Astronomical tuning of the Late Cretaceous geomagnetic polarity time scale (from top Chron C34n to base Chron C30n)

The Geomagnetic Polarity Time Scale (GPTS) is the backbone of the time scale for at least the last ~84 Myr (Late Cretaceous–Quaternary). Astronomically calibrated ages for the Cenozoic portion (C-Sequence) of the GPTS are provided as part of the Cenozoic Global Reference benthic foraminifer carbon and oxygen Isotope Dataset (CENOGRID1), but not for the late Cretaceous portion of the C-Sequence. We aim to provide astronomically calibrated age for the late Cretaceous magnetic Chron boundaries. We generated preliminary magnetic polarity stratigraphy data and bulk carbon stable isotope data from a series of deep-sea drilled record recovered in the South Atlantic Ocean: Ocean Drilling Program (ODP) Site 1267 2 (Leg 208), Deep Sea Drilling Project (DSDP) Site 5253 (Leg 74), and International Ocean Drilling Project (IODP) Site U15764 (Exp. 391) from Walvis Ridge, and DSDP Site 5165 (Leg 72) from the Rio Grande rise. The sampled records are generally characterized by a stable magnetic remanence with either normal (up-pointing) or reverse (down-pointing) inclination of the remanence vector. The integration of magneto- and carbon isotope-stratigraphy will be used to calibrate the GPTS from the top of Chron C34n to the base of Chron C30n. To achieve this, we will use a new approach based on the correlation of the obtained magnetostratigraphy to an astronomically tuned reference by using the bulk carbonate stable carbon isotope data. This effort represents the first step toward a fully astronomically calibrated C-sequence of the GPTS that is consistent with CENOGRID. References1 Westerhold, T. et al. An astronomically dated record of Earth’s climate and its predictability over the last 66 million years. Science (1979) 369, 1383–1388 (2020).2 Zachos, J. C., Kroon, D. & Blum, P. Site 1267. Proceedings of the Ocean Drilling Program, 208 Initial Reports 208, 1–77 (2004).3 Chave, A. D. Lower Paleocene–Upper Cretaceous magnetostratigraphy, Sites 525,527, and 529, Deep Sea Drilling Project Leg 74. in Deep Sea Drilling Project preliminary report, Vol. 74 (eds. Moore, T. C. & Rabinowitz, P. D.) 525–531 (DSDP, Washington DC, USA, 1984). doi:10.2973/dsdp.proc.74.1984.4 Sager, W. et al. Site U1576. International Ocean Discovery Program: Preliminary Reports 391, 1–65 (2023).5 Barker, P. F., Carlson, R. L., Johnson, D. A. & Al., E. Site 516. Deep Sea Drilling Project preliminary report, Vol. 72 (1983).