The role of crustal heterogeneity in controlling vertical coupling during Laramide shortening and the development of the Caribbean-North America transform boundary in southern Mexico: insights from analogue models

Abstract

Analogue models of polyphase deformation involving crustal differences in strength, thickness and density give insights into lateral and vertical strain propagation during Late Cretaceous shortening and Early Tertiary left-lateral shearing related to the early development of the North America-Caribbean plate boundary in southern Mexico. Analogue models reproduce a two-phase deformation characterized by a first stage of compression orthogonal to the plate boundary, simulating deformation induced by the Laramide orogeny, followed by a later stage of left-lateral transpression associated with the transfer of the Chortis block from the North American to the Caribbean plate during the early stage of development of the new plate boundary in Early Tertiary times. Based on detailed structural observations in the Guerrero-Morelos platform and the western part of the Mixteco terrane of southern Mexico, we document that a transpressive regime affected continental red bed sequences of Early Paleocene to Late Eocene, and rotated and refolded Laramide structures during this second phase. Our model ends before the transtensional regime that affected the region, which is marked by a volcanic episode of Late Eocene-Oligocene. This change in the deformation regime records the passage of the NW tip of the Chortis block (North America-Cocos-Caribbean triple junction), when subduction replaced transform faulting along the southern Mexico margin. The models focus on the structures formed around the flanks of a thicker/more rigid crustal block that simulates the rock assemblages of the Palaeozoic orogens of southern Mexico (Mixteco-Oaxaca-Juarez block, MOJB). The comparison of the mechanism of deformation of three different analogue models with the natural prototype explains most of the structures observed around the MOJB. Counterclockwise vertical-axis rotations of pre-existing structures in the western flank of the MOJB observed in the Guerrero-Morelos platform are consistent with the modelled structures. Vertical movements of the modelled MOJB induced by the transpressive regime can explain the Papalutla thrust and the basement upheaval and gravitational sliding of the cover in the Tentzo Ranges observed at the western and northern margins of the MOJB, respectively. The growth and propagation of thrusting controlled by the geometry of the block along the eastern margin also correlates with the Vista Hermosa fault. The propagation of strain to the north increases with higher contrast in strength of the thick block with respect to the adjacent modelled crust. Analogue modelling failed to reproduce all the structural details of southern Mexico and, specifically, the structures observed inside the MOJB. The latter, however, are controlled by pre-existing discontinuities, which are not simulated in the model. As a whole, the results demonstrate that crustal heterogeneity in a developing left-lateral plate boundary zone produces a stronger vertical coupling between ductile and brittle crust and a widening of the deformation zone along the...

Analogue models of an Early Cenozoic transpressive regime in southern Mexico: implications on the evolution of the Xolapa complex and the North American-Caribbean Plate boundary

“…The overall structural evolution exhibited by the experiments was similar to previous models of Cerca et al (2004). Our analysis focuses on structures formed during the strike -slip-dominated second phase of deformation with two end-member experiments.…”

“…Our brittle -ductile two-layer crustal analogue models represent a further development of the series reported by Cerca et al (2004). Two phases of deformation documented in southern Mexico were simulated:…”

“…We realize that the use of this highly cohesive material is out of scale with respect to natural systems (Table 1), but it has the effect of enhancing the deformation patterns around the stronger block. For further details in scaling and material properties see Cerca et al (2004). Thus deformation patterns in the brittle layer are enhanced.…”

La evolución tectónica y magmática cenozoica del suroeste de México: avances y problemas de interpretación

“…En la zona occidental del sur de México hay edades de magmatismo considerado postorogénico desde el fi nal del Maastrichtiano en la zona occidental (OrtegaGutiérrez, 1980;González-Partida et al, 2003;Levresse et al, 2004;Cerca et al, 2004). También dentro de esta zona hay algunas estructuras como el pliegue de Tzitzio, cuya cinemática y edad de deformación no están bien comprendidas y parecen constituir una anomalía con respecto al patrón de deformación progresiva por acortamiento en la región.…”

“…El reconocimiento de este basamento de características contrastantes ha permitido comprender mejor algunos aspectos de la evolución tectónica mesozoica y cenozoica del sur de México. Otros antecedentes importantes son los trabajos en los que se han reconocido y descrito los aspectos generales de la estratigrafía cenozoica en diferentes zonas del sur de México (i. e., Fries, 1960Fries, , 1966De Cerna y Fries, 1981;Ferrusquía-Villafranca, 1976Martiny et al, 2000) y en los que se describen algunos rasgos tectónicos sobresalientes (Ratschbacher et al, 1991;Tolson et al, 1993;Riller et al, 1993;Meschede et al, 1996;Nieto-Samaniego y AlanizÁlvarez, 1995;Alaniz-Álvarez et al, 2002;Cerca et al, 2004). Existen además numerosas contribuciones recientes sobre la geocronología y la geoquímica de las rocas magmáticas cenozoicas en esta región que han permitido defi nir patrones espacio-temporales de la actividad magmática y algunos de los aspectos petrogenéticos más sobresalientes (i. e., Herrmann et al, 1994;Schaaf et al, 1995;Morán-Zenteno et al, 1999Martiny et al, 2000;Meza-Figueroa et al, 2003;González Partida et al, 2003;Ducea et al, 2004a).…”