The Cretaceous-Paleogene Mexican orogen: Structure, basin development, magmatism and tectonics

Abstract

The Mexican orogen is the expression in Mexico of the Cordilleran orogenic system. The orogen extends the length of Mexico, a distance of 2000 km from the state of Sonora in the northwest to the state of Oaxaca in the south. The Mexican orogen consists of (1) a western hinterland of accreted oceanic basinal rocks and magmatic arc rocks generally known as the Guerrero volcanic superterrane, (2) a foreland orogenic wedge, commonly termed the Mexican fold and thrust belt (MFTB), composed of imbricated and folded Upper Jurassic-Lower Cretaceous carbonate rocks and Upper Cretaceous foreland-basin strata, and (3) an assemblage of variably folded and inverted Late Cretaceous to Eocene foreland basins that lie northeast and east of the MFTB. The Mexican orogen encompasses the entire country, spanning several physiographic provinces and deformational domains that display both thin-skinned and thick-skinned structural styles determined by inherited crustal structure and contrasting pre-kinematic sedimentary sections. The orogen contains kinematic characteristics of both the Sevier and Laramide orogens in the United States (U.S.), and deformation in the Mexican orogen spanned the deformational history of those U.S. orogens. The overall trend of the Mexican orogen is NW-SE, although it displays local trend variations. At presently exposed levels, the orogen consists of folded and reverse-faulted Mesozoic-Eocene strata. Lower Cretaceous strata of the deformed foreland are dominated by carbonate rocks, whereas time-equivalent strata in the hinterland consist of deformed plutons belonging to one or more magmatic arcs, as well as turbidites, pillow lavas and altered mafic rocks deposited in an offshore basin prior to consolidation of fringing arc systems to mainland Mexico. Upper Cretaceous syntectonic strata of the foreland orogenic wedge constitute siliciclastic turbidite successions that grade eastward to carbonate pelagites of the distal foreland basin, which was starved of siliciclastic sediment input. Uppermost Cretaceous and Paleogene strata of the foreland basin constitute a shelfal, deltaic and coastal plain fluvial succession in northeastern Mexico and a succession of turbidites in the Tampico-Misantla basin east of the MFTB.

Structural geometry of the orogen was controlled by the spatial distribution of pre-Cretaceous crustal elements, such as Jurassic extensional basins and basement blocks, and detachment horizons at varying stratigraphic levels, as well as the direction of structural vergence, which is dominated by NE-directed tectonic transport throughout the belt. Jurassic evaporite horizons and Upper Jurassic carbonaceous shale units provide detachment surfaces in some parts of the orogen. The structural style of the MFTB is generally thin-skinned, although high-angle faults are present at several localities, where the steep faults cut thin-skinned, shallowly-dipping faults, detachment horizons and associated folds. Strain magnitude decreases toward the foreland and generally satisfies critical wedge predictions. Values of shortening > 70% are present in the hinterland of central Mexico; these decrease systematically to values < 15% to the front of the fold belt where upper Eocene onlap successions in the Gulf of Mexico coastal plain unconformably overlie deformed strata of the orogenic wedge. Exceptions to this pattern of regional shortening values are well documented and are related to lateral variations in mechanical properties caused by facies variations, notably massive platformal carbonates as contrasted with thinly-bedded basinal carbonates.

Shortening history in the Mexican orogen approximately spanned Late Cretaceous-Eocene time. Deformation timing has been constrained using Ar-Ar systematics on illite generated by layer-parallel slip in the limbs of chevron folds. Estimates of deformation timing are in good agreement with the age of synorogenic sedimentary successions, and with ages of syn-tectonic plutons. Published data from central Mexico suggest episodic pulses of deformation between 93–80 Ma, 75–64 Ma and 55–43 Ma, which postdate the closure of the Arperos basin. Each of these shortening events affects rock units lying progressively farther to the east to yield a temporal eastward advance of deformation and sedimentation. Effects of successively younger shortening were superimposed on the westernmost exposures of the thrust belt and are evidenced on a map scale by abrupt trend variations in orogen-interior folds, compared to generally linear or broadly arcuate axial traces of frontal folds.

