“…As part of the Deep Sea Drilling Project (DSDP) and the Ocean Drilling Program (ODP), hydraulic and advanced hydraulic piston corers have been used to obtain mechanically undisturbed Plio-Pleistocene sediments for paleomagnetic studies. Among the numerous cores recovered in the past two decades, less than 30% contain clear polarity zonations (Clement et al, 1996), and only a few have yielded long and detailed oxygen isotope records back into the Pliocene (e.g., DSDP Site 607 and ODP Sites 677 and 846; Ruddiman et al, 1989;Raymo et al, 1989;Shackleton et al, 1990Shackleton et al, , 1995. So far, the most widely referenced Plio-Pleistocene time scale (0-2.6 Ma) derived from astronomically tuned δ 18 O records is from ODP Site 677 (Shackleton et al, 1990), because its age estimates for the last major geomagnetic reversals have been confirmed not only by other independent astronomical ages (Hilgen, 1991) but also by high-precision 40 Ar/ 39 Ar dating on lava flows (Berggren et al, 1995 and references therein).…”