DRILLING STRATEGY
To provide structural, physical properties, and geochemical gradients across the accretionary
prism, Leg 190 will core a series of sites along the eastern Nankai transect, including a reference
site (Site ENT-01A), one into the PTZ (Site ENT-03A), two sites into the out-of-sequence thrusts
(OOSTs) higher on the slope (Sites 06A and 07A), and a reference site along the western transect
(WNT-01A). Alternate sites are in the OOST (Sites ENT-04A and ENT-05A), the LDRZ (Sites
ENT-08A and 09A), and the western PTZ (Site WNT-03B). Experience on Legs 87 and 131 has
shown that the shallow sedimentary section usually contains thick beds of poorly consolidated
sand. Casing the upper part of Hole 808C on Leg 131 provided enough stability to allow drilling to
proceed to more than 1300 m. Since Site ENT-03A is close to Hole 808, we have included a
deployment of drill-in casing (DIC) in the operations time estimate to ~100 mbsf at this site. We
will have additional drill-in-casing capabilites for other sites, if required. Core recovery on Leg 131
was good after stabilizing the shallow sands, so we anticipate similar success on Leg 190. Sites
ENT-01A, 03A, and 06A will use advanced hydraulic piston corer (APC)/extended core barrel
(XCB) to ~350 mbsf and rotary core barrel (RCB) to total depth (TD). Site ENT-07A will use only
APC/XCB and, and Site WNT-01A will use only RCB.
Logging Plan
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