The Caribbean-North America-Cocos Triple Junction and the dynamics of the Polochic-Motagua fault systems: Pull-up and zipper models (original) (raw)
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The Polochic-Motagua fault system (PMFS) is a segment of the sinistral transform boundary between the North American and Caribbean plates. To the west, it interacts with the subduction of the Cocos plate, with which it forms a triple junction of subduction-subduction-transform type (SST). The North American plate moves westward relative to the Caribbean plate. However, this differential displacement of the two overriding plates does not result in a wrenching of the subducted Cocos plate. This implies that this deformation is accommodated entirely within the two overriding plates. Structural data, fault kinematic analysis, and geomorphic observations provide new elements to understand how this triple junction has evolved during the late Cenozoic. In Miocene time, extension and shortening occurred respectively to the south and north of the Motagua fault. This strain parting shifted northward onto the Polochic fault after the Late Miocene. This shift is interpreted as the result of the "pulling-up" of North American blocks and their attachment to the Caribbean domain. In the west the PMFS interacts with a trench-parallel fault zone that comprises the Tonala fault and the Jalpatagua fault. These faults delimitate landward a forearc sliver that is shared by the two overriding plates. We propose that the dextral Japatagua fault merges with the sinistral PMFS, leaving behind a suture, the Tonala fault. This tectonic "zipping" allows the triple junction to migrate towards the Caribbean Plate. As a result, the forearc sliver comes into contact with the North American plate and helps maintaining a linear subduction zone along the trailing edge of the Caribbean plate. All these processes currently make the triple junction increasingly diffuse as it propagates eastward and inland within both overriding plates. distance to the Cocos subduction zone as the Jalpatagua fault [Guzmán-Spéciale and Meneses-Rocha, 2000; Witt et al., in review].
The Triple Junction of the North America, Cocos, and Caribbean Plates: Seismicity and tectonics
Tectonics, 1989
The triple junction of the North America, Cocos, and Caribbean plates is ambiguously defined, mainly because the North America-Caribbean plate boundary does not clearly continue beyond its known surface trace (the Motagua fault zone) in western Guatemala to intersect the Middle America trench. Well-located regional shallow earthquakes (h_<70 km) show that there is no intermediate or large-magnitude seismic activity associated with a presumed extension of the North America-Caribbean plate boundary to the west, beyond its well-defined surface trace. There is, however, a clear zone of shallow seismic activity from the western section of the fault system through southern Mexico. Fault plane solutions for these events indicate a left-lateral strike-slip displacement, which is in good agreement with surface faulting. We suggest that these strike-slip faults, together with the Salina Cruz fault in the isthmus of Tehuantepec, mark the boundaries of a broad zone of deformation in southern Mexico and northern central America which takes up the interactions of the three plates. In this sense, no single point constitutes the triple junction. The geologic record suggests that the Motagua fault zone developed because the westernmost portion of the Caribbean plate became locked against North America.
Tectonophysics, 1991
The left-lateral relative motion between the Caribbean and the North American plates has previously been inferred as occurring along a fault zone located north of Hispaniola. East of the northern Dominican Republic, a relatively linear fracture zone {the Septentrional Fault Zone, SFZ) extends into the Puerto Rico subduction zone. Similarly, south of Haiti, the &race of the inactive Enriquillo-Plantain Garden Fault Zone (EPGFZ) extends into the Muertos Trench and may represent a major fault along the plate boundary. Between these two major strike-slip fault systems, the central part of Haiti shows a diffuse fracture zone that trends N130. The chronology of deformation involves an initial Paleocene to Eocene suturing of allochthonous terranes, a Late Miocene development of a strong spaced cleavage within the late Paleocene to Late Miocene strata that overlap the terrane suture, and diffuse Pliocene to Pleistocene strike-slip faulting along traces that reactivate the older spaced cleavage planes. During the Pleistocene, basalts ranging in age from 0.4 to 1.3 Ma were extruded in pull-apart basins associated with N130-trending faults (antithetic features of the SFZ) and N30 normal faults (antecedent synthetic features of the SFZ). This event is coeval with the compression recorded at the Muertos-Beata collision front in the southwestern Dominican Republic. The most recent phase of tectonism involves strong uplifts and broad, open folding along NW-striking axes, which is consistent with the regional maximum deformation pattern predicted for E-W left-laterai shear along the North America-Caribbean plate boundary.
