The controlling tectonic features of Sakhalin are the East Sakhalin horst, the northern fold belt, the western flank of the Tatar Strait geosyncline and the block-faulted area east and north of Aniwa Bay. The linear folds are associated with the Tatar Strait geosyncline. The block faulting is treated as Miocene, and earlier than the folding. — M. E. Burgunker.