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Epochs and SC...

Epochs and SC

11/5/2006 5:17:20 AM

legacyForum

725 posts

Epochs and SC

Hi-Been doing some shark tooth hunting and investigating on the internet the different epochs. Saw that Peachtree Rock outside of Columbia is in the Eocene Epoch which is the same as the Harleyville stuff. Very fascinating. Also found some great teeth out at Dorchester Creek - thank you for the tip. The fact that I dug up a tooth (from what I can tell)from the Olgiocene in the Chandler Bridge formation is just crazy! These teeth have not seen the light of day in 37 million years! If anyone would like to try to explain the geology/history/amazingness/what was the world like?/where was the ocean?/what was the climate like?/etc to me in the Geology of SC for Dummies, I would love to learn more. Please teach me. This journey of fossil hunting has been just a blast of education and fun!
Thanks - Laura

11/14/2006 3:15:32 AM

legacyForum

725 posts

RE: Epochs and SC

Hi Laura,
It looks like you are really enjoying fossil collecting, and unless I miss my bet, you have really been bitten by the collecting bug.
I have been collecting in the lowcountry for many years now and I think I can give you a rough idea of the major formations and epochs found around here. I don't have a total grasp of all of them and I still can't figure out where I am digging sometimes, but after talking with geologists and paleontologists who have worked in this area, they have given me some insights as to what is what.
The oldest formations around here (Summerville, Harleyville)are in the limestone quarries, of course. I believe the oldest formation found is the Santee Limestone, and it is probably early Eocene. For those of you who might have collected in the old Cross Quarry, this limestone is the extremely hard stuff found at the bottom of the quarry. It generally was so hard that you could break a pick handle trying to bust it apart. I suspect that the Santee Limestone is also at the very bottom of the Giant Cement quarry, too. The next youngest formation is the Pregnall member of the Tupalo Bay formation. A paper was written recently by Weems, Geisler and Lou about the Tupalo Bay formation, based largely on Basilosaurus (commonly referred to as archeocetes)fossils found in the formation. They determined that the majority of the limestone overlying the harder Santee Limestone was this Pregnall member of the Tupalo Bay formation. This is the limestone that everyone collects in at Giant and LaFarge. If I remember right, it is assumed to be late middle/or early late Eocene in age. The crumbly, yellowish limestone that overlies the Tupalo Bay and is just below the overburden at Giant Cement quarry is probably late Eocene, and therefore slightly younger than the Tupalo Bay. The "green cap" that is sometimes found above the Tupalo Bay at Giant and LaFarge is the Harleyville formation and it is late Eocene in age. There is a difference in the fauna from the Tupalo Bay Eocene and the Harleyville Eocene, so there was a different deposition involved. Now, back to Cross quarry for a minute. There is a layer that sits on top of the Tupalo Bay at Cross quarry and looks like it would not have any fossils at all in it. I can't remember the name of this late Eocene layer, but it contained several incredible whale skulls of protocetid whales collected almost single-handedly by Billy Palmer, a volunteer with the Charleston Museum. Above this protocetid whale layer is the Goose Creek formation, which is Pliocene in age. There were several locations at the Cross quarry that were loaded to the hilt with fossil shells, and this was the easiest way to recognize the Goose Creek formation.
At the quarries, these formations I listed are the easiest to recognize. I have left out one, though. According to knowledgeable people at the LaFarge quarry, there is also an exposure of the Ashley formation, but I have not been able to recognize it there and can't give too much info on it. The Ashley formation is late Oligocene, though.
Before leaving the quarries, though, I should mention that there is a scattering of Pleistocene terrestrial fossils found in the overburden above the limestone. I have no idea what formation they originated in, though. The one exception is the Camelot fauna that is still under excavation by the state museum at the Giant Cement quarry. This late/middle Pleistocene layer is dated at 450,000 to 500,000 years old and corresponds to the Coleman 2A fauna from the Leisey Shell pit in Florida. The Camelot site has produced thousands of fossils from just about everything that lived during that time, including saber toothed cats and lots of camels (hence the name "Camelot").
