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Semiquantitative Modeling of Strain and Kinematics Along the Caribbean&Sol;North America Strike&Hyphen;Slip Plate Bounda

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Semiquantitative Modeling of Strain and Kinematics Along the Caribbean&Sol;North America Strike&Hyphen;Slip Plate Bounda JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 98, NO. B5, PAGES 8293-8308, MAY 10, 1993 SemiquantitativeModeling of Strain and KinematicsAlong the Caribbean/North America Strike-Slip Plate BoundaryZone ERIC CALAIS1 AND BERNARDMERCIER DE LI•PINAY Institut de G•odynamique,CNR$, Valbonne,France Recent structural and geophysicalstudies conducted along the northern Caribbean plate bound- ary, at sea and on land, have led to a precise description of the geometry and the tectonic regimes along this major transcurrent zone which separates the Caribbean and North American plates. In order to interpret its tectonic features in terms of plate motion, we use a simple numerical model of strike-slip faulting to test previously proposed kinematic models and to compute new motion parameters. We show that none of the previously proposed models correctly accounts for the observed deformation along the whole plate boundary. On the basis of the deformation pattern obtained from geological data we compute a motion parameters set that integrate rigid plate rota- tion and "a plate boundary zone deformation component." Our results show that the deformation along the northern Caribbean plate boundary zone is controledby regional kinematics (i.e., the Caribbean/North America relative motion) rather than by local effects(e.g., small block rotation, intraplate deformation). INTRODUCTION the previously proposed kinematic parameters are used as boundary conditions to compute the predicted deformation The Caribbean domain and Central America form a small along the plate boundary. Comparison of this theoretical lithosphericplate (Caribbean plate) between North and result with the observeddeformation permits evaluation of South America (Figure 1). The Caribbeanplate is moving the tested kinematic parameters. In the secondstep, the eastwardrelative to North and South America alongtwo ma- geometry of the plate boundary trace and the observedde- jor strike-slip fault zones: Boconoand E1 Pilaf faults along formation pattern are usedas boundary conditionsto calcu- its southernboundary and the Polochic-Motagua,Swan, and late motion parameters. A simple direct formulation is used Oriente faults along its northern boundary. It is bounded to to minimize the scatter between observed and theoretical the east by the Lesser Antilles subduction zone, to the west deformation patterns. This approach leads to the motion by the Central America subduction zone. Despite this ap- parameters that best fit the observed deformation. parently well-constrainedkinematic frame, the present-day Our approachallows the useof qualitative geologicaldata motion of the Caribbean plate is one of the more poorly to control and compute quantitative kinematic parameters. knownamong all major plates[DeMets et al., 1990]. It is to be noted, however,that this approachdoes not rely Due to recent field and marine investigations,the North- on the fit of absolutedeformation values (usually not ob- ern Caribbean plate boundaryis one of the world'smost de- tainable from field observations)but on the fit of an overall tailedstudied transcurrent plate boundaryzones [e.g., Mann deformationpattern at the scale of the entire plate bound- et al., 1984, 1991; De Zoeten, 1988; Mercier de Ldpinay ary. et al., 1989; Heubeck et al., 1990; Calais and Mercier de Ldpinay, 1991; Masson and Scanlon,1991; Speedand Larue, NORTHERN CARIBBEAN PLATE BOUNDARY ZONE 1991; Rosencrantzand Mann, 1991]. Its geometryand asso- ciated structuresare known well enoughthat they cannot be From west to east, the northern Caribbean plate bound- neglectedin evaluating kinematic models of the Caribbean ary consistsof two major faults, the Oriente and Swanfaults, plate motion[Heubeck and Mann, 1991]. connectedto eachother by the Mid-Cayman spreadingcen- The first step of this paper is to test the proposed kine- ter (Figure 1). The Swanfault is the eastwardmarine exten- matic modelsof the Caribbean plate [Mac Donald, 1976; sion of the Polochic-Motaguafault zone of Central America. Minster and Jordan, 1978; Sykes et al., 1982; Stein et al., The Oriente fault continues to the east on land into the 1988]. The secondstep is to computenew kinematicparam- northern Dominican Republic and mergesfarther east with eters accordingto the most recentgeological and geophysical the Puerto Rico trench. The following discussionsumma- results in the northern Caribbean. For these purposes,we rizes the main structural features of these fault segments, used a simple numerical model of strike-slip faulting that basedon the most recent investigationsalong them. These takes into account the precise trace of