Flesh Pit's time of deposit

The PBSO is in the Permian basin, but it had to of been deposited much earlier than the Permian. This is because the earliest rock found in the basin is from the Proterozoic eon, meaning it had to of been there before then, because there is no warping of the geological timescale of the Permian basin caused by the PBSO, so it had to be deposited in the Proterozoic. Then, we are left with the problem of water, it was submerged until the Carboniferous period, then was resubmurged in the late Cretaceous, and then resurfaced in the earliest Paleocene. This means it must have some water breathing abilities, but this gets complicated when it chokes on the rain on the 4th of July, so it most likely needs to adapt to water and the rain came in too fast.