Data Report: Site Survey Results from Cruise EW9903

Velocity structure of upper ocean crust at Ocean Drilling Program Site 1256

“…Water depth (3645 m) and sediment thickness (250 m) are similar to that at Hole 504B (3460 m water and 275 m sediment), where crust was formed 6.6 Ma ago at 98 mm/a full spreading rate [ Swift et al , 1998b]. Seafloor and basement topography changes <50 m over 10 km [ Shipboard Scientific Party , 2003b; Wilson et al , 2003b]. Basement depth is near that predicted from plate cooling models [ Wilson et al , 2003a].…”

“…The site survey obtained refraction profiles using ocean bottom hydrophones and a 20‐air gun array shot at 130–180 m intervals [ Wilson et al , 2003b; Hallenborg et al , 2003]. Inversion of a profile shot parallel to magnetic anomalies to a receiver located at Site 1256 gives a velocity solution for the upper crust that is very similar to velocity profiles collected determined from refraction experiments at Hole 504B (“NE” profile in Figure 16 in the work of Shipboard Scientific Party [2003a]; A. Harding, personal communication, 2008).…”

The MoHole: A Crustal Journey and Mantle Quest, Workshop in Kanazawa, Japan, 3—5 June 2010

“…At its western limit on 15-Ma crust, this area includes the Ocean Drilling Program (ODP) Hole 1256D (Wilson et al, 2006;Teagle et al, 2006), a site of ongoing Integrated Ocean Drilling Program (IODP) deep drilling into intact ocean crust. MCS Wilson et al, 2003) and wide-angle ocean bottom seismometer (OBS) data exist for the 15-17 Ma area in the vicinity of Site 1256. This region sits in superfast crust (half-spreading rate 110 m yr -1 ), within a corridor that includes a complete tectonic plate life cycle, making it an excellent candidate for understanding ocean crust evolution from a spreading center to subduction.…”

The MoHole: A Crustal Journey and Mantle Quest, Workshop in Kanazawa, Japan, 3&ndash;5 June 2010

“…At its western limit on 15-Ma crust, this area includes the Ocean Drilling Program (ODP) Hole 1256D (Wilson et al, 2006;Teagle et al, 2006), a site of ongoing Integrated Ocean Drilling Program (IODP) deep drilling into intact ocean crust. MCS (Hallenborg et al, 2003;Wilson et al, 2003) and wide-angle ocean bottom seismometer (OBS) data exist for the 15-17 Ma area in the vicinity of Site 1256. This region sits in superfast crust (half-spreading rate 110 m yr -1 ), within a corridor that includes a complete tectonic plate life cycle, making it an excellent candidate for understanding ocean crust evolution from a spreading center to subduction.…”