[dead]

I understand carbon dating and all that, but I never understand this part:

They know how old the rock is, but how do they know when the rock became an arrowhead?

And they know how to date the surrounding soil, but how do they know when something came to reside in that soil? When did humans first invent burying stuff?

[Red Badger]

I assume that the arrowheads were embedded in some organic material that could be reliably dated, but carbon dating is good only for about 50k years. After that you have to use some other method..............

http://en.wikipedia.org/wiki/Carbon_dating

[Sacajaweau]

I’m always screaming about this “dating” bit with the same logic. In 1989, I was on a lonely road in Virginia, got out and with real mason tools, carved 1789 and initials in an old boulder just a bit off the road....I would love it if someone defined the initials and date someday...and it got a big write up.

[null and void]

They know how old the rock is, but how do they know when the rock became an arrowhead?

Cleaving rock exposes a fresh surface, that surface oxidizes and hydrates slowly over time.

If you know the minerals and know the rates of oxidation/hydration, and can measure the depth of the altered crust, you can get a pretty good idea of how fresh the surface is.