and the ODP Leg 06 Scientific Partydoi:10.0/iodp.sd..01.007 Summary The Integrated Ocean Drilling Program’s (IODP)

Expeditions 309 and 312 successfully completed the first sampling of an intact section of upper oceanic crust, through lavas and the sheeted dikes into the uppermost gabbros. Hole 1256D, which was initiated on the Ocean Drilling Program’s (ODP) Leg 206, now penetrates to>1500 mbsf and>1250 m sub-basement. The first gabbroic rocks were encoun-tered at 1407 mbsf. Below this, the hole penetrates ~100 m into a complex zone of fractionated gabbros intruded into contact metamorphosed dikes. Deep Drilling of the Ocean Basement Drilling a complete in situ section of ocean crust has been an unfulfilled ambition of Earth scientists since the inception of ocean drilling that followed the audaciously ambitious Project MoHole, which was targeted to sample the first order seismic boundary named the Mohorovičić discontinuity (‘Moho’; see Bascom, 1961; Greenberg, 1974). The principal emphasis of Project MoHole was to understand the nature of the oceanic crust and the underlying uppermost mantle thought to be separated by the Moho at roughly 6 km depth below the ocean basins. Unfortunately, many of the key questions regarding the formation and evolution of the oceanic crust remain unanswered despite a further forty years of research; moreover, our sampling of the ocean crust remains extremely cursory (see compilations in Teagle et al., 2004; Wilson et al., 2003). Although offset drilling strategies, where deeper parts of the ocean crust are sampled by drilling in tectonic windows, have had notabl