Subduction of the Caribbean Plate and basement uplifts in the overriding South American Plate
Tectonics, 1982
The new tectonic interpretations presented in this paper are based on geologic field mapping and gravity data supplemented by well logs, seismic profiles, and radiometric and earthquake data. The present Caribbean-South American plate boundary is the South Caribbean marginal fault, where subduction is indicated by folding and thrusting in the deformed belt and a seismic zone that dips 30o to the southeast and terminates 200 km below the Maracaibo Basin. The Caribbean-South American convergence rate is estimated as 1.9 +_. 0.3 cm/yr on the basis of the 390-km length of the seismic zone and a thermal equilibration time of 10 n.y. The Caribbean-South American convergence has produced a northwest-southeast maximum principal stress direction o 1 in the overriding South American plate. The mean Ol direction for the Maracaibo-Santa Marta block is 310 ø _+ 10 ø based on earthquake focal mechanism determinations, and structural and gravity data. On the overriding South American plate, basement blocks have been uplifted 7-12 km in the last 10 n.y. to form the Venezuelan Andes• Sierra de Perija, and the Colombian Santa Marta massif. Crystalline basement of the Venezuelan Andes has been thrust to the northwest over Tertiary sediments on a fault dipping about 25 ø and extending to the mantle. In the Sierra de Perija, Mesozoic sediments have been thrust 16-26 km to the northwest over Tertiary sandstones along the Cerrejon fault. A thrust fault dipping 15 ø +_ 10 ø to the southeast is consistent with field mapping, and gravity and density data. The Santa Marta massif has been uplifted 12 km in the last 10 n.y. by northwest thrusting over sediments. The basement block overthrusts of the Perijas, Venezuelan Andes, and the Santa Marta massif are Pliocene-Pleistocene analogs for Laramide orogenic structures in the middle and southern Rocky Mountains of the United States. The no•magmatic basement block uplifts along low-angle thrust faults reveal horizontal compression in the overriding plate over 500 km from the convergent margin. Present-day east northeast-west southwest (080 ø) compression is indicated by earthquake focal mechanisms and strike slip motion on the Bocono fault. These earthquakes are intraplate deformation associated with east-west (080 ø) Nazca-South American convergence. INTRODUCTION The Caribbean-northwestern South American plate boundary has been the most controversial and difficult Caribbean boundary to interpret tectonically (Figures 1 and 2). The high seismicity and Holocene ,
Tectonics, 1992
Recent marine and onland geophysical and geological investigations along the northern Caribbean plate boundary call for a review of its tectonic interpretation, in the light of a new compilation of the seismological data avalaible from Cuba to Puerto Rico. We show that the shallow seismicity in the northeastern Caribbean is concentrated along an east-west trending lineament corresponding to the trace of the major strike-slip fault system. The most intense seismicity is located around restraining bends such as southern Cuba and northern Hispaniola. The stress and strain distribution deduced from focal mechanisms and microtectonic analysis lead us to infer a small N-S convergence component associated with the major eastward strike-slip motion of the Caribbean plate versus North America. Earthquake distribution and focal mechanisms suggest the existence of a lithospheric slab inherited from the frontal subduction under the Lesser Antilles diping down under Puerto Rico and eastern Hispaniola. We propose a model in which this slab is disconnected from the Atlantic oceanic lithosphere by transcurrent faulting along the plate boundary. INTRODUCTION As evidenced by Molnar and Sykes [1969], the Caribbean domain and Central America form a small lithospheric plate inserted between North and South America that is moving eastward relative to North America (Figure 1). Its northern boundary is a left-lateral transcurrent fault system connected around its eastern end to the subduction of the Atlantic oceanic lithosphere under the Lesser Antilles. Recent geophysical and geological investigations have been conducted along the northern Caribbean plate boundary, both at sea [Scanlon et al.,
Scientific Reports
Different kinematic models have been proposed for the triple junction between the North American, Cocos and Caribbean plates. The two most commonly accepted hypotheses on its driving mechanism are (a) the north American drag of the forearc and (b) the cocos Ridge subduction push. We present an updated GPS velocity field which is analyzed together with earthquake focal mechanisms and regional relief. The two hypotheses have been used to make kinematic predictions that are tested against the available data. An obliquity analysis is also presented to discuss the potential role of slip partitioning as driving mechanism. The North American drag model presents a better fit to the observations, although the cocos Ridge push model explains the data in costa Rica and Southern nicaragua. Both mechanisms must be active, being the driving of the Central American forearc towards the NW analogous to a pushpull train. The forearc sliver moves towards the west-northwest at a rate of 12-14 mm/yr, being pinned to the North American