Carbon 14 dating flawed
Such sediment, even if from nearby hills, would normally carry very little organic material as the weathering slopes, themselves, would not have much to begin with.
Sediment, in the form of dust, would normally come from very dry areas where organic material would be quickly oxidized.
Those "scientific" creationists who trot this plum about must be delirious!
Do they really believe that we should wind up with x miles of topsoil (or some such nonsense) after billions of years?
Take the soil in my mother's backyard, for example.
That means less chemical weathering from bacteria and fungi.
Whatever damage is done to the clay by the few penetrating roots may, for all I know, be patched up by clay particles sifting down through the soil.
The yard is located, along with much of San Diego, on a plateau, and meandering streams over thousands or millions of years have brought rocks down from the hills and rounded them into boulders.
(Topsoil is full of microbes that love to munch away on organic material, and don't forget the earthworms.
Those earthworms don't get their calories from rock and clay!
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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.