The whole formation picture changes when you get into Summerville, North Charleston, etc. The earliest formation here is the Ashley formation, a deep water ocean deposit. This is the hard marl that you typically see on the bottom of the drainage ditches, and typically stops eroding fairly quickly after being exposed. The Ashley formation has been dated at about 28-30 million years old (late Oligocene). Typically overlying the Ashley is the Chandler Bridge Formation, and this is the formation that has largely made Summerville famous for it's fossils. It was deposited during a time when there was a shallow back bay ocean behind a barrier island along the coast. It is dated at 26-28 million years old (late Oligocene).The Chandler Bridge formation is comprised of three beds. The bottom-most, oldest bed is a dark olive green to brown color with very few phosphate nodules or rocks. It was an estuarine deposit. The other two beds are the most commonly seen and are blue-grey in color, often with blotches and streaks of iron oxide rust color in it, and with phosphate nodules mixed in. Overlying the Chandler Bridge, you normally start seeing the Pleistocene formations. However, in *extremely* rare locations you might see the Pliocene Goose Creek formation present. This Goose Creek looks very different from what was seen at the Cross quarry, and it is an off-white colored soft matrix, sort of like a soft marl. It looks like the matrix has been sprinkled full of coarse ground black pepper...very strange looking. When the surface weathers, it turns to a dingy yellow color. This formation is crammed full of fossil shells and re-worked miocene and oligocene fossils. They are usually poorly preserved and black in color. This is a very rare formation and I have only seen it four or five times in 40+ years of collecting. Assuming you do not see the Goose Creek formation, you will instead see one or more of the Pleistocene formations lying on top of the Chandler Bridge formation, depending on the elevation above sea level. The two most commonly found Pleistocene formations are the Wando formation and the Ten Mill Hill Formation. The Wando formation consists of three beds ranging in age from 130,000 to 70,000 years. The base of bed one (the lowest bed) typically has a large number of phosphate nodules mixed in with fossils that are black or brown in color. The matrix in this bed and the other two are *very* similar in color to the matrix of the Chandler Bridge formation and it can be very difficult to determine where one leaves off and the other begins. Other than the difference in the fossils found in each layer, the difference in the consistency of the matrix is usually the only way to tell them apart. I believe the Wando is a little more sandy and has small, crusty nodules of iron oxide mixed in. The Wando is extremely rich in fossils and yields fossils from micro-mammals like mice and shrews up the megafauna beasts. It also can yield snake and amphibian fossils. At a higher elevation, the Ten Mile Hill formation occurs, and it is about 200,000 years in age. Why is the older formation at a higher elevation than the younger? This can be confusing and is a logical question. The Wando formation (which has marine fossils of oligocene *and* Pleistocene age in it) was deposited when a Pleistocene ocean intruded inland but did not rise as high in elevation as the top of the Ten Mile Hill formation. So, it eroded the base of the Ten Mile Hill and deposited younger sediments and fossils there.
In a nutshell, those are the main fossil formations you will find in Summerville and outlying areas. But...this is *not* the complete story. There are other Pleistocene formations, some un-named, that are sometimes found. The Penholloway (1 mill. yrs.) and the Ladson formation (450,000 yrs.) are a couple. And I have seen a handful of others that I can't identify at all. So there are others thrown into the mix that really mess up the picture.
On a closing note, I often hear people talk about the "Hawthorn formation" in Summerville. I talked with Dr. Robert Weems of the USGS about this matter, and Dr.Weems (who is also a ph.d paleontologist) worked for many years in the Summerville and outlying areas drilling core samples in an attempt to locate the source of the huge earthquake that struck Charleston in the late 1800's. He knows more about the stratigraphy in this area than just about anyone. He told me that the Hawthorn formation was originally described from a locality in southern coastal Georgia and northern Florida. It is a Miocene formation, if I recall correctly. It has been changed from the status of a formation to a "group" which means that it encompasses one or more formations. There is also some question about the correct name for it, with the Tiger Leap formation often suggested as the proper name. At any rate, the Hawthorn probably existed at one time in this area, and it contained much of the phosphate that accounted for the phosphate mining industry in Charleston. This Miocene formation was eroded away by the oceans that intruded during the Pleistocene epoch and the phosphate rock and marine fossils (megs)ended up being re-worked into the Pleistocene formations. That is why you find megs mixed in with horse teeth. So, since the fossils from the Hawthorn were completely eroded away and re-deposited in the Pleistocene formations around here, it is improper to say that the Hawthorn can still be found in this area.
This is just a rough description of what can be found in our area, and I do not claim that everything I described is absolutely correct. There may be other explanations and descriptions elsewhere on the web or in publications that may differ from my interpretation, and I am only an amateur collector. So, read whatever you can and add to your understanding of the geology of our area whenever you can. I welcome any questions, corrections, other explanations or other input from anyone else who might like to jump in on this topic. Good luck collecting, Laura, and I hope the fossil Gods smile on you.
Vance McCollum

