In the summer of 1997-98, we have investigated the Lower-Middle Triassic section at the Abrek Bay in South Primorye, between Vladivostok and Nakhodka. The first information on the Abrek Bay outcrops was published by Kiparisova (1972), who investigated some fossils (Kiparisova, 1961) collected by other geologists in 1936-56. Brachiopods collected by them at the Abrek locality were described by Dagys (1974) as a new genus of rhynchonellid brachiopods (Abrekia). Some years ago, the section that lies in ravine about 1.6 km NE of Tri Kamnya Cape (Ussuri Gulf) in South Primorye was proposed as a stratotype for the Induan/Olenekian boundary by Zakharov (1996).
The second section (Abrek Bay) can be also recommended as a GSSP candidate for the I/O boundary because a lot of ammonoids and brachiopods are present in the Lower Olenekian here. It is interesting that the all brachiopod representatives of Abrekia sulcata Dagys (more than 180 specimens) were found by us only within the single level of the Hedenstroemia bosphorensis Zone at the type locality, 2.6-3.1 m above the Induan/Olenekian boundary, associating with Lower Olenekian ammonoids - Meekoceras boreale Diener and Ambites sp. They were consid ered to be Induan in age till now (Dagys, 1974). Abrekia sulcata seems to be a good index for the lowermost Olenekian in Far East. As for inarticulate brachiopods, Lingula borealis Bittner and Orbiculoidea sp. are presented in both uppermost Induan and lowermost Olenekian in the Abrek section, with a dominance of Orbiculoidea in the Upper Induan Gyronites subdharmus Zone.
The Induan -Middle Olenekian shelf facies
in the Abrek section substitute very quickly by uppermost Olenekian-Lower
Anisian slope facies with radiolarians (not good preserved spherical
Spumellaria). They are currently being investigated by Dr. E. Panasenko.
Dagys, A.S. 1974. Triassic
brachiopods (morphology, classification, phylogeny, stratigraphical significance,
and biogeography). Nauka, 388 pp., Novosibirsk (in Russian).
Kiparisova, L.D. 1961. Palaeontological
basis of Triassic stratigraphy of Primorye region. 1. Cephalopods. Trudy
VSEGEI, n.s., 48: 1-278 (in Russian).
Kiparisova, L.D. 1972. Palaeontological
basis of Triassic stratigraphy of Primorye region. 2. Late Triassic bivalves
and general stratigraphy. Trudy VSEGEI, n.s., 181:
1-246
(in Russian).
Zakharov, Y.D. 1996. The
Induan-Olenekian boundary in the Tethys and Boreal realm. Ann. Mus. Civ.
Rovereto, sez.: Arch., Sc. Nat., 11 (1995):133-156.
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