High-resolution benthic oxygen isotope record from Core MD972143 has been calibrated to extend the astronomical timescale back to 2.2 Ma for the western Pacific Ocean. All oxygen isotope stages down to Stage 83 were recognized and validated by comparison with the magnetostratigraphy of the same core of Horng (2000). The astronomical timescale of Core MD972143 was constructed by correlating the delta (super 18) O record to the low-latitude stack timescale of Bassinot et al. (1994) for the past 0.9 Ma and to the astronomical timescale of ODP Site 677 of Shackleton et al. (1990) for the period of 0.9-2.2 Ma. The resultant delta (super 18) O time series reveals global ice-volume variability in both time and frequency domains. Spectral analyses and filtering of the calibrated time-series reveals the evolutive nature of the respective 41-kyr and 100-kyr components through the past 2.2 Ma. In contrast to the constancy of the 41-kyr response in the record, the amplitude of the filtered 100-kyr band exhibits characteristics worthwhile for further examination. High-amplitude of 100-kyr periodicity appeared initially at about 1.2 Ma and remained stable until about 0.9 Ma. After that, the 100-kyr component began to predominate and accentuated eventually to its full dominance at approximately 400 ka. The results suggest that the occurrence and evolution of the 100-kyr cycles went through multi-step transitions. The mid-Pleistocene revolution is characterized by the increase of 100-kyr cyclicity over the ever-lasting 41-kyr component, and an increase in amplitude of global ice volume fluctuation.