This attempt at a new topic is a result of message 347
at the "Why is evolution so controversial?" topic. That topic has a pretty good discussion going. Unfortunately that discussion has wandered very far from the original topic theme.
That message 347 writes:
Pretty damn bogus reply.
I can't see AT ALL how the deep ocean basin deposition model really has anything to do with any with the sediment deposition of the Grand Canyon area rocks. At best, MAYBE the bottom-most pre-Cambrian rocks that are now high grade metamorphics MIGHT have some sort of deep ocean origins. MAYBE.
Maybe you are right.
I assumed that the limestones and shales were from an ocean deposition and I thought the sandstones were from deposition closer to continental shelf. Obviously, the crossbedded sanddune deposits were deposited when it was dry land.
Can you tell me what the depositional environment was?
The accumulations of sediment you can point to here and there are paltry little collections by comparison.
It seems to me that deposition happening in the present in the Pacific cannot be described as here and there or paltry on a timescale of millions of years.
Now, some of the sediments of the Grand Canyon and are are of non-marine (above sea level) origin, but here I'm going to try to focus on depositions of on to/off of the continents sea transgressions/regressions.
A (the?) central focus of said are sedimentary facies and Walther's Law. I've tried in the past to find good Walther's Law references and graphics, and have never been real happy with what I've found. Go ahead and Google "Walther's Law" and see what you can find.
One (sort of) good starting point I did find is facies
. Please also look at this
Basically, Walther's Law is that, in sea transgressions/regressions, the coarsest clastic sediments (sand to become sandstone) are deposited nearest to the shoreline. As you go further from shore (and deeper) the clastics get progressively finer to silts (siltstone) and then clays (shale). As you get far enough from shore the clastic sediments become less and less until what sedimentation you have left happening is carbonate (limestone).
For a sea transgression, this results in a vertical sequence of upward fining - Sand at the bottom, carbonate at the top. For the sea regression, the order is opposite - Carbonate at the bottom, sand at the top.
The transgressive sequence:
Source is "Please also look at this" link, above. There are also other diagrams and explanations at that site.
Well, not a prize winning PNT, but perhaps it will work to get geology discussion back into a geology topic.
Edited by Minnemooseus, : "vertical sequence of upward fining" not "vertical sequence of upward coursing(sic)"