spe383-10 page 1 of 15 1 INTRODUCTION An important number of salients and recesses in fold-and- thrust belts on Earth have been studied using kinematic, geo- metric, and paleomagnetic data to document their development (e.g., Eldredge and Van der Voo, 1988; Marshak et al., 1992; Van der Voo et al., 1997; Gray and Stamatakos, 1997; Mitra, 1997; Norris, 2001; Marques and Cobbold, 2002). Alternatively, some arcuate thrust belts have been studied using numerical and analogue modeling (e.g., Cobbold and Davy, 1988; Colletta et al., 1991; Gutscher et al., 1996; Macedo and Marshak, 1999; Hindle and Burkhard, 1999; Marques and Cobbold, 2002). In Chávez-Cabello, G., Cossío-Torres, T., and Peterson-Rodríguez, R.H., 2004, Change of the maximum principal stress during the Laramide Orogeny in the Monter- rey salient, Northeast México, in Sussman, A.J., and Weil, A.B., eds., Orogenic Curvature: Integrating Paleomagnetic and Structural Analyses: Geological Society of America Special Paper 383, p. XXX–XXX. For permission to copy, contact editing@geosociety.org. © 2004 Geological Society of America. Geological Society of America Special Paper 383 2004 Change of the maximum principal stress during the Laramide Orogeny in the Monterrey salient, Northeast México Gabriel Chávez-Cabello Posgrado en Ciencias de la Tierra, Centro de Geociencias, Universidad Nacional Autónoma de México, Campus Juriquilla, Querétaro, Qro. 76230, México, and Facultad de Ciencias de la Tierra, Universidad Autónoma de Nuevo León, A.P. 104, Kilómetro 8, Carretera Linares-Cerro Prieto, Linares, N.L. 67700, México Tomás Cossío-Torres Facultad de Ciencias de la Tierra, Universidad Autónoma de Nuevo León, A.P. 104, Kilómetro 8, Carretera Linares-Cerro Prieto, Linares, N.L. 67700, México Rolando Heberto Peterson-Rodríguez Facultad de Ciencias de la Tierra, Universidad Autónoma de Nuevo León, A.P. 104, Kilómetro 8, Carretera Linares- Cerro Prieto, Linares, N.L. 67700, México, and PEMEX, Exploración y Producción, Reynosa, México ABSTRACT Detached folds in the Monterrey salient of the Sierra Madre Oriental fold-and- thrust belt, México, show macro- and mesostructures that demonstrate a change of the regional maximum principal stress from NNE-SSW to approximately E-W com- pression, during the late stages of the Laramide event. Data were collected along a N-S trending section in the central part of the Monterrey salient. Paleostresses were determined by means of fault slip data inversion. These estimates where corrobo- rated with those from meso-scale structures. Macro and mesostructures suggest that mechanisms of folding are mainly flexural shear and orthogonal flexure at both local and regional scales. The change in orientation of the paleotensor in the central part of the Monterrey salient from NNE to approximately E-W appears to be a local effect of progressive deformation in the Monterrey salient. We conclude that a regional orthogonal flexure of the Sierra Madre Oriental fold-and-thrust belt occurred at the late stage of the Laramide Orogeny and controlled: (1) change of the paleotensor, (2) a fan shaped arrangement of joints and, (3) divergence of paleostress estimated using fold axes from NNW to NE in the leading edge of the Monterrey salient. Keywords: Laramide, Sierra Madre Oriental, Monterrey, salient, fault analysis.