Coasts of Colombia

Caribbean Coast: Southern Caribbean coast

Between Galerazamba and the Gulf of Urabá (Fig. 2), Oligocene to Pliocene sequences of turbidities, hemipelagic, and terrigenous marine deposits form the Sinú Belt, a stratigraphic unit strongly affected by differential tectonic movement driven in part by mud diapirism and associated phenomena (Page 1986, Vernette et al. 1992). Along the littoral fringe, rocks of the Sinú belt are mainly claystones, mudstones, and conglomerates. Coral reef limestones crop out on the tops of coastal hills, which are up to 150 m high. Offshore and inland mud diapirs and mud volcanoes are common on the Sinú Belt, some of them with violent historical eruptions that modified the bathymetry and surface topography on the order of meters (Ramírez 1959, Martínez et al. 1994). Quaternary deposits of the Sinú Belt's coast are mainly sandy-muddy deltas (Sinú-Tinajones deltaic complex, Turbo and Atrato deltas) and alluvial valley fills. Along the coast, there are also Holocene, muddy wave-cut depositional terraces up to 36 m high. The terraces are best developed south of the Gulf of Morrosquillo. Holocene reefs on the shallow platform of the Sinú Belt are located on positive-relief bottom features formed by mud diapirism (Page 1986, Briceño and Vernette 1992) and are most common between Cartagena and the Gulf of Morrosquillo (El Rosario Islands).

Figure 19. Aerial photograph of the northern part of the Gulf of Morrosquillo. The Gulf shores are extensively altered by engineering structures. Photo by I. Correa.

The southern Caribbean coast of Colombia extends for about 550 km from the Barú Peninsula to the Gulf of Urabá. Except for the Gulf of Morrosquillo, the region is cut into sedimentary rocks of the Sinú Belt (Fig. 2). The Gulf of Morrosquillo, 100 km south of Cartagena, is a greatly modified, low wave-energy environment. Internal lagoons and mangrove swamps are fronted by protective beaches and by extensive reclamation projects (Fig. 19).

Southwest of the Gulf of Morrosquillo, the coastal plain is composed of extensive detrital deposits of the Holocene Sinú River delta. The main entrance to the Bay of Cispatá changed abruptly in 1938 as the Sinu River enlarged an irrigation channel cut at Tinajones sector (Koopmans 1971, Serrano 2004) (Fig. 20). As a result of channel widening, the Cispatá bay area became depleted of sediments and was submerged by the sea. More than 10,000 Ha of cultivated rice land was lost at its margins. The lobate, symmetrical Tinajones delta has an approximate area of 26 km²; both flanks are subjected to intense beach erosion (Fig. 21).

Figure 20. Landsat image of Cispata Bay and mangrove swamps (red) and the new Tinajones delta. Reproduced by permission of Invemar.

Figure 21. Shore erosion along the San Bernardo del Viento beaches, on the southwest flank of the Tinajones delta. Photo by M. Hermelin.

From Punta La Rada to the Gulf of Urabá, the southern Caribbean coast has a S 50º W trend and is dominated by cliffs cut into deformed sequences of Tertiary mudstone and claystone. The cliffs, which are up to 36 m high, form the seaward limit of late Holocene wave-cut and depositional marine terraces (Page 1986). The coast exhibits a serrated pattern controlled by hard rocky headlands coinciding with structural axes (Fig. 22). Shore retreat is the dominant historical trend along most of this coastline (Correa and Vernette 2004).

A recent example of land loss along the southern Caribbean coast is in the Arboletes-Punta Rey area (Fig. 22). There the effects of natural shore and cliff erosion are exacerbated by intensive beach-sand extraction to build up the village of Arboletes. The natural processes and human activities caused complete erosion of the 1.5-km-long Punta Rey Peninsula between 1957 and 2000 (Morton and Correa 2004, Correa and Vernette 2004) (Fig. 23). Elimination of the wave protection provided by the peninsula triggered extensive cliff and beach erosion to the south (Figs. 24 and 25). Accelerated erosion also affected the Arboletes mud volcano, the main tourist attraction of the city (Fig. 26). Currently stable shores along the southern Caribbean coast are found only at a few specific, unmodified stretches that receive relatively high sand supply (Fig. 27).

Figure 22. Landsat (band 4) image showing the serrated erosive pattern of the southern Caribbean coast from the Tinajones delta (TD) and the Cispatá Bay (CB) to Punta Caribana, at the northern end of the Gulf of Urabá. On the southwest side of the Gulf is the progradational "bird foot" Atrato River delta. Reproduced by permission of the Corporación para el Desarrollo de los Valles del Sinú y San Jorge (CVS).

Figure 23. Aerial photograph taken in 1957 showing the former Punta Rey peninsula, between the mainland and Isla Rey (22). Dotted lines represent the approximate configuration of the present coastline. Reproduced by permission of Instituto Geográfico Agustín Codazzi (IGAC).

Figure 24. Cliff retreat at Arboletes and other inhabited shores of the southern Caribbean is associated with rainwater percolation in cracked soils and with inadequate management of residual water. Photo by María Carmona.

Figure 25. Erosion of a 10-m-high terrace south of Arboletes. Cliffs are cut into subhorizontal claystone and mudstone strata. Photo by I. Correa.

Figure 26. Aerial view of Arboletes mud diapir, showing the two main volcanoes. One volcano (top center) is being eroded by waves of the Caribbean Sea (upper left corner). Photo by R. Morton.

Figure 27. Vegetated bluffs and beaches recently stabilized, south of Arboletes. Photo by I. Correa.

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U.S. Department of the Interior | U.S. Geological Survey
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Page Last Modified: May 06, 2013 @ 09:24 AM (JSS)