Mid-Cretaceous tectonic evolution of the Tongareva triple junction in the southwest Pacific Basin
Principal Investigators:
R. L. Larson and Rob Pockalny, University of Rhode Island
This oceanographic expedition is currently scheduled on Scripps Institution's R/V Melville. We plan to leave Tahiti, French Polynesia on 11 November, 2000 and arrive at Apia, (Western) Samoa on 22 December 2000. This expedition will gather underway geophysical data between those ports. No oceanographic stations, bottom sampling, or island stops are planned. The geophysical systems that will be operated continuously are the SeaBeam 2000 (multibeam bathymetry), 3.5 kHz echo sounder, total field magnetometer and gravitymeter. The ship and geophysical data will be positioned with GPS satellite data.
We shall use these data to map the track of a tectonic triple junction that marked the intersection of three tectonic plates in mid-Cretaceous time (120-80 Ma). Sea floor spreading from two of the remaining three plate boundaries produced lineated abyssal hill topography parallel to each of the spreading centers during this tectonic evolution. This lineated topography should still be visible beneath the thin sediment cover in this area and should be detectable with both the multibeam and magnetometer data. In addition, these spreading centers operated at markedly different spreading rates that should have produced oceanic crust of different thickness. We hope that geophysical models of the gravitymeter data will detect these differences in crustal thickness and thus support the multibeam and magnetometer mapping results.