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Climate of the Past An interactive open-access journal of the European Geosciences Union
https://doi.org/10.5194/cp-2017-108
© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 4.0 License.
Research article
28 Sep 2017
Review status
This discussion paper is a preprint. It is a manuscript under review for the journal Climate of the Past (CP).
Reinforcing the North Atlantic backbone: revision and extension of the composite splice at ODP Site 982
Anna Joy Drury1, Thomas Westerhold1, David Hodell2, and Ursula Röhl1 1MARUM - Center for Marine Environmental Sciences, University of Bremen, Germany
2Department of Earth Sciences, University of Cambridge, Cambridge CB2 3EQ, UK
Abstract. Ocean Drilling Programme (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 stable isotope stratigraphy and astrochronology between 4.5 and 8.0 Ma. Splice revisions and verifications resulted in ~ 11 m of gaps in the original Site 982 isotope stratigraphy. Our new stratigraphy reveals previously unseen benthic δ18O excursions, particularly prior to 6.65 Ma. The benthic δ18O 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 δ13C and δ18O 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 an interval of average higher δ18O and large precession and obliquity-dominated δ18O excursions between 6.4–5.4 Ma, coincident with the culmination of the late Miocene cooling. The two largest benthic δ18O excursions ~ 6.4–6.3 Ma and TG20/22 coincide with the coolest alkenone-derived 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 high-resolution astronomically tuned benthic δ18O stratigraphies from ODP Site 926 (equatorial Atlantic) and Ain el Beida (north western Morocco) show that prior inconsistencies in short-term excursions are now resolved. Our new integrated deep-sea benthic stable isotope stratigraphy and astrochronology from Site 982 will facilitate future high-resolution late Miocene to early Pliocene climate research.

Citation: Drury, A. J., Westerhold, T., Hodell, D., and Röhl, U.: Reinforcing the North Atlantic backbone: revision and extension of the composite splice at ODP Site 982, Clim. Past Discuss., https://doi.org/10.5194/cp-2017-108, in review, 2017.
Anna Joy Drury et al.
Anna Joy Drury et al.
Anna Joy Drury et al.

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Short summary
North Atlantic Site 982 is key to our understanding of climate evolution over the past 12 million years. However, the stratigraphy and age model are unverified. We verify the composite splice using XRF core scanning data and establish a revised benthic foraminiferal stable isotope astrochronology from 8.0–4.5 millions of years ago. Our new stratigraphy accurately correlates the Atlantic and the Mediterranean and suggests a connection between late Miocene cooling and dynamic ice sheet expansion.
North Atlantic Site 982 is key to our understanding of climate evolution over the past 12...
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