Geomorphology of the Caribbean Coastal Plains of Northern Costa Rica: The Realm of Avulsive Fluvial Systems

The Caribbean coastal plainsCaribbean coastal plains of northern Costa Rica have drawn little attention from geomorphologists even though this region possesses singular landforms resulting from exogenous and endogenous processes that shape the Costa Rican landscape. The Quaternary plain is the surface of a back-arc sedimentary basin called North LimónLimón Basin that is fed by tropical rivers flowing down from the Central and Talamanca cordilleras. These rivers create spectacular fluvial sceneries, their channels changing from pure braided to anabranching and meandering types; they form meanderMeander necks and leave oxbow lakesLake and paleo-channels scattered across the floodplain. The western sector of the plain is covered by a complex volcanogenic megafan (Late Pleistocene to recent), which is the first modern landform of this type described in the international scientific literature. The eastern sector is a coastal plain where active thrust faultsFault divert and strangle rivers as the movements of these faultsFault slowly uplift the ground. The southern limit of the plain is also remarkable in that it shows unique tectonic ridgesTectonic ridges in alluvial deposits, where the deformation produced by active folding can be observed clearly in tilted and faulted sediments. All the landforms that can be admired in this region contribute to an understanding of how a landscape changes due to climatic, volcanic, tectonic, and marine processes.