Data report: refinement of calcareous nannofossil biostratigraphy from the late Oligocene to the Pleistocene, IODP Expedition 363 Hole U1490A

Abstract

An Oligocene to recent sedimentary sequence was recovered in Hole U1490A in the northern portion of the Eauripik Rise (western Pacific Ocean) during International Ocean Discovery Program (IODP) Expedition 363. High-resolution sampling and moderate to good calcareous nannofossil preservation allowed us to adjust the depths for nannofossil events reported shipboard. This study identified 22 zonal boundary markers and 30 secondary calcareous nannofossil events. Because of better preservation of the calcareous nannofossils in the Pliocene–Pleistocene units, more calcareous nannofossil events were observed in that interval than in the older units. In the Miocene units, the discoasters and helicosphaerids (which are important zonal boundary markers) are poorly preserved (fragmented and recrystallized), making it difficult to identify nannofossil zones. In lieu of zonal boundary markers, secondary calcareous nannofossil events were used to refine the biostratigraphy in the Miocene interval.