Therefore, original plastic deformation cannot be identified although it may have existed within these clay-rich intervals. From 340-350 mbsf, we find that fracture networks, stratal disruption, veins, and incipient scaly clay structures are common. Locally, a very intense fracture fabric is formed. From 350-360 mbsf, brittle deformation gives way to plastic deformation in sticky clays. Throughout Unit P1, cores are highly disrupted by drilling, with evidence of both flow-in and intensive torque transfer to the cores.
Paleomagnetic studies indicate that the more plastic intervals have cork screwed tens of times.
Below 371 mbsf, the intense fissility, fracture networks, and stratal disruption disappear, and evidence for torque transfer to the cores decreases markedly. Burrows, a primary sedimentary structure, are common. Mud-filled veins are present. Steep bedding dips are measured in the interval 420 to 484 mbsf. At 460 mbsf, microfaulting is more abundant in the cores, and fluid escape breccias were noted.