Site 1140 lies on the northernmost Kerguelen Plateau approximately 270 km north of the Kerguelen Archipelago. The sedimentary section above igneous basement consists entirely of pelagic oozes and chalks and appears to rest unconformably on the underlying submarine basalt flows. I predominantly consists of light greenish gray foraminifer-bearing nannofossil ooze and nannofossil chalk. Biostratigraphic data, as well as preliminary interpretation of reversed and normal magnetic chrons, indicate that Lithologic Unit 1 is middle Miocene to early Oligocene or latest Eocene in age. At the base of Subunit IB, just above igneous basement, clear rhombic dolomite crystals are disseminated throughout the sediments.
All physical properties change abruptly at the sediment-basalt boundary.
We observe a magnetic reversal at the boundary between Basement Units 1 and 2. Unit 1 is normal polarity, and Units 2 through 6 are reversed, indicating a hiatus in volcanism as construction of the northernmost Kerguelen Plateau's igneous crust ended. Downhole logs of density, resistivity, and velocity show high values in the interiors of basalt flows, and lower values at flow margins and in the interbedded sediments. At the top of Basement Unit 3, a thin bed of well-burrowed, greenish white nannofossil chalk is latest Eocene in age. Basement Unit 4 contains a sedimentary bed with a top and bottom composed of rusty orange dolomite separated by a bed of well burrowed, very pale brown dolomitic nannofossil chalk.