A Pliocene stage is documented in southern Death Valley, and a lake in the Furnace Creek basin of northern Death Valley reached a highstand 3.35 million years ago; a number of tephra layers provide controls on the ages of this lake. Thus, a very early lake existed in northern Death Valley between 3.5 and 1.7 million years ago, or between 3.4 and <3 million years ago, probably coinciding with the beginning development of a glacial climate in North America at that time. Such a lake was connected with the Owens Valley because Coso volcanic field tuffs have been found in Death Valley. The basins occupied by early lakes were probably not the same as those of Lake Manly; tectonic deformation has lifted the Nova basin above the current floor of Death Valley. This lake was most likely of limited extent. The 1.7-1.9-million-year-old Glass Mountain tuffs formed deposits in such early lakes.