EVIDENCES OF VOLCANIC ACTION 15 
least to the Avam (Dudypta) river confluence, if not farther on; it 
is a typical surface flow, or several ones, as shown on the shores 
of the Piasina lake. Along the river downstreams they are markedly 
bound to the river beaches and the broader old valley has grown 
young again by the filling lavaflows, the present water wrinkle 
being compressed by nearly perpendicular cuts through the basalt 
‘bed. The connection of these basalts to the Tunguska river plateau 
passing over the upper Khantaika, Kureika, Kheta and Kotui rivers 
seems to be uninterrupted. Pebbles of upper silurian fossiliferous 
limestone on the Piasina lakeshore prove the old age of the floor 
rocks. The coal measures of the Noril lakes and their metamorphic 
aequivalents farther south will be made‘mention of in a further 
chapter, and some explanation is also be given of the great exten- 
sion of the mesozoic area as presented on the compilative geological 
map by Ahlburg. ? 
The diabases of the Yenisei mouth, specially these of the Kuzkin 
Island, were described earlier by the writer;? no new records upon 
them are reported. 
The plant remains of upper mesozoic age from the Solitude Island 
are strongly silicified, but the short visit of captain Sverdrups expe- 
dition of 1915 revealed no volcanic rocks as were to have been 
expected here. ® 
Erratic pebbles of basalt (diabase) from the Pancratieff Island on 
the northwest coast of the northern island of Novaia Zemlia were 
already mentioned by the writer. >? Since that time there were from 
this island brought home specimens of diabase (basalt) from the 
1 Joh. Ahlburg, Die neueren Fortschritte in der Erforschung der Goldlagerstatten 
Sibiriens. Zeitschrift für prakt. Geologie 1913, p. 105. 
2 Holmes (l. c. p. 221) supposes that the Kuzkin Island is identical with the 
Sibiriakoff Island; on older Russian maps the Kuzkin Island lies nearer the shore 
and is outfitted with the excellent harbour Port Dickson, meanwhile the 
Sibiriakoff Island is situated farther westward. 
3 H. Backlund, On fossil plants from Solitude Island. Geol. Féren. i Stockholm 
Förh. 38. 1916, p. 265. 