11/16/2006 12:22:45 AM

legacyForum

725 posts

RE: Epochs and SC

Hey Vance:

Very nice write-up on the Harleyville/Summerville geology. Thanks for taking the time to prepare and post the info.

scott

11/16/2006 12:34:17 AM

legacyForum

725 posts

RE: Epochs and SC

Mr. McCollum:

Thanks for the informative response to Laura's question! I've read it several times over and have printed myself
a hard copy to keep as reference material. I visit the
Ladson SC area to dig in the bank of Eagle Creek for fossils
and have found (as you stated in your post) both pleistocene
fossil teeth along with much older material from the oligocene, such as squaladon and angustiden teeth. It looks
to be the grainy orange or yellow sand of the Wando formation under a layer of grayish white clay and on top of
a dark brown clay. The teeth/fossils come from the thin
layer sandwithed in between these layers of clay. I was
wondering if I am digging between two formations - the
Wando and Ashley to get this great mix of fossil material?

11/16/2006 2:00:13 AM

legacyForum

725 posts

RE: Epochs and SC

As you can imagine, it is very difficult to determine the layer a person is digging in when it is described in writing. Everyone, including myself, seems to have their own ways of describing different layers, and it gets confusing to try to sort it out. From your description, I can't seem to figure out exactly what layer you are in when you are digging in the Eagle Creek at Ladson. First of all, I have dug in the Wando extensively in Eagle Creek, and particularly near the bridge over the Eagle Creek on Ladson road. The Wando in this area is almost always grey to dark grey in color at the base and middle part of the layer, and then tends to be more of a brown color (more like a top soil) as you get towards the top of the Wando. There are fossils throughout the layer, including reworked Miocene and Oligocene fossils, as you described. In this area, if you find the Wando, it is sitting right on top of the Chandler Bridge formation, and may even be sitting on top of the Ashley formation in some isolated spots where the Chandler Bridge was completely eroded away. The Wando formation is found in scattered locations along the entire length of the Eagle Creek from the bridge on Ladson Rd. by the Old Fort fire station to where Miles Road (Jamison Rd) crosses the Eagle Creek at Greenhurst subdivision. Man...the stories I could tell you about what was found behind Greenhurst! But, I digress... I can't figure out what sandy orange layer you are digging in, and if it sits on top of a brown soil layer, it probably isn't the Wando. As you walk down the length of Eagle creek between Ladson and Miles road, there are numerous undescribed layers that have Pleistocene fossils in them, so you may be digging in one of these non-descript formations I can't name. I wish I could help you more, but without seeing where you are digging, it is hard to picture.
Just for a little background on the Wando, I will tell you that I did a collection in the late 1980's along a stretch of Eagle Creek, within sight of the bridge on Ladson road. I kept the bakk scraped free of growth for almost two years and collected the surface of the Wando for micro-mammal, amphibian, bird and reptile fossils. I would crawl on my hands and knees with tweezers and pill bottles after every rain and I collected literally well over a thousand specimens. The Wando produced a great abundance of frog and snake fossils, including several partially articulated skeletons. Other abundant fossils included mice and rats, shrews, some lizard fossils, bird bones, tons of fresh water turtle shell, many mid sized animals fossils like raccoon, and opposum, and much more. This was the first systematic collection ever made of the micro fossils in the Wando, and I eventually donated the entire collection to the State Museum. If anyone was inclined to do the bank clearing work, another collection like this could probably still be made.
One last bit of fossil collecting trivia and I am done: Back in the late 1970's, the Charleston Museum made a major dig in the Chandler Bridge formation, using grant money from the Smithsonian. They did a 70 x 70 foot excavation about 150 or 200 yards from the bridge on Ladson Road. The first whale skull ever reported from Summerville was found near there, so the excavation was made right next to where it had been found. At any rate, when it came time to actually name the formation where the whale skull was found, the name Chandler Bridge was selected because that is the name of the bridge over Eagle Creek on Ladson Road.
Good luck collecting in the Eagle Creek. If you take the time to clear the vegetation, you can still find some goodies there.

