Dating organic material within clay

[WVCaver2011]

Hey Cavechat,

I'm currently working on setting up a research project which may either be turned into a Bachelors or Masters Thesis in the near future. Since i'm a geology major and I dont want to get into the petroleum industry (due to the high probability of being layed off before retirement) so Im trying to do something that is hydrogeology related. I have some questions for you before I can get really started on this thing.

1) Is there enough organic material in thin black clay layers (< or = 5mm) to allow for a precise radiometric date to be placed on these organic materials?

2) If #1's answer is yes then where can I find a cheap or free way/place to get these dates taken? Grants of great amounts would be nice but if i'm taking tens of samples then i'm going to need more money than what a grant will most likely offer...

3) Before I even think about getting started with this topic has anyone done significant research on a topic such as this?

You are probably asking yourself... What does this have to do with hydrogeology? Well if you think about it, clays are indicative of a water being at these levels of caves in the past. If I can get a date on the organic materials I can then figure out roughly how long ago the water was at certain levels within caves.

[wyandottecaver]

a note of caution.

sediments in caves are invariably sediments transported there. Seems obvious. But when you think about organic material, or even the entire sediment layer, being deposited topside..perhaps in a shallow marsh, stream bank, etc etc. then 20,000 yrs later sediments get washed away by erosion and re-deposited in a cave. Then, 100 yrs later some guy comes along and says hey look...this was put here 20,000 yrs ago.

I was once in a cave that had tall sediment banks about 6' tall on each side of a small stream. The sediments were very nicely layered with alternating bands of differing fine silts and clays material. As we were walking along we too were speculating on age of the sediments and wondering about finding bears teeth or pleistocene mammal bones. Then we saw a very modern broken in half 8" clay pot like youd buy at wallmart.. completely imbedded in the sediment like you had just cut a cake and exposed it about halfway up. Thus, 3 FEET of silt and clay sediments from topside had been deposited over that pot in no more than the last 50-75 years and probably less.

Something to think about.

[Anonymous_Coward]

Hey WVcaver,

Wyandotte is right on with his words of caution. You might want to look into cosmogenic dating where they determine how long a rock or clay has been shielded from cosmic rays. This has been done in many caves to determine the age of sediments. Maybe someone here will remember the Journal article on this subject from several years ago and point you towards it. It describes the ages of many large well-known caves in TN using this method.

[WVCaver2011]

a note of caution.

sediments in caves are invariably sediments transported there. Seems obvious. But when you think about organic material, or even the entire sediment layer, being deposited topside..perhaps in a shallow marsh, stream bank, etc etc. then 20,000 yrs later sediments get washed away by erosion and re-deposited in a cave. Then, 100 yrs later some guy comes along and says hey look...this was put here 20,000 yrs ago.

I was once in a cave that had tall sediment banks about 6' tall on each side of a small stream. The sediments were very nicely layered with alternating bands of differing fine silts and clays material. As we were walking along we too were speculating on age of the sediments and wondering about finding bears teeth or pleistocene mammal bones. Then we saw a very modern broken in half 8" clay pot like youd buy at wallmart.. completely imbedded in the sediment like you had just cut a cake and exposed it about halfway up. Thus, 3 FEET of silt and clay sediments from topside had been deposited over that pot in no more than the last 50-75 years and probably less.

Something to think about.

Yea that would be something to think about IF there were a river or some sort of pool. What I was referring to is what about the clays in upper levels of the caves? For example you have water at 200 feet below datum and you can still find layered clay with organic material 100 feet below datum. I doubt that the water will have risen to this point anytime in the recent past. The caves I will be researching will be caves that are not high traffic caves and will have clays fairly well preserved with mudcracks that are easy to remove. Shaving or peeling the layers off or just looking at a side profile view will reveal the organic material (if there is any).

[wyandottecaver]

think in geologic time scales. Not to put too fine a point on it... Lots of geologic work has been done on caves by people who dont really understand them. You CAN NOT assume anything about the history of any sediment in a cave short of some of the cosmic ray dating and even that has assumptions. That clay 100ft above the CURRENT water table wasn't always. It still had to get transported there by water sometime.

Example 2.
Clays and organics get layed down topside 30,500 yrs ago. 30,000 yrs ago the glaciers melt and they get washed into a ancient cave. 15,000 yrs ago a landslide plugs a local stream creating a temporay lake that re-infiltrates the old cave passages on the valley wall and then when the landslide plug is breached and the water levels rapidly drop again washes the old sediments to the oxygen poor bottom of the new marsh in the valley floor and burys them under new recently created sediments . 10,000 yrs ago both the "new" sediments above them and the "old" sediments are once again washed from the now dry marsh by erosion from a seasonal flood event downstream into yet another smaller, younger (5,000 yrs old at that time.) cave and the old sediments deposited OVER the younger stream bank sediments that were eroded first. Both these are deposited in the "upper" levels of the cave.... Shortly after that the cave stream breaches a chert layer and in 100 yrs rapidy downcuts through shales and soft limestones allowing it to pirate more water and reach another strata 80ft below where it cuts another 20 ft in 10,000 years leaving our sediments safe from further disturbance.

