Hence, the age and composition of Skiff Bank's igneous crust, and its relationship to the contiguous northern Kerguelen Plateau are not established. Site 1139 lies at a depth of 1427 m on Skiff Bank's southwestern terrace, which is more than 1000 m lower than the crest, located less than 50 km to the northeast. We chose this location as representative of the entire Skiff Bank on the basis of its relatively simple structural setting and thin sedimentary section. The top of acoustic basement is flat-lying, and overlying basement is a sediment sequence approximately 500 m thick. We were especially interested in testing the hypothesis that the age of the uppermost igneous basement at Skiff Bank is Sediments were recovered from the upper 461 mbsf of Hole 1139A, whereas extensively altered felsic volcaniclastic rocks and mafic to intermediate composition lava flows were recovered from the lower 233 m of the hole.
Trace fossils are very common.
Unit II records a substantial influx of terrigenous clay from an adjacent volcanic landmass. Sediments become semilithified by 100-110 mbsf. We observed very rare tephra layers and disseminated volcanic ash, locally concentrated in burrows. Within this depth interval, three volcanic ash layers have high compressional wave velocities. Units I to III represent deep-marine pelagic sedimentation.