What do all these layers mean?

[olddude]

I had this question posted in another thread but didn't get much action so another member suggested I post it here so here goes.

 

I have been hunting this spot I found years ago for 6 or 8 months now and I have been finding some things that I never had any idea you could find in a spot so far away from the closest river. That river is the James River here in Virginia. There were a lot of Indians that lived in this area and pretty much any place you can find a lot of loose rocks laying around you can bet there may be arrow heads and other tools these people depended on for survival. A lot of the spots we were hunting have been bought up by the Government and we no longer have access to so I was thinking of new places to hunt. Sitting back one day drinking a cold Bud Lite and racking my brain for spots to try I remembered this place and decided to give it a try. Searching this small creek bed I found several arrow heads, some tools such as scrapers, knives, and even a stone ax head. I really thought I was on to something until I came upon a part of the creek where the creek bed was littered with hundreds of shells, pieces of coral and other things that just seemed out of place. Soon I became so fascinated by all this that arrow heads were way on the back burner of things to do and since then my life has not been the same. I knew I had to get to the bottom of this or die trying.

 

I have posted pictures of some of the things that I have dragged off those hills here on this site and as I posted in one of those threads The more I find out the more confused I get. This hill/cliff is around 120 feet or so tall from the bottom to the top and there are different shell layers pretty much all over. I  found one spot about 5 feet from where it flattens out on top where the soil is, loose fine sand and has thousands of broken pieces of all kinds of shell and other organic material. I have found this same type of layer also 50' lower down the side of the cliff. I don't have any pics of the upper layers but I posted some pics of where these small creeks, that flow out of the sides of the cliff have cut into layer after layer of different type material. I assume that the deeper layers are the oldest. But what about the shell bearing layer all the way on top? How do you date something like this without heading off to some lab with samples from each layer?

 

The formation is listed as The Chesapeake Group which may include the following formations-Chowan River, Yorktown,  Eastover, St.Marys, Choptank and Calvert. Time:Upper Pliocene to lower Miocene. What I want to know when looking at the different layers cut out by these creeks is there any way to tell what they are or how old?

 

This is the question as I presented it in my other thread :

 

"Could someone look at these pics and give me a general idea of what these different layers are. The top layer is grey softer clay like material. Then the shell bearing layer a little harder more compact looking but still rather soft. The third layer is a blue grey sand/clay material that is a bit harder but still not like stone. There is a layer under the last one that is compacted sand, small pebbles and some iron looking material that is quite hard. In some places this layer is quite thick several feet, but in other places it's only a four or five inches thick. I assume these layers are all different time periods but I'm not really sure about that.

There is another layer on top of these that is light, fine, brown looking sand and pea gravel material that is several feet thick and is the layer that is holding a lot of the shark teeth I have been finding. I have found small shark teeth and other teeth in most all these layers just sticking out the sides. It just seems strange that the larger teeth are in the higher up layers."

[Pterygotus]

A lot of layers are defined by the species found inside them .

[Fossildude19]

@MarcoSr  @Al Dente

[Tidgy's Dad]

Well, the bottom layer looks like a limestone, a gully has been eroded through it in a classic 'v' shape. 

Above that is a bivalve coquina - lots of storm crushed bivalves deposited en masse in a clayey matrix. This may, of course, represent several storms over a long period of time.

Above that a rough marl, judging by the uneven distribution of pieces and the lack of clear layering, probably deposited in a high energy environment. This is also supported by rough pieces of transported rock like the lump in your second picture, but as it's irregular, as in not very rounded and smooth, but not completely sharp and angular, i would suggest it has been transported, but not very far. 

Just under the seemingly quite thin soil layer at the top, is a subsoil of what appear to be quite well preserved bivalve shells, suggesting more gentle deposition of this marl, which hasn't been compacted or compressed enough yet to crush all the shells. 

That's what I see, anyway, i'm sure others will have their own take. 

