Textura, Composición y Foraminíferos Bentónicos de los Sedimentos Superficiales en los Bancos de Salmedina, Caribe Colombiano

Abstract

Salmedina reef banks are mud diapirs that include three main (and smaller) shoals conforming true submarine mesas. A surface sediment study was performed with detailed sampling of the mesas and more spaced sampling of the mesas and more spaced sampling of the pre-reefal zone. Granulometry of sediments, calcium carbonate content, organic matter, composition of particles > 150 micrometers, and relative abundance of benthonic foraminifera were measured. Distribution maps and cluster analysis enable us to differentiate four different sedimentary facies: (1) Bioclastic sands of reef mesas (2) Lithoclastic sand gravels of diapiric origin from the Burbujas shoal (3) Lithobioclastic perirreefal silts (4) Biolithoclastic peri-reefal very fine sands and silts. Burbujas shoal is an active mud volcano that present a zones of lithoclastic sandy gravels caused by the degradation of the volcano cone stucture, while westward sediments grades toward typical sediments of reef mesas. Salmedina shoal, by contrast, presents two kinds of reef mesa supply of calcareous algae. Differences in peri-reefal mud sediments are possibly ti the northern influence of the magdalena river, and the southern reefal mesas calcareous supply. Amp istegina gibbosa is the dominant specie of benthonic foraminifera and it is associated to the reef production. In contrast, Anomalina globulosa is associated to areas the terrogenous continental influence.