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25G: Fossils of Oaky Woods
By Thomas Thurman
By Thomas Thurman
Thomas Thurman's
Ongoing Citizen Scientist Project
Fossils of Oaky Woods
Attention:
For Observation and Photography Only
No Collecting in Oaky Woods
Excavations
and/or removing of artifacts
is illegal.
Collection by photography only please!
Be aware; Oaky Woods is actively hunted. Be thoughtful of other users
and dress accordingly.
Orange vests are strongly recommended.
Location 1:
Oligocene Undifferentiated Residuum
Oligocene Epoch; 33.9 to 23.03 million years old
Approximate elevation 435 to 475 ft, variable. (Google Earth)
Throughout most of the Oaky Woods highlands sea shells, of various descriptions, occur abundantly in chert boulders & dornicks (dornicks are hand samples). These boulders and dornicks are abundant and diverse in coloration and content.
Frequently the boulders and dornicks are seen clustered or piled on top of each other. These have been relocated either during road building or by farmers over the last two centuries, clearing their land.
These fossils occur 150 miles inland from the nearest modern coastline. It is not uncommon to see a single boulder containing many thousands of shell fossils. Small, fingernail sized cavities created by the shells are often geodes, containing small calcite or quartz crystals.
This is the sedimentary rock chert, often as jasper and agate; typically in hues of red but other colors are present. It was the preferred tool making material of Native Americans which once lived and hunted in this area. It is also popular material for modern lapidary work. This is fully silicified limestone, no reaction to weak acid.
Both early and late Oligocene material is present, representing two distinct high stands of sea levels. These animals lived on long-lost limestone reefs; once sea levels retreated silica rich groundwater converted some of the limestone to chert which is very hard and resistant to weathering. The remaining limestone was slowly dissolved by groundwater until all that was left was the chert dropped in place as these boulders and dornicks.
To the author’s knowledge these fossils have never been studied in detail to determine contemporary marine conditions. The general distribution and occurrence of this material was researched and reported in 1993 by Paul F. Huddlestun; who also confirmed its age by its fossil content.
For more information on fossils of this type see; Public Fossil Locations, South Houston County, of this website.
Oligocene Undifferentiated Residuum
Oligocene Epoch; 33.9 to 23.03 million years old
Approximate elevation 435 to 475 ft, variable. (Google Earth)
Throughout most of the Oaky Woods highlands sea shells, of various descriptions, occur abundantly in chert boulders & dornicks (dornicks are hand samples). These boulders and dornicks are abundant and diverse in coloration and content.
Frequently the boulders and dornicks are seen clustered or piled on top of each other. These have been relocated either during road building or by farmers over the last two centuries, clearing their land.
These fossils occur 150 miles inland from the nearest modern coastline. It is not uncommon to see a single boulder containing many thousands of shell fossils. Small, fingernail sized cavities created by the shells are often geodes, containing small calcite or quartz crystals.
This is the sedimentary rock chert, often as jasper and agate; typically in hues of red but other colors are present. It was the preferred tool making material of Native Americans which once lived and hunted in this area. It is also popular material for modern lapidary work. This is fully silicified limestone, no reaction to weak acid.
Both early and late Oligocene material is present, representing two distinct high stands of sea levels. These animals lived on long-lost limestone reefs; once sea levels retreated silica rich groundwater converted some of the limestone to chert which is very hard and resistant to weathering. The remaining limestone was slowly dissolved by groundwater until all that was left was the chert dropped in place as these boulders and dornicks.
To the author’s knowledge these fossils have never been studied in detail to determine contemporary marine conditions. The general distribution and occurrence of this material was researched and reported in 1993 by Paul F. Huddlestun; who also confirmed its age by its fossil content.
For more information on fossils of this type see; Public Fossil Locations, South Houston County, of this website.
Oligocene/Eocene Transition
Globally, there was a serious extinction event at about 33.9 million years ago separating the Oligocene Epoch and the Eocene Epoch.
This was a major glacial event and retreat in coastlines lasting 2 million years which ended the hot-house Eocene Epoch and introduced the cooler Oligocene Epoch.
In Georgia sea levels fell to, or near, the continental shelf, far below modern levels. So there is a gap, a discontinuity, in the Oaky Woods fossil record.
The Oligocene begins with a warming of the Earth and a return of high sea levels. Though the Oligocene would never be as warm as the Eocene, at least twice in the 10 million year span of the Oligocene Epoch sea levels rose far enough to submerge Oaky Woods.
It is the author's opinion, who is admittedly an amateur, that the Ocmulgee & Tobacco Road Sand Formations represent Georgia at the very close of the Eocene Epoch.
