ICE 2022


Regional-scale reprocessing of seismic data offshore Colombia in the Caribbean has revealed new insights into the structure and deformation of the entire northern accretionary margin. A framework of 60,000 line km of 2D seismic surveys was processed and analyzed as a single contiguous dataset during this study, supported by well log and gravity data. The Magdalena Fan lies between the compressional domain of the Sinu accretionary foldbelt to the southwest and the South Caribbean Deformed Belt (SCDB) as well the extensional and transtensional environments of Bahia and Guajira basins to the northeast. Using the newly re-imaged data, we can clearly contrast the thick, relatively undeformed sediments of the Magdalena delta with the adjacent accretionary sections. The lack of deformation could be due to the high volume of young sediment input from the Magdalena River since Late Miocene, influenced by a slab tear in the Caribbean Plate. The stratigraphic section of the 8 km-thick Magdalena Fan has created regionally extensive MTCs across the Colombian basin, several of which were mapped during this study. We demonstrate that there is a high variability in the complexity of deformation from west to east across the sediment accretion zone. Structural styles within the accretionary foldbelts have developed in different magnitudes and appear to correlate with the angle of obliquity of the downgoing Caribbean Plate. A single basal detachment has been observed in the eastern Sinu prism; a second, mid-section detachment develops in the western Sinu area. The SCDB in the Guajira region contains two detachments over the majority of the belt and a third in the eastern reaches. This dataset has allowed for a regional-scale correlation between these areas for the very first time and allowed us to examine the transition between the structural domains along the northern margin. In this study we present our updated understanding of the evolution of accretionary belts and development of marginal basins and foldbelts in offshore Colombia.