Expedition 368X was planned to reoccupy a site started by Expedition 368. Due to equipment breakdown during Expedition 368, Hole U1503A was abandoned after installing casing to 991.5 m below sea floor. Expedition 368X was able to take advantage of a unique opportunity in the JOIDES Resolution schedule. At Site U1503 the key operational objectives are to:

1) sample the lowermost ~300 m of sediments on top of basement to constrain the age and subsidence history of the crust at this location, the timing of normal faulting, and the environment of the early half-graben fill.

2) sample the igneous stratigraphy to at least 100 m below the basement to obtain deep, representative sampling of the basaltic material at this site which will provide an important reference frame for the modeling of breakup.