We generated a high resolution (~8 ky) benthic record from a West Pacific marginal basin to investigate the detailed structure and spectral characteristics of deep water isotope fluctuations during the middle Miocene. The benthic record from ODP Site 1146 allows unprecedented resolution of the structure of the middle Miocene delta13C excursion, as well as tighter control on the chronology of climatic events. Spectral analysis of the variance in the delta18O and delta13C records from ODP Site 1146 reveals spectral power concentrated in the eccentricity band (400-, ~100-ky) over the time interval between 13 and 17 Ma. The amplitude evolution in the 400-ky band is strikingly similar to that of the long eccentricity in Laskar's solution. There is an abrupt switch to the obliquity band in the delta18O record at -14.9 Ma, suggesting a shift in the ocean/climate response to orbital forcing (from low latitude eccentricity to high latitude obliquity forcing). The obliquity signal is pervasive in the delta18O record until -13.9 Ma, when a sharp increase in delta18O values indicates a major climatic transition. Comparison of delta18O and delta13C profiles from DSDP Site 588 (SW Pacific Ocean), ODP Site 761 (E Indian Ocean) and ODP Site 1146 (South China Sea) reveals significantly cooler deep water in the NE Indian Ocean throughout the middle Miocene and a restricted deep water exchange between the Pacific Ocean and Indian Ocean.

Stable isotopes were measured on Planulina wuellerstorfi and Cibicidoides mundulus, except in a few samples which did not contain these species. In those rare instances, we substituted other Cibicidoides. Full details are given in the Methods section of the paper.

Supplement to: Holbourn, Ann E; Kuhnt, Wolfgang; Schulz, Michael (2004): Orbitally paced climate variability during the middle Miocene: High-resolution benthic stable isotope records from the tropical western Pacific. In: P Clift, P Wang, W Kuhnt, D Hayes (Eds.), Continent-ocean interactions within East Asian marginal seas, American Geophysical Union, Washington DC, 321-337