PULL-APART BASINS ALONG THE CONTINENTAL TRANSFORM FAULTS IN THE CENTRAL AND SOUTH AMERICA

Transform margin are important tectonic features which accommodate horizontal displacements in all plate tectonic settings on all scales in both oceanic and continental crust. The resulting strike-slip faults show that most of known transform margins accommodate oblique displacements with a wide assemblage of related structures. Pull-apart basins associate with releasing bends or step-overs are one the geological features that form as a consequence of this geometrical pattern in a transtensional context. Caribbean and Scotia Seas are two physiographic features nearly identical in size and shape that contain two transform boundary with opposite vergence joined by a frontal subduction arc. They are respectively located between North and South America, and South America and Antarctica, joining the North American Cordillera to the Andes, and the Andes to the Antarctic Peninsula continental orogen. Their tectonic evolutions can be related to the relative motion between the two pairs of landmasses. Morphological, structural and tectonic analogies characterize both Arcs, in particular the transform systems that mark their respective plate boundaries. The Magallanes-Fagnano continental transform system, which represents the western termination of the South America-Scotia plate boundary, traverses broadly E-W the entire Tierra del Fuego region. The principal displacement zone is composed of distinct tectonic fault arrays arranged in a step-over and the realasing bend geometries that developed asymmetric pull-apart basins on-shore and in the Atlantic off-shore. The Polochic and Motagua fault systems mark the western part of the North America-Caribbean plate boundary .This transform systems cut the central and eastern Guatemala. A large pull-apart basin, the Lago Izabal, was developed within the principal displacement zone and it is characterized by a remarkably asymmetric configuration of the sedimentary fill. This sedimentary architecture, in which the thick end of the depositional wedge abuts the transform segment, suggest simultaneous strike-slip motion and transform-normal extension. Both transform systems in the Scotia and Caribbean regions, may suggest a common tectonic mechanism responsible for the development of the corresponding plate boundaries, and possibly for the entire Arcs.