NOAA/WDS Paleoclimatology - Southern Ocean (ODP 751) Oxygen and Carbon Isotopes from the Early Miocene

We present orbital-scale resolution (~10 kyr) benthic foraminiferal d18O and d13C records from the Kerguelen Plateau (Ocean Drilling Program Sites 751 and 747) from 14.5 to 20.0 Ma spanning the Miocene climate optimum (15-17 Ma). Our records fill a critical gap from ~17 to 18 Ma, a time when many other deep-sea records are affected by dissolution. We tested the fidelity of published magnetobiostratigraphic age models for these sites by astronomically tuning to the 405 kyr eccentricity cycle. A comparison of spectral estimates between the untuned and tuned records, as well as coherency with Laskar's (2004) eccentricity solution, revealed quasi-100 kyr cyclicity in d18O and d13C. There is only a weak signal associated with the 41 kyr obliquity cycle, likely due to the 10 kyr sampling limiting resolution. The d18O variations point to persistent 405 and quasi-100 kyr modulations of temperature and sea level changes through the early to middle Miocene as predicted by astronomical solutions, with changing dominance of the 100 and 41 kyr beat. Comparison of d18O records with early to middle Miocene sequences from the New Jersey shelf, northeast Australian margin, Bahamas, and Maldives suggests that the dominant sea level period preserved is the 1.2 Myr obliquity cycle, with sequence boundaries associated with d18O increases or maxima. On the New Jersey margin, higher-order sequences reflect the quasi-100 kyr eccentricity.