GEOMORPHOLOGY OF THE COASTAL ZONE ADJACENT TO THE WESTERN FOOTHILLS OF SIERRA NEVADA DE SANTA MARTA BETWEEN POZOS COLORADOS AND CÓRDOBA RIVER, COLOMBIAN CARIBBEAN

Abstract

A geomorphologic study was carried out in the coastal zone adjacent to the western foothills of Sierra Nevada de Santa Marta (SNSM) between the area of Pozos Colorados (outside of Santa Marta) and Córdoba River. This zone is characterized by landforms of several origins that are the result of tectonic, denudative and fluvial processes. From this point of view there are units of structural-denudative origin, represented by igneous and metamorphic-basament mountains and hills,; units of fluvial origin, as alluvial fans and fluvial terraces; and units of marine origin, like coastal plains, elevated wave-cut platforms, and acient and recent beaches. The structural-denudative units correspond to the steepest relief of the zone and are a consequence of the intrinsic features of the rocks they are made of and the tectonic activity of the Santa Marta Fault System. This effect is reflected on the abrupt change from a steep topograpgy to a flat relief, which is maked by a post-eocene (upper Miocene?) wave-cut platform made in the Batolith of Santa Marta rocks that was later uplifted; this erosive surface is partially covered by a series of alluvial fans made up of sand-sized sediments from the mountainous part of the SNSM. Based on stratigraphic relationships between the elevated wave-cut platform and the overlying sedimentary deposits, it is proposed that an uplifting of this sector of the western foothills of the SNMS was probably produced during Pliocene or even Quaternary as a consequence of inverse movements of the Santa Marta Fault or other parallel faults not detected to the west.