HR: 0800h
AN: T41A-1163    [Abstracts]
TI: Bathymetry and Seafloor Reflectivity of the Intra-transform Spreading Center Along the Rivera Transform at 108ř15'W
AU: * Mortera-Gutierrez, C A
EM: carlosm@ollin.igeofcu.unam.mx
AF: Universidad Nacional Autonoma de M‚xico, Instituto de Geofisica, Coyoacan, DF 04510 Mexico
AU: Bandy, W L
EM: bandy@tonatiuh.igeofcu.unam.mx
AF: Universidad Nacional Autonoma de M‚xico, Instituto de Geofisica, Coyoacan, DF 04510 Mexico
AU: Michaud, F
AF: Universit‚ Pierre-et-Marie-Curie, UMR-G‚osciences Azur, Villefranche-sur-Mer, 06230 France
AU: Bourgois, J
AF: Escuela Politecnica Nacional, IRD/CNR, Quito, 00000 Ecuador
AU: Calmus, T
AF: Universidad Nacional Autonoma de M‚xico, Instituto de Geologia, Estacion Regional del Noroeste, Hermosillo, SON 83000 Mexico
AU: Dyment5, J
AF: Universit‚ Pierre-et-Marie-Curie, Centre National de la Recherche Scientifique, Plouzan‚, 29820 France
AU: Ortega-Ramirez, J
AF: Universidad Nacional Autonoma de M‚xico, Instituto de Geofisica, Coyoacan, DF 04510 Mexico
AU: Pontoise, B
AF: Universit‚ Pierre-et-Marie-Curie, Institut de Recherche pour le Developement, Paris, 75252 France
AU: Royer, J
AF: Universit‚ Pierre-et-Marie-Curie, Centre National de la Recherche Scientifique, Plouzan‚, 29820 France
AU: Sichler, B
AF: IFREMER, BP 70, Plouzan‚, 29280 France
AU: Sosson, M
AF: Universit‚ de Nice-Sophia Antipolis, G‚osciences Azur, Sophia Antipolis, 06560 France
AU: Bigot-Cormier, F
AF: Universit‚ de Nice-Sophia Antipolis, G‚osciences Azur, Sophia Antipolis, 06560 France
AB: The first proposal of an intra-transform spreading center along the Rivera transform at 108ř15'W was based on microseismicity data. During projects BART and FAMEX, conducted during 2002 aboard the N/O L'Atalante, 100% of the Rivera transform was covered by multibeam bathymetric and seafloor reflectivity data. These data show that the Rivera transform is marked by a broad, deep basin between 107ř30'W and 109ř12'W and can be subdivided into two smaller basins based on morphologic characteristics. The previous proposed intra-transform spreading center is located within the eastern basin which lies between 107ř30'W and 108ř35'W. This basin is approximately 110 km long, 18 to 20 km wide and exhibits a rhomboidal shape elongated in a NW-SE direction. Broad sediment filled depressions lie at the basin's eastern and western sides. The surface sediments in these depressions are undisrupted. Narrow bathymetric troughs lying at the base of prominent escarpments form the basin's northern and southern sides. The reflectivity data suggests that along the northern trough recent faulting is occurring only west of the proposed intra-transform spreading center, whereas along the southern trough recent, discontinuous faulting is occurring only east of the spreading center. The seafloor within the central part of the basin is rough and domed shaped. Seismic reflection and seafloor reflectivity data indicate a lack of sediments over the dome. This dome is broken by a deep sediment free trough at the location of the intra-transform spreading center indicated by the microseismicity data (108ř15'W). Several small discontinuous faults trending oblique to the trend of the northern and southern boundary troughs are observed within the basin. The above characteristics suggest that the intra-transform spreading center does indeed exist. The magnetic lineations associated with this spreading center are difficult to model. However, assuming a spreading rate of 7 cm/yr, as is predicted from several proposed Rivera-Pacific relative motion models, the magnetic anomaly pattern is consistent with an initiation of spreading sometime between Chron 2 and the Jaramillo event, and that spreading has been asymmetric (2 cm/yr to the west and 5 cm/yr to the east). The discontinuous faulting along the southern trough and the presence of small discontinuous oblique faults in the center of the basin seems indicate a recent reorganization of the transform boundary. This reorganization may involve an extinction of the intra-transform spreading and the formation of a single transform running through the center of the basin. In support of this proposal, the Rivera transform east of the basin is very well fit by a single small circle and that the projection of this small circle runs through the center of the basin, oblique to the trend of the northern and southern boundary troughs.
DE: 8010 Fractures and faults
DE: 8150 Plate boundary--general (3040)
DE: 8158 Plate motions--present and recent (3040)
DE: 3040 Plate tectonics (8150, 8155, 8157, 8158)
DE: 3045 Seafloor morphology and bottom photography
SC: Tectonophysics [T]
MN: 2004 AGU Fall Meeting