I have lost count of the posts I've made to get Faith to acknowledge the existence in the geologic record of depositional environments. However, it doesn't take a genius to figure out that Faith cannot do so without completely compromising her Creationist worldview.
Her vehement and irrational denial of what the geologic record actually shows, is evidence enough for me. I have no doubt at all that she sees and understands what we have been showing her all these years.
Her fight here is nothing more than a desperate attempt to maintain her own dignity. It's not easy admitting you've been duped.
Why would I need to know any more about their criteria than that their theory tells them it must be so?
That is absolutely FALSE, Faith, and I would go so far as to say it is a lie. You should know that by now. In the privacy of my own home or your own brain, yes, we can say anything we want and hardly a person, outside of ourselves, would every be able to contest our statements.
But because geology is a science and geologists conduct a lot of research and write a lot of papers, our interpretations are scrutinized by thousands of other geologists and scientists. Our interpretations and conclusions (yes, yours included) must be reasonable, logical, and drawn exclusively from the rocks themselves. Not pictures of the rocks. I would be extremely surprised if you've ever gone outside and actually put your hands on the rocks and taken a close look at them.
If a geologist calls a contact "erosional," they have multiple pieces of evidence for doing so. We want to know the truth of how the rocks formed, not assuage our ego by supporting our alleged old-earth pet theory. For us, an old earth is a forgone conclusion, and no further evidence is required to prove it. What we seek to do today, is unravel the history of the rocks.
You absolutely DO have to have some "criteria" for why you're calling it one thing rather than the other -- whether you use mine or your own. But you have none. None whatsoever.
For one thing, the Vishnu did not start out life as a metamorphic rock. It's protolith are sedimentary and volcanic rocks. In addition, the Vishnu complex itself rests atop even older basement rocks (the Elves Chasm Gniess and the Trinity Gniess), which themselves have their own volcanic and/or sedimentary protoliths AND subsequent metamorphism PRIOR to deposition of the Vishnu protoliths.
For the older Elves Chasm and Trinity gneisses alone, this means that:
1) the protolith sedimentary rocks and volcanic rocks had to have been depositied by non-Flood-related sea water and volcanoes to several kilometers depth, 2) the rocks then had to undergo lithification, 3) the rocks had to be uplifted, 4) then weathered / eroded, 5) then surficially exposed, 6) then covered by more sedimentary and volcanic flows and who knows how much more sedimentary/volcanic material, to some depth, 7) then buried and undergone metamorphism 8) then uplifted, 9) then exposed to weathering and erosion.
Only after all these events can the deposition of the Vishnu protolith sediments finally start, which essentially begins the numbered sequence above, again:
For the Vishnu Metamorphic Complex, this means that:
1) the protolith sedimentary rocks had to have been deposited by non-Flood-related sea water and volcanoes to several kilometers depth, 2) the rocks then had to undergo lithification, 3) the rocks had to be uplifted, 4) then weathered / eroded, 5) then surficially exposed, 6) then covered by more sedimentary and volcanic flows and who knows how much more sedimentary/volcanic material, to some depth, 7) then buried and undergone metamorphism
Also! The entire package of rocks from the gneisses to the Vishnu complex were intruded by numerous igneous plutons, dikes, sills, etc. (the Zoroaster Plutonic Complex) during pre-, syn-, and post metamorphic events (i.e., more than one metamorphic event is suggested by the minerals and textures of the rocks). These igneous rocks take time to cool, too, and the deeper the emplacement of these igneous bodies, the longer they will take to cool.
It is only until after all the above has happened that the entire package of basement rocks can be uplifted, exposed to weathering and erosion, and form the surface upon which more sedimentary rocks (the Grand Canyon Supergroup) can be deposited -- this is, of course, the surface which we today have named the Great Unconformity. The fact is, this is only one of several major unconformities, it just happens this one is the easiest to recognize in the field.
And that, in short, is part of why the Vishnu is a problem for Creationists.
Limestone would have been laid down as per Walther's Law. It's laid down in rising sea water so certainly should have been laid down in the rising Flood water.
I would be interested in seeing your chemistry on how flood waters can precipitate and deposit thousands of feet of carbonate. Carbonate precipitates and deposits only under very specific conditions, none of which are reasonable during a global catastrophic flood.