The multi-brown "hand" at the middle of this image is the Verkhoyansk Mountain Range in northeastern Russia. The best information I got regarding its age is simply "Cretaceous". But when in the Cretaceous? Because that is a pretty extensive chapter in Earth's geological history, spanning from 145 to 66 million years ago.
1$\begingroup$ Do you want the age of the rocks, or the age of the orogeny (the building of the range)? They can be quite different, as rocks can wait for millions of years before eventually being turned into mountains. The orogeny itself can be a long process: the Alps began to form in the late Cretaceous, and are still rising today. Some of its rocks were formed during the Jurassic. That being said, you should find some answers in the references cited here (31 & 33 seem promising): en.wikipedia.org/wiki/… $\endgroup$– Jean-Marie PrivalFeb 4, 2020 at 16:02
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.