 

[JohnJ]

@non-remanié

[Al Dente]

3 hours ago, olddude said:

The formation is listed as The Chesapeake Group which may include the following formations-Chowan River, Yorktown,  Eastover, St.Marys, Choptank and Calvert. Time:Upper Pliocene to lower Miocene. What I want to know when looking at the different layers cut out by these creeks is there any way to tell what they are or how old?

People who are very good at shell identification can usually tell the different formations apart. Chesapectens (a type of large scallop) are useful index fossils in these formations.

 

 

[Mark Kmiecik]

6 hours ago, olddude said:

"Could someone look at these pics and give me a general idea of what these different layers are. The top layer is grey softer clay like material. Then the shell bearing layer a little harder more compact looking but still rather soft. The third layer is a blue grey sand/clay material that is a bit harder but still not like stone. There is a layer under the last one that is compacted sand, small pebbles and some iron looking material that is quite hard. In some places this layer is quite thick several feet, but in other places it's only a four or five inches thick. I assume these layers are all different time periods but I'm not really sure about that.

There is another layer on top of these that is light, fine, brown looking sand and pea gravel material that is several feet thick and is the layer that is holding a lot of the shark teeth I have been finding. I have found small shark teeth and other teeth in most all these layers just sticking out the sides. It just seems strange that the larger teeth are in the higher up layers."

Yup, all of this work has already been done by one or more of the United States Geological Survey, the Virginia State Geological Survey, or the County or the Township or the nearest municipality. All you have to do is head over to the nearest library and look in the reference section. If you're not sure of what you're doing, get the librarian to help you. Most of this information has probably been available for more than 100 years. The types and species of fossils found in each layer are indicative of the age and presence of each layer. Look up the term "index fossil" if you're not familiar with it. Surveys are generally done over broad areas, so local stratigraphy may vary slightly, or even drastically in some areas, from that shown in the papers that describe it. If there's a local geologist - for instance, associated with a local museum - that person could be of more help than others. Good research leads to good results. Good luck and remember to have fun with it.

[MarcoSr]

8 hours ago, Fossildude19 said:

@MarcoSr  @Al Dente

 

Dr. Lauck Ward has written over the years a number of guidebooks that show the stratigraphy along rivers in Maryland and Virginia and which describe the different formation layers.  Dr. Ward mostly used invertebrate shells to separate and describe the different layers.  The USGS typically uses calcareous nannofossils and/or dinoflagellates to identify and date these different marine formation layers.  A guidebook that would have the Chesapeake Group with the formations described that you mentioned is:  Lauck Ward and Kathleen Krafft, May 1985,  "Stratigraphy and Paleontology of the Outcropping Tertiary Beds in the Pamunkey River Region, Central Virginia Coastal Plain".

 

I really can't tell much from your pictures or descriptions.  I would need to see the stratigraphy in person to be able to identify the different formations at your sites.  Most times I use the fossil species that I'm finding in the different layers to help confirm a layer id.  The only way to confirm the id for sure is a nannofossil and/or dinoflagellates analysis of the matrix itself.

 

Marco Sr.

[Ash]

What a beautiful place. Looks like a feast for the eyes.

[olddude]

19 hours ago, Al Dente said:

People who are very good at shell identification can usually tell the different formations apart. Chesapectens (a type of large scallop) are useful index fossils in these formations.

 

 

Thank you for that table. I have been looking for something like this for awhile because I suspected that some of the large Chesapecten shells I have found here look different from one another but never could find anything that would show a difference. This table will at least give me an idea of what to look for. Most of the shell and fossil remains that I have found have already been washed out of the layers and rolled and tumbled down the hill side by these streams and also by run off from storms. When we get large thunder storms in the summer it's not uncommon for the water level to rise in these creek beds by as much as 4 feet or more so they get quite a bit of a ride on their way down. 

