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Thread: Questions about geological column, fossils

  1. #1 Questions about geological column, fossils 
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    I have been reading some things about the geological column and fossils and am interested in evolutionists' responses.

    First, why is the geological column presented in textbooks as an definite thing when it does not appear to actually exist anywhere in the world? That is, except for a claim by one site on the Internet, http://www.talkorigins.org/faqs/geocolumn/ Is this generally accepted to be true information? If so, I do not understand how his various layers have any relation whatsoever to the age of the layers listed in tables. He seems to be saying that each layer is made up of different types of materials. If this is correct, then how do we know how old each layer is unless all the materials are radioactive? I understand that it is said that each layer is not everywhere on earth because it didn't accumulate everywhere all the time, but why, for millions of years, whenever it did accumulate, should it have been one kind of material, and then a completely different type of material be deposited for the next millions of years?

    But maybe layers aren't identified by composition. Some sites seem to be saying that the different layers are simply labeled stretches of earth based on what fossils we find in the sediment. The pro-evolution sites I have found tend to agree that they date fossils based on the layers in which they are found, but what about fossils found in sedementary layers for which there are no radioactive materials to use dating methods? And does this mean that if there are no fossils found we cannot identify the layer?

    "If you want to find Pre-Cambrian or Palaeozoic strata you must go to the Grand Canyon. If you want to find Mesozoic you must travel to eastern Arizona. To find Tertiary, you must then travel to New Mexico..." For the overwhelming majority of the earth, why is the distribution of layers so random and varied? For example, the Grand Canyon is reported to contain layers "one, five, six and seven, with small portions here and there of the fourth system, the Devonian." Why should a given area have deposited hundreds of feet during one time period but nothing during the next?

    I am also interested fossilization in general, as creationists tend to ascribe it to the flood. The main argument I see is that "Rapid burial and lithification are essential for the formation and preservation of fossils; otherwise, they would decay or be destroyed by scavengers. The fact that large scale fossilization is not occurring anywhere in the world today is a serious problem for uniformitarian geologists." Is this true? Am I to believe that every single one of the billions of fossils we find today were either "covered in sediment" before they had a chance to deacy or "frozen, desiccated, or comes to rest in an anoxic (oxygen-free) environment such as at the bottom of a lake" (taken from Wikipedia, for what it's worth)? A hundred billion fossils, for instance, over four billion years should require an average of 25 fossils a year, right? Whether or not the actual number found (plus all we haven't found) is a hundred billion (probably more?), are we seeing a comparable average formed each year today?

    Another thing that struck me ~ perhaps there's an obvious answer for it ~ is where all this stuff that's accumulating is coming from, since matter is not created or destroyed. Let's rewind back to the Cambrian. All the stuff that today is on top of it ~ where was it back then? And does that mean that if there was less land the sea covered a lot more of Earth's surface? How much would not be underwater?

    Finally, I am interested in the accepted response to so-called "poly-strate trees" that span several fossil layers. (This also relates back to my earlier question of how we tell the difference between layers) I have searched and found responses in years-old topics from forums that I did not completely understand or that I would like to ask further questions of.

    In the interest of honesty I'll reveal that I'm a creationist, but don't label me as irrational and ignorant. I'm trying to gain a real understanding of how what the geologic layers are, how it is believed that they were formed, and how it relates to fossils and dating, because whenever I read things I have questions and you can't ask authors to clarify, expound, or rebut.

    Thank you for any responses to all or any of these questions.


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    WYSIWYG Moderator marnixR's Avatar
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    obviously there is no one area where the complete geological column can be examined layer after layer

    what happens is that local geological sections can in many instances be compared with other sections nearby or further on the basis of lithological criteria, fossil content and relative alterations of consecutive strata

    this was the only method available until radioactive dating came on the scene, but even then, a good consensus was already achieved on the broad outlines and relative age of the various portions of the geological column

    the first principle applied is that of superposition, i.e. unless the strata have been disturbed (e.g. during mountain building) younger layers lie on top of older ones
    the second one was the recognition that strata of a certain age often had characteristic fossils in them which consistently matched the age inferred from the superposition principle - having 2 independent methods that cross-check one another is a great way to suss out apparent anomalies

    this relative dating could be put on a more firm footing in terms of million years old with the advent of radio-active dating, which, as you rightly say, can only be applied to volcanic material, which does not appear everywhere
    however, volcanic layers are common enough to be able to date several portions of the geological column in various parts of the world - combined with the 2 other methods cross-correlation of various sections across the world form a consistent enough picture of the geologic column to be pretty confident of its reliablity, especially when applied to the most recent 500 million years

    as to why certain parts of the geologic column are found in one place, and others elsewhere, just apply the principle that sedimentation usually takes place in the sea or in lakes and that most parts of dry land is prone to erosion - sedimentation produces strata of a certain age, erosion takes them away


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    the first principle applied is that of superposition, i.e. unless the strata have been disturbed (e.g. during mountain building) younger layers lie on top of older ones
    so upper layers are younger unless they're not? I guess that makes sense...

    the second one was the recognition that strata of a certain age often had characteristic fossils in them which consistently matched the age inferred from the superposition principle - having 2 independent methods that cross-check one another is a great way to suss out apparent anomalies
    Please clarify. Does "strata of a certain age" refer to identifying ages by the compositional characteristics of the layer? If so, why would one age lay down a similar type of sediment over the entire planet, and why would it change to form a new age?

