Firstly, because basically you are saying that I have said things that I have not said
I would say - "the petrified wood does not have an igneous origin, because it originated 26 My years after the basalt formed, from wood perhaps deposited 1 My earlier than the petrification - at a time after the lava coolled completely and started to be weathered". Lefty might say "it is in tuff which is a volcanic rock which is igneous so the bloody thing has an igneous origin". I would say, no, it didn't originate then, it originated 25 My later (its genesis was 25 My later), so we cannot possibly say its origin (genesis) is igneous - the two things (tuff and petrified wood) originated at vastly different times. Do you see why I say we are going around in circles?
I'd like to understand how timber can still be timber in the ground for One My still holding its grain perfectly for so long and then still undergo petrification processes all that time later
silver said:I'd like to understand how timber can still be timber in the ground for One My still holding its grain perfectly for so long and then still undergo petrification processes all that time later ,... I find it much easier to conceive that during the volcanic upheaval (as cataclysmic as it was) the surrounding humus and macro environment for some extent undergoing extraordinary circumstances being put through the immediate (in geological terms) transformational batch of geochemical soup required to give the on the ground verification of Just That Process that is being seen and found by the man on the ground, is what we are seeing (whew ,.... big sentence right there).
Some beautiful pieces Lefty, some of the bits in the fourth photo look like stalactites.
In saying that i believe there are cases where the lava flow itself has preserved wood, such as the basalt flow at Crinum, Central Queensland. Where fossilized wood is pulled directly out of the basalt.
Lefty a quick question, the wood in your area you find, i assume you mainly grab it out of the creeks/rivers but do you know what rock it is coming out of or has shed from?
silver said:I'd like to understand how timber can still be timber in the ground for One My still holding its grain perfectly for so long and then still undergo petrification processes all that time later ,... I find it much easier to conceive that during the volcanic upheaval (as cataclysmic as it was) the surrounding humus and macro environment for some extent undergoing extraordinary circumstances being put through the immediate (in geological terms) transformational batch of geochemical soup required to give the on the ground verification of Just That Process that is being seen and found by the man on the ground, is what we are seeing (whew ,.... big sentence right there).
"I think that the silicate that precipitates onto the walls has to be a little bit polymerized. Not long strings of molecules, as in a protein, but repeat units of five to ten molecules. If the concentration of silica in water gets high enough, the silica polymerizes. This is how it happens;" He crosses to the blackboard and writes:
formula for oxygen and silicon atoms
"The oxygen serves as a bridge between two silicon atoms.
"These polymers get pulled out of the solution and get incorporated into the crystal very quickly. When things are polymerized, they'll crystallize very rapidly. You've overcome some of the initiation energy needed to make the crystal. And because the crystallization occurs so quickly, mistakes are made and weird minerals like moganite are formed.
"Soon, though, the polymers get depleted from the solution, leaving isolated Si(OH)4 units. You can crystallize perfect quartz crystals without moganite from these, but it's very slow. At room temperature, you can let the solution sit for two years before you'll see the beginning of the crystallization process."
Between the crystal fibers are channels that work by capillary action to pull water into the center of the hole in the rock. "If you have a continuous supply of water feeding silica to the system," Heaney says, "then when the concentration gets higher, the silica will begin to polymerize again and it will begin to crystallize rapidly again. That's why I think an agate has its banding pattern.
"This has not been experimentally shown," Heaney says. "You'd have to make an agate, and no one has ever made an agate, though Robert thinks we should try." Heaney and a Russian mathematician, an expert in fractal geometry, are submitting a grant proposal to simulate this oscillating pattern of crystal growth on a computer.
"There is a competing theory that I don't like at all," Heaney adds, "and it's one that Robert favors. You have a gel, a silica jello embedded in the rock, and by adding chemicals you produce periodic bands in it. You can make a silica gel in the lab very easily. You can even get the banding. But when you let the gel dry, it dries to an amorphous or non-crystalline form of silica." While high temperatures or pressures might cause the gel to crystallize, those forces do not come into play. "We know agates form close to the surface of the earth, at low pressures and temperatures," Heaney says, "and not only in volcanic rock, but in dinosaur bones."
We also know agates invariably outlast their surroundings. The encasing rockor boneweathers away, leaving just a roundish, rough-coated lump waiting to be picked up and cut and polished.
Lefty said:Still chugging through it all.
I would say - "the petrified wood does not have an igneous origin, because it originated 26 My years after the basalt formed, from wood perhaps deposited 1 My earlier than the petrification - at a time after the lava coolled completely and started to be weathered". Lefty might say "it is in tuff which is a volcanic rock which is igneous so the bloody thing has an igneous origin". I would say, no, it didn't originate then, it originated 25 My later (its genesis was 25 My later), so we cannot possibly say its origin (genesis) is igneous - the two things (tuff and petrified wood) originated at vastly different times. Do you see why I say we are going around in circles?
I'm sure you're just hypothesizing there - because otherwise it would be misrepresenting what I'm saying by simplifying it in the extreme and neglecting to mention a variety of other observations that go along with it You can accurately date petrified wood by looking at photographs?
