With respect to Grand Canyon being carved by the receding floodwaters, I don’t know whether that’s the common understanding among creationists, but it isn’t my view – and neither is it Steve Austin’s view. Steve’s view, which I share, is that the canyon was carved by a catastrophic breaching event some time into the post-Flood era, which resulted in the drainage of large post-Flood lakes that had developed on the Colorado Plateau.

Nor do I think we are forced to hypothesize that organisms were building wave-resistant, framework-bound reefs during the Flood as some critics suggest, although it’s possible that in isolated spots where sedimentation rates were low some small structures of this kind might have developed. I suspect that the structures described as reefs in the Flood-deposited part of the geological record are mostly not reefs in that sense. Many are simply piles of transported reef organisms or fossil fragments floating in a finer matrix of carbonate mud. Others may represent re-deposited pre-Flood reef blocks. In addition, microbial blooms during the Flood probably played a role in rapidly binding loose accumulations of fossiliferous carbonate mud – the importance of microbes for depositing and lithifying carbonates being increasingly recognized in the literature.

On mud cracks, John Whitmore’s chapter in Rock Solid Answers reviews the various kinds of cracks that occur in the sedimentary record (including desiccation cracks, synaeresis cracks, diastasis cracks, molar tooth structures, clastic dikes and sand intrusions). He describes the characteristics of each based on surveys of the relevant literature and highlights some of the problems of identification and interpretation. As John points out, mud crack horizons need to be carefully studied to see whether is actually evidence of desiccation and he implies that many times conclusions are reached on inadequate evidence.

No, you did not claim that the receding floodwaters carved the Grand Canyon. I assumed you believe as much because this is the common understanding among creationists. Steve Austin is often quoted on this matter, and I have not seen any creationist contradict him. If you have a different interpretation about how the canyon formed, I would be interested in hearing it.
You also made no mention of reef formation during the Flood, but this must have been the case as reefs are known from throughout the fossil record.
I don’t have access to the Whitmore article you cited. Does he make the case that all mud cracks in the sedimentary record are syneresis cracks? This is the creationist argument I’m familiar with, though I don’t find it likely.

Reference

Whitmore J. 2009. Do mud cracks indicate multiple droughts during the Flood?, in: Oard M., Reed, J. K. (editors), Rock Solid Answers: The Biblical Truth Behind 14 Geological Questions, Master Books, Green Forest, Arkansas, pp.167-183.

I’d also advise a little caution when you proclaim the evidence for underwater deposition of the Coconino to be “shaky”. The team I’m working with has been intensively studying the Coconino Sandstone for the last several years, with hundreds of hours of fieldwork, literature review and petrography behind us. I can tell you that many of the confident statements about the Coconino in the published literature are incorrect and can be shown to be so.

The earth was completely covered by day 40, and the land animals and birds were dead by day 40, or soon enough thereafter to make no difference (some birds might have survived for a while by flying – Albatross for example).

So within that 40 day window of time, the waters had to rise at least a mile, probably more. That’s over 130 feet per day! Afterward they may have continued to rise, but you know by at least day 40 the land was completely covered and all the animals were dead.

With water rising like that (ripping up and depositing massive amounts of soil which just points out these were NOT calm waters) there’s no opportunity for the up and down, up and down motion to be bringing land in and out of the Flood waters and land animals to survive swimming in that environment and be washed in and out, in and out, in and out to leave their tracks and build their nests.

Rinse and repeat multiple times, all within 40 days!?!

There are tracks in each and every layer of strata all the way down through the Cambrian (and below, but some things I’ve read have put the Cambrian as the first Flood layer, which causes its own set of issues) – which means there must have been dozens of instances where a section of land came back up above the waters, animals left tracks, and then the land went back down (or the waters again rose over it – 130 ft per day, remember).

How do you get tracks in different strata AND in different layers within the strata on top of each other? Permian, Triassic, Jurassic, Cretaceous, etc, etc.

With the land appearing and reappearing time after time after time, with hundreds of feet of sediment being deposited constantly, presumably with currents strong enough to be moving said sediment, how on earth can there be animals surviving swimming for days/weeks on end (and many of those animals, like Acrocanthosaurus for example, REALLY weren’t made for swimming!) to be washed in, time after time after time, to keep leaving prints and nests?

On one hand you seem to be requiring a relatively calm water environment for animals to be able to survive swimming for extended periods of time.

Then you also need incredibly violent waters rushing along to rip up, transport, and deposit soil.

You need extremely violent tectonic movement to shove land up dozens of feet to get above the waters, and you need it to happen many times in that 40 days, and then you need the waters to again over take the land, or have the land sink back down. (violent tectonics doesn’t suggest swimming waters for animals) Let’s say it takes 10-15 days for the waters to flood the ground the first time, and then it’s all over (for the animals) by day 40 at the very latest – that gives around 25-30 days for the different layers of tracks to be laid down? (there’s an area in Massachussetts that has 20+ different layers with tracks in all of them!) That’s what? A day for each entire cycle to happen, up and down. (and any animals swimming would be washed AWAY from the uprising land)

But you also need for the animals to have time to do things like building nests which takes a lot longer than a day or two.

You have wildly conflicting needs. Flood geology seems to make rationales for specific possibilities without considering the larger picture.

Wild waters vs Swimming waters.
Rapid up and down tectonics vs time for animals to do things like nests.
Deep, rapid water for sand waves vs slow shallow water for some prints.

It’s one thing to say something internally-coherent, and then argue about evidence pro or con.

It’s a totally different thing for the proposition to have self-contradictory requirements.

Are there other studies that show sudden ratio changes of any sort between the pre-Cambrian and later layers like the Ordoclavian, Silurian, etc?

Especially if the RATE study is taken seriously with its claim of million times faster radioactive decay during the Flood, various ratios between all sorts of elements should be drastically different in the Pre-, Intra-, and Post-Flood soils.

(I’m asking this somewhat facetiously since I already know the answer is a “No.” Mainly I’m interested in an idea for why they aren’t drastically different.)