HORIZONS OF CARBONACEOUS ROCKS IN TRIASSIC AND LOWER JURASSIC CHERTY DEPOSITS OF THE DAL'NEGORSK REFERENCE SECTION (PRIMOR'E)

Abstract

Three horizons of phthanites and black carbonaceous mudstones are distinguished in the key section of Triassic and Jurassic cherty deposits of the Gorbusha Sequence near the Settlement of Dal'negorsk (Sikhote Alin). The first horizon in the lower part of the section is pre-Olenekian, probably Induan in age, related in origin to events of the Paleozoic-Mesozoic boundary time. The second horizon of local distribution is dated back to the early Anisian. Its deposition was likely associated with local events. The third horizon in the lower Toarcian beds can be interpreted, with a high probability, as a record of the early Toarcian anoxic event.