Deep crustal structure of the Adare and Northern Basins, Ross Sea, Antarctica, from sonobuoy data

- 71 new sonobuoy records constrain crustal structure near Cape Adare, Antarctica.
- Adare Basin has velocities indicating lower oceanic crust at 3-5 km subseafloor.
- This is consistent with an oceanic core complex formed at a slow-spreading ridge.
- Northern Basin sediments are >3 km thick, consistent with reflection seismic data.
- Deep 2D velocity contours indicate a continuity of crustal type between the basins.

Extension associated with ultraslow seafloor spreading within the Adare Basin, in oceanic crust just north of the continental shelf in the Ross Sea, Antarctica, extended south into the Northern Basin. Magnetic and gravity anomaly data suggest continuity of crustal structure across the continental shelf break that separates the Adare and Northern Basins. We use sonobuoy refraction data and multi-channel seismic (MCS) reflection data collected during research cruise NBP0701, including 71 new sonobuoy records, to provide constraints on crustal structure in the Adare and Northern Basins. Adjacent 1D sonobuoy profiles along several MCS lines reveal deep crustal structure in the vicinity of the continental shelf break, and agree with additional sonobuoy data that document fast crustal velocities (6000-8000 m/s) at shallow depths (1-6 km below sea level) from the Adare Basin to the continental shelf, a structure consistent with that of other ultraslow-spread crust. Our determination of crustal structure in the Northern Basin only extends through sedimentary rock to the basement rock, and so cannot help to distinguish between different hypotheses for formation of the basin.