    Or are layers identified by the types of fossils found in them? If so, then of course, by definition, one layer in different places will have the same characteristic fossils ~ if it didn't, it wouldn't have been labeled that layer in the first place. That would tell us nothing.

    Or do you mean that each layer, with its own composition, consistently had the same kinds of fossils in it? Then you'd be on to something, although that still wouldn't tell us that each given layer was laid down at the same time as all of the other similar layers... and if so, that goes back to my first question: why shouldn't different types of sediment be deposited at the same time at different parts of the world? Is that more likely than the entire world depositing an identifiable layer for millions of years, and then switching to a new kind of deposit? Or is that not even how it works?
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    Quote Originally Posted by General Veritas
    the first principle applied is that of superposition, i.e. unless the strata have been disturbed (e.g. during mountain building) younger layers lie on top of older ones
    so upper layers are younger unless they're not? I guess that makes sense...
    Layers are initially laid down with younger layers on the top, but they can be overturned by tectonic activity. There are a number of "way up structures" that can be used to tell if layers have been overturned.


    why shouldn't different types of sediment be deposited at the same time at different parts of the world? Is that more likely than the entire world depositing an identifiable layer for millions of years, and then switching to a new kind of deposit? Or is that not even how it works?
    What makes you think they are not? You get massive variation in what is deposited at any one time. Look at the lower carboniferous in Britain- shallow water limestones surrounded by deep ocean shales across much of England, and river deltas advancing from the north all forming at the same time. Deposits at any one place change over time too. Again in the British carboniferous, you can see the progressive change from offshore deep water shales through to deltas and then rivers and swamps on the delta tops as the deltas progressively fill in the ocean basins.
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    Quote Originally Posted by The Matt
    Quote Originally Posted by General Veritas
    the first principle applied is that of superposition, i.e. unless the strata have been disturbed (e.g. during mountain building) younger layers lie on top of older ones
    so upper layers are younger unless they're not? I guess that makes sense...
    Layers are initially laid down with younger layers on the top, but they can be overturned by tectonic activity. There are a number of "way up structures" that can be used to tell if layers have been overturned.
    Alright, thanks.


    why shouldn't different types of sediment be deposited at the same time at different parts of the world? Is that more likely than the entire world depositing an identifiable layer for millions of years, and then switching to a new kind of deposit? Or is that not even how it works?
    What makes you think they are not? You get massive variation in what is deposited at any one time. Look at the lower carboniferous in Britain- shallow water limestones surrounded by deep ocean shales across much of England, and river deltas advancing from the north all forming at the same time. Deposits at any one place change over time too. Again in the British carboniferous, you can see the progressive change from offshore deep water shales through to deltas and then rivers and swamps on the delta tops as the deltas progressively fill in the ocean basins.
    Good, I'm learning things. Specific examples help a lot. I'm assuming that the limestone and shales of the British lower carbonifeorus are not radioactive. How do we date that?
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    Well, we can obtain relative dates from looking at how the rocks lie in relation to one another- we can say A is older than B which is younger than C etc. There are also some lavas in the limestones which can provide absolute dates.

    This is also where the fossils come in. Just to put this in to context- during the time the deltas were forming, we know that the sea level changed rapidly because we can see shallow water and river deposits overlain by marine deposits, which in turn are overlain by more shallow water deposits. The marine layers contain fossils called goniatites, and their shell structure changed subtlety but quickly throughout the period meaning that normally there is a visible difference between those in one layer and another, therefore if we find the same fossil in two rocks 100 miles away, we can say with some certainty that they were deposited at around the same time.

    Fossils that allow us to do this are called 'zone fossils' and are very useful for dating. This also means that if we have an absolute date from radiometric dating for just one area that contains a zone fossil of some sort and we find the same fossil elsewhere, we can put the same date to this rock too.
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    WYSIWYG Moderator marnixR's Avatar
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    should you be interested, a nice book showing the initial detective work behind finding out about the geological column is The Map That Changed the World: William Smith and the Birth of Modern Geology

    basically it shows how William Smith in his capacity as a surveyor (mainly for digging canals in late 18th century britain) started to see repeating patterns of deposition which enabled him to predict the geological succession in areas he had not yet examined

    this was a purely empirical method and did not depend on evolutionary ideas (which did not really become mainstream until half a century later) or absolute dating

    in the 19th century other geologists tried to apply similar methods to areas outside the UK and (presumably to their amazement + delight) found that the principles developed for britain could be expanded across europe and further afield
    "Reality is that which, when you stop believing in it, doesn't go away." (Philip K. Dick)
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