Oligocene and Miocene Siliceous Units of Sakhalin Island, Russia: Diatom Biostratigraphy and Correlation With the Monterey Formation of California

Lisa D. White, Joyce R. Blueford, and Yuri B. Gladenkov

Four siliceous formations were investigated in central Sakhalin Island that are, in part, correlative to the Monterey Formation and associated units of the Neogene basins of California. From oldest to youngest these units are: the Pilengskaya, Borskaya, Uranaiskaya, and Khuzinskaya formations. The Pilengskaya Formation consists mainly of chert and porcelanite, the Borskaya Formation consists of tuffaceous sandstone and siliceous siltstone, the Uranaiskaya Formation consists of tuffaceous to siliceous sandstone, and the Khuzinskaya Formation consists of unconsolidated fine-grained sandstone.

Diatom preservation in the four formations is variable and carbonate concretions often yield moderately preserved diatoms. Of considerable interest to our research is the age of the oldest of these four siliceous units, the cherts of the Pilengskaya Formation. Diatoms recovered from carbonate concretions in the Pilengskaya Formation include species of Hemiaulus and Pyxllla that suggest an Oligocene age for this unit, considerably older than lithologically equivalent middle Miocene units of the Monterey Formation. Cherts and related biosiliceous units around the Pacific Rim accumulated in response to Cenozoic glaciation and global cooling, which intensified upwelling and diatom productivity. The Oligocene through Miocene formations of Sakhalin Island suggest that sedi entation patterns in this region of the northwestern Pacific responded earlier to high latitude cooling than lower latitude areas in the northeastern Pacific.

AAPG Search and Discover Article #91019©1996 AAPG Convention and Exhibition 19-22 May 1996, San Diego, California