The timing of termination I in benthic δ18O of the Atlantic, Pacific, and Mediterranean basins
Abstract:Terminations used to be regarded as effectively globally synchronous events. As such they were used (amongst other features) in aligning cores by Lisiecki and Raymo (2005) in their widely accepted global benthic stack. Skinner and Shackleton (2005) showed, however, that this assumption of synchronicity may not hold. In a detailed study of the last glacial-interglacial transition, an Atlantic record from the Iberian Margin and a record from the deep eastern equatorial Pacific – both dated by 14C for a solid, independent age estimate – show a significant discrepancy in timing: ~4,000 years. Indeed, in 2009 Lisiecki and Raymo published a separate reconstruction for the Atlantic and Pacific records in their stack, and found indications for diachronous termination signals for the last five terminations.
We compared the Atlantic and Pacific records of Skinner and Shackleton (2005) to the benthic isotope record of ODP site 968 in the eastern Mediterranean published by Ziegler et al. (2010), to see how the Mediterranean record feeds into this discussion. The age model for this record is constrained by the carbon dated boundaries of saproprel 1 as well as correlation to the radiometrically dated cave record of Sanbao-Hulu (Wang et al., 2008). The benthic δ18O record of ODP site 968 resembles the Pacific record much more than the geographically closer Iberian Margin record.
This raises questions: whether the Late Glacial/Early Holocene benthic record of MD99-2334K on the Iberian Margin is representative of Atlantic benthic δ18O; what oceanographic factors could have influenced the benthic δ18O of the sites involved; whether there is, after all, a globally synchronous, two-step deglaciation in the Mediterranean, Atlantic, and Pacific basins.
Lisiecki and Raymo, 2005. DOI: 10.1029/2004PA001071
Lisiecki and Raymo, 2005. DOI: 10.1029/2009PA001732
Skinner and Shackleton, 2005: DOI: 10.1016/j.quascirev.2004.11.008
Wang et al. 2008: doi:10.1038/nature06692.
Ziegler et al., 2010: DOI: 10.1016/j.quascirev.2010.03.011