Although potential tectonic mechanisms for shortening in the Mexican orogen remain debated, our analysis indicates that orogenic wedge development took place in a retroarc setting that postdated consolidation of the hinterland oceanic assemblages, which lay offshore western Mexico during Albian time. Orogen development followed a protracted period of early Mesozoic extension that affected most of the Mexico due to the combined effects of Laurentia-Gondwana separation and long-term Triassic-Jurassic rollback of a paleo-Farallon plate. Slab rollback ultimately resulted in the development of a marginal basin, the Arperos basin, between a rifted Late Jurassic magmatic arc and mainland Mexico. Initial shortening in the Mexican orogen, which followed Arperos basin closure and Guerrero superterrane accretion by ~ 5–10 Ma, was coeval with voluminous magmatism on the Pacific margin of Mexico, drowning of the western carbonate platforms and onset of foreland-basin sedimentation in Cenomanian time. Subduction of the Farallon slab from early Late Cretaceous to Eocene time was thus the primary driving mechanism of shortening in the Mexican orogen.

Introduction

The Mexican orogen is the areally most extensive tectonic feature in Mexico and has a spectacular topographic expression in the Sierra Madre Oriental and the Sierra Madre del Sur (Fig. 1). Because it includes the entire Sierra Madre Oriental physiographic province, the belt has been termed the Sierra Madre Oriental orogenic belt or Sierra Madre Oriental orogen in the literature, but temporally equivalent shortening deformation in fact encompassed the entire modern crustal domain lying between the Pacific Ocean and the Gulf of Mexico. The Mexican orogen has a length of > 2000 km and is hundreds of km wide along an elongate zone that extends northward from the Tehuantepec Isthmus in Oaxaca to northwestern Sonora. The structures in the foreland of the Mexican orogen have a generally NW-SE trend in central Mexico that changes to almost E-W in northeastern Mexico at the Monterrey salient and back again to NW-SE in northwestern Mexico at the Torreón reentrant (Fig. 1). To the south, the MFTB bifurcates to form two separate belts of deformation that flank the southern Mexico metamorphic terranes block, including an eastern belt that continues into the Morelos-Guerrero platform (Fries, 1956) and a western belt that follows the Zongolica range (Fig. 1).

The Mexican orogen consists of thrust faults and folds involving Mesozoic and Paleogene sedimentary strata of eastern Mexico (de Cserna, 1956, Suter, 1984, Suter, 1987, Eguiluz de Antuñano et al., 2000, Gray and Lawton, 2011, Fitz-Díaz et al., 2014a, Fitz-Díaz et al., 2014b; Fig. 2), and locally involves basement rocks (e.g., Chávez-Cabello, 2005, Zhou et al., 2006, Mauel et al., 2011). As in the thrust belt of the Canadian Rocky Mountains (Bally et al., 1966, Price, 1981) and the Sevier and Laramide orogens in the United States (Armstrong, 1974, Weil and Yonkee, 2012), the Mexican thrust belt (Coney, 1981, Campa, 1985) was formed on the external, foreland side of the Cordilleran orogenic system (Fig. 2), which resulted from protracted Jurassic-Paleogene subduction along the western edge of the North America plate (Coney, 1989, Oldow et al., 1989, Dickinson and Lawton, 2001, Dickinson, 2004, DeCelles, 2004, Evenchick et al., 2007). We regard the Mexican thrust belt, or Mexican fold and thrust belt (MFTB) as only the foreland part of the overall orogenic wedge that developed in Late Cretaceous-Paleogene time. A western hinterland part of the wedge occupies much of western Mexico (Fig. 1). The hinterland is composed of young crustal elements assembled by terrane accretion (Centeno-García, 2005), arc-related magmatism (Tardy et al., 1994, Jones et al., 1995), low-grade metamorphism (Elías-Herrera et al., 2000) and localized penetrative deformation (Salinas-Prieto, 1994, Johnson et al., 1999). Pre-orogenic rocks formed coeval with Jurassic rifting (Salvador, 1987) and Early Cretaceous drifting (Goldhammer and Johnson, 2001) in the Gulf of Mexico. The hinterland and foreland domains of the Cordilleran orogenic system in Mexico are separated by a suture of complexly deformed rocks of the Arperos basin, which opened between the Late Jurassic and the Early Cretaceous (Freydier et al., 1998, White and Busby, 1987, Almazán-Vázquez, 1988, Martini et al., 2014) and was deformed in the Albian (Johnson et al., 1999, Martini et al., 2013, Martini et al., 2014, Martini and Ortega-Gutiérrez, in press, Martini et al., 2016, Ortega-Flores et al., 2015).

