It is how extrapolation works. We do not have data on the deaths of a sufficient number of whales to give an exact likelihood of preservation, but I am pretty confident that it is above 1/100,000,000,000, given the number of intact human skeletons we have.
They fall apart easily. The pieces of crinoids and bivalves are primarily held together by organic components and usually fall apart after death (bivalve ligaments are very tough organic components, and can last for hundreds of millions of years under optimal conditions). They are sometimes buried soon after death (or, in the case of bivalves that burrow under the seafloor, they may be buried before death).
And that is the point. They can also be unchanged for millions of years.
That’s what my question is based on too: a bucket of water from washing fossils sitting in the garage for a few days.
Not particularly, I focus on upper Tertiary deposits.
Yes, the order in some material that I am familiar with goes
Erosion surface, with riverine sand and freshwater clams
Abundant conoideas, and other mid-shelf taxa
Abundant shallow-shelf taxa like Oliva, Busycon, and truncatellidans
Beach sand with Donax and Crassostrea
Riverine sand with freshwater clams
Erosion surface
Which reflects a succession of environments in the same location, each around for at least a few decades (given that many of the large shells live that long).
I am talking about deposits which are primarily marine in origin.
With fossils in them which are much bigger than the individual sediment grains. The sediment which forms the matrix is sorted, but the deposit as a whole is not. Busycon contrarium (to 270 mm), Limacina (to 1.2 mm), and clay-sized mud (to 0.06 mm) present in a single deposit is not very size-sorted. Pyconodonte surrounded by lithified clay was not size-sorted after the Pycnodonte was alive.