https://onlinelibrary.wiley.com/doi/10.1111/sed.12724 gives a current overview of tsunami sedimentation. Carefully going through the references in that will give a good idea of what should or shouldn’t be present in tsunami deposits.
Mid-ocean rifting is generally pretty calm. You seem to be envisioning a solid plate suddenly breaking in two, but even that would not be good at generating tsunamis. Earthquakes that move significant amounts of the underwater crust up or down are good at making tsunamis. Plus, the seafloor deposits indicate a slow, gradual production of new seafloor at the ridges since around the beginning of the Zuni sequence (most older seafloor has been subducted away and can’t be checked).
Subduction is much more likely to generate tsunamis. However, tectonic-caused earthquakes cannot get much bigger than the largest experienced in historic times. You could produce more big earthquakes if the process of plate motion were given more energy, but rock can only take so much energy before it will break. Roughly a moment magnitude of 10 is the biggest possible. Of course, you also need to explain where that extra energy is coming from and how come all the extra heat doesn’t vaporize the earth, given the second law of thermodynamics and the amount of plate motion that occurs in a short time under a young-earth scenario.
It is possible to have a larger earthquake and tsunami if the cause is not internal. An incoming asteroid can produce a bigger earthquake, up to about magnitude 15, which would destroy the planet. Even a bunch of magnitude 10 quakes would likely be causing problems for the ark.
Again, if these waves are being generated in the Pacific, they should wash from the Pacific. But the sedimentary record shows a gradual rise of sea level all around the edges of the continent. Carbonates are not the finest, and you are mixing up the Stokes law aspect with Walther’s law. The Walther’s law pattern is NOT compatible with a tsunami. It is the pattern produced by gradual change in sea level or other environmental parameters. Stokes’ law (with modifications in light of the shape variation) explains the bigger/heavier particles settling first and finer/less dense last. As the backwash from a tsunami wave carries mixed sediment back into the ocean, we should see this type of pattern. But the Tonto group has sand not just to the bottom, but to the uphill/inland side. The shale was deposited in deeper/more offshore water while sand was being deposited shallower. Limestone dominated yet further from the land while sand was being deposited near the beach. The trace fossils indicate plenty of time involved in the deposition, not a single tsunami. The forewash of a tsunami would produce a jumble including big stuff near the coast, then as the flooding water slows down there would be mostly sand, with the silt-size furthest up. Carbonate would not be separate; carbonate comes in various sizes and would be mixed in with similarly sized non-carbonate in a tsunami, so the presence of a carbonate unit as part of a sequence stratigraphic unit does not fit with a tsunami explanation. The occasional relatively complete fragile fossil in fine-grained sediments is typically associated with evidence of low oxygen levels, though occasional rapid burial in a landslide or the like does happen, and mud underwater can be very soupy and allow things to sink in quickly. Low oxygen requires little mixing of the water, which doesn’t fit with loads of tsunamis.
A tsunami would not result in large ocean sediment deposits all along the west coast. It would result in deposits of very mixed ocean and terrestrial deposits. The deposits indicate a calm rise in sea level, not a tsunami. You need to think through the implications of your hypothesis, check the evidence, and then change what doesn’t work in the hypothesis, rather than claiming that the hypothesis is supported by evidence that actually contradicts it.
