Data report: stable isotope composition of Eocene bulk carbonate at Sites U1331, U1332, and U1333

Abstract

Coring during Integrated Ocean Drilling Program Expedition 320/321 recovered Eocene sediment sequences at Sites U1331–U1333. These sequences, originally deposited near the Equator of the Pacific Ocean, are characterized by major fluctuations in carbonate content, which may signify past changes in carbonate saturation horizons and perturbations in the global cycling of carbon. Stable carbon and oxygen isotopes were analyzed for 373 samples of bulk sediment across Eocene sequences in Holes U1331C (n = 8), U1332A (n = 100), U1332B (n = 106), and U1333A (n = 159). Bulk carbonate δ13C and δ18O values for lower Eocene sediment at Site U1331 range from 0.9‰ to 1.6‰ and –0.89‰ to 0.19‰, respectively. Middle Eocene to lowermost Oligocene sediment at Site U1332 has δ13C and δ18O values between –1.02‰ and 5.06‰ and between –3.63‰ and 0.58‰, respectively. At Site U1333, values across middle Eocene to lowermost Oligocene sediment fluctuate between 1.41‰ and 3.49‰ for δ13C and between –1.85‰ and 0.28‰ for δ18O. The records are not straightforward enough to interpret with available information. Certain trends in Eocene bulk isotope records observed at other locations appear in the data. However, the absolute magnitudes and variance are significantly different.