Although we focus in this review on advances in understanding the Late Cretaceous-Paleogene deformation, syn-orogenic sedimentation and magmatism of the MFTB in the foreland of the Mexican orogen, we also consider new findings on the evolution of the Guerrero terrane in order to establish temporal and spatial connections of deformation episodes, syn-orogenic sedimentary patterns, and magmatism that permit an integrated view of tectonic processes, test existing tectonic models and support those models that consistently explain the origin and evolution of the MFTB. We define the rocks of the Guerrero volcanic superterrane (e.g., Dickinson and Lawton, 2001), or simply Guerrero terrane, which have debated affinity to continental basement of Mexico by virtue of their oceanic character, to constitute the hinterland of the Mexican orogen.

This review also offers a perspective on how knowledge regarding the MFTB has built up through time, as well as on knowledge of different aspects of the tectonic evolution of Mexico that might have influenced the development of the MFTB, including the post-Pangea crustal architecture of Mexico and Mesozoic paleogeography and stratigraphy, Late Cretaceous-Paleogene deformation patterns, timing of deformation in the MFTB, syn-orogenic sedimentation, opening and evolution of the Arperos-Alisitos basin and subsequent accretion of the Guerrero terrane, as well as arc-related magmatism and subduction dynamics on the Pacific flank of Mexico. We also compare the parallelism of deformation processes in the hinterland and foreland Cordilleran domains (Guerrero terrane and MFTB, respectively) and review tectonic models to explain the formation of the MFTB. In particular we address four key points:

• The architecture of Mexican fold and thrust belt, and the influence of inherited paleogeographic elements on Late Jurassic-Paleogene stratigraphy and deformation patterns;

• Spatial and temporal relations of deformation and sedimentation;

• Evolution of subduction-related magmatism within the MFTB;

• A review of tectonic models that integrally explain deformation propagation, magmatism and foreland basin migration within a broad paleotectonic framework that integrates the Guerrero terrane, the Arperos-Alisitos basin and the MFTB.

Prior to the 1950s and into the 1960s, most geological studies in Mexico were focused on mining exploration and definition of regional stratigraphy (e.g., Baker, 1922, Kellum, 1930, Imlay, 1936, King, 1944, Rogers et al., 1961). Only a few pioneer studies were dedicated to describing structures of the Sierra Madre Oriental in NE Mexico (e.g., Böse, 1923, Kellum et al., 1936, Heim, 1940, Álvarez, 1949). Because many of these studies were carried out by geologists from the U.S., a connection or continuity of structures of the Sierra Madre Oriental to structures farther north was suggested (e.g., Humphrey, 1956). The first classic work on the Sierra Madre Oriental by Zoltan de Cserna (1956) presented a map, detailed structural cross-sections, and a kinematic interpretation of folds and thrusts of a broad area that included the Monterrey salient and the Parras transverse sector between Monterrey and Torreón (Fig. 1). De Cserna later included these features in the first tectonic map of Mexico (de Cserna, 1961) and framed the patterns of deformation in a broader tectonic context (Guzman, 1963). Guzman and de Cserna (1963) also applied the term, “Mexican structural belt,” to a group of structures in eastern Mexico formed between the Late Jurassic and Pliocene, and proposed the term, Hidalgoan orogeny, for an early Eocene shortening event, which they correlated with the Laramide orogeny.