Globally, there was a serious extinction event at about 33.9 million years ago separating the Oligocene Epoch and the Eocene Epoch.
This was a major glacial event and retreat in coastlines lasting 2 million years which ended the hot-house Eocene Epoch and introduced the cooler Oligocene Epoch.
In Georgia sea levels fell to, or near, the continental shelf, far below modern levels. So there is a gap, a discontinuity, in the Oaky Woods fossil record.
The Oligocene begins with a warming of the Earth and a return of high sea levels. Though the Oligocene would never be as warm as the Eocene, at least twice in the 10 million year span of the Oligocene Epoch sea levels rose far enough to submerge Oaky Woods.
It is the author's opinion, who is admittedly an amateur, that the Ocmulgee & Tobacco Road Sand Formations represent Georgia at the very close of the Eocene Epoch.
Location 2: Tobacco Road Sand Ravine
Uppermost Eocene Epoch; 33.75 to 33.90 million years old
Oaky Woods Rarest Fossils
Approximate elevation 412ft (Google Earth)
The Tobacco Road Sand is a member of the Barnwell Group; sediments which are terrestrial in origin and dominated by sands but clays are also common.
The Tobacco Road Sand outcrops in only one currently confirmed Oaky Woods location; an erosion feature; a “Y” shaped ravine just beyond the southern border of the Wildlife Management Area and just off the road. (See Section 13E; Oaky Woods Report for details on the Tobacco Road Sand.)
Location 6 of this piece records what may be an additional hilltop exposure within the boundaries of Oaky Woods.
Overall the Tobacco Road Sand is sparsely fossiliferous; however, in the ravine three well-defined beds of fossils occur, one atop the other, with each containing distinct, extinct, species of the Periarchus of sand dollars (echinoids).
Gastropods also occur commonly as shells, not molds.
The brick red, fossil bearing rock in these beds is silicified, stratified sandstone, no reaction to weak acids.
The fossiliferous Tobacco Road Sand is chert. It was silicified after it formed. It is also deeply rust-stained (oxidized iron), as post deposition.
The deep red coloration of the Tobacco Road Sand is not continuous, if you break open the rock; the coloration of the interior is much lighter.
This tells us that both iron & silica inundated the rock after it formed. The source for the iron and silica was probably ground water. The fossil bearing layers in the Tobbaco Road Sand originally formed as limestone, inundation by iron & silica rich ground water turned the limestone to chert and stained it red.
This feature is actively eroding doe to road drainage.
In 1978 Paul F. Huddlestun reported a potential new transitional species of Periarchus sand dollars occupying the center bed, but subsequent investigations in 2015 could locate no specimen sufficiently complete to confirm a new species.
In the same report Mr. Paul also reported the Twiggs Clay as underlying the Tobacco Road Sand at this location in Oaky Woods. And though I deeply respect Mr. Paul I disagree on this point.
In Section 13E of this website Mr. Paul's return to Oaky Woods is reported along with confirmation that the Ocmulgee Formation is present in Oaky Woods.
In 1978 Mr. Paul reported that the Tobacco Road Sand & Ocmulgee Formation are of the same age and should interfinger. Since then it has been shown that both are present in Oaky Woods.
Location 5 of this report describes a possible interfingering location.
The author strongly suspects that the grey clay bed underlying the Tobacco Road Sand in this ravine is actually from The Ocmulgee Formation, not the Twiggs Clay.
Uppermost Eocene Epoch; 33.75 to 33.90 million years old
Oaky Woods Rarest Fossils
Approximate elevation 412ft (Google Earth)
The Tobacco Road Sand is a member of the Barnwell Group; sediments which are terrestrial in origin and dominated by sands but clays are also common.
The Tobacco Road Sand outcrops in only one currently confirmed Oaky Woods location; an erosion feature; a “Y” shaped ravine just beyond the southern border of the Wildlife Management Area and just off the road. (See Section 13E; Oaky Woods Report for details on the Tobacco Road Sand.)
Location 6 of this piece records what may be an additional hilltop exposure within the boundaries of Oaky Woods.
Overall the Tobacco Road Sand is sparsely fossiliferous; however, in the ravine three well-defined beds of fossils occur, one atop the other, with each containing distinct, extinct, species of the Periarchus of sand dollars (echinoids).
Gastropods also occur commonly as shells, not molds.
The brick red, fossil bearing rock in these beds is silicified, stratified sandstone, no reaction to weak acids.
The fossiliferous Tobacco Road Sand is chert. It was silicified after it formed. It is also deeply rust-stained (oxidized iron), as post deposition.
The deep red coloration of the Tobacco Road Sand is not continuous, if you break open the rock; the coloration of the interior is much lighter.
