Integrated chronostratigraphy of Magellan Seamount KC-7 in the western Pacific Ocean for Late Neogene paleoceanographic studies

Integrated chronostratigraphy of core WPGPC230202, which was taken from the summit of seamount KC-7 located in the Magellan Seamounts of the western Pacific Ocean, was established using planktonic foraminifera biostratigraphy, calcareous nannofossil biostratigraphy, and magnetostratigraphy.Planktonic foraminiferal biostratigraphy clearly shows 17 biohorizons from Pliocene Zones PL1 to Pleistocene Subzone PT1b.Calcareous nannofossils yielded 12 biostratigraphic index taxa, revealing 15 biohorizons from Plio-Pleistocene Zones CNPL2 to CNPL11.In addition, 6 paleomagnetic reversal events were recorded, which correlate continuously to the geomagnetic polarity time scale, ranging from the Brunhes (C1n) to the upper Gilbert (C3n.1n).As a result, the integrated chronostratigraphy provided an age of ~ 4.3 Ma, which can be applied to regional stratigraphic correlations and to better understand Late Neogene paleoceanographic changes in the study area.The age-depth model of core WPGPC230202 shows the distinct decrease of sedimentation rates from ~ 0.19 to ~ 0.07 cm/kyr at ~ 2.4 Ma, which corresponds to the Northern Hemisphere Glaciation (NHG).Core WPGPC230202 primarily consists of biogenic carbonate ooze (foraminifera and nannofossils) and due to the shallow water depth at the core site limiting the effect of dissolution, the sedimentation rate is mainly dependent on the degree of paleoproductivity.The NHG is characterized by the gradual global cooling and change in the deep-water circulation patterns.During the NHG, surface water cooling and reduced formation of the North Pacific Deep Water may degrade carbonate productivity in the subtropical ocean including the study area, similar to what is recorded in the subarctic North Pacific.