 

I have found whale bone and vertebra, Sea Cow bone scattered in these creek beds along with coral pieces, shark teeth, many different types of shell that I don't even know what they are, sand dollars, Oh and I think, even some poop. I have found Hundreds of pieces of what I think are smaller teeth and parts of smaller fish in places, also some teeth (or what I think are teeth) that are not so small that could be from some kind of large fish or mammal. Anyway thanks for the table and I'll look see if I can find the differences in some of the shells I have collected.

[olddude]

23 hours ago, Tidgy's Dad said:

Well, the bottom layer looks like a limestone, a gully has been eroded through it in a classic 'v' shape. 

Above that is a bivalve coquina - lots of storm crushed bivalves deposited en masse in a clayey matrix. This may, of course, represent several storms over a long period of time.

Above that a rough marl, judging by the uneven distribution of pieces and the lack of clear layering, probably deposited in a high energy environment. This is also supported by rough pieces of transported rock like the lump in your second picture, but as it's irregular, as in not very rounded and smooth, but not completely sharp and angular, i would suggest it has been transported, but not very far. 

Just under the seemingly quite thin soil layer at the top, is a subsoil of what appear to be quite well preserved bivalve shells, suggesting more gentle deposition of this marl, which hasn't been compacted or compressed enough yet to crush all the shells. 

That's what I see, anyway, i'm sure others will have their own take. 

 

Thanks, the 4th pic and the last 3 are of the same spot just at different angles and distance. The water level at the bottom is roughly 7 feet lower than it is at the top where it starts eating into the marl. When you climb up that little fall to the top there is about a 30' section of this same type material exposed It is much flatter and seems to be a little harder material. There the water has only carved our less than maybe a foot or less but I guess that could be because it is so flat there.

 

The second and third pic are shots of a spot a little lower down stream from the ones talked about above. It's a place where the water has cut out from under a giant tree. You can almost stand up under there on your way up the creek. Those pieces of rock sticking out of the marl are harder material and some contain bone material while others are just clusters of shell massed together. I have a pic of one of these pieces that had completely washed out and was laying in the stream bed. When I got it to my shop and dried it out I was wondering what might be inside so I decided to peck away at it to see what I could find and after a couple beers I finally discovered it had a round hollow spot in the middle. There was some much harder material inside this hollow area but when I started to poke around I found that it was fractured and came out in pieces, at least for the first couple inches. I still don't know what that might be.

 

Oh, and that 5th shot is a spot just a bit lower downstream than the others where the creek first started it's steep rise upward. This is a shot of a section of the bank where the creek is real narrow and is probably 4 feet from the water lever. It shows that these layers seem to run on an upward path rather than being flat like the others.

[olddude]

On 4/7/2020 at 12:03 PM, olddude said:

Thanks, the 4th pic and the last 3 are of the same spot just at different angles and distance. The water level at the bottom is roughly 7 feet lower than it is at the top where it starts eating into the marl. When you climb up that little fall to the top there is about a 30' section of this same type material exposed It is much flatter and seems to be a little harder material. There the water has only carved our less than maybe a foot or less but I guess that could be because it is so flat there.

 

The second and third pic are shots of a spot a little lower down stream from the ones talked about above. It's a place where the water has cut out from under a giant tree. You can almost stand up under there on your way up the creek. Those pieces of rock sticking out of the marl are harder material and some contain bone material while others are just clusters of shell massed together. I have a pic of one of these pieces that had completely washed out and was laying in the stream bed. When I got it to my shop and dried it out I was wondering what might be inside so I decided to peck away at it to see what I could find and after a couple beers I finally discovered it had a round hollow spot in the middle. There was some much harder material inside this hollow area but when I started to poke around I found that it was fractured and came out in pieces, at least for the first couple inches. I still don't know what that might be.

 

Oh, and that 5th shot is a spot just a bit lower downstream than the others where the creek first started it's steep rise upward. This is a shot of a section of the bank where the creek is real narrow and is probably 4 feet from the water lever. It shows that these layers seem to run on an upward path rather than being flat like the others.