This tells us that both iron & silica inundated the rock after it formed. The source for the iron and silica was probably ground water. The fossil bearing layers in the Tobbaco Road Sand originally formed as limestone, inundation by iron & silica rich ground water turned the limestone to chert and stained it red.
This feature is actively eroding doe to road drainage.
In 1978 Paul F. Huddlestun reported a potential new transitional species of Periarchus sand dollars occupying the center bed, but subsequent investigations in 2015 could locate no specimen sufficiently complete to confirm a new species.
In the same report Mr. Paul also reported the Twiggs Clay as underlying the Tobacco Road Sand at this location in Oaky Woods. And though I deeply respect Mr. Paul I disagree on this point.
In Section 13E of this website Mr. Paul's return to Oaky Woods is reported along with confirmation that the Ocmulgee Formation is present in Oaky Woods.
In 1978 Mr. Paul reported that the Tobacco Road Sand & Ocmulgee Formation are of the same age and should interfinger. Since then it has been shown that both are present in Oaky Woods.
Location 5 of this report describes a possible interfingering location.
The author strongly suspects that the grey clay bed underlying the Tobacco Road Sand in this ravine is actually from The Ocmulgee Formation, not the Twiggs Clay.
Location 3: Ocmulgee Formation
Uppermost Eocene Epoch; 33.75 to 33.90 million years old
Low Cliffs on Oaky Woods' Flood Plain
Approximate elevation 310ft (Google Earth)
The Ocmulgee Formation is a highly variable Ocala Group limestone deposit formed in a near-shore environment. (See Section 13E; Oaky Woods Report for details on the Tobacco Road Sand.)
At this location the Ocmulgee Formation is exposed as a series of low limestone cliffs, no more than 20 feet high, which are highly fossiliferous and form “toes” at the base of well weathered, forested ridge rising 80 to 100 feet above the floodplain of Oaky Woods.
The limestone cliffs stand on the floodplain, the floor, of Oaky Woods at the NE base of the ridge. It is the same ridge where the Tobacco Road Sand occurs in a SW ravine, so the two formations inter-finger within the ridge.
The limestone reacts actively to weak acid.
Big Grocery Creek is shown as nearby in the map but it is likely at least 100 years north of the Ocmulgee Formation outcrop through some moderately dense woods. It is beyond sight from the ridge base.
At this site the Ocmulgee Formation reveals scallops, a great wealth of bryozoan debris and a several Periarchus pileussinensis. Gastropods are present as molds, with shells dissolved.
Between the low cliffs there are often shallow, rain-weathered seams in the hillside where loose fossils can be seen. Often whole, pristine, Periarchus pileussinensis sand dollars (echinoids) can be found. These will typically have superb preservation.
The genus Periarchus is a Late Eocene guide fossil.
Basilosaurids (See Section 11 of this website)
In May 2008 Warner Robins Cub Scout Pack Leader Amanda Rhonemus found an end-of-tail vertebra from a Basilosaurus in Oaky Woods Wildlife Management Area, Houston County, Georgia. (Known age & coloration of the fossil show that the source matrix was the Ocmulgee Formation)
John Trussell, a Middle Georgia hunter and author, was guiding the scouts on a tour when the specimen was accidentally discovered. The Macon Telegraph covered the story with pictures by John Trussell on Sunday, May 11Th, 2008.
To give an idea of the true size of Basilosaurus cetoides one of the members of the Mid-Georgia Gem and Mineral Society, Jim Nix, has a single Basilosaurus vertebra, the size of a mailbox, which he collected from an overburden mound at a kaolin pit just southeast of Gordon, Georgia in Wilkinson County.
All the basilosaurids were active predators hunting warm seas. They should not be considered gentle giants as many whales are today, these were advanced apex predators.
Uppermost Eocene Epoch; 33.75 to 33.90 million years old
Low Cliffs on Oaky Woods' Flood Plain
Approximate elevation 310ft (Google Earth)
The Ocmulgee Formation is a highly variable Ocala Group limestone deposit formed in a near-shore environment. (See Section 13E; Oaky Woods Report for details on the Tobacco Road Sand.)
At this location the Ocmulgee Formation is exposed as a series of low limestone cliffs, no more than 20 feet high, which are highly fossiliferous and form “toes” at the base of well weathered, forested ridge rising 80 to 100 feet above the floodplain of Oaky Woods.
The limestone cliffs stand on the floodplain, the floor, of Oaky Woods at the NE base of the ridge. It is the same ridge where the Tobacco Road Sand occurs in a SW ravine, so the two formations inter-finger within the ridge.
The limestone reacts actively to weak acid.
