Strata Deposition and Dating Fossils

GARPIER
Would someone please provide an explanation for polystrate fossils if in fact the layers through which it goes were laid down gradually over long periods of time.


DAVEW
Here ya go:
"polystrate" tree fossils http://www.talkorigins.org/faqs/polystrate/trees.html


EDGE
The layers were not laid down over long periods of time. I don't know a single geologist who does not believe that some deposits are rapidly emplaced.


GARPIER
What I find amazing is that we have to attribute sediments in which polystrate fossils are found to a rapid depositing. But other sediments must be laid down slowly because that is the only way to account for the long years necessary for evolution. This not only is unproveable but also illogical.


RADIOCHEMIST
Let's consider your statement: "But other sediments must be laid down slowly because that is the only way to account for the long years necessary for evolution".

Your statement is simply a strawman, an argument that has not been made by mainstream science. The time required to lay down sediments is what it is, and no one has ever used the thickness of sediments as a way to account for the passage of time.


DAVEW
Sediments get deposited at different rates under different conditions, but that doesn't have much to do with evolution or the earth's age. Charles Lyell (a creationist who disbelieved Darwin's theory for years after it came out) was the first one to definitively show that the patterns in the earth of mountains being thrust up and then eroded, several times over, meant that the earth had to be far older than a few thousand years. The earth is thought to be old not because of how long it takes to make a fossil, but because of how long it takes to make a mountain (especially smooth, eroded mountains like the Appalachians).


GARPIER
I made no statement saying that I believed anything about how long it took a layer of sediment to form. Ask Edge about the time it takes. He was the one who suggested that polystrate fossils were laid down rapidly and inferred that others were laid down slowly. My comment was for him to show how that can be the case. It just seems awfully convenient to say layers that include polystrate fossils must have been laid down rapidly, while also claiming other took long periods of time. The burden of proof is on him not me.

Since I wasn’t there to watch any of the sedimentary layers form, I am not in a position to tell you how long they took to form. My point was and still is, you can't claim rapid formation for layers containing polystrate fossils and then claim long periods of time for others if you haven't been there. Edge made the statement about rapid deposition for polystrates and inferred slow deposition for others.

Maybe you have proof showing one was rapid and the other slow.


THE BARBARIAN
You can't make any assumptions at all about the rapidity with which any particular layers were laid down. We notice that in real life, some of it is very slow, and some of it is very rapid.

I don't think it's a surprise that the layers in which upright trees are embedded would have formed quickly, as we still see happening from time to time today.

If very slow and very fast sedimentation (and everything in between)happens now, what makes you think it couldn't have happened in the past?


RUFUS ATTICUS
My point was and still is, you can't claim rapid formation for layers containing polystrate fossils and then claim long periods of time for others if you haven't been there.

Why not? This is what I am asking you to support.


JOE MEERT
Let me ask you the following question. Suppose you discover two accidents involving the same cars. In one accident, the fenders of both cars are slightly dented. In the other, both cars are completely totaled. Which accident is more likely to have involved a higher rate of speed? Remember, you were not there to see it!


TOMR
All you have to do to see differing sedimentation rates is to wade across your nearest meandering stream. On the inside of meanders you'll see point bars, evidence of deposition. The highest rate of sedimentation on point bars typically occurs at its downstream point, while non-submerged portions of the bar aren't receiving sediment at all.
On the outside part of the meander you can see evidence of negative sedimentation, refered to in some circles as erosion, or scouring, because that is were the stream is the most energetic.

This idea that sedimentaion rates must have at all times been uniform in space and time holds no water. It is a Creationist characture of uniformitarianism.


DIMO
In one hand we have sedimentary layers in the geological strata. And in the other we have the biome that is the cause of these layers. Certain layers are the result of certain types of biomes. In some cases we have layers that were laid down by a desert, then a marine environ, then a tropical forest, then a temperate forest, then a desert again, and followed by a shallow marine biome. This succession of layers along with the distinct fossils found in the layers can only be explained by a period of time that is greater than 10,000 years.


[Administrator: the following is from a different, but related, thread.]


JOHN PAUL
What I want to know is if you guys think fossilization can occur without the dead organism being buried. Because if rapid burial IS a requirement that would put a damper on biostratigraphy


RADIOCHEMIST
Could you please elaborate? I am not sure why you think it would "put a damper" on anything.


JOHN PAUL
If a dead organism is rapidly buried- say by sediments carried by a flood- and then it is unearthed allegedly eons later, wouldn't the person finding the fossil assume gradual burial and give that fossil an older age than it really is?

For example- the same flood buries one dead organism deep in its sediments. Another organism, contemporary with the dead one, dies in the flood but is buried in the top layers. Wouldn't the organism on the bottom be presumed older than the one at the top? By everything I have read that would be the case.


