This photograph, taken in 1995, shows a Middle to

Upper Paleolithic site in eastern Siberia called the

Tolbaga stie.  The Russian archaeologist is standing

on the surface of a 43,000 year old Mousterian site and

pointing to a 23,000 year old Aurignacian stratum. Note

the Aurignacian layer and how it undulates. This type

of soil movement is one indicator of cold climate geology.

The dark soil layer above the undulating lighter colored

thermo-clastic layer belongs to the Duyktai or Dyktai

micro-blade industry which dates to 19,000 years ago.