CENTRAL

Begin of project: August 1, 2004

End of project: September 30, 2006

Status of project: March 19, 2007

East Pacific: bathymetric map with fracture zones, spreading centers and area of BGR-geophysical survey. Source: BGR

In the early Miocene, the Farallon plate in the East Pacific broke into two pieces along a fracture zone to form the Cocos and Nazca plates. A new spreading center established along the fissure and has been active since 23 Ma. Most of the remains of the fissure have already been subducted beneath Central- and South America leaving us with little evidence about the tectonic processes that were involved in the break-up of the Farallon plate. There are three main reasons why we want to know more about the Farallon break-up and the following development of the Cocos-Nazca spreading center:

(1) The formation of a new spreading center along a preexisting fracture zone and perpendicular to another active spreading center seems to be unique and is poorly understood.

(2) A possible influence of the nearby Galapagos hotspot has been discussed but remains speculative until its position relative to the fissure at the time of the break-up can be reconstructed.

(3) The changes in the tectonic regime of the area probably had major consequences for the subduction zones in Central- and South America.

Since Central America is one of the focus areas where the international scientific community studies subduction zone processes in detail, a better reconstruction of the changes in the subduction system over time is much desired.

The project CENTRAL tries to answer these questions by collecting geophysical data in an area of the Pacific plate (Fig. 1) which is conjugate to the remains of the Farallon fissure that are today being located offshore Costa Rica and Equador, resp.. Until now, very few data exist from the CENTRAL study area. The tectonic structures which formed at the west side of the East Pacific Rise (EPR) while at the same time the Farallon plate fell apart on the east side of the EPR have not yet been discovered. With magnetic and bathymetric measurements we will determine the age of the oceanic crust and define structural elements which finally allow us to reconstruct the full plate tectonic history of the Pacific, Cocos, and Nazca plate for the last 23 Mill. years.

Literature:

• U. Barckhausen, C. R. Ranero, R. von Huene, S. C. Cande & H. A. Roeser (2001), Revised tectonic boundaries in the Cocos plate off Costa Rica: Implications for the segmentation of the convergent margin and for plate tectonic models, J. Geophys. Res., 106, 19207-19220.

Partner:

GEOMAR (Kiel)
Scripps Institution of Oceanography (San Diego, USA)

Promotion / document number:

Bundesministerium für Bildung und Forschung (BMBF) 03S0168