The 1960s and 1970s saw more modern structural studies and kinematic interpretation of the MFTB. Carrillo-Bravo, 1961, Carrillo-Bravo, 1965, Carrillo-Bravo, 1971 contributed iconic works on stratigraphy and structure of the MFTB in central Mexico. Mark Tardy (Tardy et al., 1975, Tardy, 1980) revised the geology of the Sierra Madre Oriental in the Mesa Central and Monterrey salient, and applying concepts of Alpine geology, analyzed the effect of pre-orogenic basin architecture on deformation styles of the region.

In the 1980s, with significant advances in understanding of Cordilleran tectonics, Campa and Coney (1983) divided the Mexican territory into tectono-stratigraphic terranes and defined the Sierra Madre terrane as: “…a sequence of folded and imbricated thrust-faulted upper Mesozoic limestones, shale, and sandstone layers of the superjacent Gulf of Mexico transgressive sequence deformed during the Late Cretaceous-early Tertiary Laramide orogeny.” Mesozoic strata were inferred to overlie a succession of Paleozoic sedimentary and metamorphic units with a Precambrian basement in this terrane. Campa (1985) pointed out that the Mexican thrust belt also includes parts of adjacent tectono-stratigraphic terranes, including the Juárez, Mixteco, Coahuila and Chihuahua terranes. Campa (1985) considered the Mexican thrust belt as a transposed tectonic element emplaced at the border between the Guerrero terrane to the west and the eastern autochthonous foreland terranes of Mexico, in the Cordilleran orogenic system.

The 1990s saw continued growth in general understanding of MFTB structural geology and kinematics. As the result of regional mapping projects, Suter (1990) and Carrillo-Martínez (1997) generated remarkable advances in understanding the MFTB in central Mexico (Suter, 1984, Suter, 1987, Suter, 1990, Carrillo-Martínez, 1989, Carrillo-Martínez, 1990); through their work, this is probably the best known part of the MFTB. Padilla y Sánchez mapped and analyzed the geometry of structures of the Monterrey salient (Padilla y Sánchez, 1982, Padilla y Sánchez, 1985). Based in part on this mapping, Marrett and Aranda-García (1999) interpreted the structures of the Monterrey salient and central Mexico in light of advances on kinematic models of structures in fold-thrust belts, and of the orogenic wedge theory. Eguiluz de Antuñano et al. (2000) likewise presented an integrated review of the tectonics of the Sierra Madre Oriental that synthesized published and unpublished data by PEMEX on stratigraphy and large-scale structure of the belt.

Since 2000, studies have focused on understanding kinematics and tectonics (Salinas-Prieto et al., 2000, Ortuño-Arzate et al., 2003, Zhou et al., 2006, Nieto-Samaniego et al., 2006, Alzaga-Ruiz et al., 2009, Roure et al., 2009, Fischer et al., 2009, Fitz-Díaz et al., 2008, Fitz-Díaz et al., 2011a, González-León et al., 2012, Martini et al., 2013), sedimentation (Hernández-Romano et al., 1998, Giles and Lawton, 1999, Lawton, 2008, Lawton et al., 2009, Gray and Lawton, 2011, Ocampo-Díaz et al., 2016), magmatism (González-León et al., 2000, González-León et al., 2011, Valencia-Moreno et al., 2001, Chávez-Cabello, 2005, Cerca et al., 2007, Ramos-Velázquez et al., 2008, Martini et al., 2009), fluid-rock interaction and thermal structure (Gray et al., 2001, Fischer et al., 2009, Ferket et al., 2003, Fitz-Díaz et al., 2011b, Nemkin et al., 2015) and timing and propagation of deformation (Gray et al., 2001, Gray and Lawton, 2011, Cuéllar-Cárdenas et al., 2012, Fitz-Díaz and van der Pluijm, 2013, Fitz-Díaz et al., 2014a, Fitz-Díaz et al., 2014b, Heller and Liu, 2016) along specific transects or areas of the thrust belt. This manuscript is based on a review of classic and recent publications to produce an updated overview of the MFTB.

