The micropaleontological character of anomalous calcareous sediments of late Pliocene through early Pleistocene age below the CCD in the northwestern North Pacific Ocean

Calcium carbonate was preserved more than 1 km below the modern calcite compensation depth (CCD) at ODP Site 1179 over several short intervals around 2.5–2.4, 1.65 and 0.9–0.7 Ma. This anomalous preservation resulted from a combination of increased production of planktonic foraminiferal tests at the sea-surface and increased rate of sedimentation to the sea floor. The abundance of dinoflagellate cysts in calcareous sediments records intense plankton blooms, and the preservation of oxidation-susceptible round brown Brigantedinium cysts in foraminifer-rich samples supports the theory of rapid burial. The rise in sea-surface productivity was driven by enhanced flux of continentally derived limiting nutrients, consistent with the pollen evidence of continental aridification, cooling, and an increase in wind strength. The abundant pollen, dominated by steppe herb and montane–boreal conifer taxa, contrasts with lower pollen concentrations dominated by temperate-subtropical deciduous tree and Taxodium-type pollen in non-calcareous sediments.