Here are a couple pics of that rock looking pieces that are sticking out of those banks. These were already washed out of the bank and I thought they looked cool so I dragged them home. Of-course to me everything looks like a major discovery LOL and worthy of being dragged off the hill. My buddy's laugh at me sometimes and often head the other direction when I start down off the hill because they know what ever bag I have will be loaded to the brim. and are afraid I might ask them for help.

 

I have no idea what this stuff is or is even worth hauling out of the woods but I would like to know what happened to cause something like this. I have another pic somewhere of the other half of the specimen in #2 pic. I thought it looked like head of some kind of whale or something when I saw it and when I wacked it with the hammer this chunk broke off.

[FranzBernhard]

Rhizolith?? (Just a shoot in the dark...)

https://en.wikipedia.org/wiki/Rhizolith

Franz Bernhard

[Shamalama]

What those layers look like is an awesome fossil site!  The harder chunks that are washing out look similar to some that I see on the beach along the Chesapeake at Matoaka Cottages. I think they are Limestone or clay. Not sure.

[olddude]

On 4/6/2020 at 9:37 PM, MarcoSr said:

 

Dr. Lauck Ward has written over the years a number of guidebooks that show the stratigraphy along rivers in Maryland and Virginia and which describe the different formation layers.  Dr. Ward mostly used invertebrate shells to separate and describe the different layers.  The USGS typically uses calcareous nannofossils and/or dinoflagellates to identify and date these different marine formation layers.  A guidebook that would have the Chesapeake Group with the formations described that you mentioned is:  Lauck Ward and Kathleen Krafft, May 1985,  "Stratigraphy and Paleontology of the Outcropping Tertiary Beds in the Pamunkey River Region, Central Virginia Coastal Plain".

 

I really can't tell much from your pictures or descriptions.  I would need to see the stratigraphy in person to be able to identify the different formations at your sites.  Most times I use the fossil species that I'm finding in the different layers to help confirm a layer id.  The only way to confirm the id for sure is a nannofossil and/or dinoflagellates analysis of the matrix itself.

 

Marco Sr.

Thanks......I looked up that guide book and from what I found it mostly talked about bird species but I never have been good at internet search. It did lead me to about a 6 hour journey into looking up what all those big words meant. The people that came up with all these names of different things must have really had a lot of time on their hands. LOL I did find some really good information from all of it now if I can just remember any of it tomorrow. I did copy and print a few things that will help when I find different things in the future.

 

I have been told this before but as I have tried to explain most all of the stuff I have found here is not in the layers any longer it has long been washed out and mixed up all together. I found some more teeth yesterday along with some more bone and coral. 

[olddude]

On 4/10/2020 at 10:23 AM, Shamalama said:

What those layers look like is an awesome fossil site!  The harder chunks that are washing out look similar to some that I see on the beach along the Chesapeake at Matoaka Cottages. I think they are Limestone or clay. Not sure.

There are a lot of these laying all about one of these creeks not so much in the others. Some of them contain mostly shell and other rock pieces while others have quite frankly I don't know what. Those two pic I posted are where I tried to dissect a couple pieces. Really great findings huh?? LOL Hopefully when all this coro 19 snarge is over with I can box up some of this stuff and haul it over to the science museum and see if someone will be able to put me on the right trail. 

[MarcoSr]

3 hours ago, olddude said:

Thanks......I looked up that guide book and from what I found it mostly talked about bird species but I never have been good at internet search. It did lead me to about a 6 hour journey into looking up what all those big words meant. The people that came up with all these names of different things must have really had a lot of time on their hands. LOL I did find some really good information from all of it now if I can just remember any of it tomorrow. I did copy and print a few things that will help when I find different things in the future.

 

I have been told this before but as I have tried to explain most all of the stuff I have found here is not in the layers any longer it has long been washed out and mixed up all together. I found some more teeth yesterday along with some more bone and coral. 