Big Grocery Creek is shown as nearby in the map but it is likely at least 100 years north of the Ocmulgee Formation outcrop through some moderately dense woods. It is beyond sight from the ridge base.
At this site the Ocmulgee Formation reveals scallops, a great wealth of bryozoan debris and a several Periarchus pileussinensis. Gastropods are present as molds, with shells dissolved.
Between the low cliffs there are often shallow, rain-weathered seams in the hillside where loose fossils can be seen. Often whole, pristine, Periarchus pileussinensis sand dollars (echinoids) can be found. These will typically have superb preservation.
The genus Periarchus is a Late Eocene guide fossil.
Basilosaurids (See Section 11 of this website)
In May 2008 Warner Robins Cub Scout Pack Leader Amanda Rhonemus found an end-of-tail vertebra from a Basilosaurus in Oaky Woods Wildlife Management Area, Houston County, Georgia. (Known age & coloration of the fossil show that the source matrix was the Ocmulgee Formation)
John Trussell, a Middle Georgia hunter and author, was guiding the scouts on a tour when the specimen was accidentally discovered. The Macon Telegraph covered the story with pictures by John Trussell on Sunday, May 11Th, 2008.
To give an idea of the true size of Basilosaurus cetoides one of the members of the Mid-Georgia Gem and Mineral Society, Jim Nix, has a single Basilosaurus vertebra, the size of a mailbox, which he collected from an overburden mound at a kaolin pit just southeast of Gordon, Georgia in Wilkinson County.
All the basilosaurids were active predators hunting warm seas. They should not be considered gentle giants as many whales are today, these were advanced apex predators.
Location 4: Ocmulgee Formation
Uppermost Eocene Epoch; 33.75 to 33.90 million years old
Hilltop Bryozoan Colonies, Uppermost Eocene.
Possibly Uppermost Ocmulgee Formation.
Approximate elevation 422ft (Google Earth)
Occurring in the loose soil about .25 miles SE along Bait Barrell Road, on the north side of Oaky Woods, bryozoan colonies, as golf-ball sized and smaller specimens occur in the soil. The location is the weathered, wooded crest of a low, gentle hill which had been recently logged when I last visited on 17/Feb/2016.
As mentioned previously,
Globally, there was a serious extinction event 33.9 million years ago separating the Oligocene Epoch and the Eocene Epoch. This was a major glacial event (glaciation) and retreat in coastlines lasting 2 million years which ended the hot-house Eocene Epoch and introduced the cooler Oligocene Epoch.
In Georgia sea levels fell to, or near, the continental shelf, far below modern levels. So there is a gap, a discontinuity, in the Oaky Woods fossil record.
The Oligocene begins with a warming of the Earth and a return of high sea levels. Though the Oligocene would never be as warm as the Eocene, at least twice in the 10 million year span of the Oligocene Epoch sea levels rose far enough to submerge Oaky Woods.
The author suspects that this hilltop Ocmulgee Formation occurrence represents the Uppermost Ocmulgee Formation, Uppermost Eocene Epoch. If that's true, that could mean these bryozoa lived when the End-Of-Eocene glaciation event and sea level retreat began.
The bryozoa colonies occur as loose specimens in the loose dove-grey, sandy clay. Specimens were even observed in the road bed.
Some specimens show extensive, even complete clogging and fill of structures and apertures from post-mortem (?) sedimentation. Some have apertures recrystallized with calcite. Others are nearly free of secondary sedimentation and the structures and apertures are free, or nearly free, of recrystallization and sediments.
Specimens tested with weak acid reacted actively.
All show a small degree of probably post-mortem transportation with rounded edges, but none show extensive wear. Due to the very fragile nature of the branch structure it seems unlikely that this material was transported very far or violently.
While most, if not all, show abrasive wear (rounding) on outer-most tips of branches, very little breakage of branches is evident suggesting transportation by gentle tides or currents.
No source matrix or mass of specimens was observed, all the recovered individuals were loose in the soil. A mass might exist but further field exploration would be required.
One excellent specimen, nearly golf-ball in size, was almost pristine. It had originally formed on a gastropod shell, but that shell has long ago dissolved away.
I had no luck identifying the species, so I have no information about environmental preferences, but the Ocmulgee Formation is held as a coastal marine.
These occur in the uppermost Ocmulgee Formation, they are limestone, reacting actively to acid. This seems to be the sandy, clay rich, uppermost Ocmulgee Formation which is noted (Huddlestun 1986) for being resistant to weathering.
Uppermost Eocene Epoch; 33.75 to 33.90 million years old
Hilltop Bryozoan Colonies, Uppermost Eocene.
Possibly Uppermost Ocmulgee Formation.
