Being able to find large amounts of old rock atop newer rock isn’t a scientific anomaly-for it to be even considered, there must be a large deposit of this old rock rather than just a few stones.
For something like this, you’d need a significantly altering event to disrupt the ecosystem in such a fashion. Depending on how old the samples are, a volcanic eruption could’ve set old layers above new ones during the height of the eruption. More commonly, however, it is a meteor impacting the surface of the earth that dislodges large amounts of earth and causes the older layers to be moved to the top.
Plate tectonics can also play a role, as shifting components can “crawl” underneath other plates, thus changing the chronological order of the rocks underneath; typically, the asteroids are the most common cause of layer shifting though.
