La falla tamazula, límite suroriental del bloque jalisco, y sus relaciones con el complejo volcánico de Colima, México
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This work shows the results of a microtectonic study carried out in the southern part of the Colima Rift, where four deformation phases were obtained. Phase I is related to a series of subvertical left-lateral faults with orientations from N120° to N150° in Late Cretaceous limestones; this phase is estimated to be of the early Tertiary. Phase II corresponds to lateral and reverse faults oriented from N100° to N130° and N40° to N80°, respectively; the age of this phase is estimated to correspond to the middle Tertiary. Phase III was identified in epiclastic and fluviolacustrine rocks of the Colima Volcanic Complex (CVC), and consists of normal faults of NE-SW direction; an age of less than 20,000 yr can be attributed to this phase. Phase IV corresponds to the Alseseca-Atenquique Graben, with NE-SW direction; this phase is affecting volcanic products of the Paleovolcán de Fuego de Colima and controls activity of the Volcan de Fuego de Colima. Based on this data, this work proposes to consider that the eastern boundary of the Jalisco block is different from that one proposed in previous works. It is possible to observe that the eastern limit of the Jalisco Block is controlled by two regional structures. The Colima Rift changes its geometry at the point where it is intersected by the Tamazula Fault, which allows to conclude that the CVC is located at the intersection of two regional structures. And the Nevado de Colima is being affected by a graben that appears to be a response to the geometry of the Tamazula Fault. The locations of the epicenters plot on a line that is consistent with the ubication of this fault; this fact and the presence of volcanism in the intersection point of this fault with the Colima Rift indicate that this fault is active. The new proposed geometry of the Jalisco Block is confirmed by the seismicity in the Manzanillo-Colima zone, which is controlled by NE-SW faults: the Tamazula Fault, which is fragmenting not only the Jalisco Block, but the Michoacán Block as well. The Tamazula Fault is a basement structure that has governed the geometry of the Colima Rift and the volcanic evolution of the CVC, and has a NE-SW direction and a length greater than 160 km. The normal faults that affect the recent sedimentary deposits present a σ3, which is possibly related to the activity of the Tamazula fault and to the gravitational collapses of the CVC that triggered the big avalanches of its southern sector.
