Polystrate Fossils

[RickG]

Petrified wood (tree, or anything) needs cations in groundwater to replace the wood. On land, the most common one is Fe or Ca. But if there is volcanic material nearby, it could also be Si. And the Si is the source for chert.

I am not surprised if the polystrate fossil is replaced by carbonates. But if it chert, then the source becomes a big problem. That is why volcanic material is suggested even no trace of the original material is found.

I live in northwest Georgia where fossils are very plentiful and are almost entirely consisting of chert. There are no volcanoes anywhere near here. What you seem to be ignoring is the fact that silicon is the most plentiful element in the earth's crust. It doesn't just come from volcanoes.

I don't have time now, but I'll post my background when I get home from work this afternoon. Cheers.

 

[juvenissun]

I live in northwest Georgia where fossils are very plentiful and are almost entirely consisting of chert. There are no volcanoes anywhere near here. What you seem to be ignoring is the fact that silicon is the most plentiful element in the earth's crust. It doesn't just come from volcanoes.

I don't have time now, but I'll post my background when I get home from work this afternoon. Cheers.

Dissolved Si and crystalline Si are two entirely different systems.

In fact, abundant chert in the foothill Appalachian (both sides) is an interesting feature. The one on Georgia side is easier to understand than the one on Kentucky side. They are most likely of different origin.

I guess you are probably in fog on what I said. That is OK, as long as you know I do understand your comment.

 

[juvenissun]

You don't need to say a thing. Your silence is enough. What good would it do? Not a darn thing. Wouldn't change a thing.

It would be nice, in a kind of "friendly" sort of exchange of our experiences in geology.

I've read enough of your stuff that frankly I have enough information to form an "opinion" of what your background is.

The fact that you will not give us even an inkling of your bona fides is probably more telling than anything.

I'm just saying: this is who I am. So if I speak on a geophysics you know that it is likely from a less-informed point than if I speak on geochemistry. If I talk about metamorphic mineral phase assemblages it is probably less informed than if you ask me about crystallography or organic petrology.

I'm proud of my path. It didn't end up where I wanted it to. But I loved the ride to get where I am.

I find people's backgrounds to be absolutely fascinating. I can read scientists biographies all day long! My bookshelves at home are filled with histories of science and I love to hear where a scientist comes from.

If you have nothing to say about who you are or where you are coming from then it is a loss. But it really changes nothing.

Let's say we knew even on iota about what your actual background was? We might be able to frame a response to your questions around things like polystrate fossils in terms of your background that might resonate with what you are familiar with.

But we don't have that luxury. We are left with a cypher. A placeholder with more questions than answers.

(Although to be fair, left without answers the temptation is to infer many, many interesting hypotheses.)

If you are good enough, you can certainly see my special interest in geology by what I have said in this thread. That should not be a secret at all. One says well on what he knows.

 

[juvenissun]

What an interesting claim. So what about chert nodules in Missouri? Which nearby volcano supplied the Si?

(I am also fascinated by the phrase "Si is the source for chert", I would rather assume that Si was not transported as Si4+ ions but rather as variants of silicic acid; Si(OH)4 )

A "big problem"? Why?

Sure, dissolved silica.

First, you do not need active volcano to provide Si in the groundwater. Ancient volcanic material would give Si to its neighboring strata. However, this would have some time limitation.

Second, chert can be found everywhere in any rock. However, abundant chert would demand special source of Si. Normal sedimentary material (under normal sedimentary environment) can not provide that much Si to significant amount of chert. If you look at how much chert the polystrate fossil was taking (assume it is cherty, I still don't know for sure), then the best explanation would be a Si source from volcanic material. Again, the timing is crucial. A slow silicification of a buried standing tree in a slowly subsiding sedimentary basin is a very unlikely case.

 

[thaumaturgy]

Sure, dissolved silica.

First, you do not need active volcano to provide Si in the groundwater. Ancient volcanic material would give Si to its neighboring strata. However, this would have some time limitation.

So are you really saying the only source of dissolved silica in ground water would have to be some sort of volcanic material?

Really?

Second, chert can be found everywhere in any rock. However, abundant chert would demand special source of Si.

Yeah, like in the state of Missouri where chert nodules are quite abundant.

Special source? I wasn't aware of that. Can you be more specific?

Normal sedimentary material (under normal sedimentary environment) can not provide that much Si to significant amount of chert.

Really? Now I will readily grant SiO2 is only sparingly soluble but this is the first time I've heard of such extreme conditions necessary to transport dissolved silica.

Can you elaborate? Some references would be nice (but certainly not expected from you).

