Miocene radiolarian assemblages from the submarine Vityaz Ridge, Northwest Pacific: Biostratigraphy and paleoceanography

Abstract

This study presents the first data on radiolarian fauna from Miocene deposits of the submarine Vityaz Ridge (SVR) and paraxial zone of the Kuril-Kamchatka Trench. Twenty-two dredge samples were studied, and 214 radiolarian taxa were identified. Taxonomic composition allowed their assignment to Miocene assemblage zones, including Lipmanella japonica conica-Gondwanaria dogieli, Pentactinosphaera hokurikuensis, Dendrospyris sakaii, Eucyrtidium inflatum Subzone a, Lychnocanoma magnacornuta, and Lychnocanoma parallelipes zones. These radiolarian assemblages correlate with studied sequences of many deep-sea cores in the northern Pacific and some sections of onshore Japan. As a result, we designed a biostratigraphic scheme of Miocene radiolarians for the SVR and reconstructed the environmental conditions in this area. In particular, two Miocene climatic optima that were previously established in the northern Pacific were identified in the Middle and Upper Miocene sediments of the southern plateau and Middle Miocene sediments of the northern plateau of the SVR.