Factors Influencing the Distribution and Characteristics of Surface Sediment in the Bay of Cartagena, Colombia

This study evaluated patterns of coastal sediment movement and deposition under different seasonal conditions (warm and cold phases of the El Nino-Southern Oscillation [ENSO] and normal conditions) in Cartagena Bay, Colombia. A calibrated numerical model (MOHID modeling system) was applied to assess the spatial distribution of sediments transported by the Canal del Dique to the bay and studied the spatial distribution and major textural characteristics of 234 surface sediment samples. Currents in the Bay of Cartagena are controlled primarily by the strength and direction of the wind. Model results show major sediment deposition in the southern sector of the bay during the dry season. More homogenous spatial distribution of sediments throughout the Bay of Cartagena occurs with an increase in river inputs from the Canal del Dique. These patterns were enhanced or weakened, respectively, by cold and warm phases of the ENSO. Predominant sediments were medium size (phi = 5.35 +/- 1.2), poorly sorted (sigma = 1.63 +/- 0.8), with notable asymmetry (Sk = -0.052 +/- 0.2) and kurtosis (k = 0.84 +/- 0.4). Sediments with lower sand content (<5%) are located along a latitudinal axis from the Canal del Dique delta to the western end of the island of Tierrabomba. CaCO3 content of the sediments is <10%. Water and sediment flow, controlled by the Canal del Dique, has favored the transport and deposition of poorly sorted, symmetric, and mesokurtic mud in most of the Bay of Cartagena. As a result, autogenous calcareous sediments have been covered by fine terrigenous sediments that were delivered via the Canal del Dique. Thus, the channel plays a more prominent role in sediment transport and deposition in the Bay of Cartagena than thought previously.