If you look at how much chert the polystrate fossil was taking (assume it is cherty, I still don't know for sure)

It sounded more like the Joggins formation trees were carbonate.

, then the best explanation would be a Si source from volcanic material.

Again, why? A silicic volcanic material still has the same solubility of the silica as say a big ol' sandstone.

So explain to me why one needs a volcanic rock as the source of the SiO2 for chert? What about felsic crystalline basement rocks? What about nearby sandstones? etc.

Again, the timing is crucial. A slow silicification of a buried standing tree in a slowly subsiding sedimentary basin is a very unlikely case.

I don't think that is necessary how anyonethinks this happened. In most cases the organic material can and is buried quickly and the permineralization happens after the burial.

Once you remove the organic material from access to oxygen you can do lots of stuff to it diagenetically. Including but not limited to replacement by silica.

I have never heard a geologist express such "mystery" around something that appears to happen quite a bit. Silica is a rather common phase found in permineralized fossils.

Please explain again where the great mystery is.

 

[thaumaturgy]

If you are good enough, you can certainly see my special interest in geology by what I have said in this thread. That should not be a secret at all. One says well on what he knows.

I do indeed get a rather clear idea of your "special interest in geology". I think it is abundantly clear.

I'm just curious how this corresponds to your vague indications of having taught geology.

That's where I'm having trouble with the correlation.

 

[juvenissun]

So are you really saying the only source of dissolved silica in ground water would have to be some sort of volcanic material?

Really?



Yeah, like in the state of Missouri where chert nodules are quite abundant.

Special source? I wasn't aware of that. Can you be more specific?



Really? Now I will readily grant SiO2 is only sparingly soluble but this is the first time I've heard of such extreme conditions necessary to transport dissolved silica.

Can you elaborate? Some references would be nice (but certainly not expected from you).



It sounded more like the Joggins formation trees were carbonate.



Again, why? A silicic volcanic material still has the same solubility of the silica as say a big ol' sandstone.

So explain to me why one needs a volcanic rock as the source of the SiO2 for chert? What about felsic crystalline basement rocks? What about nearby sandstones? etc.



I don't think that is necessary how anyonethinks this happened. In most cases the organic material can and is buried quickly and the permineralization happens after the burial.

Once you remove the organic material from access to oxygen you can do lots of stuff to it diagenetically. Including but not limited to replacement by silica.

I have never heard a geologist express such "mystery" around something that appears to happen quite a bit. Silica is a rather common phase found in permineralized fossils.

Please explain again where the great mystery is.

I will make it simple. For details, you can read any sedimentary petrology book.

* Shallow groundwater only has trace amount of dissolved Si. It is not enough to do anything.
* Dissolved Si becomes more abundant in deep groundwater. The deeper the more. But unless something happened, most of it just stay there with a slow leak into the ocean.
* Volcanic material weathered very faster, particularly ashes. It quickly releases large amount of Si in to groundwater. But they won't go far, but only ppted in nearby rocks. It is most likely the only shallow source of dissolved silica for a large quantity.

What else? I think that is enough. You are a chemist. Check the behavior of dissolved Si in natural water. You will see them all. I never know it is such a mystery since my undergraduate year (pretty long time ago).

 

[thaumaturgy]

I will make it simple. For details, you can read any sedimentary petrology book.

Or I could grab my copy of Iler, which is the definitive silica book out there. (I have spent much of my career in colloidal silica for coatings).

* Shallow groundwater only has trace amount of dissolved Si. It is not enough to do anything.

Silica is sparingly soluble, yes, I have already noted that in an earlier post. But I don't think the phrase "not enough to do anything" is correct. No matter where you source the silica, you will need to form chert from dissolved silica. So seems like your first point right off the bat is incorrect. (I assume you do not have another source of chert nodules up your sleeve, or another source of silicious replacement of fossils).

* Dissolved Si becomes more abundant in deep groundwater. The deeper the more. But unless something happened, most of it just stay there with a slow leak into the ocean.

Citation please.

* Volcanic material weathered very faster, particularly ashes. It quickly releases large amount of Si in to groundwater.

Not to harsh your mellow with chemistry, but groundwater can only hold so much silica dependant upon pH and the chemistry of the ground water.

Put a lot of silica in the way of the groundwater whether it is in the form of a volcanic ash or a siltstone, the limiting factor will be the solubility of silica.

As an example here's the solubility curves (vs pH and temp) for amorphous silica (it would be a bit different from crystalline silica like quartz):

It's pretty low solubility. And of course there are graphs comparing pressure and solubility.

But again, you seem to be limiting silica transport rather severely to some narrow range of conditions that I'm not so very sure are necessary.

