48 ARCTIC BASALT PLATEAU 
quence of the basalt outbreak period and geological incidents to be rela- 
ted below a capturing of river heads on a large scale took place, partly 
changing the main drainage in general and completely changing it 
in details. Thus this ribbon of mesozoic deposits represents 
an ancient river course (with affluents) of mesozoic age, which 
drained the central-asiatic mesozoic (Angara)-continent. 
From the top of the main plateau (e. g. from a point at 68° N 
and 102° E) there are often seen, generally in the direction of les- 
sened basaltic action, smaller isolated table mountains, which seem 
to surpass in height the surroundings. They are crowned by a 
basalt cap and the slopes are completely covered with basalt-debris, 
which do not permit any conclusion upon the base of the roofing 
basalt.! The connection of the basalt with the main flows is un- 
certain. On the slopes, but never on the top-basalt of these table 
mountains there were encountered waterworn pebbles of palaeozoic 
rocks, which in this strange company and ‘at this exposed point 
‚lead the thought to glacialdrifted erratics, no other vestiges of gla- 
ciation being recorded. A development step by step of the percep- 
tion reported above forces to analogical conclusions with respect to 
these table mountains too, that they represent the bottom of ancient 
river courses, perhaps affluents to the main system, filled out by a 
basalt flow; the sedimentary rocks served as frame. In sequence 
the lesser resistant country rock of the frame was strongly denuded 
and the more resistant basalt flow was brought into relief by its 
greater resistance to the denudation agents; the pebbles thus derive 
from underneath the basalt cap. The landscape was morphologi- 
cally inverted. This statement affirms that far from all water courses, 
even principal ones at the present time, have persisted as such from 
mesozoic time, and that in many cases, when the valleys were filled 
out by basalts, the river courses eroded a new bed sideways of the 
old basaltfilled valley, no „valley-in-valley“-structure having been 
developed. | 
1 „Witnesses of erosion". 
PUST 
