HR: 0800h
AN: G21C-0688    [Abstracts]
TI: Fore-arc Counterclockwise Rotation In Southern Mexico: Implications For The NA-CA-CO Triple Junction
AU: * Andreani, L
EM: andreani@cdf.u-3mrs.fr
AF: College de France - Chaire de Geodynamique, Europole de l'Arbois, Batiment Trocadero, BP80, Aix-en-Provence, 13545, France
AU: Le Pichon, X
EM: lepichon@cdf.u-3mrs.fr
AF: College de France - Chaire de Geodynamique, Europole de l'Arbois, Batiment Trocadero, BP80, Aix-en-Provence, 13545, France
AU: Rangin, C
EM: rangin@cdf.u-3mrs.fr
AF: College de France - Chaire de Geodynamique, Europole de l'Arbois, Batiment Trocadero, BP80, Aix-en-Provence, 13545, France
AU: Martinez-Reyes, J
EM: jmr@geminis.geociencias.unam.mx
AF: U.N.A.M. - Centro de Geociencias, Campus de Juriquilla, Queretaro, 76230, Mexico
AB: Numerous studies, mainly based on structural and paleomagnetic data, consider the Southern Mexico as a crustal block (Southern Mexico Block, SMB) uncoupled from the North American plate with a southeast motion with respect to North America accommodated by extension through the central Trans-Mexican Volcanic Belt (TMVB). On the other hand, the accommodation of this motion on the southeastward boundary, especially at the Cocos/Caribbean/North American triple junction is still debated. The boundary between the SMB and the North American plate is constituted by three connected zones of deformation: (1) left-lateral transtension across the central TMVB, (2) left-lateral strike-slip faulting along the eastern TMVB and Veracruz area and (3) reverse and left- lateral strike-slip faulting in the Chiapas area. We show that these three active deformation zones accommodate a couterclockwise rotation of the SMB with respect to the North American plate. We specially discuss the Quaternary motion of the SMB with respect to the surrounding plates near the Cocos/Caribbean/North American triple junction. The model we propose predicts a Quaternary couterclockwise rotation of 0.45 deg/Ma with a pole located at 24.2N and 91.8W. Finally we discuss the geodynamic implications of this counterclockwise rotation. The Southern Mexico Block motion is generally assumed to be the result of slip partitioning at the trench. However the obliquity of the subduction is too small to explain slip partitioning. The motion could be facilitated by the high thermal gradient and gravitational collapse that affects central Mexico or by partial coupling with the eastward motion of the Caribbean plate.
DE: 8002 Continental neotectonics (8107)
DE: 8158 Plate motions: present and recent (3040)
DE: 9350 North America
SC: Geodesy [G]
MN: 2007 Fall Meeting