The Pacific Equatorial Age Transect, IODP Expeditions 320 and 321: Building a 50-Million-Year-Long Environmental Record of the Equatorial Pacific Ocean

In March 2009, the R/V JOIDES Resolution returned to operations after its extended refit and began with a drilling program ideally suited to its drilling strengths, the Pacific Equatorial Age Transect (PEAT, IODP Exp 320/321; Fig. 1A). The PEAT drilling program was developed to understand how a major oceanic region evolved over the Cenozoic Era (65–0 Ma) and how it interacted with global climate. It specifically targeted the interval between 52 Ma and 0 Ma and drilled a series of sites that originated on the paleoequator. These sites have since been moved to the northwest by plate tectonics.

The equatorial Pacific is an important target for paleoceanographic study because it is a significant ‘cog’ in the Earth’s climate machine, representing roughly half of the total tropical oceans that in turn represent roughly half of the total global ocean area. Prior drilling in both the Deep Sea Drilling Project (DSDP) and the Ocean Drilling Program (ODP) outlined the changes that have occurred through the Cenozoic (eg, van Andel et al., 1975; Pisias et al., 1995). Not only did the earlier work fail to cover sufficient time intervals but also many of the sites were cored with ‘first-generation’scientific drilling technology with incomplete and disturbed sediment recovery and thus cannot be used for detailed studies.