Reinforcing the North Atlantic backbone: revision and extension of the composite splice at ODP Site 982

• Published in: Climate of the Past
• Main Authors: A. J. Drury, T. Westerhold, D. Hodell, U. Röhl
• Format: Article in Journal/Newspaper
• Language: English
• Published: Copernicus Publications 2018
• Subjects: Environmental pollution; TD172-193.5; Environmental protection; TD169-171.8; Environmental sciences; GE1-350; Ice Sheet; North Atlantic
• Online Access: https://doi.org/10.5194/cp-14-321-2018; https://doaj.org/article/58a93ab56d7643e49874ef8f1b59d2d7

Ocean Drilling Program (ODP) Site 982 represents a key location for understanding the evolution of climate in the North Atlantic over the past 12 Ma. However, concerns exist about the validity and robustness of the underlying stratigraphy and astrochronology, which currently limits the adequacy of this site for high-resolution climate studies. To resolve this uncertainty, we verify and extend the early Pliocene to late Miocene shipboard composite splice at Site 982 using high-resolution XRF core scanning data and establish a robust high-resolution benthic foraminiferal stable isotope stratigraphy and astrochronology between 8.0 and 4.5 Ma. Splice revisions and verifications resulted in ∼ 11 m of gaps in the original Site 982 isotope stratigraphy, which were filled with 263 new isotope analyses. This new stratigraphy reveals previously unseen benthic δ 18 O excursions, particularly prior to 6.65 Ma. The benthic δ 18 O record displays distinct, asymmetric cycles between 7.7 and 6.65 Ma, confirming that high-latitude climate is a prevalent forcing during this interval. An intensification of the 41 kyr beat in both the benthic δ 13 C and δ 18 O is also observed ∼ 6.4 Ma, marking a strengthening in the cryosphere–carbon cycle coupling. A large ∼ 0.7 ‰ double excursion is revealed ∼ 6.4–6.3 Ma, which also marks the onset of an interval of average higher δ 18 O and large precession and obliquity-dominated δ 18 O excursions between 6.4 and 5.4 Ma, coincident with the culmination of the late Miocene cooling. The two largest benthic δ 18 O excursions ∼ 6.4–6.3 Ma and TG20/22 coincide with the coolest alkenone-derived sea surface temperature (SST) estimates from Site 982, suggesting a strong connection between the late Miocene global cooling, and deep-sea cooling and dynamic ice sheet expansion. The splice revisions and revised astrochronology resolve key stratigraphic issues that have hampered correlation between Site 982, the equatorial Atlantic and the Mediterranean. Comparisons of the revised Site 982 stratigraphy to ...