Chauna subterrane 

(passive continental margin) 

(Northern part of Russian Northeast)

Consists chiefly of: (1) chlorite-quartz and sericite-chlorite schist, phyllite and metasandstone including 
Ordovician granite with a Rb-Sr isochron age of 439±32 Ma; (2) Lower and Middle Devonian subarkose 
and quartz sandstone, slate, fine-grained, organogenic limestone that contain various benthic fauna and 
sometimes fish armor and psilophyte remnants; (3) Upper Devonian subarkose and arkose sandstone, 
subordinate slate, and limestone with foraminifers; (4) unconformably overlying Lower and Middle 
Carboniferous arkose, sandstone, and conglomerate with granite and quartzite boulders, slate, calcareous 
sandstone, and limestone with corals, brachyopods, and foraminifera; (5) local Upper Carboniferous-
Permian carbonaceous slate and sandstone with fossil flora; (6) Lower Triassic graywacke and slate; and 
(7) middle and upper Norian sandstone, conglomerate, and argillaceous limestone with abundant Monotis. 
The Lower Triassic graywacke and slate contain a Carnian and Norian fauna and lie transgressively on the 
older Paleozoic units. Both the Paleozoic and Triassic units are folded and thrusted toward the north. 
Numerous diabase and gabbro-diabase folded sills intrude the terrane. The Paleozoic units are interpreted 
as continental shelf deposits, and the Triassic units are interpreted as a turbidites. REFERENCES: 
Gorodinskiy, 1963; Rozogov and Vasil'eva, 1968; Drabkin, 1970; Til'man, 1973; Tibilov and others, 1986; 
Kos'ko and others, 1970; Bychkov, 1991.