Sediment Undulations on the Llobregat Prodelta: Signs of Early Slope Instability Or Sedimentary Bedforms?
JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 112, B05102, doi:10.1029/2005JB003929, 2007 Sediment undulations on the Llobregat prodelta: Signs of early slope instability or sedimentary bedforms? Roger Urgeles,1 Ben De Mol,1 Camino Liquete,1 Miquel Canals,1 Marc De Batist,2 John E. Hughes-Clarke,3 David Amblàs,1 Pedro A. Arnau,1 Antoni M. Calafat,1 José L. Casamor,1 Víctor Centella,1 Koen De Rycker,2 Joan Fabrés,1 Jaime Frigola,1 Sara Lafuerza,1 Galderic Lastras,1 Anna Sànchez,1 Diana Zuñiga,1 Wim Versteeg,2 and Verónica Willmott1 Received 6 July 2005; revised 6 June 2006; accepted 15 November 2006; published 5 May 2007. Abstract. A field of sediment undulations has been mapped by means of high resolution multibeam bathymetry and seismic reflection profiles in the Llobregat River prodelta, off the city of Barcelona, Catalonia, Spain. Similar features had previously been recognized in other prodelta environments and interpreted either as downslope sediment deformation or sedimentary structures induced by bottom currents or hyperpycnal flows. Since the study area is undergoing significant offshore development, proper interpretation of such sediment undulations is needed for a correct risk assessment. The occurrence of the sedi- ment undulations is restricted to the prodelta front on slope gradients between 3 and 0.2º. The undulations have developed at the edge and atop an area of gas bearing sediments within the Late-Holocene high-stand mud wedge. An evaluation is made of the character- istics of the sediment undulations in order to determine the most likely process for the origin of these structures.
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