New structural, geochronological, and petrological data highlight which crustal sections of the North American–Caribbean Plate boundary in Guatemala and Honduras accommodated the large-scale sinistral offset. We develop the chronological and kinematic framework for these interactions and test for Palaeozoic to Recent geological correlations among the Maya Block, the Chortís Block, and the terranes of southern Mexico and the northern Caribbean. Our principal findings relate to how the North American–Caribbean Plate boundary partitioned deformation; whereas the southern Maya Block and the southern Chortís Block record the Late Cretaceous–Early Cenozoic collision and eastward sinistral translation of the Greater Antilles arc, the northern Chortís Block preserves evidence for northward stepping of the plate boundary with the translation of this block to its present position since the Late Eocene. Collision and translation are recorded in the ophiolite and subduction–accretion complex (North El Tambor complex), the continental margin (Rabinal and Chuacús complexes), and the Laramide foreland fold–thrust belt of the Maya Block as well as the overriding Greater Antilles arc complex. The Las Ovejas complex of the northern Chortís Block contains a significant part of the history of the eastward migration of the Chortís Block; it constitutes the southern part of the arc that facilitated the breakaway of the Chortís Block from the Xolapa complex of southern Mexico. While the Late Cretaceous collision is spectacularly sinistral transpressional, the Eocene–Recent translation of the Chortís Block is by sinistral wrenching with transtensional and transpressional episodes. Our reconstruction of the Late Mesozoic–Cenozoic evolution of the North American–Caribbean Plate boundary identified Proterozoic to Mesozoic connections among the southern Maya Block, the Chortís Block, and the terranes of southern Mexico: (i) in the Early–Middle Palaeozoic, the Acatlán complex of the southern Mexican Mixteca terrane, the Rabinal complex of the southern Maya Block, the Chuacús complex, and the Chortís Block were part of the Taconic–Acadian orogen along the northern margin of South America; (ii) after final amalgamation of Pangaea, an arc developed along its western margin, causing magmatism and regional amphibolite–facies metamorphism in southern Mexico, the Maya Block (including Rabinal complex), the Chuacús complex and the Chortís Block. The separation of North and South America also rifted the Chortís Block from southern Mexico. Rifting ultimately resulted in the formation of the Late Jurassic–Early Cretaceous oceanic crust of the South El Tambor complex; rifting and spreading terminated before the Hauterivian (c. 135 Ma). Remnants of the southwestern Mexican Guerrero complex, which also rifted from southern Mexico, remain in the Chortís Block (Sanarate complex); these complexes share Jurassic metamorphism. The South El Tambor subduction–accretion complex was emplaced onto the Chortís Block probably in the late Early Cretaceous and the Chortís Block collided with southern Mexico. Related arc magmatism and high-T/low-P metamorphism (Taxco–Viejo–Xolapa arc) of the Mixteca terrane spans all of southern Mexico. The Chortís Block shows continuous Early Cretaceous–Recent arc magmatism.

Abstract.Structural

The Chortfs block is undergoing deformation as a direct result of large-magnitude sinistral strike-slip faulting on the North America-Caribbean plate boundary. We have studied the Chortfs block using geologic mapping, remote imagery, and earthquake seismology to evaluate the effect that large-magnitude strike-slip faulting has on an adjacent microcontinental block. In the eastern part of the Chortfs block, recent geologic mapping has shown that the northeast striking Guayape fault is dextral instead of sinistral as previously assumed. Because this is a major fault that cuts most of the Central America isthmus, the new evidence for dextral slip necessitates a reinterpretation of the active tectonics of the Chortfs block. The presence of several north trending rifts in the western part of the Chortfs block has led previous workers to propose that the Chortfs block is divided into smaller, independently rotating blocks. We use earthquake seismology and remote imagery data to extend this interpretation to the central portion of the Chortfs block. However, we have modified their model to account for dextral slip on the Guayape fault. We believe that rotation of the Chort/s block causes dextral slip on the Guayape fault even though Central America is undergoing large sinistral displacement with respect to North America.Paper number 94TC00923. 0278-7407/94/94 TC-00923 $10.00 plate boundary. We conclude that the major deformation occurs on the plate boundary strike-slip faults. The active plate boundary transform fault separating North America from the Chorffs block has probably migrated with time, and no single fault accounts for all of the offset.Interest in the Neogene deformation of the Chortfs block has resulted in several models. Mann and Burke [1984a] showed that rifts open as the Caribbean plate rotates past Yucatfin (Figure 1). Burkart and Self [1985] proposed that block rotation and segmentation of the volcanic arc dominate the deformation in the region. Manton [1987] proposed that Honduras is divided into domains within which the faults rotate. These studies demonstrate that the deformation of the Chorffs block is associated with the North America-Caribbean plate boundary zone. Several previous discussions of the Neogene deformation consider the Guayape fault as a major tectonic element of the Chortfs block. Previous workers have considered the fault to be a major sinistral fault [Burkart and Self, 1985; Manton, 1987] although geologic data from this region were not yet available. Offset drainage was used to show a sinistral sense of slip of --50 km for the fault [Ritchie and Finch, 1984], but they subsequently interpreted the offset drainage to have occurred during an earlier period of faulting [Finch and Ritchie, 1991]. Fieldwork along the Guayape fault demonstrates that the most recent episode of faulting has been dextral [Gordon, 1990; Finch and Ritchie, 1991]. Clearly, the reinterpretation of the sense of slip of a major fault necessitates a reinterpretation of the tectonic model for the deformation o...

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