High‐Resolution Integrated Cyclostratigraphy From the Oyambre Section (Cantabria, N Iberian Peninsula): Constraints for Orbital Tuning and Correlation of Middle Eocene Atlantic Deep‐Sea Records

Abstract

AbstractThe astronomical timescale accuracy generally exceeds other dating methods. Precise age models are pivotal for paleoclimatic research. The middle Eocene astronomical timescale has been poorly constrained due to scarcity of suitable records leading to the so call “Eocene astronomical timescale gap.” We present magnetic susceptibility and color proxy records from an expanded 60 m long cyclic hemipelagic succession from the Oyambre Cape in northern Spain (∼1.3 My long stratigraphic section tuned to the ∼43.1–44.4 Ma interval in the Lutetian stage). We use the strong eccentricity amplitude modulation of precession in the sedimentary record for orbital tuning. The tuned record is correlated at precession level with previously tuned Ocean Drilling Program (ODP) Site 1260 from the equatorial Atlantic (the only oceanic record that registers geochemical variations in the precession band) and to other lower resolution deep‐sea records at eccentricity level from the Southern Atlantic. Our data is consistent with a very long eccentricity minimum (driven by a ∼2.4 My periodicity) at 43.15 Ma in the orbital solutions and an age for the C20n/C20r reversal boundary at ∼43.45 Ma. However, we challenge previous correlations between these Atlantic sites (shifts of one 100 ky eccentricity cycle). Data allows to rule out correlation to either younger or older 405 ky eccentricity cycles, which constrains chronologies for the middle Eocene, emphasizing the need for consistent astrochronological frameworks involving expanded outcrops. This should aid to overcome oceanic drilling shortcomings and sedimentary complexities. Our study highlights this integration need to achieve accuracy and stability of orbital timescales underpinning Eocene paleoclimatic records.