Middle to Late Cretaceous radiolarian zonation of the Bering region, U.S.S.R.

Abstract

The Middle-Upper Cretaceous volcanogenic-siliceous geological sections of the Koryak highland, the submerged Shirshov Ridge, and northern, central and eastern Kamchatka are investigated micropaleontologically. Radiolarians were extracted from siliceous rocks by means of HF. Their preservation is satisfactory. As a result of biostratigraphical research, six radiolarian assemblages are distinguished. The oldest is the Albian-Turonian assemblage with Pseudodictyomitra pseudomacrocephala. The age of this complex is controlled by planktonic foraminifers co-occurring with radiolarians. The following is the Coniacian-Early Santonian assemblage with Archaeospongoprunum bipartitum, which is accompanied by Early Santonian planktonic foraminifers. The Late Santonian-Early Campanian age of the assemblage with Pseudoaulophacus floresensis is confirmed by macrofossils. A Middle-Late Campanian age of the Amphipyndax enesseffi assemblage is proved by the widespread Inoceramus schmidti. A Late Campanian-Early Maastrichtian age of the radiolarian assemblage with Clathrocyclas diceros is in good agreement with diatoms and silicoflagellates. A Late Maastrichtian-Danian age of the assemblage with Bothryopyramis sanjoaquinensis is proved by foraminifers. These radiolarian assemblages can be considered as zonal for the boreal area of the northeast of the U.S.S.R. and as a key for further biostratigraphic research.