We describe in detail the late Pliocene to Quaternary paleoenvironmental change associated with the newly defined Pliocene/Pleistocene boundary based on calcareous nannofossil biostratigraphy. The period from . Ma to . Ma just prior to Datum plane A, is characterized by warm water conditions named mid-Pliocene Golden age. In contrast, the paleoenvironment was drastically changed to increase of the ice sheet in the Arctic Ocean at . Ma (climate crash) which is caused by closure of the Central American Sea Way. The Quaternary style biogeography of calcareous nannoplankton and planktic foraminifer, and the ocean current system flowing from the Bering straight through the Arctic Ocean to the East Greenland Sea, were established at this time. This indicates that the main Quaternary style climate system was completed at . Ma as a response to the emergence of the Isthmus of Panama.

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