would suggest wonderful research opportunities.)
These circumstances render it highly probable that the carcasses of the various animals were floated or fell into the then lake or stream and, sinking to the sandy bottom, were gradually covered to their present depth by the alluvial deposit from the water. All the bones of the terrestrial Mammalia were found at nearly the same depth below the surface resting on the same stratum of sand and embedded in the same alluvial formation.
Many of the specimens were quite perfect and beautifully fossilized, and in no instance, except when they had been washed out into a salt-water creek, was there any abrasion of the surface or incrustation of marine shells. (The reported condition of the fossils would suggest wonderful research opportunities.)
These circumstances render it highly probable that the carcasses of the various animals were floated or fell into the then lake or stream and, sinking to the sandy bottom, were gradually covered to their present depth by the alluvial deposit from the water. All the bones of the terrestrial Mammalia were found at nearly the same depth below the surface resting on the same stratum of sand and embedded in the same alluvial formation.
Recent Deposition Series
Cooke, 1943
As has already been stated, the final epoch of the Pleistocene series was a glacial stage (late Wisconsin), during which the level of the sea was considerably lower than now, and the shore lay some distance seaward from its present location. The space between the present high-tide line and the late Wisconsin seashore was then dry land crossed by extensions of all the present streams and further drained by a system of rapidly growing gullies and rivulets.
Just when the Pleistocene epoch ended, and the Recent epoch began is perhaps debatable (1943). A logical time would seem to be when the Wisconsin ice caps began to melt, the sea rose, and a transgressing series of marine sediments began to be deposited on the old land surface.
Cooke, 1943
As has already been stated, the final epoch of the Pleistocene series was a glacial stage (late Wisconsin), during which the level of the sea was considerably lower than now, and the shore lay some distance seaward from its present location. The space between the present high-tide line and the late Wisconsin seashore was then dry land crossed by extensions of all the present streams and further drained by a system of rapidly growing gullies and rivulets.
Just when the Pleistocene epoch ended, and the Recent epoch began is perhaps debatable (1943). A logical time would seem to be when the Wisconsin ice caps began to melt, the sea rose, and a transgressing series of marine sediments began to be deposited on the old land surface.
Flooded by continual additions of glacial meltwater from (monsoonal rains, the rivers flooded,) the sea crept higher and higher, ponded the lower courses of all the streams, and converted their valleys into estuaries.
Finally, a period of approximate equilibrium between melting and freezing was reached, and the sea level became nearly stationary, a condition that appears to have persisted for some thousands of years.
During this comparatively short period of stability the streams have been filling up their estuaries with sand and mud, converting them into tidal marshes. The growth of aquatic plants has hastened this process by retarding the currents and by the accumulation of vegetable matter. Some of the shoals. thus formed, have been raised above high tide by the addition of sediments deposited on them during floods.
The waves and winds have added to the accumulation of Recent deposits by distributing sand along the beaches, by raising it above water level, and by blowing it inland across preexisting lowlands. It thus happens that the Pleistocene core of the sea islands is covered by a veneer of wind-blown sand.
This author, Thomas Thurman, strongly encourages Georgia’s geology and paleontology researchers and institutions to renew their efforts in understanding Coastal Georgia’s Pleistocene sediments and the diversity of animals which once wandered the area.
There’s science to do!
Finally, a period of approximate equilibrium between melting and freezing was reached, and the sea level became nearly stationary, a condition that appears to have persisted for some thousands of years.
During this comparatively short period of stability the streams have been filling up their estuaries with sand and mud, converting them into tidal marshes. The growth of aquatic plants has hastened this process by retarding the currents and by the accumulation of vegetable matter. Some of the shoals. thus formed, have been raised above high tide by the addition of sediments deposited on them during floods.
The waves and winds have added to the accumulation of Recent deposits by distributing sand along the beaches, by raising it above water level, and by blowing it inland across preexisting lowlands. It thus happens that the Pleistocene core of the sea islands is covered by a veneer of wind-blown sand.
This author, Thomas Thurman, strongly encourages Georgia’s geology and paleontology researchers and institutions to renew their efforts in understanding Coastal Georgia’s Pleistocene sediments and the diversity of animals which once wandered the area.
There’s science to do!
References
- Cooke, C. Wythe; Geology of the Coastal Plain of Georgia, United States Geological Survey (USGS), Bulletin 941, 1943
- J.P. Manker & B.D. Carter; Paleoecology and Paleogeography of an Extensive Rhodolith facies from the Lower Oligocene of South Georgia and North Florida. Society for Economic Paleontologists and Mineralogists (Now the Society for Sedimentary Geology) Published in Palaios, 1987, Vol.2, pg. 181-188.
- Cooke, C. Wythe; Cenozoic Echinoids of the Eastern United States, Geologic Survey Professional Paper 321, U.S. Dept of Interior, USGS, 1959
- Alfred J. Mead, Robert A. Bahn, Robert M. Chandler and Dennis Parmley Preliminary Comments on the Pleistocene Vertebrate Fauna from Clark Quarry, Brunswick, Georgia. Paleoenvironments: Vertebrates, Vol.23. 2006
- Voorhies; M.R.; The Watkins Quarry, A New Late Pleistocene Mammal Locality in Glynn County, Georgia; Bulletin of the Georgia Academy, 29, Pg128, 1971