But they won't go far, but only ppted in nearby rocks. It is most likely the only shallow source of dissolved silica for a large quantity.

Citation please.

What else? I think that is enough. You are a chemist. Check the behavior of dissolved Si in natural water.

As I said I've spent the last several years working with amorphous silica in coatings, so...

You will see them all. I never know it is such a mystery since my undergraduate year (pretty long time ago).

You seem to be piling "Mystery upon Mystery" in your posts, but they all seem to be pretty non-mysterious. I really don't understand why you must add these mysteries to relatively non-mysterious topics in geology.

Your classes must be fun to listen to.

 

[juvenissun]

Or I could grab my copy of Iler, which is the definitive silica book out there. (I have spent much of my career in colloidal silica for coatings).



Silica is sparingly soluble, yes, I have already noted that in an earlier post. But I don't think the phrase "not enough to do anything" is correct. No matter where you source the silica, you will need to form chert from dissolved silica. So seems like your first point right off the bat is incorrect. (I assume you do not have another source of chert nodules up your sleeve, or another source of silicious replacement of fossils).



Citation please.



Not to harsh your mellow with chemistry, but groundwater can only hold so much silica dependant upon pH and the chemistry of the ground water.

Put a lot of silica in the way of the groundwater whether it is in the form of a volcanic ash or a siltstone, the limiting factor will be the solubility of silica.

As an example here's the solubility curves (vs pH and temp) for amorphous silica (it would be a bit different from crystalline silica like quartz):

It's pretty low solubility. And of course there are graphs comparing pressure and solubility.

But again, you seem to be limiting silica transport rather severely to some narrow range of conditions that I'm not so very sure are necessary.



Citation please.



As I said I've spent the last several years working with amorphous silica in coatings, so...



You seem to be piling "Mystery upon Mystery" in your posts, but they all seem to be pretty non-mysterious. I really don't understand why you must add these mysteries to relatively non-mysterious topics in geology.

Your classes must be fun to listen to.

I won't say it this way in my class. Just the first line will probably take more than 1 hour to explain to students. I briefed the content because I thought you are a chemist and should have little problem to understand it.

For the volcanic one, do not forget this is in geological conditions and it takes so much time to deteriorate anything. It is not like dump a bucket of silica into the ground. The so-called high amount of silica means it raised from, e.g. 50 ppm to 150 ppm. It is still very little compared to what you have in a test tube.

Exactly, since shallow groundwater does not have much silica, so the Si for chert must come from either volcanic material or from deep burial. Siliceous fossils are mainly found in ocean, not on land. Yes, that is a source of Si for chert. But it is not likely the case for petrified wood.

If you have question, I try to answer if I could. You better leave those sarcastic remarks aside. It does not make you look any better.

 

[thaumaturgy]

I won't say it this way in my class. Just the first line will probably take more than 1 hour to explain to students. I briefed the content because I thought you are a chemist and should have little problem to understand it.

If you can't explain it don't be condescending.

For the volcanic one, do not forget this is in geological conditions and it takes so much time to deteriorate anything.

Why do you keep going on about "volcanic"? Again, why not crystalline basement rocks?

I understand that since quartz is of such low solubility one is left with much of the silica sourced in ground water coming from the incongruent dissolution of various minerals like feldspars or other silicates (not so much the quartz), but again, I'm mystified by why volcanics?

Can you please cite me where you are getting this limitation from. Yes a volcanic rock will likely contain various silicates that can be dissolved, but that is a limitation. Why not other silicate phases that are not necessarily limited to volcanics?

It is not like dump a bucket of silica into the ground. The so-called high amount of silica means it raised from, e.g. 50 ppm to 150 ppm. It is still very little compared to what you have in a test tube.

What test tube are you talking about here?

Exactly, since shallow groundwater does not have much silica, so the Si for chert must come from either volcanic material or from deep burial.

Ok, why "deep burial"? In Georgia for instance the kaolinite deposits are largely thought to have been formed from the erosion of granitic highlands which came down in the streams (dissolution of the k-spar etc.) and hit small lakes at the "Fall Line" and dumped out the kaolinite.

This is an example of the incongruent dissolution of a silicate. So why do we need "deep burial" involved here to produce the Si(OH)4 dissolved in the stream water?

Siliceous fossils are mainly found in ocean, not on land.

Can you give me your citation here?

Yes, that is a source of Si for chert. But it is not likely the case for petrified wood.

Huh? Any reason to think this the case? Citation?

If you have question, I try to answer if I could. You better leave those sarcastic remarks aside. It does not make you look any better.

