How long does it take for 4 feet of dirt to be laid down over old campsites?

Question

My daughter found an old arrowhead in some recently turned dirt which had got around 4 feet down.
Are there any good sites that can tell the age of something like that?
The area is near a lake, in a very dry, desert/mountainous place.

It was on private property that had the dirt turned for a septic tank a couple of years ago.
No flash flooding, lots of rainfall over the winter-- no people tramping around, as it is private property.

It was on private property that had the dirt turned for a septic tank a couple of years ago.
No flash flooding, lots of rainfall over the winter-- no people tramping around, as it is private property.
Oh, and yes, the homeowners know where she found it and when. She came in all excited to show them...

Answer 1

I looked around and couldn't really find anything beyond "take it to a local university and ask the anthropology people"

but gut feeling was "one or 2 thousand years" ... considering that if the dirt got 4 feet deeper there, it got 4 feet shallower somewhere else .. or the dirt came from somewhere else ..., so somewhere else "lost" that dirt .. hmmm ... dunno, but it's a nice question that's tough to answer
without seeing the "where" .. like if it's at the base of mountains, then the dirt would have likely come from erosion-effects on the mountain .. sorta makes you think about time in a global-millenia basis .. knida neat

Answer 2

Impossible to say without properly examining the surrounding area - could be days (flash-flooding, landslide), weeks (rainfall), years or centuries.

Now you've taken the arrowhead out of context, it will be very difficult, perhas impossible to date it properly.