How Old Are the Verkhoyansk Mountains in Northeastern Russia?
Depends on what exactly you are looking for.

The mountains contain material which is much older, some as old as the Permian. This material is hosted in detrital sandstones, so obviously that area was not a mountain back then.

The deformation of that area, is indeed Cretaceous:


  The early stage of deformations dated as 160 Ma, the main stage dated as from 70 to 90 Ma.


So to answer your question, the mountains formed throughout the entire Cretaceous duration, but mostly in later (younger) times.