Again, I'll be frank with you Juvie, I don't think you're much of a geologist. And if you are, I am sore afraid for your classes. Honestly. Is this honestly how you teach? Really?

 

[juvenissun]

If you can't explain it don't be condescending.



Why do you keep going on about "volcanic"? Again, why not crystalline basement rocks?

I understand that since quartz is of such low solubility one is left with much of the silica sourced in ground water coming from the incongruent dissolution of various minerals like feldspars or other silicates (not so much the quartz), but again, I'm mystified by why volcanics?

Can you please cite me where you are getting this limitation from. Yes a volcanic rock will likely contain various silicates that can be dissolved, but that is a limitation. Why not other silicate phases that are not necessarily limited to volcanics?



What test tube are you talking about here?



Ok, why "deep burial"? In Georgia for instance the kaolinite deposits are largely thought to have been formed from the erosion of granitic highlands which came down in the streams (dissolution of the k-spar etc.) and hit small lakes at the "Fall Line" and dumped out the kaolinite.

This is an example of the incongruent dissolution of a silicate. So why do we need "deep burial" involved here to produce the Si(OH)4 dissolved in the stream water?

Can you give me your citation here?

Huh? Any reason to think this the case? Citation?

Again, I'll be frank with you Juvie, I don't think you're much of a geologist. And if you are, I am sore afraid for your classes. Honestly. Is this honestly how you teach? Really?

I can answer your questions easily. These are geological questions at 400 or 500 level. If you do not think I am a geologist, then I just won't bother.

Do you want answer from me or not? If you do, take your words back.

 

[RickG]

I can answer your questions easily. These are geological questions at 400 or 500 level. If you do not think I am a geologist, then I just won't bother.

Do you want answer from me or not? If you do, take your words back.

I only have a moment to respond as I have been preoccupied with other things the past couple of days and perhaps can respond more and at length this evening.

Juvie, the reason thaumaturgy and others (myself included) question your knowledge of geology is that you seemingly appear to lack some of the most basic understanding in geologic processes and even in basic chemistry. None of us doubt you have taken geology courses, but your source of that material appears to be well outside the basic knowledge of well founded and understood geology. Giving citations to support what you are saying would go a long way for a better understanding for everyone.

Cheers!

 

[thaumaturgy]

I can answer your questions easily. These are geological questions at 400 or 500 level. If you do not think I am a geologist, then I just won't bother.

The standard Juvie answer. He's a teacher who, when he decides to (which is most of the time) will not teach because he's mad at you.

Here's some of Juvies previous classics along this vein:

Not a wise hope. Even I do have something, I won't tell you. The reason is obvious.

It is VERY EASY to explain that what you said above does not apply to the situation of a global flood. But I am NOT going to tell you why this time. Why should I educate you if you do not appreciate anything I have said? I have posted many idea along this thread. However, to you, it seemed I have said nothing. If so, why should I continue?

You are confused on who you are in this forum. I am not obligated to explain anything to you.

To your benefit, if you do not understand, then humble yourself and start to ask some basic questions. One of the purpose for me to hang around here is to educate.

(The last one there is added for irony!)

Do you want answer from me or not? If you do, take your words back.

I don't need an answer from you. You made a claim, I just wanted to know why your claim was what it was.

I'm not begging you for anything. I don't think you have much to offer. I'm quite happy with a real geologic education and can move along quite well with my BS, MS and PhD.

I just thought as a teacher you might accidentally teach something. Or at least act like a teacher once in a while.

So, do whatever you like. It's not important to me. Just curious.

 

[RickG]

Well, I guess it time I posted my background since the other geology types are.

I was born in 1948 in Asheville, NC, the son of a chemist. Oh! never mind that. But I was, really I was.

But seriously, I received my B.S.E. in 1972, M.Ed. 1975 and M.S. in 1977. The latter degree was in Physical Earth Science, concentrating in geologic processes and paleoclimatology. For most of my adult career I was employed as an R&D Chemist and Process Engineer. Later on I spent several years teaching in the public school system. I then retired for a few years until a former employer called and asked me to come back for a few years. So that's what keeps me occupied now. Cheers and blessings to all.

 

[Mr Strawberry]

One would almost think that juvenissun had something to hide. Surely not. What a sceptical lot we are. He couldn't possibly be making things up as he went along could he? Outrageous thought. Obviously it is entirely normal for geology teachers to be confused by and even ignorant of basic geology. They frequently spend their lessons making great claims of deep wisdom without actually imparting any of it. When pressed for information they usually resort to petulance and silence. That's what they do. Isn't it? No?

