Viliga terrane 

(passive continental margin) 

(East-Central part of Russian Northeast)

Consists chiefly of a thick sequence of Carboniferous, Permian, Triassic, and Jurassic marine clastic rocks. 
The sequence ranges up to 10 km thick. Major units are: (1) Lower Carboniferous sandstone and 
interbedded conglomerate, mafic tuff, and basalt flows; (2) Upper Carboniferous to Permian sandy 
argillite, siltstone, sandstone, tuff, chert, basalt, and shale that gradationally overlie the older units; (3) 
Triassic shale, siltstone, intermediate tuff, and limestone; and (4) Jurassic argillite, siltstone, intermediate 
tuff, sandstone, conglomerate that contain brachiopods, gastropods, Kolymia, Monotis, Belemnites, and 
Inoceramus. The Jurassic units locally contain leaf imprints and fossilized tree trunks. The terrane is 
deformed into linear folds and domes with gently-dipping limbs. For paleomagnetic determinations, one 
locality of Cretaceous age yields grade C results, and indicates a northward displacement with respect to 
the Siberian platform of about -18o+10o. The other Middle Jurassic locality yields grade B results that 
indicate little displacement (9o+17o). The Jurassic rocks of the Viliga terrane are interpreted as a back-arc 
basin assemblage that was tectonically paired to the Kony-Murgal island arc terrane. REFERENCES: 
Pechersky, 1970; Epstein, 1977; Polubotko and others, 1977; Terekhov, 1979; Bychkov and Kiseleva, 
1990.