Where would you get enough scavengers to fully eat, destroy and scatter the bones of a 75 whales more quickly than surf and sand can bury them?
Or if as LachlanMinnesota theorizes they were washed ashore by a tsunami, they would have been stranded at some distance from the beach, well above the high tide line. This would prevent the bodies and bones from bring scattered by tidal action.
The west coasts of the Americas tend towards dry and desert conditions, not many large predators as there simply isn’t enough food to sustain huge populations. It’s a race between few scavengers, dessication/mummification, decay and burial by wind blown sand, slit washed down from higher ground (you do know that there’s a whole continent of higher ground inland from the beach, right?) and ash from any number of Chile’s active volcanoes.
You assume the bodies had to be buried quickly. You base this entirely false assumption on HUGE numbers of MASSIVE predators and scavengers instantly descending on the beach and tearing 75 whale carcases to tiny bits and chewing telephone pole sized bones down to gravel every time there is a stranding.
Perhaps something like this does happen 99% of the time. There are, after all, a few mass strandings a year even now. Over the 6000 years of time even you will admit to, that’s say 10,000 cases? 1% of 10,000 would leave about 100 fields of fossilized whales.
Of course in the absence of lots of really MASSIVE predators, the carcases would collapse down from ten foot tall mountains of rotting flesh to one foot tall piles of bones (other that gravity, not much moves them, so they would still be more-or-less articulated, the ribs would stay in the middle, the jaw and skull would stay on one end, the tail on the other, etc.) in a year or so. It doesn’t really take all that much sand, ash, and silt to entomb them at that point. Anyone who has lived in the desert or through America’s dust bowl has swept that much out of their house in the course of a year!
Once buried, there is plenty of time for groundwater to infuse them with minerals (Unless you insist on the entire universe being a few millennia old, then you’re back to “God did it”).
In the mean while the same tectonic forces that caused the earthquake that triggered the initial tsunami haven’t stopped, indeed they are still active today, and the west coast of Chile is rising at an average rate of about a millimeter a year, más o menos. At about 2,000 to 2,500 m elevation and 1 mm a year rate that says the desert was at sea level 2-1/2 million years ago, within the 2-7 million year estimate for the age of the fossils.
Unless, of course you insist “God did it” in less than 6000 years, in which case he could do anything he darn well pleases, and ANY attempt to understand the universe is doomed from the start.
Worse, you have a god who deliberately plants false clues to deceive the inquiring mind, a trickster, a Prince of Lies.
If you look at any beaching, the corpses rot rather quickly, and if left to the motion of the waves, the bones get worn down by normal, pedestrian forces over a few years.
Unless they can be significantly moved away, tidal action is still problematic.
The other posters theory of a tidal wave might explain getting the corpses above tide line, true. If you assume the tidal forces were not acting on the corpses, then burying/covering the bones with a subsequent volcanic event makes sense.
As far as the 'dry and desert conditions' goes, you are projecting the current conditions backward.
In any case, if we ASSUME the present conditions also existed 2.5 million years ago, the dessicated bones would still wear to nubs with the sand/tide friction acting on them, unless of course, they were not subject to tide action, which has been my point.
A tidal wave stranding the corpses in a low lying area away from the beach, followed by a volcanic eruption or other stratifying event is plausible.
Plate tectonics are too slow, UNLESS you allow for rapid motion in the past, not a millimeter a year.