Latin american journal of aquatic research
On-line version ISSN 0718-560X
The morphology of a submarine dune field developed in a tidal inlet that connects the Argentinean continental shelf with Anegada Bay (southern Buenos Aires province) was studied. The sediment circulation was inferred from the differential displacements of the bedforms evaluated by comparing consecutive surveys. An echosounder and a Phase Measuring Bathymetric System (PMBS) called GeoSwath were used to obtain a detailed submarine morphology. Large dunes, with heights between 4.5 and 5.0 m and from 100 to 120 m separating them, were present near the southern limit of the dune field at 24 m depth. These dunes move towards the outer part of the channel at a speed of 18 to 75 m year-1. At the northern end of the dune field, at 21 m depth, the dunes are smaller, being 2.0 to 2.5 m in height and separated by 40 to 80 m. The smaller dunes move towards the interior of Anegada Bay at 18 to 36 m year-1. The distribution of the water flow in the entire water column was obtained through a perpendicular profile of the channel by means of an ADCP. Maximum current speeds were 2 m s-1, and were found during flood tide. The results obtained indicate a circulatory transport model of sedimentary sands, with the formation of ebb and flood deltas at both ends of the deep inlet throat, which lacks of unconsolidated sediments.
Keywords : dune field; migration velocity; sediment transport; GeoSwath; ADCP; Argentina.