CRETACEOUS IN SAKHALIN AND CRETACEOUS EVENTS IN N.PACIFIC

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The Cretaceous System in the Naiba, Sinegorsk, Ai, Pugachevo and Makarov area of southern Sakhalin, Russia has been investigated from a viewpoint of paleontology, biostratigraphy and paleomagnetics in connection with the Cenomanian-Turonian marine anoxic event and the Cretaceous terminal mass extinction event.1. The Cretaceous in the Naiba area ranges continuously from the Albian to Maestrichtian in age, and is devided into four stratigraphic units. Well-stratiphied, fossil-less, dark-colored mudstone of the upper part of the Ai Formation and the lower half of the Naiba Formation (Albian to Turonian age) appears to have deposited under marine anoxic events. Upper part of the Bykov Formation includes ammonites and inoceramids abundantly and can be assinged to Santonian age. Krasnoyarka Formation ranges from Campanian to Maestrichtian, within which three characteristic ammonite assemblages have been recognized. The Canadoceras multicostatum assemblage (upper Campanian) and the Zelandites … More varuna assemblage (Maestrichtian) ares in common with those found in the contemporaneous strata of the Soya area, Wakkanai and the Awaji area, respectively. There is some possibility to exist Danian strata in the upper part (200 to 300 meters thick) of the Krasnoyarka Formation in the Naiba and Sinegorsk areas, but we have yet get any reliable fossil evidence. If this is so, however, there is no characteristic geologic phenomena in the Naiba area that suggest the Cretaceous terminal event.2. The Cretaceous succession in the Makarov area ranges from Santonian to Maestrichtian in age. We have recognized four fossil assemblages (Anapachydiscus sutneri Ass. , A.naumani-Inoceramus orientale Ass. , Eupachydiscus haradai-I.schmidti Ass. , Canadoceras kossmati Ass.) in the Bykov Formation and three fossil assemblages (C.multicostatum -Saghalinites teshioensis Ass. , Gaudryceras tombetsense-Pseudophyllites indra-Inoceramus hetonaianus Ass. , Pachydiscus cf. flexuosus-Gaudryceras sp. Ass.)in the Krasnoyarka Formation. We can not detect the Cretaceous-Tertiary boundary in this area. Less