Approximate elevation 422ft (Google Earth)
Occurring in the loose soil about .25 miles SE along Bait Barrell Road, on the north side of Oaky Woods, bryozoan colonies, as golf-ball sized and smaller specimens occur in the soil. The location is the weathered, wooded crest of a low, gentle hill which had been recently logged when I last visited on 17/Feb/2016.
As mentioned previously,
Globally, there was a serious extinction event 33.9 million years ago separating the Oligocene Epoch and the Eocene Epoch. This was a major glacial event (glaciation) and retreat in coastlines lasting 2 million years which ended the hot-house Eocene Epoch and introduced the cooler Oligocene Epoch.
In Georgia sea levels fell to, or near, the continental shelf, far below modern levels. So there is a gap, a discontinuity, in the Oaky Woods fossil record.
The Oligocene begins with a warming of the Earth and a return of high sea levels. Though the Oligocene would never be as warm as the Eocene, at least twice in the 10 million year span of the Oligocene Epoch sea levels rose far enough to submerge Oaky Woods.
The author suspects that this hilltop Ocmulgee Formation occurrence represents the Uppermost Ocmulgee Formation, Uppermost Eocene Epoch. If that's true, that could mean these bryozoa lived when the End-Of-Eocene glaciation event and sea level retreat began.
The bryozoa colonies occur as loose specimens in the loose dove-grey, sandy clay. Specimens were even observed in the road bed.
Some specimens show extensive, even complete clogging and fill of structures and apertures from post-mortem (?) sedimentation. Some have apertures recrystallized with calcite. Others are nearly free of secondary sedimentation and the structures and apertures are free, or nearly free, of recrystallization and sediments.
Specimens tested with weak acid reacted actively.
All show a small degree of probably post-mortem transportation with rounded edges, but none show extensive wear. Due to the very fragile nature of the branch structure it seems unlikely that this material was transported very far or violently.
While most, if not all, show abrasive wear (rounding) on outer-most tips of branches, very little breakage of branches is evident suggesting transportation by gentle tides or currents.
No source matrix or mass of specimens was observed, all the recovered individuals were loose in the soil. A mass might exist but further field exploration would be required.
One excellent specimen, nearly golf-ball in size, was almost pristine. It had originally formed on a gastropod shell, but that shell has long ago dissolved away.
I had no luck identifying the species, so I have no information about environmental preferences, but the Ocmulgee Formation is held as a coastal marine.
These occur in the uppermost Ocmulgee Formation, they are limestone, reacting actively to acid. This seems to be the sandy, clay rich, uppermost Ocmulgee Formation which is noted (Huddlestun 1986) for being resistant to weathering.
Location 5:
Ocmulgee Formation;
Uppermost Eocene Epoch; 33.75 to 33.90 million years old.
An erosional stream & ravine between two gentle hills
First known report of exposure.
Approximate elevation;
From 410ft to 310ft over about .50 mile (Google Earth)
To date only about 200 yards of this stream has been explored by the author.
Well above the Oaky Woods floodplain there is a shallow, narrow, rainwater fed stream between two weathered hills along a weathered ridge.
It descends the hillsides like a long, gentle, natural staircase seeking the floodplain. There’s a series of low falls, the highest being maybe 10 feet with several others being a foot high or less. The stream bed is fascinating, and often dense with Eocene fossils.
After a rain the stream gurgles and burbles happily. But tread carefully… much of the stream runs over dense clay and the bed is magnificently slick.
The highest point on this ridge is a hill standing 515ft above sea level which is highish for Oaky Woods.
The stream has cut into the Ocmulgee Formation which is typically resistant to weathering and highly variable in character.
This same ridge also hosts the Tobacco Road Sand exposure described in Location 2 of this report and Section 13E of this website.
On a map, the ravine is about half a mile east-northeast of Ocmulgee Formation stream bed described here.
Why this is interesting;
In the narrow stream bed debris from Ocmulgee Formation limestone is intermingled with Tobacco Road Sand chert.
Over a distance of approximately .25 to .75 mile the stream descends from approximately 410ft to 310ft.
To date I haven’t explored the full length of this ravine.
Ocmulgee Formation;
Uppermost Eocene Epoch; 33.75 to 33.90 million years old.
An erosional stream & ravine between two gentle hills
First known report of exposure.
Approximate elevation;
From 410ft to 310ft over about .50 mile (Google Earth)
To date only about 200 yards of this stream has been explored by the author.
Well above the Oaky Woods floodplain there is a shallow, narrow, rainwater fed stream between two weathered hills along a weathered ridge.
