The history of separation of the Pacific and Antarctic plates, along the Pacific-Antarctic ridge and transform fault system in the SW Pacific Ocean, is important to a variety of global plate motion problems. For example, this is the only boundary we can use to reconstruct the motion of the Pacific plate relative to any continental plate for times older than a few million years. In trying to understand the plate motions in this region, any deformation that may have occurred within the Antarctica plate is also very important. In order to study this problem, the National Science Foundation gave us support to conduct a series of geophysics cruises in the Pacific and Antarctic regions:
These cruises were collaborations with Steve Cande of Scripps Institution of Oceanography, Carol Raymond of the NASA-Jet Propulsion Lab, and Dietmar Mueller of the University of Sydney.
On these cruises, we collected gravity, magnetics, seismics (multi-channel and single-channel) and swath bathymetric data. These data have allowed us to determine more details of the early history of spreading of the Bellingshausen plate relative to Pacific, and have allowed us to constrain very well the original position of the Campbell Plateau relative to the Iselin Bank and Marie Byrd Land crust of West Antarctica. We also identified NNW-striking magnetic anomalies in the northern Ross Sea which appear to have been formed by Early Tertiary seafloor spreading between East and West Antarctica.
In collaboration with Steve Cande we also collected geophysical data on transit cruises on the Nathaniel B. Palmer across the south Pacific ocean. The following cruises were included under this program: NBP9908a, NBP0007b, NBP0008, NBP0403, NBP0501B, NBP0804. In addition we collected underway geophysical data on cruise NBP-01-02 in the South Atlantic Ocean, and cruise NBP02-07 in the Pacific Ocean as part of a Caltech at-sea marine geophysics class, Ge211 .
Cruise NBP0209, from Lyttelton to McMurdo, surveyed the western side of the Campbell Plateau, surveyed some of the westernmost segments of the Pacific-Antarctic ridge, and did detailed surveys, including some single- channel seismic reflection profiles, in the region of the southern Adare Trough. This allowed us to establish its structural and magnetic continuity a bit farther south from the region surveyed on NBP9702. Cruise NBP0501 continued this work on a transit from McMurdo back to Lyttelton, by surveying gravity, magnetics, and additional swath bathymetry.
Cruises NBP0304 and NBP0304B went from Lyttelton to Dutch Harbor, Alaska, and back, via Honolulu. On these cruises we collected transit geophysical data in the Kermadec trench, across the Osbourn Trough, across the Manihiki Plateau, across some seafloor features south of Hawaii, and across some of the major Pacific plate tectonic features north of Hawaii (including the eastern end of the Chinook Trough).
Cruise NBP0406 went from Cape Town to Lyttelton through the Indian Ocean and surveyed along the southern boundary of the rifted margin of the Australian plate (Diamantina zone).
Click here for a plot of the ship tracks from the main cruises and the transit cruises in the South Pacific.
Metadata for these cruises is filed with the US Antarctic Data Coordination Center http://gcmd.nasa.gov,
Cruise NBP0602 surveyed from McMurdo to Punta Arenas to continue our study of the West Antarctic margin and the Bellingshausen plate. In addition we did a bathymetric survey of part of the Antarctica-Scotia plate boundary at the trench and slope west of the Straits of Magellan.
Cruise NBP0607A surveyed from Chile to New Zealand, providing additional constraints on the history of Pacific-Antarctica spreading.
Cruise NBP0607C was an equipment testing cruise (for seismic equipment) which also hosted a marine geophysics class, Ge211, with students from Caltech, UC Santa Barbara, and numerous other institutions.
Cruise NBP0701 collected multichannel seismic data, sonobuoy data, and multibeam bathymetry in the northern Ross Sea to better understand the formation of new crust along the early Tertiary rift system between East and West Antarctica.
Cruise NBP0804 collected transit geophysical data between Chile and New Zealand.
This material is based upon work supported by the National Science Foundation under grant numbers 9814579, 0126334 and 0338317.
