CHANGES IN GLOBAL MEAN SEA LEVEL DETERMINED FROM DEEP-SEA BENTHIC FORAMINIFERAL δ18O AND MG/CA RECORDS OVER THE PAST 40 MYR: IMPLICATIONS FOR MARGIN AND PLATFORM DEPOSITION

We complied a splice of benthic foraminiferal δ¹⁸O records over the past 40 Myr, including recently published records from Indian Ocean Site 751 from ca. 17-20 Ma that fill in an astronomical gap. We scale our benthic foraminiferal δ¹⁸O values to sea level using a smoothed record (>2 Myr) of Cenozoic Mg/Ca variations to account for the effects of temperature changes. We used the paleotemperature equation of and a calibration of -0.25‰/°C, assuming that shorter term (Milankovitch scale, 10⁴-10⁵ year) temperature changes comprise ~33% of the benthic foraminiferal δ¹⁸O changes, as in the Pleistocene. The resultant δ¹⁸O_seawater estimate was scaled to Global Mean Sea Level (GMSL) change using a calibration of 0.13±0.02‰ δ¹⁸O_seawater/10 m. Our record provides an estimate of ice volume and attendant GMSL changes with errors of approximately ±10 m, but are not true GMSL estimates because they do not account for effects that change the volume of the ocean basin, other tectonic effects, or changes due to sediment input. Examination of our ice-volume and sea-level estimates show: 1) individual 41-kyr sea-level amplitudes were generally small (~10 m) and did not cause observable changes in margin and platform strata; 2) quasi-100-kyr cycles are associated with attendant sea-level changes of ~15-20 m; 3) 405-kyr cycles are associated with rapid δ¹⁸O decreases in the mean of the 41-kyr variations, with sea-level falls of ~20 m; 4) 1.2-Myr scale changes represents a changes of 20-35 m and are the dominant control of sequences on margin and platform strata. Sea-level variability recorded by the δ¹⁸O record can be compared with the early-middle Miocene sequence stratigraphic record from the New Jersey margin, Marion and Queensland Plateaus (NE Australian), the Bahamas, and the Maldives. For example: Mi1b (ca, 17.3 Ma) is correlated with Myr scale sequences m5.4 in New Jersey, MSB1.2 on the Marion Plateau, sequence O in the Bahamas, and PS6 in the Maldives. Mi2 (~16 Ma) is correlated with Myr scale sequences m5.3 in New Jersey offshore, QU2 on the Queensland Plateau, MSB2.1 on the Marion Plateau, sequence N in the Bahamas, and PS7 in the Maldives. Slight differences in ages assigned to these sequence boundaries (<0.5 Myr) may be due to uncertainties in age correlations or more likely to dating of different higher order sequences as can be shown in New Jersey.