Relative age dating diagrams
The geologic history of the strata making up the Grand Canyon is as much a history of erosion as it is of deposition!
Consequently, a patch of soil cannot be older than the last local erosion--whenever that might have been.
Geologically speaking, any given patch of land is seldom in equilibrium for long.
Either it is collecting sediment or being eroded away, usually the latter. Water-borne sediment will be washed in from higher ground, perhaps hills and mountains hundreds of miles away.
However, the deeper that soil gets, the more insulated the parent rock becomes to weathering.Thus, topsoil does not accumulate like most sediment, by simply piling up.In the case of erosion, the topsoil, of course, is removed.At about the three-foot level (in the center of the yard) the red-brown clay is abruptly terminated by a reddish conglomerate we call hardpan.
A few sickly-looking roots, long dead for all I can tell, do penetrate the clay, usually by hugging the surfaces of the boulders, before being stopped cold by the hardpan.
) Just because a patch of topsoil takes x centuries to build up doesn't mean that the land is x centuries old.