The term, “fold-thrust belt” is a concept in structural geology that describes a province, generally of significant topography, dominated by shortening structures (folds and thrusts) affecting stratified rocks at very low metamorphic facies to surface conditions. Such belts lie on the continental, or foreland, edges of wider orogenic belts. Because of the belt's proximity to the surface, deformation, erosion and sedimentation are interacting processes in fold-thrust belts (Dahlstrom, 1970, Chapple, 1978, Price, 1981, Beaumont, 1981, Beaumont et al., 1992, McClay, 1992, DeCelles, 1994, Lawton, 2008) and advances in orogenic wedge numerical models have illustrated the intimate feedback relationships among these processes (Willett, 1999, Stockmal et al., 2007, Cruz et al., 2010); nevertheless, deformation, magmatism and metamorphism are dominant processes in the internal, hinterland part of orogenic belts in the vicinity of plate boundary (Monger et al., 1982, Barton and Hanson, 1989, Brown, 1993).

For the foreland orogenic wedge, we use a slight modification of the term, Mexican thrust belt, proposed by Campa (1985) because it perfectly suits the topical content of this review. The Mexican fold thrust belt, as defined here (Fig. 1), constitutes a widespread geographic province distributed along a mountainous fringe from southern Oaxaca to Sonora (Fig. 1). The belt includes all shortening structures involving Mesozoic sedimentary units, and locally basement rocks that were formed in the Late Cretaceous-Paleogene in the Mexican foreland of the Cordilleran orogenic system. We add the word “fold”, to the term “Mexican Thrust Belt” of Campa (1985) because a significant portion of this belt is dominated by folds that are unrelated to thrusts (Fitz-Díaz, 2010, Fitz-Díaz et al., 2011a, Fitz-Díaz et al., 2012), which is a characteristic style in Mexico and is different from the thrust belt style of the Rocky Mountains, which is dominated by thrusts (Bally et al., 1966; Armstrong, 1968, Price and Fermor, 1985). The MFTB includes thin-skinned and thick-skinned structures, which are represented in two domains, green and light orange in map of Fig. 2, with an overlap among them in pale brown. The Sevier and Laramide belts of the U.S. are also mapped with similar colors, respectively.

The Sevier belt or Sevier orogen is distributed along a sinuous band on the western side of the Colorado Plateau in the southwestern U.S. (Fig. 2; Armstrong, 1968) and western Canada (Price and Fermor, 1985). The Sevier orogen consists of folds and thrusts that in cross-section are confined within an orogenic wedge tapering to the east (Fig. 2 in Weil and Yonkee, 2012). The age of deformation in this belt took place between the Hauterivian and early Eocene (see Fig. 12 and references in Yonkee and Weil, 2015) and crustal shortening has been attributed to an increase in convergence rates between the North American plate and subducting Farallon oceanic plate from the Jurassic to the Early Cretaceous. It has been speculated that the rate of trench rollback was likely lower than the rate of the overriding North American plate motion, thus causing convergence of the subduction hinge, with intraplate shortening and development of the Sevier belt as a consequence (DeCelles, 2004; Fig. 6B–D, in Yonkee and Weil, 2015).

Coney (1976) defined the Laramide orogen on the basis of deformation style and time of formation between Maastrichtian and middle Eocene (Dickinson et al., 1988, DeCelles, 2004). The faults in the Laramide province are typically high-angle reverse faults with 10s of km of along-strike extent that accommodate significant vertical displacements, involve basement rocks, and are commonly associated with km-scale drape folds (Friedman et al., 1976; Figs. 5D and 6D of Yonkee and Weil, 2015). Despite contrasting styles of deformation, there is substantial temporal overlap of shortening in the Sevier and Laramide belts. In central Utah, displacement along low-angle thrusts at the front of the thrust belt continued until middle to late Eocene time and thus temporally overlapped the main phase of basement deformation that occurred farther to the east (Lawton and Trexler, 1991, Lawton et al., 1993). Moreover, as Lawton (2008) pointed out “basement-involved disruption of the orogenic foreland never did take place in the Canadian Cordillera; therefore, the temporal definition of the Laramide orogeny is an artificial construct in Canada.” In addition to basement-cored uplifts of the Colorado Plateau (Davis, 2009), thick-skinned structures are also present in California, Arizona, New Mexico, and extend into the states of Sonora, Chihuahua and Coahuila in northern Mexico (Fig. 2; Drewes, 1988, Hennings, 1994, Pubellier et al., 1995, Jacques-Ayala, 1999, Jacques Ayala et al., 2009, Lawton, 2008, Haenggi, 2002, Chávez-Cabello, 2005). The development of crustal-scale basement-involved structures has been associated with an increase in basal traction as a consequence of flat-slab subduction (Dickinson and Snyder, 1978, Jordan and Allmendinger, 1986), or subduction of thick, buoyant oceanic plateaus (Liu et al., 2010).

