Apparent Diachroneity of Calcareous Nannofossil Datums During the Early Eocene in the High‐Latitude South Pacific Ocean

• Published in: Paleoceanography and paleoclimatology 2024-04, Vol.39 (4), p.n/a
• Main Authors: Niederbockstruck, B., Jones, H. L., Yasukawa, K., Raffi, I., Tanaka, E., Westerhold, T., Ikehara, M., Röhl, U.
• Format: Article
• Language: English
• Subjects: Age; age model; biostratigraphy; Calcium; Calcium carbonate; Calcium carbonates; Carbon 13; Carbonates; early Eocene; Eocene; Equatorial regions; IODP Site U1553; Iron content; late Paleocene; Latitude; Multiship expeditions; Oceans; Palaeocene; Paleocene; stable isotopes
• ISSN: 2572-4517; 2572-4525
• DOI: 10.1029/2023PA004801

The late Paleocene to early Eocene interval is characterized by a series of carbon perturbations that caused transient warming (hyperthermal) events, of which the Paleocene‐Eocene Thermal Maximum (PETM) was the largest. These hyperthermals can be recognized in the pelagic sedimentary record as paired negative δ13C and δ18O excursions, in addition to decreased calcium carbonate and increased iron content caused by carbonate dissolution. However, current data are predominantly sourced from the equatorial‐to subequatorial regions. Here we present a new high‐latitude late Paleocene—early Eocene record, recovered during International Ocean Discovery Program (IODP) Expedition 378 on the Campbell Plateau off New Zealand, in the southwest Pacific Ocean. To construct an age model, we correlated our chemostratigraphic and biostratigraphic data to existing astronomically‐tuned age models from Walvis Ridge (South Atlantic Ocean) and Demerara Rise (equatorial Atlantic Ocean). Our results indicate that the Site U1553 composite section spans ∼7 million years of the latest Paleocene to early Eocene (50.5–57.5 Ma), and preserves many of the early Eocene hyperthermals; including a PETM interval that is more expanded than elsewhere in this region. However, construction of the age model also revealed discrepancies between the chemostratigraphic and biostratigraphic tie points used for correlation. This is likely due to latitudinal diachroneity in the calcareous nannofossil biostratigraphic datums, which are primarily based on low‐to mid‐latitude assemblages. Therefore, our study highlights the need to establish a revised calcareous nannofossil biozonation that is more appropriate for high‐latitude age models. Key Points A new chemostratigraphic age model (50.5–57.5 Ma) was developed for IODP Site U1553 in the high‐latitude South Pacific Ocean Commonly used calcareous nannofossil datums show significant offsets at Site U1553 compared to records from lower latitude regions This study highlights the need to revise early Eocene calcareous nannofossil biostratigraphic datums to be applicable to high‐latitude sites