S'pose we could call it the smudge factor!
The myths talk about a crushing drought that proceded the pre-dynastic Flood event. Probably that is the one that left the biggest mark in the sediment layers. Alternatively, the "smudge factor" needs to be adjusted such that the drought layer corresponds to a more recent and reasonable date for the end of the Old Kingdom.
© Charles N. Pope, US Library of Congress. All rights reserved.