Dirt is so important that archaeologists don't do anything so vulgar as actually dig it. They sort of gently coax it aside: "Please, Mr. Dirt Clod, would you kindly move?"
I know this because Heather Bouslog , assistant archaeologist for the Maryland-National Capital Park and Planning Commission, invited me to help excavate a Civil War-era site not far from the Chesapeake & Ohio Canal.
It's a neat little article and what he says is true so read the whole thing. One caveat though: Artifacts found in the same layer of dirt come from the same time, so it's important to know exactly what kind of dirt you're working with. Almost correct: artifacts in the same layer of dirt can be assumed to have been deposited at the same time; but they were not necessarily produced at the same time.