Comparing changes in regional response to orbital forcing in the Equatorial Pacific and Atlantic during the Miocene

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During the Miocene, the period in Earth's history from 5.33 to 23.03 million years ago, the modern ocean thermohaline circulation evolved accompanied by fundamental changes in global ocean chemistry and continental climate. Drastic and repeated reductions of calcium carbonate contents characterize pelagic sediment sequences in the equatorial Pacific and equatorial Atlantic at that time. Atmospheric CO2 was similar to today. Temporarily, during the Miocene Climate Optimum (13.9 to 17 Ma), CO2 levels were even as high as predicted for the Year 2100 if greenhouse gas emissions will not be reduced. Despite numerous studies the exact sequence of events in the Miocene between equatorial Pacific and equatorial Atlantic as well as their causal relationship is poorly understood. Reason for this dilemma is the lack of a synchronized highly accurate astronomical age model for both regions. In this project, we intend to change this situation by generating an astronomically calibrated high-resolution deep-sea benthic isotope reference curve for the equatorial Atlantic on sediments retrieved from Ceara Rise during Ocean Drilling Program (ODP) Leg 154 spanning the interval from 5 to 23 Ma. Benthic stable isotope records from the equatorial Pacific (IODP Exp. 320/321) will be completed and then synchronized with the proposed Ceara Rise benthic reference curve for the entire Miocene. Synchronized benthic stable isotope records combined with X-ray fluorescence core scanning data generated in this project for Ceara Rise sediments will allow an unprecedented detailed view on changes in carbonate accumulation between equatorial Pacific and equatorial Atlantic in relation to the evolving modern ocean circulation pattern. In particular, with the new data of this project we will be able to solve the questions if drastic changes in carbonate accumulation in the Pacific and Atlantic are synchronous, if there are leads and lags, which orbital cycles dominate in what period, if changes in carbonate mass accumulation rates in both regions are connected, and if changes in the Carbonate Compensation Deep on Milankovitch time scales are in-phased or anti-phase between equatorial Pacific and Atlantic.