1970s. Modern folks find remains of Mu and Atlantis (survivors), using some sort of statuette

[Jubal_Harshaw]

So, modern folks find a statuette (green jade, as I recall) that eventually leads to them learning that Mu and Atlantis were real and destroyed themselves (and all civilization) tens of thousands of years ago in a great war. As I recall, the war shift Earth on its axis. Mu was what is now Antarctica, and Atlantis sunk into one of the oceans. As I recall, modern folks found a remnant of one or both of the earlier civilizations.

 

[Mon0Zer0]

The Illuminatus Trilogy by Robert Anton Wilson?

 

[HareBrain]

Possibly The Philosopher's Stone by Colin Wilson (another Wilson!). I think that features a statuette from the British Museum that turns out to be much older than originally thought, which leads the character to learn that the Atlanteans (and maybe Mulians) were aliens that are still controlling humanity after the destruction of their civilisation. However, I don't recall the axis-shifting.