 

The entire guidebook is 280 pages.  There are lots of different articles in it.  The one on birds is only one article of many.  The front of the guidebook explains all the different formations.   There are lots of plates showing the different shells found at the different localities along the river. Lots of stratigraphic figures of the different localities. Full maps of where the localities are along the river.  However, I've never found a PDF of the entire guidebook on-line, only a few PDFs of some of the individual articles in the guidebook.  I have a hard copy that I bought at an Aurora Fossil Festival years ago.

 

Marco Sr. 

[olddude]

20 hours ago, MarcoSr said:

 

The entire guidebook is 280 pages.  There are lots of different articles in it.  The one on birds is only one article of many.  The front of the guidebook explains all the different formations.   There are lots of plates showing the different shells found at the different localities along the river. Lots of stratigraphic figures of the different localities. Full maps of where the localities are along the river.  However, I've never found a PDF of the entire guidebook on-line, only a few PDFs of some of the individual articles in the guidebook.  I have a hard copy that I bought at an Aurora Fossil Festival years ago.

 

Marco Sr. 

Ok Thanks I'll look some more. 

[Daleksec]

The top is Yorktown: Rushmere Member the bottom is  Eastover: Cobham Bay member.

 

[Daleksec]

Could you post some pictures of the sea cow bones and other vertebrates you have found?

[Daleksec]

The bigger vertebrate fossil are coming out of the Eastover /Yorktown contact. Acording to Dr. lauck Ward is the best layer to find teeth and bones.

[olddude]

7 hours ago, Daleksec said:

The top is Yorktown: Rushmere Member the bottom is  Eastover: Cobham Bay member.

 

Which one of the pictures are you referring to?

[olddude]

9 hours ago, Daleksec said:

Could you post some pictures of the sea cow bones and other vertebrates you have found?

I'll see what I have and post some up. This should keep you busy for awhile.LOL

[Daleksec]

2 hours ago, olddude said:

Which one of the pictures are you referring to?

The top layer that is compacted with lots of shells is the Yorktown. the bottom grey layer with all the white shells is the Eastover Formation.

[olddude]

19 hours ago, Daleksec said:

The top layer that is compacted with lots of shells is the Yorktown. the bottom grey layer with all the white shells is the Eastover Formation.

 

I'm sorry, I'm having trouble with which picture is what. Too many pictures can be good or bad depending on how you look at them. I am still confused about this layering thing and it sure would be helpful if I could get a little better understanding of how all this worked. I do understand that over millions of years the earths sea levels have risen o,r were at levels to where much of the US was under water. Then there were times that the water levels dropped to where the sea shore was 60 miles out from where Va Beach is today. As the levels would rise they would deposit the remains of what ever was floating around, or living in the water at that time period. Water levels would rise again later and cover up what had been deposited at a earlier time and so on. Some periods were shorter in length and some were much longer which led to some layers being thicker than others. Now understanding, there was a lot more going on through all of this time than this old guy can put to words that is how my simple mind works I guess. 

 

This place is a little different than most all of the surveys and reports that others have written over the years in that most examples given come from along river banks where there are sometimes miles of different exposed layers showing along the way. This place is pretty much the same I guess except we are in a time where the sea level has dropped to where the water level that once was here is 5 miles away now and covered with thick vegetation. The only indication of the past is marked by these few creek beds that flow out of the sides of the hill cutting deep paths as the ground water flows downhill. Sometime there is only a few feet in the banks you can see these actual layers because the rest is covered up by vegetation. Not as easy as riding down the river in a boat.

 

Picture #1 is a spot where there is very little of the layer showing that is not covered with heavy mat. Is this the one you referred to as the Yorktown layer? Then the third picture is the Eastover formation?

 

I assume there are three layers showing in picture #2. It seems like it to me. This spot is downhill a ways from the other pics and appears to be sloping upward as compared to the other pics which seem flat. I just assume that here or about, the sea bed was deeper and on an upward slope to where it flattened off in the other pics where it seems flatter.

 

Sorry for being such a pain.

 

#1

 

#2

 

#3