plate in Chiapas and western Guatemala, where the strike-slip motion on the volcanic arc must be very small. After the establishment of plate tectonics as a paradigm of geology throughout the 1960s, in the 1970s numerous works attempted to explain tectonics in this new theoretical framework. Different kinematic models were proposed to explain the motion of the forearc sliver along the Cocos-Caribbean subduction, in the framework of the triple junction between the North American, Cocos and Caribbean plates, and particularly for the north of Central America. In one of the first proposals it is suggested that the relative drift of the Caribbean plate to the east gave rise to the formation of N-S grabens in Honduras while southern Guatemala and western Honduras remained pinned to North America 1. This basic model, which did not consider the existence of a forearc sliver yet, was refined, suggesting the existence of a weakness zone along the Volcanic Arc that facilitates the displacement of a forearc sliver dragged laterally, or pulled, by the North American plate motion towards the Northwest 2,3. These works define the basis of the dragging hypothesis (DH) and the deformation in the trailing edge of the Caribbean plate 4,5. The higher South America-North America convergence towards the west has been also proposed as mechanism for the Caribbean-North America pinning on its western edge and the relative extrusion of the Caribbean Plate towards the east 6,7. As an alternative model to explain the north-westward drift of the forearc sliver the slip partitioning in the subduction was proposed 8. This model of slip partitioning has been refuted as the subduction interface is not coupled enough to transmit the necessary forces to drive the upper plate forearc 4,9-12. In addition, it has an insufficient obliquity angle to generate the partition 13 , although it will be discussed below. Towards the southeast of the forearc, in southern Nicaragua and Costa Rica, the GPS vectors show a centrifugal arrangement in front of the
Transtensional deformation of the western Caribbean-North America plate boundary zone
2007
Divergence, expressed as the angle between the plate motion vector and the azimuth of a plate margin fault, has been proposed to explain development of contrasting styles of transtensional deformation along transform margins. We present the western North America-Caribbean plate margin as a test of this hypothesis. Here, geologic, earthquake, marine geophysical, and remote sensing data show two distinct structural styles: (1) east-west extension along north-trending rifts normal to the plate margin in the western study area (western Honduras and southern Guatemala); and (2) NNW-SSE transtension along rifts subparallel to the plate margin in the eastern study area (northern Honduras and offshore Honduran borderlands region). Orientations of rifts in each area coincide with the angle of divergence between the GPS-derived plate motion vector and the azimuth of the plate boundary fault, such that the western zone of east-west extension has an angle >10°, while the eastern zone of NNW-SSE extension occurs when the angle of divergence is between 5° and 10°. A narrow transition area in north-central Honduras separates the plate boundarynormal rifts of western Honduras from the plate boundary-parallel rifts to the east. Faults of the offshore Honduran borderlands extend onshore into the Nombre de Dios range and Aguan Valley of northern Honduras where tectonic geomorphology studies show pervasive oblique-slip faulting with active left-lateral river offsets and active uplift of stream reaches. Offshore, seismic data tied to wells in the Honduran borderlands reveal active submarine faults bounding asymmetric half-grabens filled by middle Miocene clastic wedges with continued deposition to Pliocene-Pleistocene. The north-trending rifts of western Honduras form discontinuous half grabens that cut the late Miocene ignimbrite strata. Plate reconstructions indicate the northtrending rifts of western Honduras developed in response to increased interplate divergence as the western margin of the Caribbean plate shifted from the Jocotan fault to the Polochic fault in the middle Miocene.
Journal of South American Earth Sciences, 2000
We propose a model for the western end of the North American±Caribbean plate boundary. We suggest that, beyond the surface trace of the Motagua±Polochic fault system, interplate strain is distributed along the Reverse Faults Tectonic Province, a zone of long, narrow anticlines cut along their¯anks by reverse faults that generally eliminate the intervening synclines, and the strike-slip faults of southeastern Mexico, a system of at least nine major faults with left-lateral displacement and documented seismic activity. The reverse faults act as a stepover (fault jog) between the strike-slip faults and the Motagua±Polochic system. Comparison with available stress data and models of the stress ®eld at a stepover agree well with the observed pattern of folding and faulting in the area. Proposed displacement and seismicity along each individual fault in the SE Mexico strike-slip system must be small because interplate strain is shared between at least seven major strikeslip faults. We suggest that motion between North America and the Caribbean dies out at the northwestern end of the strike-slip faults.