Thus our 30,500 yr old clay is now in a 15,000 yr old cave and has spent 500 yrs on the surface, 5,000 yrs buried under younger sediments and water in a anoxic marsh, 25,000 yrs underground and 10,000 yrs ago was deposited on top of sediments only 10-15,000 yrs old in a passage 100ft above the current water table. A guy comes in looking for organics.....

[ArCaver]

Several years ago a friend and I were digging in a rather good sized trunk passage completely filled with layered clay. We were a good 20'-25' above any flood level I've seen in the cave, yet as we dug we found the piece of foil from the top of a modern cigarette pack. Before that I had never considered that the fines in a cave could be so recently deposited.
I also remember reading about fossilized pollen used in arguments to "prove" the age of cave passages in a couple of cases. Other researchers pointed out that the pollen could be reworked material washed in from outside of the cave.
Anyway, this is one of a few papers that argue deforestation has lead to some of the infilling of caves. http://www.doc.govt.nz/upload/documents ... SFC198.pdf

[WVCaver2011]

think in geologic time scales. Not to put too fine a point on it... Lots of geologic work has been done on caves by people who dont really understand them. You CAN NOT assume anything about the history of any sediment in a cave short of some of the cosmic ray dating and even that has assumptions. That clay 100ft above the CURRENT water table wasn't always. It still had to get transported there by water sometime.

Example 2.
Clays and organics get layed down topside 30,500 yrs ago. 30,000 yrs ago the glaciers melt and they get washed into a ancient cave. 15,000 yrs ago a landslide plugs a local stream creating a temporay lake that re-infiltrates the old cave passages on the valley wall and then when the landslide plug is breached and the water levels rapidly drop again washes the old sediments to the oxygen poor bottom of the new marsh in the valley floor and burys them under new recently created sediments . 10,000 yrs ago both the "new" sediments above them and the "old" sediments are once again washed from the now dry marsh by erosion from a seasonal flood event downstream into yet another smaller, younger (5,000 yrs old at that time.) cave and the old sediments deposited OVER the younger stream bank sediments that were eroded first. Both these are deposited in the "upper" levels of the cave.... Shortly after that the cave stream breaches a chert layer and in 100 yrs rapidy downcuts through shales and soft limestones allowing it to pirate more water and reach another strata 80ft below where it cuts another 20 ft in 10,000 years leaving our sediments safe from further disturbance.

Thus our 30,500 yr old clay is now in a 15,000 yr old cave and has spent 500 yrs on the surface, 5,000 yrs buried under younger sediments and water in a anoxic marsh, 25,000 yrs underground and 10,000 yrs ago was deposited on top of sediments only 10-15,000 yrs old in a passage 100ft above the current water table. A guy comes in looking for organics.....

Wyandottecaver,

Thanks for pointing these things out! I fully understood that the current water table is there because of the overlying topography. The past overlying topography was higher and therefore the watertable was higher. There were just some concepts that I was having trouble grasping a hold of... Perhaps it was all the numbers lol.

This was a topic I thought up just this morning lol...

Are there any research project idea that people would like to see researched? Its hard to come up with ideas on your own especially when you dont know if it's been done before... I will be trying to think of others and lay them down for you. You can murder the ideas if you like thats what they will be there for.

I want to do something that relates to caves and geology or hydrogeology that hasnt been thought of yet... If you guys have any ideas I will take them into serious thought and present you with questions or my ideas on that topic.

[Joseph W. Dixon]

You might want to take some preliminary samples and test them to see how much organic matter is even in them. Any soil testing lab in the country should be able to tell you that and it isn't very expensive. If you have a soils or agronomy department on campus they might even do it for free. I'd also talk with someone at your college or university in the soils department, especially someone who has worked with paleosols, since that is essentially what you'd be working with. I have never used a Munsell chart on cave sediments, but all of the cave sediments I can recall (here in Iowa) have a high chroma which would be indicitive of low amounts of organic matter. I would honestly be curious to know just how much organic matter you'd find in your samples.

[WVCaver2011]

You might want to take some preliminary samples and test them to see how much organic matter is even in them. Any soil testing lab in the country should be able to tell you that and it isn't very expensive. If you have a soils or agronomy department on campus they might even do it for free. I'd also talk with someone at your college or university in the soils department, especially someone who has worked with paleosols, since that is essentially what you'd be working with. I have never used a Munsell chart on cave sediments, but all of the cave sediments I can recall (here in Iowa) have a high chroma which would be indicitive of low amounts of organic matter. I would honestly be curious to know just how much organic matter you'd find in your samples.

