HR: 0800h
AN: T41A-06    [Abstracts]
TI: Seismotectonic results relative to the Isthmus of Tehuantepec: Mexico
AU: * Velasquillo, L G
EM: lgvelas@imp.mx
AU: Barrier, E
EM: eric.barrier@lgs.jussieu.fr
AF: Roland Gaulon, 19 rue Jean-Jacques Rousseau, Paris, 75001, France, Metropolitan
AU: Gaulon, R
EM: roland.gaulon@wanadoo.fr
AF: Roland Gaulon, 19 rue Jean-Jacques Rousseau, Paris, 75001, France, Metropolitan
AU: Chavez, M
EM: chavez@servidor.unam.mx
class='hr'> AB: The Isthmus of Tehuantepec (IT) is located at the southeastern of Mexico and at the North of the Zone of Fractures of Tehuantepec (ZFT), which subducts with the Cocos plate under the North American plate at the level of the Gulf of Tehuantepec. The seismotectonic study of the area of the IT showed that the current structure of the Isthmus results from the superposition of three distinct extensional types of tectonisms which took place since the upper Miocene (10 Ma). The oldest one took place between 10 Ma and 8 Ma, and had as a consequence a zone of trans-isthmian rupture along a major normal N-S fault system. This fault system is responsible for the tilting to the NW of the Chiapas batholith and the folded belt of the Sierra of Chiapas. After this first extensional phase, two distinct extensive episodes developed simultaneously and independently, respectively in the North and South areas of the IT. They are still active. One of then is linked to the multi-directional extension, and was highlighted by the study of the brittle structures in the North of the Isthmus, which is assigned to the evolution of the passive margin of the Gulf of Mexico. The other one is associated to the N-S and NNE-SSW extensions, related to the collapse of the coastal plain of Tehuantepec towards the southern part of the isthmus, which are associated with the subduction process of the ZFT. The field work made it possible to highlight the presence of recent N-S at NNE-SSW normal fault systems which mark the western limit of the Tehuantepec plain and that of the coastal Pacific plain of Central America.
DE: 8000 STRUCTURAL GEOLOGY
DE: 8002 Continental neotectonics (8107)
DE: 8107 Continental neotectonics (8002)
SC: Tectonophysics [T]
MN: 2007 Joint Assembly