Late Quaternary shelf-margin wedges and upper slope progradation in the Gulf of Cadiz margin (SW Iberian Peninsula)
Published:January 01, 2005
F. J. Lobo, J. M. A. Dias, F. J. Hernández-Molina, R. González, L. M. Fernández-Salas, V. Díaz Del Río, 2005. "Late Quaternary shelf-margin wedges and upper slope progradation in the Gulf of Cadiz margin (SW Iberian Peninsula)", Submarine Slope Systems: Processes and Products, David M. Hodgson, Stephen S. Flint
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The distribution patterns and internal geometries of recent shelf-margin wedges off the Guadiana River, Gulf of Cadiz margin, were studied in order to discern the effects of varying trends of falling sea-level and lowstand on upper slope progradation. A seismic-sequence stratigraphic analysis was conducted, based on the interpretation of a dense grid of high-resolution seismic profiles.
Five major shelf-margin wedges deposited during late Quaternary sea-level fall and lowstand periods were documented. Most of the studied shelf-margin wedges produce upbuilt-outbuilt upper slopes. The analysis of their internal geometries reveals two distinct types of configuration: the four older shelf-margin wedges are mainly composed of forced regressive deposits developed during stepped sea-level falls. The scarceness of lowstand deposits suggests abrupt sea-level fall to rise transitions; and the most recent shelf-margin wedge shows both forced regressive deposits and low-stand deposits significantly preserved. This architecture probably resulted from the occurrence of a long-lived sea-level lowstand after a prolonged period of gentle sea-level fall.
Two types of shelf-margin wedges have been recognized: wedges with elongate parallel depocentres, laterally constant thickness and uniform seaward shelf-break migration, related to linear source supply and high lateral sediment redistribution during gently falling sea level; and wedges with (multi) lobate depocentres with laterally variable thickness, leading to uneven shelf-break migration during periods of faster sea-level fall, due to delta lobe switching and significant shelf valley incision.
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Submarine Slope Systems: Processes and Products
Submarine slopes provide the critical link between shallow-water and deep-water sedimentary environments. They accumulate a sensitive record of sediment supply, accommodation creation/destruction, and tectonic processes during basin filling. There is a complex stratigraphic response to the interplay between parameters that control the evolution of submarine slope systems, e.g. slope gradient, topographic complexity, sediment flux and calibre, base-level change,tectonic setting, and post-depositional sediment remobilization processes. The increased understanding of submarine slope system has been driven partly by the discovery of large hydrocarbon fields in morphologically complex slope settings, such as the Gulf of Mexico and offshore West Africa, and has led to detailed case studies and improved generic models for their evolution. This volume brings together research papers from modern, outcrop and subsurface settings to highlight these recent advances in understanding of the stratigraphic evolution of submarine slope systems.