Superfast Spreading on the East Pacific Rise, 26-32 deg. South

Preliminary Results of a GLORI-B & SeaBeam 2000 Survey

Chief Scientist: R.N. Hey

Co-Chief Scientist: F. Martinez

Research Assistant: P.D. Johnson

Introduction

During the spring of 1993 we conducted a 42 day oceanographic expedition, leaving from Tahiti and ending at Easter Island, to survey the East Pacific Rise between the Easter and Juan Fernandez microplates. Figure 1 shows the survey track (the red line) as well as the regional features of interest. The survey utilized the new GLORIA system (GLORI-B), that is now capable of collecting both sidescan and bathymetric data, and the Sea Beam 2000 system. Gravity and magnetics geophysical data were collected as well.

Figure 1. Location map showing the ship track for the GLORI-B/SeaBeam 2000 survey. Click on the image for an expanded color view.

Preliminary Interpretation

The survey was designed to examine the end member case of fast seafloor spreading. Portions of this region had been previously surveyed but little was known of the tectonic history of the area. The cruise was successful in imaging the spreading center between the two microplates as well as a significant portion of the seafloor surrounding the ridges. Among the most notable findings of the cruise was that this region has undergone a repeated history of spreading center reorganization intermediate between a duelling propagator system and a proto-microplate.

The color shaded-relief bathymetric map (Figure 2) was generated from the SeaBeam 2000 and GLORI-B data. It reveals a giant duelling propagator system near 29S. This system, which is the largest one currently known, is presently forming (or recently attempted to form) a small microplate, much like the Easter microplate to the north or the Juan Fernandez microplate to the south.

GLORI-B Processing

As this was the trial cruise for the GLORI-B system many artifacts were present in the bathymetric data. These artifacts were corrected by using the SeaBeam 2000 and other bathymetric data as a reference for the GLORI-B data. Through a series of steps using the GMT program the artifacts were removed and a low resolution data set was constructed. The SeaBeam 2000 was overlaid on top of the low resolution GLORI-B data so that the final image shown above has the GLORI-B data filling the gaps between the SeaBeam 2000 swaths. To see more information on this topic click HERE.

Papers (or Abstracts) on this Topic

• Hey,R.N., Martinez,F., Johnson,P.D., Korenaga,J., Somers M., Huggett.Q., Campbell,J.,Le Bas,T., Beale,R., Rusby,R., Korenaga,J. GLORI-B / Sea Beam 2000 Survey of the Fastest Seafloor Spreading Center Tran. Am. Geophys. Union. 74 (43), 1993
• Hey,R.N., Johnson,P.D., Martinez,F., Korenaga,J., Protoplate Tectonics Along the Fastest Seafloor Spreading Center Trans. Am. Geophys. Union 75 (44), 1994
• Johnson,P.D.,Hey,R.N.,Martinez,F.,Recent Development of the Large-scale Overlapping Ridge System, EPR 30S Revealed by a new GLORI-B Processing Technique Trans. Am. Geophys. Union 75 (44), 1994