Long build up of Sediments

I have to jump in here. Faith wrote:

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Again, the more I think about this, the more difficult it becomes to imagine where such an incredible depth of sediments could have come from under the gradual accumulation theory. Kilometers of depth?

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Here's something to think about, Faith: If we accept, as you argued yesterday, that the global Flood was only 15 cubits (~7 meters) deep, how could it have deposited sedimentary layers several kilometers thick? Please address this, as I would be very interested in hearing an explanation for this.

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The rate of deposition affects the plausibility of fossilization, for one thing, which requires more than just burial to prevent decomposition, which is a pretty rapid process under most conditions. What all it requires I'm not sure, compression at least I think, oxygen depletion perhaps?

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All that, yes. Anoxic environments help to prevent decomposition. And finally, diagenesis/lithification.

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But about the fastest rate of deposition I can come up with, even given kilometers of depth accumulated in the usual millions of years alloted to a given layer, is still only about a maximum of a foot a year and I don't see how even that rate would favor fossilization.

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First, let's clear up another misconception you seem to hold to: Fossilization is not common. We may have found hundreds of thousands of fossils, maybe even millions, but this is only a fraction of what would have once been alive on earth. You yourself just admitted above that it takes some very special conditions for fossilization to occur (rapid burial in fine sediment, anoxicity, etc.) Typically, dead bodies don't get covered in sediment and are left to decompose in the elements.
Second, your above logic fails because you keep making reference to 'average deposition rates' within an entire sequence. These rates do matter with regards to fossilization. What matters is the rate of deposition at the time the fossil was burried. Say I bury a corpse under two feet of sediment within a year, and then the rate of deposition in the area drops off to just a few centimeters a year for the next hundred years (say, due to retreating sea levels). If you average out the overall depositional rate within the entire deposit, it might seem to you that the average rate of deposition is not enough to favour fossilization, but you should be able to recognize that this isn't the case.

Faith wrote:

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You want me to believe that the deposition of one kind of sediment came to a screeching halt and was immediately followed by the deposition of some other kind of sediment as a result of mountain building etc.

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No. Typically, adjacent layers of differing rock types are separated by unconformities, representing x number of years of non-deposition.

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It seems to me that half the land area now in existence must once have been at the bottom of the sea considering how much of this layering makes up its mass and how much must be explained by underwater formation. Or what is geology's estimation of this?

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You're absolutely right. For example, here in North America, there once stretched a giant seaway called the Western Interior Seaway (in the Cretaceous). In a package of strata (known as the Bearpaw Fm or the Pierre Shale) found here in Canada, we can find fish, and sea-going birds, and mosasaurs, and turtles, and plesiosaurs -- all evidence that North America was once covered in a great inland sea. Note that this 'marine package' of strata that I'm referring to is bound both above and below by terrestrial strata, bearing terrestrial fossil animals (dinosaurs, little mammals, birds, lizards, etc.).

Faith wrote:

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Are these unconformities ever seen dividing the SAME rock type, right through a layer instead of between layers? Why would nondeposition always occur only at the end of a long long period of deposition of one kind of sediment and not during?

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Yes, we see unconformities even between same rock types.
But just to clarify, when you're talking "same rock types" are you referring to entire sequences such as the "Devonian Period" or the "Triassic Period"? Because I get the impression that you think these sequences all contain exactly the same type of rock. They don't. Cretaceous rocks, for example, may contain a whole slew of different sediments layered on top of one another, including marine sediments, terrestrial sandstones, mudstones, bentonite, etc. These major sequences are typically classified based on a particular pattern of sediment they might show (facies), or based on the kinds of fossils they exhibit, or any number of other objective factors (geochemical signatures, etc.). It might do you some good to do some reading about 'facies concepts', for starters on this issue.

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Interesting. I thought the order of fossil deposition always had the more "primitive" on the bottom.

