Triassic biogenic limestones in Sikhote-Alin are not ubiquitous, but are found only in the central part of the Dalnegorsk region (Rudnaya River basin), where they compose individual massifs within a Lower Cretaceous olistostrome. The massifs range from 6–8 m to 3,500 m across. In the Lower Cretaceous terrigenous matrix there are smaller fragments of limestone (side by side with bodies of cherty composition). In the Dalnegorsk region there are, in all, about 10 limestone massifs. Their characteristic limestones show that they were formed in middle and late Triassic time. Recently, I proposed a stratigraphic scheme on the basis of the corals in the Dalnegorsk region. The following beds have been distinguished: (1) Coryphyllia moisseevi beds (Ladinian–Lower Carnian), (2) Volzeia badiotica beds (Upper Carnian), (3) Margarosmilia charlyana beds (Lower Norian), (4) Gablonzeria kiparisovae beds (Middle Norian), (5) Meandrostylis tener beds (Upper Norian), and (6) Retiophyllia buonamici beds (Rhaetian) (T. A. Punina, unpublished data).
As a type for the lowest subdivision, I offer the section in trench no. 1558 (southwest slope of Bolnichnaya Mountain). Other beds with corals are recognized in a single section on Sakharnaya Mountain, which is proposed as a type for those subdivisions.
The characteristics of the main limestone massifs in the Dalnegorsk region are described in the following sections. This should help to correlate the Middle and Upper Triassic strata of the region and to compare the Triassic coral assemblages of Sikhote-Alin with those of the circum-Pacific region.