It descends the hillsides like a long, gentle, natural staircase seeking the floodplain. There’s a series of low falls, the highest being maybe 10 feet with several others being a foot high or less. The stream bed is fascinating, and often dense with Eocene fossils.
After a rain the stream gurgles and burbles happily. But tread carefully… much of the stream runs over dense clay and the bed is magnificently slick.
The highest point on this ridge is a hill standing 515ft above sea level which is highish for Oaky Woods.
The stream has cut into the Ocmulgee Formation which is typically resistant to weathering and highly variable in character.
This same ridge also hosts the Tobacco Road Sand exposure described in Location 2 of this report and Section 13E of this website.
On a map, the ravine is about half a mile east-northeast of Ocmulgee Formation stream bed described here.
Why this is interesting;
- The Tobacco Road Sand is primarily a terrestrial sourced formation, sands and clays.
- Ocmulgee Formation is primarily marine sourced limestone and clay.
- The Tobacco Road Sand is deeply stained red from iron oxidation.
- The Ocmulgee Formation is only mildly and discontinuously stained with iron oxidation
- The Tobacco Road Sand is cherty, silicified limestone weak acid has no effect on it. (As explained in the Location 2 text of this report.)
- The Ocmulgee Formation Limestone reacts actively to weak acid, it has never been silicified.
In the narrow stream bed debris from Ocmulgee Formation limestone is intermingled with Tobacco Road Sand chert.
Over a distance of approximately .25 to .75 mile the stream descends from approximately 410ft to 310ft.
To date I haven’t explored the full length of this ravine.
Uppermost observed large fall (Location 5):
The largest fall yet explored is on the upgrade end of the stream, maybe 10 feet high and supported by a bed dense, seemingly pure tan colored clay. The fall has created a semi-circular hollow on the forest floor, 20 to 25 feet wide, whose walls are pure clay.
Both topping and flooring the fall are flat ledges of hardened limestone. The fall itself is actually a retreat between two ledges. The beds of clay forming the retreat wall are thicker at the base, maybe a foot thick for the lowest three beds, but much thinner at the top, many less than an inch thick. Casual observation suggests 30 to 50 beds overall.
Macrofossils (easily visible) weren’t observed in the clay beds, no sample was taken for microscope observation. Close inspection was not performed as the stream bed has dangerous footing. The hike to this site is in relatively rugged terrain, I was alone, no one knew exactly where I was and I had no cell service.
This was not a place to get injured.
It is worthwhile to note that in 1970 Sam Pickering reported that such clay beds in other Houston County locations contained calcite lenses which were often dense with echinoid (sand dollar & sea urchin) fossils.
The upper and lower hardened limestone ledges were inspected for macrofossils as well, they were very sparsely fossiliferous, rare & random clam or scallop molds were observed in the ledges.
Weak acid field tests were performed on top and bottom ledges and the clay itself, all three reacted actively. The ledges are just hard limestone, they aren’t silicified.
The largest fall yet explored is on the upgrade end of the stream, maybe 10 feet high and supported by a bed dense, seemingly pure tan colored clay. The fall has created a semi-circular hollow on the forest floor, 20 to 25 feet wide, whose walls are pure clay.
Both topping and flooring the fall are flat ledges of hardened limestone. The fall itself is actually a retreat between two ledges. The beds of clay forming the retreat wall are thicker at the base, maybe a foot thick for the lowest three beds, but much thinner at the top, many less than an inch thick. Casual observation suggests 30 to 50 beds overall.
Macrofossils (easily visible) weren’t observed in the clay beds, no sample was taken for microscope observation. Close inspection was not performed as the stream bed has dangerous footing. The hike to this site is in relatively rugged terrain, I was alone, no one knew exactly where I was and I had no cell service.
This was not a place to get injured.
It is worthwhile to note that in 1970 Sam Pickering reported that such clay beds in other Houston County locations contained calcite lenses which were often dense with echinoid (sand dollar & sea urchin) fossils.
The upper and lower hardened limestone ledges were inspected for macrofossils as well, they were very sparsely fossiliferous, rare & random clam or scallop molds were observed in the ledges.
Weak acid field tests were performed on top and bottom ledges and the clay itself, all three reacted actively. The ledges are just hard limestone, they aren’t silicified.
Fossil littered stream bed (Location 5):
Moving downstream from the fall is a gentle incline of perhaps 15 yards where the rainwater wanders over an area maybe 10 yards wide. This area was littered with cobbles, dornicks and small boulders, abundant leaf litter and natural forest debris. Small macro fossils were everywhere.
A complete, adult Periarchus quinquefarius (imaged) was observed on the stream bed floor. It was undamaged and preservation was superb. Coloration shows that it was iron-oxide stained and no reaction to an acid test confirms that it’s silicified, this sand dollar weathered out of the Tobacco Road Sand and was transported to this location.
