The many cases on record of a formation conformably covered, after an immense interval of time, by another and later formation, without the underlying bed having suffered in the interval any wear and tear, seem explicable only on the view of the bottom of the sea not rarely lying for ages in an unaltered condition.
Formazio bat, geroagoko beste formazio batek, denbora-tarte izugarri baten ondoren eta tarte horretan azpiko geruzak erosiorik ez urraturik jasan gabe doiki estali duela erakusten duten eta ofizialki jasorik dauden kasu ugariak azaltzeko bide bakarra, dirudienez, hauxe da, itsas hondarrak aro osoetan aldagabe iraun izana gertaera bakana ez dela onartzea.