Tectonic Control of the Volcano-Sedimentary Sequence of the Chapala Graben, Western Mexico

Abstract

The Chapala graben forms part of a regional system of intra-arc and half-grabens located along the western and central portions of the Mexican Volcanic Belt. Results of a stratigraphic and tectonic study of the thick, widespread volcano-sedimentary sequence around the Chapala graben are reported. The study has concentrated on the distribution of lacustrine deposits and on the stratigraphy, geochronology, and deformation of the sequence. The volcano-sedimentary record suggests a probable link between the Tepic-Zacoalco and Chapala grabens through a basin system developed during late Miocene and early Pliocene time. The stratigraphic sections show a southward spatial migration of the basin (and lake) system. The main unit of the volcano-sedimentary succession is the Chapala Formation, which has been affected by northeast tilting, unlike the lacustrine deposits to the east in the Chapala plain (e.g., Ixtlan area), where the sequence is essentially flat lying. Two distinct units with different structural attitudes, separated by an angular unconformity, can be distinguished in the Chapala Formation. Based on differences between the stratigraphic sections and structural attitudes, we propose a model for development of the Chapala graben that involves a combination of left-lateral and extensional deformation, together with volcanic and erosional processes, all of which have contributed to shape the basin. Furthermore, we suggest that Lake Chapala is the remnant of a large Jalisco paleo-lake in westcentral Mexico.

Comparative phylogeography of livebearing fishes in the genera Poeciliopsis and Poecilia (Poeciliidae: Cyprinodontiformes) in central Mexico

“…Northern lineages in these two groups (i.e. the ones that gave rise to P. latidens and P. presidionis ) were able to migrate northwestwardly from the Lake Chapala region (which was part of a much larger lake that included the northern portion of the Colima Graben; see Rosas‐Elguera & Urrutia‐Fucugachi, 1998) through the Tepic Graben (Fig. 1) into their present distributions, along Pacific coast drainages north of the TMVB.…”

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

“…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.…”

Magnetic characteristics of fracture zones and constraints on the subsurface structure of the Colima Volcanic Complex, western Mexico

“…The Colima rift forms part of a major tectonic structure that intersects and forms a rift-rift-rift continental triple junction to the north of the CVC and south of Guadalajara region (Fig. 1), and that has been intensively studied (e.g., Luhr andCarmichael, 1980, 1990;Allan and Carmichael, 1984;Allan, 1986;Urrutia-Fucugauchi and Molina-Garza, 1992;Rosas-Elguera et al, 1996;Rosas-Elguera and Urrutia-Fucugauchi, 1998). The Colima rift has been considered as the eastern boundary of the Jalisco block; its southern segment has a general orientation that varies north-northeast-south-southwest with respect to its north-south regional trend.…”