SEDIMENTATION, TRANSPORT UND EROSION AN DER NORDKÜSTE KOLUMBIENS ZWISCHEN BARRANQUILLA UND DER SIERRA NEVADA DE SANTA MARTA

Abstract

The coast of Northern Colombia between Barranquilla and the Sierra Nevada de Santa Marta has been subject to swift morphological alterations in the near geological past. The Magdalena River mouth into the Caribbean Sea is actually in the western end of the region and has formed deltas in three phases during the recent Quaternary. The two older ones were destroyed by erosion ad can only be detected by submarine morphology. The second phase is represented by a delta, that reached its widest dimensions approximately 2.400 years ago. The then starting destruction continues untill today and is not yet finished. The recent mouth foresets the youngest delta of the Magdalena River. A westbound longshore current along the not always even shoreline is produced by north-eastern tradewinds. This current transports the eroded sediments of the second oldest delta to the mouth of the Magdalena River. Part of them helps to build its new delta, and part of them glides through submarine cañons to the deep sea. Besides the morphological evidence, sedimentary analysis of the shore sands shows: 1. a longshore drift of sediments from east to west. 2. a change in the balance of energy: sedimentation in the east; erosion in the west (placers of heavy minerals). The very important highway from Barranquilla to Santa Marta ist thus endangered by erosion in the near future. 3. the sources of the upper sedimentlayers in the shore area: in the oldest delta their provenance is the Sierra Nevada de Santa Marta; in the younger deltas the area of affluents of the Magdalena River.