TRSCUBED
Geologists do not “assume” a gradual burial; a gradualistic approach to geology was abandoned in the 19th century. That said the answer to your question is an emphatic no.

Varying rates of sedimentation are currently observed, for example – sedimentation rates occurring at the mouth of the Mississippi River and my back yard are vastly differing (even though I do have a large dog).

The earth speaks volumes to those willing to listen.


DM
If a single event occurred that buried a group of organisms, it is generally apparent in the depositional context that it was a single event, and what kind of an event it was (i.e. flood deposits, underwater slump, terrestrial mudflow, sudden volcanic eruption, and so on). Geologists are pretty good at determining that sort of thing. If it is demonstrably a sudden, single event, then any organisms buried in it, no matter where, must be dated at the same time.

I do not understand the first paragraph. Why would a competent geologist/paleontologist assume that something buried rapidly was buried slowly? Furthermore, speed of burial has nothing whatever to do with determining the age of a fossil.


TIM THOMPSON
The assumption that rapid burial is required for fossilization is arbitrary & unnecessary. See for instance, In The Beginning ("A Scientist Shows Why Creationists Are Arong"), by Chris McGowan (Prometheus Books, 1984), chapters 8 ("Fossils: How They Are Formed and What They Can Tell Us") and 9 ("Fossils and Time"). Author McGowan was at the time curator-in-charge of the Department of Vertebrate Paleontology at the Royal Ontario Museum in Toronto, Canada, and associate professor of zoology at the University of Toronto. He remains on the U of Toronto faculty, and is now a curator of palaeobiology at the museum.

As McGowan points out, the anoxic environment on a lake bottom easily can (and does) provide for the "slow" burial & fossilization of organisms that are invulnerable to scavenging and decay. Likewise, scavenging is avoided when death occurs is an individually "catastrophic" sense, such as falling into an exposed cave or sink hole (a catastrophe for the victim no doubt, but not what the creationist has in mind I think). McGowan tells his own tale of visiting New Zealand exploring caves and sinkholes in the chalk country outside Wellington. The cave openings are hidden and easily overlooked, replete with the corpses of moas, kiwis, other ground dwelling birds and even sheep. The only way a scavenger can get at them is to suffer the same fate.

It is also to be pointed out that only a relatively small fraction of any population is fossilized. The vast majority of the things that have ever lived have avoided fossilization. Hence, the fossil record has built in limitations, but we can still see the pattern of evolution therein.


JOHN PAUL
I would consider anything on a lake bottom to be buried as it is no longer on the surface. Of course that is my opinion. But it is relevant to the point I was making, which is an organism can not remian on the surface for very long without being subjected to weathering, scavenging, etc.


Likewise, scavenging is avoided when death occurs is an individually "catastrophic" sense, such as falling into an exposed cave or sink hole (a catastrophe for the victim no doubt, but not what the creationist has in mind I think).

This Creationist agrees with that scenario being pretty catastrophic for that organism and any organism that suffers the same fate. The tar pits in So. Cali. come to mind.


It is also to be pointed out that only a relatively small fraction of any population is fossilized.

It should also be pointed out that entire populations have left no trace in the fossil record.


The vast majority of the things that have ever lived have avoided fossilization.

I would agree to that.


Hence, the fossil record has built in limitations, but we can still see the pattern of evolution therein.

But from what you just said that pattern may or may not be indicative of reality.


EDGE
But there is a pattern, and evolution does explain the pattern. I have yet to hear your explanation.


RADIOCHEMIST
The best dates are not obtained by presuming anything but by exacting measurements. For example, a fossil human skull might have a depost inside it that can be dated by some radiometric means.


JEFF
It should also be pointed out that entire populations have left no trace in the fossil record.

This is interesting. Are there any examples you can cite ? The reason I ask is, depending on how long ago the alleged population existed, how would we even know of the existence of an entire population that left no fossil traces ? Perhaps the only exception would be populations that existed too recently to have been fossilized.

Evolution has no ‘problems’. It may have questions that are not fully answered but no one in the scientific community considers these to be ‘problems’. This is what theories are supposed to do; address unanswered questions.


ED BRAYTON
For example- the same flood buries one dead organism deep in its sediments. Another organism, contemporary with the dead one, dies in the flood but is buried in the top layers.
Wouldn't the organism on the bottom be presumed older than the one at the top? By everything I have read that would be the case.

If the strata in question were laid down by a flood, it would be a single lithology - a flood deposit, which are distinguishable from other types of deposits. If two organisms were found in the same lithology deposited in a single event like a flood, it would not be presumed that the one lower in that layer were older than the one higher in the layer, it would be identified as both specimens being buried in the same event.

[ January 22, 2002: Message edited by: Administrator ]