Phanerozoic Sea Level Changes: ODP Drilling Constrains the Last 100 Million Years
Kenneth Miller1, Michelle Kominz2, James V. Browning1, and James D. Wright1
1 Rutgers University, Piscataway, NJ
2 Western Michican University, Kalamzoo, MI
We review Phanerozoic sea-level changes and present a new sea-level synthesis for the last 100 Ma based on ODP Legs 150X and 174AX (onshore New Jersey). Our record compares favorably with the EPR record over the past 100 m.y. in the number and timing of sea-level events. However, the EPR amplitudes are 2.5 times or greater than ours on both the long-term and m.y. scales. Phanerozoic sea-level changes occur on various time scales with different controlling mechanisms. Variations in ocean crust production caused sea-level changes of 100-300 m on the 10 to 100 m.y. scale; changes on this scale were smaller than previously inferred, with a Late Cretaceous peak of 100±50 m, implying smaller changes in seafloor spreading rates. Ice-volume variations controlled sea-level changes of ~30-80 m on the 1-5 m.y. scale over at least the past 100 m.y. Sea-level changes mirror ?18O variations on various scales. Such covariance can be explained by ice-volume changes in concert with temperature changes on the m.y. and k.y. scales, but a long-term ?18O increase of ~4-5‰ since 50 Ma must be primarily attributed to deep-water cooling (15°C overall), rather than to ice storage. The link between ?18O and sea-level variations on the 10-100 m.y. scale must be due to tectonics through carbon dioxide. Over the past 100 m.y, sea-level changes reflect global climate evolution from a time of ephemeral Antarctic ice sheets (100-33 Ma), through a time of large and variable Antarctic ice sheets (33-2.5 Ma), to a world with large Antarctic and large, variable Northern Hemisphere ice sheets (2.5-0 Ma).