In the debris nearby were fossil rich cobbles of Ocmulgee Formation limestone which did react actively to acid. This stream bed contains a mixture of Ocmulgee Formation and Tobacco Road Sand fossils.
Moving downstream from the fall is a gentle incline of perhaps 15 yards where the rainwater wanders over an area maybe 10 yards wide. This area was littered with cobbles, dornicks and small boulders, abundant leaf litter and natural forest debris. Small macro fossils were everywhere.
A complete, adult Periarchus quinquefarius (imaged) was observed on the stream bed floor. It was undamaged and preservation was superb. Coloration shows that it was iron-oxide stained and no reaction to an acid test confirms that it’s silicified, this sand dollar weathered out of the Tobacco Road Sand and was transported to this location.
In the debris nearby were fossil rich cobbles of Ocmulgee Formation limestone which did react actively to acid. This stream bed contains a mixture of Ocmulgee Formation and Tobacco Road Sand fossils.
Four foot fall (Location 5):
Another fall is encountered after the stream runs over a very rough, softer portion of the Ocmulgee Limestone just a couple of feet wide and maybe a dozen feet long.
At the time this soft, rough span was visited, the day after a heavy rain, the thread of water was only a few inches wide but fast moving. There was obvious wear and smoothing on the rough limestone from water.
The rough limestone is underlain by another dense clay bed, creating a fall and another hollow about four feet high but much wider, maybe 20 to 30 feet. But there are actually two falls at this location, the four foot fall seems to be excess run-off. There is a lower, steady, but apparently restricted flow to one side maybe a 6” high which seems to be water cutting down through the rock.
At the time of visit the lower flow was active at maybe a few gallons a minute but the higher fall was minimally active, just a trickle of water.
This hollow is problematical; none of the sediments exposed show the typical Tobacco Road Sand stratigraphy of alternating clay rich sand beds and fossil bearing chert. Rather, the walls of the hollow are fossiliferous limestone. However, as seen in the pictures, much of it is stained light brownish-red with iron oxide and much of it is the pale beige-grey which is more typical of the Ocmulgee Formation. The presence of both, overlapping, suggests transitional conditions.
The clay rich sand of the Tobacco Road as seen at Location 2 of this report would be highly vulnerable to active water flow, quickly weathering out the fossil bearing chert. Which explains isolated Tobacco Road Sand chert nodules found in the stream bed.
One beige-grey Ocmulgee Formation boulder, maybe a couple of feet long and ten inches wide and imaged here with my Estwing Burpee pick, was extremely dense with mollusk fossils, mostly as bivalves (clam shells) but gastropods (snails) were also present. The boulder was limestone, reacting to weak acid.
Such densely fossiliferous chert boulders are common in the younger Oligocene chert (impervious to weak acid) material of the forested hilltops of Oaky Woods, as described in Location 1 of this report. To find such a boulder in late Eocene limestone (reacting to acid) is very unusual, the limestone is much softer than the chert and heavily fossiliferous boulders are easily broken up during natural transportation by water or simple erosion.
As seen in the pics, this boulder rests directly below lightly iron oxide stained Ocmulgee Formation limestone walls of the hollow.
Abundant mollusk fossils occur in the walls and as debris on the hollow’s floor.
Another fall is encountered after the stream runs over a very rough, softer portion of the Ocmulgee Limestone just a couple of feet wide and maybe a dozen feet long.
At the time this soft, rough span was visited, the day after a heavy rain, the thread of water was only a few inches wide but fast moving. There was obvious wear and smoothing on the rough limestone from water.
The rough limestone is underlain by another dense clay bed, creating a fall and another hollow about four feet high but much wider, maybe 20 to 30 feet. But there are actually two falls at this location, the four foot fall seems to be excess run-off. There is a lower, steady, but apparently restricted flow to one side maybe a 6” high which seems to be water cutting down through the rock.
At the time of visit the lower flow was active at maybe a few gallons a minute but the higher fall was minimally active, just a trickle of water.
This hollow is problematical; none of the sediments exposed show the typical Tobacco Road Sand stratigraphy of alternating clay rich sand beds and fossil bearing chert. Rather, the walls of the hollow are fossiliferous limestone. However, as seen in the pictures, much of it is stained light brownish-red with iron oxide and much of it is the pale beige-grey which is more typical of the Ocmulgee Formation. The presence of both, overlapping, suggests transitional conditions.
The clay rich sand of the Tobacco Road as seen at Location 2 of this report would be highly vulnerable to active water flow, quickly weathering out the fossil bearing chert. Which explains isolated Tobacco Road Sand chert nodules found in the stream bed.