Again, I'd like to grab myself some specimens of Agates apparently originating in non-igneous environments for my collection. In this neck of the woods, the spatial relationship between such materials and igneous rocks appears very strong. Every example I can think of comes directly out of or very close to something igneous. Conversely, it seems difficult to find examples within this region of them originating in non-igneous rocks, though I'm sure they exist.
When I can be shown significant numbers of examples of such stuff from sites widely distributed around my region, then I might have cause to review my thinking more. Literature notwithstanding, when the spatial relationship with igneous features in this area appears so strong and examples to the contrary are hard to come by - it does not make sense to put it all down to nothing more than a series of purely coincidental occurences, time and again and again.
shivan said:Some beautiful pieces Lefty, some of the bits in the fourth photo look like stalactites.
I'd like to understand how timber can still be timber in the ground for One My still holding its grain perfectly for so long and then still undergo petrification processes all that time later
This is why most of the wood preserved is from trees and wood that wend down in water or stumps that were close by the water, because you get a lot of rapid deposition associated which aids in the initial preservation. I am sure most of us have seen how devastating a good flood can be, imagine all the trees, bits of wood and stumps that can get buried during these events. Heck even think of drift wood.
With rapid deposition, whether from floods, basin, swamp, volcanic ash or lava, the wood does not have time to decay like it normally would.
But i think what goldierocks is getting at, is that even if a forest was buried in volcanic ash, this does not ensure the wood will be petrified as it still needs silica rich waters flowing through the ground to start the silica replacing the wood. This i believe is not something that happens over night, but is an extremely lengthy process.
In saying that i believe there are cases where the lava flow itself has preserved wood, such as the basalt flow at Crinum, Central Queensland. Where fossilized wood is pulled directly out of the basalt.
Lefty a quick question, the wood in your area you find, i assume you mainly grab it out of the creeks/rivers but do you know what rock it is coming out of or has shed from?
shivan said:Some beautiful pieces Lefty, some of the bits in the fourth photo look like stalactites.
I'd like to understand how timber can still be timber in the ground for One My still holding its grain perfectly for so long and then still undergo petrification processes all that time later
This is why most of the wood preserved is from trees and wood that wend down in water or stumps that were close by the water, because you get a lot of rapid deposition associated which aids in the initial preservation. I am sure most of us have seen how devastating a good flood can be, imagine all the trees, bits of wood and stumps that can get buried during these events. Heck even think of drift wood.
With rapid deposition, whether from floods, basin, swamp, volcanic ash or lava, the wood does not have time to decay like it normally would.
But i think what goldierocks is getting at, is that even if a forest was buried in volcanic ash, this does not ensure the wood will be petrified as it still needs silica rich waters flowing through the ground to start the silica replacing the wood. This i believe is not something that happens over night, but is an extremely lengthy process.
In saying that i believe there are cases where the lava flow itself has preserved wood, such as the basalt flow at Crinum, Central Queensland. Where fossilized wood is pulled directly out of the basalt.
Lefty a quick question, the wood in your area you find, i assume you mainly grab it out of the creeks/rivers but do you know what rock it is coming out of or has shed from?
Photos look texturally identical to what we see around Melbourne - some of those look like replaced root casts to me (guessing)
AtomRat said:Just throwing this out as a guess, but would it have anything to do with the decomposition of silanes, or them being able to break down and bond at a range of temps ( I could be way off )
Lefty said:Cheers Goldirocks.
I've been quite happy to accept all along the argument that something being found in close proximity to something else does not necessarily imply a causal relationship. Indeed, I would think this would often turn out to be the case. I just wasn't sure that you were taking in the fact that what I was saying ran slightly deeper than just "there's some extinct volcanoes, there's some petrified wood nearby - one must be responsible for the other. I've noted a number of factors that lead me to suspect a relationship and as you concur, "not necessarily" or "often not the case" does not automatically equal "never".
As I said, I'm at a bit of a disadvantage when it comes to being familiar with the most basic features of non-igneous geology because of I where I have always lived, where as you travel around you will always come across volcanic plugs and granite mountain ranges.
The fossil wood, the chalcedonies and other materials occur in abundance among the gravel banks of a river in the close vicinity of a volcanic area, the wood being the major constituent of the "interesting looking rocks". The river gravels themselves appear quite different to those I have seen elsewhere in that these materials are not only present, they are present in such abundance that they appear to make up some significant portion of the total gravel load of the river bed. Go some distance upstream of the site and they go from abundant to non-existent. I don't recall having seen any particular rock which may have played host but there may be pieces of it there among the gravels and I will be looking out for it next time.
Photos look texturally identical to what we see around Melbourne - some of those look like replaced root casts to me (guessing)
They also look (to my eyes at least) to be superficially texturally similar to the volcanic chalcedony image you posted. They also look very similar to material I gained in a rock swap with a bloke over in Montana who tells me he collected them from the Yellowstone volcanic region somewhere - so similar it is difficult to tell some bits apart. I assume he collected them outside the national park and I am not in possession of illegally-fossicked material
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