Three holes were drilled at two sites on Transect EG66. Site and hole summaries are provided below. Site and hole locations and core recoveries are summarized in Table T1. Drilling in all holes recovered volcanic basement and drilling sampled the overlying sediment in one hole.
Two holes were drilled at Site SEG01. The recovery from these holes are treated together as they represent essentially the same interval. During drilling of Hole SEG01A the drill string had to be retracted. On reentry the drill bit wandered off-center, partially coring the wall of Hole SEG01A. Because drilling was initiated in new basement we designated this second core as Hole SEG01B, consistent with our site/hole classification. Holes SEG01A and SEG01B penetrated 1.39 m before coring began and terminated at 3.09 meters below seafloor (mbsf). Unit I-1 is composed of 1.5 m of massive plagioclase-clinopyroxene-olivine phyric basalt. This unit constitutes a single flow without obvious internal lithologic contacts or flow tops and bases. The phenocrysts typically form glomerocrysts with 10% plagioclase, 6% clinopyroxene, and trace amounts of olivine. Plagioclase and clinopyroxene are largely unaltered, whereas olivine is completely altered to iddingsite, lizardite, and clay. The groundmass consists of plagioclase, clinopyroxene, Fe-Ti oxide minerals, and mesostasis. Minor, irregular calcite-filled veins (<1 mm wide) occur in Samples 163X-SEG01A-2-1, 46–60 cm, and 163X-SEG01B-1-2, 6–12 cm.
Drilling in Hole SEG02A penetrated 1.37 m before coring began and terminated at 11.21 mbsf. Unit S-1 is composed of 5.34 m of highly compacted diamicton. The diamicton is matrix-supported conglomerate with rounded to subangular clasts (from 0.2 to >10 cm) in a clay matrix. A diverse range of clast types, including basalt, gabbro, granite, and quartzite, are represented within the clast assemblage without stratigraphic pattern to their distribution. Unit I-1 is 3.85 m of dark gray, highly fractured, sparsely plagioclase phyric basalt. The groundmass is composed of plagioclase, clinopyroxene, and Fe-Ti oxide minerals. No mesostasis is present. Distinct banding on a decimeter scale is defined by alternating fine- and medium-grained zones. Vesicles and amygdules are rare, whereas calcite-filled veins are common throughout the unit. The fractures form conjugate sets and often show slickensides on surfaces.