HR: 15:24h
AN: GP33B-07    [Abstracts]
TI: New Insights Into the Farallon Plate Break-Up
AU: * Barckhausen, U
EM: udo.barckhausen@bgr.de
AF: BGR Fedral Institute for Geosciences and Natural Resources, Stilleweg 2, Hannover, 30655 Germany
AU: Engels, M
EM: m.engels@bgr.de
AF: BGR Fedral Institute for Geosciences and Natural Resources, Stilleweg 2, Hannover, 30655 Germany
AU: Cande, S
EM: scande@ucsd.edu
AF: Scripps Institution of Oceanography, 9500 Gilman Drive, La Jolla, CA 92093
AU: Ranero, C R
EM: cranero@icm.csic.es
AF: Instituto de Ciencas del Mar, Paseo Mar¡timo de la Barceloneta 37-49, Barcelona, 08003 Spain
AU: Weinrebe, W
EM: wweinrebe@ifm-geomar.de
AF: IfM-GEOMAR, Wischhofstrasse 1-3, Kiel, 24148 Germany
AB: The break-up of the Farallon plate was the most important event during the Early Miocene plate tectonic reorganization of the East Pacific. The opening of a new oceanic spreading center perpendicular to the existing Pacific spreading is unique and probably had far-reaching consequences for the active continental margins of Central- and South America. Most of the original fissure where the Farallon plate split into the Cocos plate and the Nazca plate has already been subducted beneath Central- and South America together with much of the oceanic crust that was formed during the early phase of Cocos-Nazca spreading. This made a full reconstruction of plate kinematics in the area back to the time of the opening poorly constrained and left many questions open about the mechanisms involved and the subduction zones affected by this event. During a R/V Sonne cruise in late 2004 the area conjugate to the Farallon remains offshore Costa Rica and Ecuador was investigated in the Central Pacific around 120° W, just south of the Equator. With the new magnetic data it was possible to identify seafloor spreading anomalies between chrons 7 and 5A for a large area in the Central Pacific. In combination with picks of the same anomalies from the Cocos- and Nazca plates it was possible to trace back the history of the Farallon break-up in a three-plate reconstruction. The plate motion of the Pacific plate in the hotspot reference frame provides the absolute position of the initial triple junction and the strike direction of the newly formed Cocos-Nazca spreading center, revealing its close relation to the Galapagos hotspot and the Central American subduction zone. The multibeam bathymetry data from the research area highlight the details of an increased magmatic activity near the newly formed triple junction and the reorganization of the seafloor spreading that followed the break-up and which finally resulted in a major ridge jump at the East Pacific Rise during chron 6.
DE: 1517 Magnetic anomalies: modeling and interpretation
DE: 1525 Paleomagnetism applied to tectonics: regional, global
DE: 3039 Oceanic transform and fracture zone processes
DE: 3045 Seafloor morphology, geology, and geophysics
DE: 8158 Plate motions: present and recent (3040)
SC: Geomagnetism and Paleomagnetism [GP]
MN: Fall Meeting 2005