*sighs*
Great, so we have to explain absolutely everything then.
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From reading the technical paper I linked to earlier, it seems the lack of a coarser grained component (i.e., the conglomeratic sequence), points to a marine depositional setting rather than a terrestrial setting for the original proto-sediments; which is consistent with previous theories regarding the geologic history of that particular terrane.
I actually thought the same thing as soon as Rox mentioned that the conglomerates were absent. Conglomerates tend to be formed in terrestrial environments like river beds because the action of the river creates the rounded pebbles. So you tend to see conglomerates in river basins but not marine basins.
If we could see the original rock (i.e. unmetamorphosed) we'd know immediately if it was formed in a terrestrial environment or not, because terrestrial rock is red or orange, on account of the iron in the rock reacting with the air. Offhand I can't remember if you can still tell from the chemical composition of the metamorphosed rock (I haven't done metamorphism for years).
As well as that, any cross-bedding or similar structures not destroyed by the metamorphism are also indicative of how the rock originally formed.
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In another thread, I briefly touched on how the U.S. grew via island arc accretion south from about the Wyoming/Montana area. Wyoming is located on the Archean Wyoming craton and everything south and basically west are progressively younger accreted terranes - generally considered to be island arc terranes (volcanic island chains similar to Japan and Indonesia that develop along subduction zones).
Look, Rox didn't pull this out of her ass or something. (Believe it or not, part of Ireland formed the same way.) An accreted terrane is a term describing a geological section that was formed from slices of rock formations; so I guess what you see is individual slices or areas, all crushed together, consisting of rock formations similar to what we see in Japan and Indonesia. We assume that, as the formations are similar and there is evidence of uplift and other tectonic action that squashed them together, they may have formed like Japan and Indonesia. Hence "progressively younger accreted terranes - generally considered to be island arc terranes" - because the evidence in the rock indicates that this is the most likely explanation.
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According to the linked paper (Ilg et al., 1996), the protosediments which later became the Vishnu Schist, are remants of one of those island arc terranes that collided with the continent back in the Precambrian (early Proterozoic time?).
The Vishnu Schist is pretty old, but still - we see marine sediments, deformed and uplifted, which were intruded by igneous rock later. That's more or less consistent with what we expect to see in an island arc terrane.
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Evidence is given, but still the interpretations have that aura of fact. No contrary interpretations are suggested. There is no way to verify or falsify such an interpretation. This is what I find so frustrating about both OE and TOE discussions.
The evidence suggests this is the most likely explanation. We verify or falsify it by examining the evidence - if we see what we expect to see if our explanation is correct, then the explanation is somewhat verified. If we see something unexpected, or something that is not possible for our explanation, it is falsified.
Call it interpretation if you will, but that is what science is. Period. There isn't another 'interpretation' in this case because we don't have another that fits the evidence as well or better than our current one. This is not imagination, or speculation - it's called scientific investigation.
Imagination and speculation are more the creationist's forte.
"Gradually it was disclosed to me that the line separating good and evil passes not through states, nor between classes, nor between political parties either, but right through every human heart, and through all human hearts. This line shifts. Inside us, it oscillates with the years. Even within hearts overwhelmed by evil, one small bridgehead of good is retained; and even in the best of all hearts, there remains a small corner of evil." --Alexander Solzhenitsyn, The Gulag Archipelago
"Those who fear the darkness have never seen what the light can do."
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