 

[juvenissun]

One would almost think that juvenissun had something to hide. Surely not. What a sceptical lot we are. He couldn't possibly be making things up as he went along could he? Outrageous thought. Obviously it is entirely normal for geology teachers to be confused by and even ignorant of basic geology. They frequently spend their lessons making great claims of deep wisdom without actually imparting any of it. When pressed for information they usually resort to petulance and silence. That's what they do. Isn't it? No?

Welcome.

I am not going to waste my time on them. You are new, so why don't you try and make your own judgement?

 

[Mr Strawberry]

Welcome.

I am not going to waste my time on them. You are new, so why don't you try and make your own judgement?

I think it is evident to even the slowest witted that I already have. (Hint: if you're a geology teacher then I'm Scooby-doo.)

 

[RocksInMyHead]

Sorry I forgot about it. My impression is that you are working in the energy or the mining field. (right or wrong, it does not matter).

Nope. I'm working in the graduate student field, planning to go into research of some sort (University/USGS). The energy field doesn't interest me at all since I'm mostly interested in crystalline rocks, though I haven't thrown out the possibility of mining.

And my background, for those of you who are curious:

I started out in geology in high school actually (I'm one of those rare geologists who entered college as a major), field assisting for a relative of mine who's a professor. He also let me do a little bit of my own research in his lab for a high school project, which was what sealed the deal for me on choosing geology. I graduated with my B.S. from a Southwestern university and, with my current advisor's support, was accepted directly into the PhD program at a Midwestern university. I'm currently in my second semester there. My teaching experience is limited to pseudo-TAing a couple of courses and tutoring, though I'm going to be TAing field camp this summer and at least one or two classes next year.

And juve, it's statements like "I could answer your questions easily, but I won't" that make us think that you're not a geologist. Typically when people talk like that, they don't know the answer and are just bluffing.

 

[thaumaturgy]

Nope. I'm working in the graduate student field, planning to go into research of some sort (University/USGS). The energy field doesn't interest me at all since I'm mostly interested in crystalline rocks, though I haven't thrown out the possibility of mining.

And my background, for those of you who are curious:

I started out in geology in high school actually (I'm one of those rare geologists who entered college as a major), field assisting for a relative of mine who's a professor. He also let me do a little bit of my own research in his lab for a high school project, which was what sealed the deal for me on choosing geology. I graduated with my B.S. from a Southwestern university and, with my current advisor's support, was accepted directly into the PhD program at a Midwestern university. I'm currently in my second semester there. My teaching experience is limited to pseudo-TAing a couple of courses and tutoring, though I'm going to be TAing field camp this summer and at least one or two classes next year.

And juve, it's statements like "I could answer your questions easily, but I won't" that make us think that you're not a geologist. Typically when people talk like that, they don't know the answer and are just bluffing.

Cool! Getting to start early with field experience is neat!

I also started out as a geology major at the start of my Freshman year. I diversified into chemistry but kept in geology to the end.

My wife (whom I met in geology grad school) was much more of a field person than I was. I was a lab monkey (hence the chemistry stuff). She ultimately ended up working in environmental. Did her time sitting rigs and collecting samples.

Crystalline, rocks, eh? You igneous pet or metamorphic pet?

Any particular type of rock?

I wish I would have spent more time in the hardrock petrology end of things. The chemistry there is pretty cool. But I was taken with organic geochem and avoided the inorganic until I could no longer.

 

[juvenissun]

Nope. I'm working in the graduate student field, planning to go into research of some sort (University/USGS). The energy field doesn't interest me at all since I'm mostly interested in crystalline rocks, though I haven't thrown out the possibility of mining.

And my background, for those of you who are curious:

I started out in geology in high school actually (I'm one of those rare geologists who entered college as a major), field assisting for a relative of mine who's a professor. He also let me do a little bit of my own research in his lab for a high school project, which was what sealed the deal for me on choosing geology. I graduated with my B.S. from a Southwestern university and, with my current advisor's support, was accepted directly into the PhD program at a Midwestern university. I'm currently in my second semester there. My teaching experience is limited to pseudo-TAing a couple of courses and tutoring, though I'm going to be TAing field camp this summer and at least one or two classes next year.

And juve, it's statements like "I could answer your questions easily, but I won't" that make us think that you're not a geologist. Typically when people talk like that, they don't know the answer and are just bluffing.

Crystalline rocks, to me, is much better than those sand and mud. What kind of crystalline rock are you working on?

It depends on people. For those who trashed me intentionally, I couldn't care less on what they think of me. I just refuse to pass my knowledge directly to them. I have four and 2/3 names on my list now. To them, I will never talk about geology again.