Yes, I'm definitely going to at least see if it's worthwhile. If the samples turn out to be really old (1my or more) then I can then conclude that the error in organic material variation from the surface will be small. I may take several samples of the same layer in different spots throughout one locality and test for the youngest date to diminish the error to minute proportions.

I have a Paleontology professor that may be able to help me out on this. If not i'll go to the soil sciences department and see what they can do to satisfy my needs. If all of this falls through and doesnt work out what do you expect the price to be?

[jharman2]

Allen,

I know of at least one MS thesis that was conducted in a nearby cave that used paleomagnetic dating to determine the age of cave sediments. I don't claim to understand the technology or its pros and cons or how it compares to radiometric methods, but it may be something you want to look into.

[WVCaver2011]

Allen,

I know of at least one MS thesis that was conducted in a nearby cave that used paleomagnetic dating to determine the age of cave sediments. I don't claim to understand the technology or its pros and cons or how it compares to radiometric methods, but it may be something you want to look into.

Sounds interesting. I'll look into that. I've heard about that kind of thing being used to date igneous rocks (or maybe i'm thinking of something else). Isnt it where you use magnetic minerals and how they are aligned to determine the age based on magnetic reversals? I didnt know this could be used in cave soils as well...but makes since I guess. Just depends on how old these paleosols really are.

[kkerrigan]

I'm also a geology student, possibly looking to do a hydrogeology related thesis (still need to figure that whole thing out, haha.) I actually just read a short article today which may be of interest to you. The authors used paleomagnetic analysis of sediment dating, but I believe used a lab at Pittsburgh university, and I doubt it was an undergrad thesis topic, but still interesting. The book in which the article I read (and probably other relevant articles) is/are found is entitled "Studies of Cave Sediments: Physical and Chemical Records of Paleoclimate", edited by Ira D. Sasowsky and and John Mylroie. Google book link: http://books.google.com/books?id=E4QCpb-3f1MC&pg=PA75&lpg=PA75&dq=kooken+cave+sediment&source=bl&ots=8SYC9elSyL&sig=zQWSlWTALnRHjY3vHirY_SfkPmI&hl=en&ei=f7bETJTBJ8OqlAfk6NDgAg&sa=X&oi=book_result&ct=result&resnum=1&ved=0CBMQ6AEwAA#v=onepage&q=kooken%20cave%20sediment&f=false This isn't the complete article, unfortunately, but if it's interesting enough I'm sure you could order it.

Page 71-82, Paleomagnetic Analysis of a Long Term Sediment Trap, Kooken Cave, Huntingdon County, PA, USA. Not precisely what you were talking about but close-ish!

[WVCaver2011]

I'm also a geology student, possibly looking to do a hydrogeology related thesis (still need to figure that whole thing out, haha.) I actually just read a short article today which may be of interest to you. The authors used paleomagnetic analysis of sediment dating, but I believe used a lab at Pittsburgh university, and I doubt it was an undergrad thesis topic, but still interesting. The book in which the article I read (and probably other relevant articles) is/are found is entitled "Studies of Cave Sediments: Physical and Chemical Records of Paleoclimate", edited by Ira D. Sasowsky and and John Mylroie. Google book link: http://books.google.com/books?id=E4QCpb-3f1MC&pg=PA75&lpg=PA75&dq=kooken+cave+sediment&source=bl&ots=8SYC9elSyL&sig=zQWSlWTALnRHjY3vHirY_SfkPmI&hl=en&ei=f7bETJTBJ8OqlAfk6NDgAg&sa=X&oi=book_result&ct=result&resnum=1&ved=0CBMQ6AEwAA#v=onepage&q=kooken%20cave%20sediment&f=false This isn't the complete article, unfortunately, but if it's interesting enough I'm sure you could order it.

Page 71-82, Paleomagnetic Analysis of a Long Term Sediment Trap, Kooken Cave, Huntingdon County, PA, USA. Not precisely what you were talking about but close-ish!

Excellent,

Thanks! Even if it's not exactly relevant it still adds some ideas. Only problem is that a sediment trap probably wouldnt work in a not active area of a cave. Im starting to think the only way i'll find a precise date on when sediments were deposited in inactive layers are to find bat skeletons within the soils at date them instead. I do know where there are some vertebra and leg bones that are relatively small but are nice and white like they have been possibly fossilized. They are located in a very dusty crawl and although they are not in layers they would still be useful to date and use as scientific data on the cave. I know in nearby caves there have been fossil bones dated to 800,000 years old. Perhaps instead of soils I should do something on fossils... I dont really care as long as its Geology based. It's just an undergrad thesis so it just looks good on a resume' and a Graduate School application. Any suggestions?