262 RevistaWeber Mexicanaet al. de Ciencias Geológicas, v. 23, núm. 3, 2006, p. 262-276 Provenance ages of late Paleozoic sandstones (Santa Rosa Formation) from the Maya block, SE Mexico. Implications on the tectonic evolution of western Pangea Bodo Weber1,*, Peter Schaaf2, Victor A. Valencia3, Alexander Iriondo4, and Fernando Ortega-Gutiérrez2 1 División Ciencias de la Tierra, Centro de Investigación Científi ca y de Educación Superior de Ensenada (CICESE), Km. 107 carretera Tijuana-Ensenada, 22860 Ensenada BC, Mexico. 2 Instituto de Geofísica, Instituto de Geología, Universidad Nacional Autónoma de México, Ciudad Universitaria, Delegación Coyoacán, 04510 México D.F., Mexico. 3 Department of Geosciences, University of Arizona, 1040 East Fourth St., Tucson AZ, 85721-0077 U.S.A. 4 Centro de Geociencias, Universidad Nacional Autónoma de México, Campus Juriquilla, 76230 Querétaro, Mexico. and Department of Geological Sciences, University of Colorado at Boulder, Boulder CO, 80309 U.S.A. *
[email protected] ABSTRACT The Santa Rosa Formation in the State of Chiapas is a sequence of fl ysch-type sediments of Mississippian to Pennsylvanian age. These sedimentary rocks correlate with the Santa Rosa Group of Guatemala and Belize and crop out along the southern limit of the Maya block north of the Motagua fault, which is currently considered the border between the North American and the Caribbean plates. Ages of individual zircon grains from sandstones of the Upper Santa Rosa Formation in southern Mexico were analyzed by Laser Ablation Multicollector ICPMS and by SHRIMP. The youngest zircon population is of Silurian age (~420 Ma), but most grains have ages that correspond to the Pan-African-Brasiliano orogenic cycle (500–700 Ma).