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If we look at the entire geologic column from top to bottom, yes, that is how it appears. But the example I just gave you (about the fossilization of the Western Interior Seaway) is just a VERY small slice of the pie. In this instance, we don't see major new body types developing in this slice of the Cretaceous. At this level, we see species and faunal turnover, as the terrestrial rocks gave way to more marine rocks (a sign that the WIS was encroaching on the land). Also, don't make the fatal mistake of assuming that just because some particular species are confined to the ocean, that that somehow makes them more 'primitive'.

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And of course an inland sea fits well with a global flood.

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Not if the strata suggesting the presence of such a sea are bordered above and below by terrestrial sediments (as they are). Also, if the sea were left by the Flood, then we would expect to find more than just a few certain types of marine fossils in the sediments. The flood ought to have killed more terrestrial animals, than anything. How could a flood possibly deposit marine animals on top of terrestrial animals on top of marine animals, etc? One would expect all the different types of marine and terrestrial animals to mix during such an event; but we don't see that in the fossil record.This message has been edited by Mallon, Mar-12-2006 10:37 AM

Faith wrote:

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I assume that even if there are mixtures of sediments that the dominating sediment exists in dramatically large proportions in the entire layer. Is this false?

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I wouldn't say that's false, no. I wouldn't use the term "dramatically large proportions", though, either. Again, these major rock sequences aren't so much distinguished by a single type of rock as by a recognizable pattern or succession of rock types.

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I really have no idea what you are saying here, sorry.

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I am simply saying that the progression from "primitive" to "advanced' body forms are only seen when we look at the fossil record from a broad perspective.

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I figure it's up to the evolutionists to define primitive, but I did have the impression that the bottom layers of the geo column are mostly small marine creatures.

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Scientists typically avoid using terms like "primitive" or "advanced" because of the connotations they carry with them. I am using them here to simplify things for you (otherwise I would use terms like 'synapomorphy', 'plesiomorphy', etc.). But you're right, at the very bottom of the geologic column, we find small, simple marine creatures -- amongst the earliest forms of life on earth. And in those marine strata preserved higher up in the column (such as in the WIS strata I've been alluding to), we find much more advanced marine creatures (mosasaurs, plesiosaurs, turtles, etc.). You will never find, say, a turtle in the lowest Cambrian rocks.

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Why not?

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Because a worldwide Flood does not deposit terrestrial strata. We would not expect to find footprints from terrestrial animals deposited during a flood, and yet we do find them. So either (a) the terrestrial animals were walking along the bottom of the floodbed as the water towered above them, or (b) the Flood is not preserved in the rock record.

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YOu mean just in this inland sea or everywhere? And why?

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Let's keep it simple and refer only to the one inland sea I brought up. And I explained to you earlier why would not expect to see the type of sorting that we do: catastrophic floods do not distinguish between terrestrial and marine animals as they are deposited. If you think otherwise, please explain why. If I threw a bunch of dead dogs, cats, fish, turtles, birds, and clams into the water, would you really expect all the terrestrial animals to settle out at different rates than the marine animals?

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It killed everything living. Presumably the land animals more frequently simply decomposed rather than being buried and fossilized.

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This is a big presumption to make. Why would that be so? All marine and terrestrial animals would be subject to the same environmental conditions as they lay dead at the bottom of the Flood floor.

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This is the problem with imaginative expectations. I find it just as hard to imagine how the strata could have formed by tiny steps over hundreds of millions of years as you do to imagine how the flood explains it.

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The difference is: we have evidence and experiments that can back up our claims. I have a hard time understanding math, as you do geology. But that doesn't pose a threat to the mathematical principles that have been in use for hundreds of years.

Faith wrote:

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I see how the rising and falling of sea level might be an explanation, at least of a stack of different kinds of sediments, although I still have trouble with the abrupt change in sediments from one to another.

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For another (very good) explanation of these sharp boundaries, besides the one I gave you (erosion surfaces), see this link:
lordibelieve.org/time/age2.PDF
(Happened upon it from a Google search.) Most significantly, see part 9: Sedimentary Deposition and Lithification.