11/17/2006 2:53:18 PM

legacyForum

725 posts

RE: Epochs and SC

Thanks so much for the great posts on local layers,formations/groups. Excellent. I have had a very hard time finding info on the local layers and your detailed explanations are terrific. Thanks very much. Paul

12/16/2006 12:34:30 AM

legacyForum

725 posts

RE: Epochs and SC

I am from Summerville and would love to take my neice to Chandler Bridge... I would love to teach her about the area. How can I find directions?

Thank you in advance!
Mary Katharine

12/18/2006 12:42:28 AM

legacyForum

725 posts

RE: Epochs and SC

Wow. This is one of the best descriptions of local layers I've seen. Thank you, Angus. I've a question. Excuse my ignorance, but in digging and walking around Summerville sites I continually run into a hard, white, rock-like layer. When broken up, this layer seems to consist of unusually shaped white rocks, looking sort of coral or pelvic bone-shaped. What is this annoying stuff? It's extremely hard to dig through. I never find any teeth IN this layer, but I always seem to find fossils when this layer is present. (If I recall correctly, I seem to find teeth in the layers ABOVE this stuff.) Anyway, what is it?

12/20/2006 3:11:24 PM

legacyForum

725 posts

RE: Epochs and SC

J.C.,
From what you said about "walking" on this layer and the "white" color, I think you are describing the ashley formation. This is the layer that underlies all the others in this area and is the oldest (until you get into the limestone quarries). When ditches or ponds are dug, the machines will often dig until they reach this layer because it makes a good hard bottom that does not erode further. Almost every large ditch will have the Ashley on the bottom of the dtich, including Eagle Creek. It typically has the remains of burrows from animals that dug down into the bottom of the ocean, and I think this is what you are describing as "coral, or pelvic like bones." Burrows are formed when animals dig into the ocean bottom. Crabs and shrimp are two examples of animals that will do this, but some fish species also burrow. Often times, these animals will secret fluids that will harden the walls of the burrows to stop them from collapsing. However, the burrows will then sometimes fill in with sediment that seeps in, forming a "mold' of the burrow. These filled-in burrows are what you will find fossilized within the Ashley formation matrix. If you look closely at them, sometimes you can actually see the telltale signs of sand that has oozed down into the burrows, sort of like a landslide of sand. I have even found tiny fossils of fish or shark's teeth that fossilized after they filled in the burrows.
There can be some extraodinary fossils found in the Ashley formation, but they tend to be very scattered and concentrated in small areas. I have walked on the Ashley for hundreds of yards and found nothing, and then all of a sudden, there will be several spectacular fossils found in a 50 foot stretch. It is really hit or miss. The fossils found in the Ashley tend to be more complete and less disarticulated since they were preserved in a marl that was more densely packed, with no rocks mixed in, and less prone to breaking apart during earthquakes. I once found a whale skull that was very large in the Ashley, and it was in one piece except for a section about the size of my palm. The density of the Ashley formation can vary quite a bit. Most of the time it is very hard to dig in, as you mentioned, but I have seen places where it was soft enough to dig in with a putty knife.
The layer above this one where you said you found lots of fossils is undoubtedly the Chandler Bridge formation, and the larger fossils in this layer tend to be more broken into pieces since the matrix is much less dense.
In reply to another forum question about where to find the Chandler Bridge formation in Summerville, the Chandler Bridge can be found just about anywhere in town where there has been a ditch or pond dug deep enough to find fossils. Although I can't think of any specific locations off the top of my head, just watch for any signs of digging and you will probably find the layer. Just remember that really high elevations, like around Sangaree development in S'ville will be too high for digging to reach the Chandler Bridge, but when you go to the southeastern and other areas, for example Oakbrook, you will be in a low enough area for any digging to reveal the layer.
I hope I have understood your question, J.C. and described the layer I think you were talking about. Good luck hunting for fossils!

12/21/2006 4:16:06 AM

legacyForum

725 posts

RE: Epochs and SC

Thanks, Angus. It's all starting to make sense now. I'm still learning to identify the layers around Charleston.

I today walked around a significant area of uncovered Ashley formation and found nothing but a few small teeth. I haven't found a decent meg in ages.

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