Late Miocene to Quaternary extension at the northern boundary of the Jalisco Block, western Mexico: The Tepic-Zacoalco Rift revised

Abstract

In the last decade several tectonic models have considered the Jalisco block (JB) as an incipient microplate which is rifting away from mainland Mexico since Pliocene time due to an eastward "jump" of the East Pacific Rise. These models predict normal and right-lateral faulting along the northern boundary of the JB, called the Tepic-Zacoalco rift (TZR). However, the Plio-Quaternary kinematics of the Jalisco block has remained unclear due to the scarcity of structural data along its boundaries. We present a new picture of the structure, the kinematics and time of deformation along the TZR obtained by geological and structural mapping integrated with subsurface stratigraphic data provided by deep geothermal drilling.What has previously been defined as the TZR is actually a combination of different fault systems developed during Late Miocene (12-9 Ma), Early Pliocene (5.5-3.5 Ma) and, to a lesser extent, in Late Pliocene to Quaternary times. These structures can be grouped in three branches: 1) a northwestern branch, named the Pochotitán fault system, consisting of listric faults belonging to the Gulf Extensional Province; 2) a central branch made of en echelon grabens which reactivated the boundary between the JB and the Sierra Madre Occidental; 3) a southern branch constituted by detachment faults located inside the Jalisco block. The Pochotitán fault system is composed of northnorthwest-trending, high angle normal faults which tilt up to 35° towards east-northeast blocks of the Sierra Madre Occidental succession. These faults accommodate at least 2,000 m of vertical displacement related to 12-9 Ma "Protogulf" extension. The central branch consists of two composite grabens developed along an older transcurrent deformation zone. The western one, the Compostela-Ceboruco graben, is a complex asymmetrical depression developed during Late Miocene and Pliocene time with vertical displacement exceeding 2,000 m. Toward the east is the Plan de Barrancas-Santa Rosa graben, a west-southwest-trending and 30-km-wide depression, bounded to the north by the Santa Rosa-Cinco Minas fault and to the south by the Plan de Barrancas fault and its buried southeastern prolongation detected by geophysical studies under the Tequila volcano and the southwestern part of La Primavera caldera. The graben displays a total vertical displacement of ~550 m mainly achieved during early Pliocene time. The southern branch is formed by the Amatlán de Cañas half-graben Ferrari, L., and Rosas-Elguera, J., 1999, Late Miocene to Quaternary extension at the northern boundary of the Jalisco block, western Mexico: The Tepic-Zacoalco rift revised, in Delgado-Granados, H., Aguirre-Díaz, G., and Stock, J. M., eds., Cenozoic Tectonics and Volcanism of Mexico: Boulder, Colorado, Geological Society of America Special Paper 334.The great majority of the 295 measured mesofaults of Late Miocene to Quaternary age have pitches higher than 45° and inclinations ranging between 45° and 75°, typical of normal faults. The paleo-stress field has been computed by fault-slip ...

Structural pattern at the northwestern sector of the Tepic-Zacoalco rift and tectonic implications for the Jalisco block, western Mexico

“…Instead, this structural pattern at the western end of the Tepic-Zacoalco rift seems consistent with dominant extensional tectonics as documented for the Pliocene and Quaternary (Nieto-Obregon et al, 1992;Rosas-Elguera et al, 1996;Ferrari and Rosas-Elguera, 2000;Ferrari, 1995). SW-directed motion of the Jalisco block could explain the formation of the depression of the Tepic-Zacoalco rift SE of the Tepic area.…”

“…Westward (and northwestward) rifting of the block requires various amounts of right-lateral strike-slip faulting along its northern boundary (Luhr et al, 1985;Allan et al, 1991). Recent studies, however, show that the Tepic-Zacoalco graben underwent dominant NE-directed extension during the Pliocene and Quaternary (e.g., Nieto-Obregon et al, 1992;Michaud et al, 1991;Ferrari, 1995;Rosas-Elguera et al, 1996;Rosas-Elguera and Urrutia-Fucugauchi, 1998;Ferrari and Rosas-Elguera, 2000). In this paper we discuss the structural pattern of the northwestern boundary of the Jalisco block as inferred from analysis of the aeromagnetic anomalies and geologic and structural mapping.…”

“…We show that major structural trends at its northernmost boundary, west of Tepic, are not consistent with recent W or NW directed motion of the Jalisco block. Ferrari (1995) and Ferrari and Rosas-Elguera (2000) have documented that the boundary between the Jalisco block and the Sierra Madre Occidental is marked by the northernmost occurrences of the Cretaceous-Paleocene igneous rock assemblage that characterizes the bulk of the Jalisco block ( Fig. 2(a)).…”

Overview of the 1997–2000 activity of Volcán de Colima, México

“…Murray and Ram| ¤rez Ruiz, 2002) Measurements of distance changes from the summit of Volca ¤n de Colima to benchmarks situated on the lower slopes of the volcano revealed abrupt shortenings during the interval 27 November to 31 December, 1997. The shortening was greatest (up to 46 cm) for the line between summit re£ector PT4 and the Fresnal station on the Johnson and Harrison (1990), Allan et al (1991), Carmichael et al (1996), and Ferrari and Rosas-Elguera (2000). These faults outline three major rift zones: CRZ, Colima Rift Zone; ChRZ, Chapala Rift Zone; and TZRZ, Tepic-Zacoalco Rift Zone.…”

Description of the Geology of the Tecolotlan Graben, Jalisco, Mexico

“…The Jalisco block is bounded by the Middle America Pacifi c Trench to the south and west, by the Tepic-Zacoalco rift on the north, and by the Colima rift on the east. The beginning of extension along these two grabens is not well constrained, but they probably started to form in the middle to late Miocene (Allan, 1986;Bandy et al, 2000;Ferrari and Rosas-Elguera, 2000;Gómez-Tuena et al, 2006Ferrari et al, 2012). Several smaller grabens in the northern part of the Jalisco block trend NW-SE and are considered part of the TepicZacoalco rift (Ferrari et al, 1994;Bandy et al, 2000;Ferrari and Rosas-Elguera, 2000;Ferrari et al, , 2012.…”