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Title: Sediment undulations on the Llobregat prodelta: Signs of early slope instability or sedimentary bedforms?
Author: Urgeles Esclasans, Roger
De Mol, Ben
Liquete García, Camino
Canals Artigas, Miquel
De Batist, Marc
Hughes-Clarke, John E.
Amblàs i Novellas, David
Arnau, Pedro A.
Calafat Frau, Antoni
Casamor Bermúdez, José Luis
Centella, Víctor
De Rycker, Koen
Fabrés Francés, Joan
Frigola Ferrer, Jaime I.
Lafuerza, Sara
Lastras Membrive, Galderic
Sànchez Vidal, Anna
Zuñiga, Diana
Versteeg, Wim
Willmott Puig, Verónica
Keywords: Sediments fluvials
Llobregat, Delta del (Catalunya))
River sediments
Llobregat River Delta (Catalonia)
Issue Date: 2007
Publisher: American Geophysical Union
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 sediment 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 characteristics of the sediment undulations in order to determine the most likely process for the origin of these structures. Amongst these characteristics are the continuity of the reflections and lack of diffractions in between different undulations, their size distribution (large to small) both from shallow to deep and with depth in section, the asymmetry (decreasing from proximal to distal), the crest to trough vertical distance on the landward side of the undulations (up to 0.5 m), and the lack of features that could indicate a progressive movement such as growth structures and drag folds. These characteristics indicate that the sediment undulations on the Llobregat River prodelta do not result from sediment deformation, but rather from the interaction of bottom currents generated by hyperpycnal flows from the Llobregat River with regional sea water circulation. Their identification as sediment waves implies that such features do not pose a major hazard for urther offshore development.
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It is part of: Journal of Geophysical Research, 2007, vol. 112, p. B05102
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ISSN: 0148-0227
Appears in Collections:Articles publicats en revistes (Dinàmica de la Terra i l'Oceà)

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