One beige-grey Ocmulgee Formation boulder, maybe a couple of feet long and ten inches wide and imaged here with my Estwing Burpee pick, was extremely dense with mollusk fossils, mostly as bivalves (clam shells) but gastropods (snails) were also present. The boulder was limestone, reacting to weak acid.
Such densely fossiliferous chert boulders are common in the younger Oligocene chert (impervious to weak acid) material of the forested hilltops of Oaky Woods, as described in Location 1 of this report. To find such a boulder in late Eocene limestone (reacting to acid) is very unusual, the limestone is much softer than the chert and heavily fossiliferous boulders are easily broken up during natural transportation by water or simple erosion.
As seen in the pics, this boulder rests directly below lightly iron oxide stained Ocmulgee Formation limestone walls of the hollow.
Abundant mollusk fossils occur in the walls and as debris on the hollow’s floor.
Limestone Steps & Smallest Observed Fall (Location 5):
Moving further downstream a series of low falls or steps are encountered (See images). Overall these are maybe twenty feet long with each step “falling” a couple of inches. The steps are individual hardened limestone ledges.
The lovely little flight of steps terminates downstream with a small hollow and perhaps two foot high fall. The hollow is maybe a couple of feet wide and four feet long. The fall is formed, once again, by bedded, dense clay. There is a tree growing diagonally across the fall.
Continuing downstream, the flow is across clay and the streambed is littered with eroded limestone and hard clay dornicks as well as assorted cobbles containing fossils.
The stream has yet to be explored further downstream; but as described in Location 3 of this report, the Ocmulgee Formation has been confirmed on the Oaky Woods floodplain at the foot of this same ridge. (See section 13E of this website for details.) It is expected that the Ocmulgee Formation continues to host the rainwater runoff of the stream until it reaches the base of the ridge.
Moving further downstream a series of low falls or steps are encountered (See images). Overall these are maybe twenty feet long with each step “falling” a couple of inches. The steps are individual hardened limestone ledges.
The lovely little flight of steps terminates downstream with a small hollow and perhaps two foot high fall. The hollow is maybe a couple of feet wide and four feet long. The fall is formed, once again, by bedded, dense clay. There is a tree growing diagonally across the fall.
Continuing downstream, the flow is across clay and the streambed is littered with eroded limestone and hard clay dornicks as well as assorted cobbles containing fossils.
The stream has yet to be explored further downstream; but as described in Location 3 of this report, the Ocmulgee Formation has been confirmed on the Oaky Woods floodplain at the foot of this same ridge. (See section 13E of this website for details.) It is expected that the Ocmulgee Formation continues to host the rainwater runoff of the stream until it reaches the base of the ridge.
Location 6; Suspected Tobacco Road Sand surface outcrop
Uppermost Eocene Epoch; 33.75 to 33.90 million years old
Approximate elevation 435ft (Google Earth)
Just as this access road crests a ridge, along the eastern road bank, a small outcrop of what appears to be Tobacco Road Sand occurs. A complete gastropod shell was observed loose on the surface, as well as matrix, at the edge of the tree line.
While not pristine, the shell was whole and detail was preserved. The specimen was silicified and did not react to acid.
Coloration and texture most resembles the Tobacco Road Sand as seen in Location 2.
Uppermost Eocene Epoch; 33.75 to 33.90 million years old
Approximate elevation 435ft (Google Earth)
Just as this access road crests a ridge, along the eastern road bank, a small outcrop of what appears to be Tobacco Road Sand occurs. A complete gastropod shell was observed loose on the surface, as well as matrix, at the edge of the tree line.
While not pristine, the shell was whole and detail was preserved. The specimen was silicified and did not react to acid.
Coloration and texture most resembles the Tobacco Road Sand as seen in Location 2.
Location 7: Big Grocery Creek bed find
Pleistocene (Ice age)
Approximate elevation 303ft (Google Earth)
While hiking Big Grocery Creek some years ago a metatarsal (toe bone) from a deer (genus; Odocoileus) was found in the stream bed just a few dozen or yards, or so, down- stream from where the access road dead ends at the creek.
No source matrix is known, but it is very likely that other Pleistocene fossils occur in the lowlands of Oaky Woods.
Pleistocene (Ice age)
Approximate elevation 303ft (Google Earth)
While hiking Big Grocery Creek some years ago a metatarsal (toe bone) from a deer (genus; Odocoileus) was found in the stream bed just a few dozen or yards, or so, down- stream from where the access road dead ends at the creek.
No source matrix is known, but it is very likely that other Pleistocene fossils occur in the lowlands of Oaky Woods.