Does accreted terrain have significance on EvC geologic debates?

It's possible I missed this discussion somewhere but I am wondering if the evidence for accreted terrain theory has been dealt with at all by the Creationist camp. For those not in the know the theory (in simpllified form) is that as the North American continental plate moved across the pacific it bumped into other land masses and added (accreted) new territory to the western edge.You can read more about this at: Requested Page Not Found (404) , and follow the "geology" link to learn more as well as other theories regarding the formation of the terrain. I will note however that competing theories still require much time to accumulate the land present as well as build it's height.I am interested in two things:1) From geology, what is the exact difference in material which allowed "new terrain" to be distinguished from regular continental plate terrain? While I have studied geology the exact nature of the material was not discussed and I'd love a good synopsis of how and why that theory developed based on what was seen. Is it good enough to defy "Flood" explanations. From what I know I think it is, but I'd love to see a robust answer from a more professional geologist.And more to the point...2) From Creationist geologists, what can account for the "accreted terrain"? It involves not just creation of rock but a change from one environment to another. That appears to defy a simple "washout" flood explanation.

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holmes
"...what a fool believes he sees, no wise man has the power to reason away.."(D. Bros)

Thread moved here from the Proposed New Topics forum.

Hmmm... interesting question... considering I was thinking about this last night as I was reading some literature on this very subject. Weird.Anyway... Primary methods of recognition might be:1) abrupt change in rocks from one area to the next or across some boundary
2) abrupt change in fossil types
3) abrupt change in paleomagnetism
4) abrupt difference in metamorphic grade across a boundary
5) abrupt differences in age datesOnce one or more of these contrasts are recognized, one can delve deeper.For example, in my study area, which happens to be right at one of these 'suture' zones, I have miogeoclinal rocks that formed on a continental platform - shallow-water sedimentary rocks like sandstones, limestones, etc. - all north of the suture. They are metamorphosed to some degree, however, not so much that they are unidentifiable. South of the suture, I have metamorphosed volcanic and sedimentary eogeoclinal rocks along with large mafic intrusions showing variable degrees of metamorphism. Pillow basalts have also been recognized. Also, the suture shows right-lateral movement and metamorphic grades differ across it.Age dates have shown Archean (and younger) rocks are only found to the north of this suture, while no rocks older than Late Proterozoic (~ 1.8 Ma) are found south of the suture. The oldest rocks south of the suture are the country rocks composed of gniesses that have been intruded by younger mafic and felsic rocks. In addition to this, age dating shows that rocks get progressively younger as you move south of the suture.The data indicate that this suture marks the boundary between Archean basement to the north and progressive continental growth to the south via accretionary tectonics. What was being accreted and obducted onto the Archean basement, were strings of island arcs that developed out in the sea, south of the Archean basement, as a result of a subduction zone.Within my study area, there are several episodes of igneous intrusion, many of which have been age-dated. The dates always match cross-cutting relationships.How this defies the Flood? I'm not really sure. Progressively younger age dates to the south are a good indicator, not only of antiquity, but of consistence. Age dates wonderfully correlate to lithologic and structural relationships as observed in the field. I'd have to look back to see what came first, though, the theory of accretionary tectonics or age-dating - in other words, did one confirm the other?Additionally, Archean-Proterozoic boundaries are often excellent areas to conduct mineral exploration studies as it is a well-known fact that many of the largest ore deposits occur at such boundaries. In my area, this is somewhat the case with much mineral wealth found further south along northeast-striking structures that parallel the northeast-striking Archean-Proterozoic suture (which is also a right-lateral shear zone). So any YEC theory would have to address these particular issues as well.I haven't thought much about how these data would affect YECism at this point, so I don't have much to offer as of yet.This message has been edited by roxrkool, 10-27-2004 01:17 PM

That's a nice start to answering the first question. I'm glad to see I'm not the only one to not have a definitive answer.As far as it's impact on Creationism I'd like to see if it has an effect without necessarily bringing in age dating techniques, since that seems to be such a problem with many YEC'ers.It seems to me that the actions required for the formation transport and alteration of rock in that region, all indicate something grander than a flood mechanism. And unless they are simply going to say God whipped it up to be like a jigsaw puzzle of rock material that just happens to suggest a conveyor belt effect, I'm at a loss for how it can be explained by their theories.

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holmes
"...what a fool believes he sees, no wise man has the power to reason away.."(D. Bros)

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2) From Creationist geologists, what can account for the "accreted terrain"? It involves not just creation of rock but a change from one environment to another. That appears to defy a simple "washout" flood explanation.

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--And you are correct. The geomorphology of accretionary prisms cannot be accounted for by some simple "washout" flood explanation. Catastrophic Plate Tectonics by means of runaway subduction is far too complex for most YEC's to consider, however CPT is required to explain copious geological and geophysical aspects of the ocean floor--including accreted terrain--for a young earth.This message has been edited by TrueCreation, 01-02-2005 00:28 AM

But HOW does CPT explain accreted terranes? For example, in areas that appear to represent several generations, ages, and terranes of island arcs (intercalated volcanic and non-volcanic sedimentary rocks intruded by igneous rocks).There must have been enough time to form these island arcs in the first place and what would have been the mode of formation for these island arcs?Also, what do you mean by the geomorphology of accretionary prisms?

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But HOW does CPT explain accreted terranes? For example, in areas that appear to represent several generations, ages, and terranes of island arcs (intercalated volcanic and non-volcanic sedimentary rocks intruded by igneous rocks).

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--The same way mainstream PT explains them. CPT is, to a first approximation, is PT on fast forward. I do not doubt that there are specific aspects of accreted terranes that may potentially conflict with that, but the mere existence of accreted terranes is not surprising.

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There must have been enough time to form these island arcs in the first place and what would have been the mode of formation for these island arcs?

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--I presume the same basic mechanisms involved in conventional PT theory would be applicable within CPT.--My time away from the geological literature may have been showing when I refered to the geomorphology of accretionary prisms. The geomorphology of accretionary prisms that I was refering to were the compressional features.

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--The same way mainstream PT explains them. CPT is, to a first approximation, is PT on fast forward. I do not doubt that there are specific aspects of accreted terranes that may potentially conflict with that, but the mere existence of accreted terranes is not surprising.

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I basically agree... with the reservation that CPT is truly imaginary. In detail, CPT cannot adequately describe many known features such as multiple accreted terranes. Those would need to evolve on their own, develop their own fossil assemblages, magma series, etc., and then move. You cannot do this all in a one year biblical timeframe. I also have a problem with accretionary wedges and CPT. Basically, I don't think you would get them in a Baumgardner scenario.