Due to the trend of structures of the MFTB and their continuity to the north, they have historically been related to the Laramide orogeny (Humphrey, 1956, de Cserna, 1956, Campa and Coney, 1983, Eguiluz de Antuñano et al., 2000, Nieto-Samaniego et al., 2006, Cerca et al., 2007, Cuéllar-Cárdenas et al., 2012), regardless of their deformation style or timing (Coney, 1976). In Fig. 2 we use the same color for thin-skinned structures in the MFTB as for those in the Sevier belt on the basis of kinematic affinity, and the thick-skinned structures have a similar color to the Laramide province. This does not necessarily imply that the thin-skinned structures of the MFTB were formed during the Sevier orogeny or that the thick-skinned features were formed during the Laramide orogeny. In fact, we now know that the thin-skinned structures of the MFTB are younger than most of the Sevier structures. Thick-skinned structures in northern Mexico, on the other hand, in general correspond better in space, time and style with Laramide structures. Most thick-skinned structures of the MFTB in northern Mexico are flanked by reactivated normal faults, previously active during the formation and subsidence of Middle Jurassic-Early Cretaceous sedimentary basins (e.g., Bisbee, Chihuahua and Sabinas basins, Fig. 3), which presumably formed as a consequence of the opening of the Gulf of Mexico and were later inverted (McKee et al., 1990, Lawton, 2000, Haenggi, 2001, Haenggi, 2002, Mauel et al., 2011, Chávez-Cabello, 2005).

In the absence of detailed kinematic studies, age or specific data about their origin, most shortening structures within the MFTB of general Late Cretaceous-Paleogene age, irrespective of geographic location, or their thin- or thick-skinned style, have been interpreted as part of the Laramide orogen. We believe that this indiscriminate correlation is inappropriate for most structures in the MFTB, which, although dominantly thin-skinned, include a variety of structural styles. Moreover, although the Sevier, Laramide and MFTB orogens all lie in the foreland of the Cordilleran orogenic system, the geodynamics along the western margin of North America were so variable, in both time and space (Hildebrand, 2009), that it would be impossible that all thrust belts were formed in the same tectonic scenario, especially considering the great length of the belt. In addition, continental-arc magmatism accompanied the entire time span of deformation in Mexico, as reviewed below, whereas the Laramide orogeny of the U.S. was largely amagmatic (e.g. Dickinson and Snyder, 1978). For the above reasons, we propose redefinition of the Late Cretaceous-Eocene deformed belt in all its structural variability as the Mexican orogen. For instance, the accretion to Mexico of the Guerrero superterrane is restricted to western Mexico, yet Guerrero rocks were the source of much of the sediment in the foreland basins.

Finally, the Laramide orogeny may have a tectonic cause related to distribution of crustal heterogeneities in the Farallon slab. Recent inverse convection models (Liu et al., 2010) have suggested that the timing and distribution of thick-thinned Laramide deformation resulted from the passage of a conjugate of the Shatsky oceanic plateau under the southwestern U.S. between 90 and 68 Ma, while its companion, the conjugate Hess oceanic plateau, passed under northern Mexico later, from 65 to 50 Ma ago. In summary, preserved evidence in the crust and poorly preserved evidence from the subducting plates deciphered from inverse convection models (Liu et al., 2010, Liu and Stegman, 2011) support the idea that the Mexican orogen has sufficient structural variation and potentially different tectonic drivers to warrant its consideration as a separate entity, distinct from its northern counterparts in the Cordilleran orogenic system.