Paper No. 4
Presentation Time: 2:10 PM


MILLER, Kenneth, Dept. of Earth and Planetary Sci, Rutgers University, 610 Taylor Rd, Piscataway, NJ 08854, WRIGHT, James D., Dept. of Earth and Planetary Sciences, Rutgers University, 610 Taylor Road, Piscataway, NJ 08854, BROWNING, James V., Department of Earth and Planetary Sciences, Rutgers University, 610 Taylor Road, Piscataway, NJ 08854, KOMINZ, Michelle A., Department of Geosciences, Western Michigan University, 1903 W. Michigan Ave, Kalamazoo, MI 49008 and BALUYOT, Ronidell, Dept. of Earth and Planetary Sci, Rutgers University, Wright Laboratories, 610 Taylor Rd, Piscataway, NJ 08854,

We provide million year-scale eustatic estimates for the late middle Eocene to middle Miocene using two approaches: 1) backstripping of sequence from New Jersey onshore (Eocene-Miocene) and shelf (early-middle Miocene) coreholes; and 2) scaling deep-sea δ18O records using Mg/Ca to constrain long-term (>2 Myr scale) temperature changes. We compiled a high-resolution (kyr-scale) composite (spliced) deep sea benthic foraminiferal δ18O record, including new Miocene data from Sites 747 and 751. We scale this to sea level by removing long-term (>2 Myr scale) temperature changes using Mg/Ca records (Cramer et al., 2011) and bracketing the ice-volume versus temperature contribution on the Myr scale as 50-50 and 80-20%. Backstripping shows that Myr sea-level changes are typically 25 m, with the largest <75 m. Comparison of backstripped and isotope-based estimates requires that only about 50% of the Myr scale variability was due to ice volume. Our scaled-isotopic and backstripped eustatic estimates show: 1) small sea-level changes (<20 m) in the Eocene other than a large 30-40 m lowering at ca. 42 Ma, to ice free just prior to the earliest Oligocene Oi1 event; 2) a remarkably large lowering (~75 m) at Oi1 time (33.8 Ma) reflecting the development of a continental-scale Antarctic Ice Sheet (AIS) that was larger in areas than the modern; as discussed previously (Katz et al., 2009; Pusz et al., 2011), a higher amplitude computed using isotopes (nearly 100 m) is partly an artifact of not fully accounting for a deep sea cooling of 1.5°C; 3) eustatic changes in the Oligocene to middle Miocene of 40-50 m for large Oi- and Mi-events and 20-40 for smaller events primarily driven by growth and decay of the entire East AIS; 4) in a series of three ice-growth events (14.6, 13.7, and 13.0 Ma), a permanent EAIS developed, resulting in lower amplitude (<25 m) Myr-scale sea-level changes during the remainder of the Neogene. The Eocene-Oligocene transition and Oi1 mark a fundamental change in the cryosphere, though Antarctic ice sheets predate this event.