Potential role of event-driven sediment transport on sediment accumulation in the Cariaco Basin, Venezuela

Abstract

A sediment density flow was observed in the eastern Cariaco Basin during September 2008. Evidence suggests that this flow was likely triggered by a magnitude 5.2 earthquake that occurred on August 11, 2008, with an epicenter located at 10.51°N, 64.17°W (off the city of Cumaná, Venezuela). Elevated suspended sediments near the bottom were observed at the mouth of the Manzanares Canyon (>90gm−2, over a depth of 165m) and decreased to ~11gm−2 (over a depth of 40m) 42km away from the canyon's mouth at the CARIACO Ocean Time-Series site. The sediment flux associated with this single event was ~10% of the total annual sediment flux that typically reaches the Cariaco Basin deep seafloor. Carbon to nitrogen ratios and isotope composition confirm that most of the organic matter transferred by the sediment flow was of continental origin (C/N ratios of ~17.67, δ13C of −27.04‰, and δ15N of 6.83‰). Our observations contribute to the growing body of evidence that suggests that submarine canyons are rapid, efficient sediment conduits of particles from shallow to deep waters, and that they should be included in efforts to constrain estimates of sediment and terrestrially derived carbon transport from the continental shelves to the deep ocean.