the main faults and features are the basic constraintson plate boundary geom- the deformationpattern along the entire plate boundary. In etry and tectonics that we used in our numerical model. the first step, the geometry of the plate boundary trace and Polochic-Motagua and Swan Faults Few geologicaldata are available concerningrecent tec- 1Nowat ScrippsInstitution of Oceanography,La Jolla, California. tonics along the Polochic-Motaguafault zone. Schwarz et al. [1976]describe Quaternary alluvial terracesaffected by Copyright 1993 by the American Geophysical Union. left-lateral displacements.They attribute the significantup- Paper number 92JB03026. lift of the mountain ranges located north of these faults to 0148-0227/93/92JB-03026505.00 active reverse and strike-slip faulting. These observations 8293 8294 CALAIS AND DE LI•,PINAY:STRAIN AND KINEMATICSIN THE CARIBBEAN NORTH AMERICA PLATE CARIBBEAN PLATE spreading ..... i:i:i:!ii!iiiiii!iiiiiiiiiiiiiii!i!i".... ':i:i:i:i:E:i:i:i:!:i:!:i:i:i:i:i:i:i:i:!:i-:.:;:;;:::;;;:;: .... ......... subduction •x strike-slip Vz crust SOUTH AMERICA PLATE ............... -i:i:!:i:!-i:!:i:!:i.i:!:i:i:!.!............. 0 500km =========================================....................... • 2O 19 Fig. 1. a. Geodynamicsetting of the Caribbeanplate; b. The northernCaribbean plate boundary in its geodynamicframe (Mex, Mexico; Ho, Honduras;LI, Lagode Isabal;SF, Swanfault; RGI, Roatanand Guajira Islands;SI, SwanIslands; CT, Caymantrough; YB, Yucatanbasin; NR, Nicaraguarise; Ja, Jamaica;CCB, Cabo Cruz basin;SDB, Santiagodeformed belt; WP, Windwardpassage; TC, Tortuechannel; CS, Cordillera Septentrionalof DominicanRepublic; MAW, Muertosacretionnary wedge; PMF, PolochicMotagua fault zone; PR, PuertoRico; PRT, PuertoRico Trench; LA, LesserAntilles; GB, Grenadabasin; VB, Venezuelabasin; BR, Beataridge; CB, Colombiabasin; Co, Columbia; Eq, Ecuador;Cu, Cuba;GM, Gulfof Mexico;OF, Orientefault zone;Hisp, Hispaniola). and the high and prominent topographyon the northern derson,1982 ; Manton, 1987]. The Swan fault, which is side of the fault zone suggest significant active transpres- the eastward marine prolongationof the Polochic-Motagua sionin this area [Burkart,1983]. The geometryof the fault faults, is locatednorth of the Bay and Swan Islands,where it zone described here takes into account the activity of both trends N65øE and bends into a N100øE direction around lon- the Polochicand Motagua fault zones,as assumedfrom seis- gitude85ø30'W [Mann et al., 1989, 1991]. Fifty kilometers mological[Cart and $toiber,1977; Plafker, 1976; Guzmdn- to the east, the major fault bends and follows a N65øE di- $pezialeet al., 1989]and geologicMdata [Erdlacand An- rection until its connectionwith the Mid-Cayman spreading CALAIS AND D•, LI•,PINAY: STRAIN AND KINI•MATICS IN THI• CARIBBI•AN 8295 center at about longitude 81ø40'W. The present-daymotion MODELING PROCEDURE along the Swan fault, therefore, occurssouth of the Swan Is- Principle and Basic Hypothesis lands, not to the north, as formerly assumed.Multichannel seismic reflection profiles perpendicular to the Swan fault Transcurrentplate boundariesare definedas segmentsof [Rosencrantzand Mann, 1991]display spectacular compres- small circles around a rotation pole, along which the rela- sivestructures (folds and reversefaults) in an active trans- tive motionof both platesis purelystrike-slip [ Wilson,1965; pressivearea (150 km long by 20 km wide) betweenthe Bay Morgan, 1968]. Sincethis theoreticaldefinition, many stud- and Swan islands. ies, on land and at sea, have shownthat transpression(re- suiting in en •chelon folds, reverse and thrust faults, up- Oriente and Septentrional Faults lift), transtension(resulting in initiation and subsidenceof elongatedbasins), and pure strike-slipcan occur along the From the Mid-Cayman spreading center to the western sametranscurrent plate boundary[Sylvester, 1990]. The edge of the Cuban margin, the geometry of the Oriente distribution of these various tectonic regimesis related to fault is poorly constrained. Along the Cuban margin, how- (1) geometriceffects which can be dividedinto local (fault ever, its trace and associatedstructures have been mapped geometry,i.e., its relaysor bends)and regionaleffects (rela- in detail [Calais and Mercier de Ldpina•t,1991]. Alongthe tive motion along the main fault, i.e., the kinematics of the western Cuban margin, the Oriente fault is mainly a sys- fault); and (2) mechanicaleffects (variations of thermody- tem of sinistrally offset en •chelon fault segments,respon- namical behavior of the lithosphere with depth and along sible for the subsidenceof pull-apart basins(Cabo Cruz, the fault strike). Chivirico, and Baitiquiri basins). In contrast, the eastern In the following, we consider a plate boundary zone cut- part of the Cuban margin is characterizedby active compres- ting a lithosphereof constant physical properties along its sionMtectonic
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