As I understand it -- and you can deny it all you want -- the fossils are dated by the rocks they are found in; and in some cases, the rocks are dated by the fossils found in them.
I could be wrong, but if I err on the side of science, I haven't lost anything.
Rocks are dated by two methods:
Absolute ages
Relative ages
Absolute ages are those derived from physical measurement of time, such as by radioactive decay. We can date various
sedimentary strata if they are near something like a volcanic ash flow layer. If the strata are below that layer we know they are likely
older than that layer (Law of Superposition).
Relative ages are when we see which layer is older than another. Is it above or below a layer? Is there evidence that the layers have been overturned (yes geologist look for "raindrop impressions" in rocks and other ways to determine original orientation of the strata).
As to your point about the fossils here's how the details work:
Fossils are mapped and if we find a particular type of fossil shows up ONLY in certain "time frames" and never really outside of that time frame we may use it as what is called an
index fossil. That will pin the rock layer to a timeframe that is defined by the existence of that Fossil. Now this doesn't give an ABSOLUTE AGE unless there is a way to measure an "Absolute Age" as mentione above (say through radiometric dating of layers nearby).
BUT once dated it may be possible, after years of establishing the limited "scope of time" that this fossil is found in to say "Ahh, this species of trilobite occured in the late Cambrian" so when we see that species of trilobite we may, indeed, estimate that the rock it is in is from the late Cambrian.
THIS is exactly the kind of stuff that makes up paleontology literature. If someone finds that an index fossil falls
outside of that time frame they will revise the timeframe that the index fossil covers. Say someone finds a bunch of those trilobite species in the
early Ordovician as well and they extensively test to make sure the fossils are not "reworked clasts" (recycled bits of rock that got into an Ordovian age rock formation...remember things like sedimentary rocks are made up of bits of often
older rocks) then they will re-establish so that the index fossil now can be late C- early O . They will not "re-date the entire geologic column", they will not "rework all of evolution to make it fit", they will readjust what the existence of that index fossil means when people see it.
There is also something in geology called
Faunal Succession in which we find that an animal's form
changes over time. AND we have never found a "rabbit fossil" in the Precambrian. We see certain life forms in the rocks that
never occur together and some that occur together.
If I find a "rabbit fossil" I will know that it is likely
not the Precambrian. In fact I'll know it is millions of years later because of nearly 150 years of observational science repeatedly finding how life developed over time.
NONE OF THESE THINGS ARE "GOSPEL". They are based on observed science. Hundreds of years of people finding rocks and fossils and looking at them and recording which ones are together and which ones are not.
The thing I find fascinating is: geology at its heart is pretty "common sensical". It really doesn't take an Einstein to make it through the first couple years of geology classes, yet I find creationists almost never seem to have darkened the door of a geology class. I'm not saying geology is "simple", because it does require at least
some effort to learn it, and it can become quite complex the deeper you go. But I'm always amazed at how
little creationists know about geology, yet they talk so
big about it.
I would love to know why Creationists seem
scared to death of taking even a couple of intro geology classes. It is a mystery to me. Are they scared of the information? Are they scared that their "preconceived notions" of what geology actually entails will be challenged? Or is it safer to sit a distance away from the topic and throw rocks at it?
Just curious.
