Chapter 8 The NW Iberian continental shelf

Abstract

The continental shelf of NW Iberia is of particular interest due to the complex North Atlantic rifting tectonics and modern oceanographic processes that led to its current geomorphological configuration and sediment dynamics. The shelf forms a narrow slow-dipping north-bearing geomorphological structure with a well-defined shelf break located at water depths of 160-180 m. It is a continental margin with sedimentation rates of about 1.5 + 2.0 mm a 21 (the highest values in recent bottom sediments of the ría) subjected to a highly energetic seasonal regime of waves and tides, seasonal upwelling and coast-parallel currents, significantly modulated by the North Atlantic Oscillation. Sediment provenance is dominated by inputs of continental sediments via runoff and riverine discharges and, to a lesser extent, by an upwelling-enhanced bioclastic input. Present-day sedimentation in the area occurs closely associated with two geomorphologically distinct sedimentary environments: the rías inner shelf sedimentary systems and the open continental shelf, and their subsequent evolution since the last glacial.

Evolution of the Galicia Interior Basin over the last 60 ka: sedimentary processes and palaeoceanographic implications

“…Progressive sea level fall (Siddall et al , ) during the glacial period caused sediment reworking and winnowing of layers along the outer shelf (cf. Lantzsch et al ., ; Rey et al ., ) and upper slope areas. Sediment transport to the lower slope increased.…”

“…Of the few palaeoenvironmental studies addressing the Atlantic NW Iberian continental margin, most have focused on the Galicia Bank (Ercilla and Vilas, , and references therein) and the Galicia shelf (e.g. Dias et al ., ; González‐Álvarez et al ., ; Martins et al ., ; Bernárdez et al, , ; Lantzsch et al ., , 2010; Mohamed et al ., ; Oberle et al ., ; Rey et al ., ). The Galicia Interior Basin (GIB), including its eastern and western slopes, have received less attention (McCave and Hall, ; Bender et al ., ; Martins et al ., , ; Plaza‐Morlote et al ., ).…”

Formation and evolution of back‐barrier perched lakes in rocky coasts: An example of a Holocene system in north‐west Spain

“…This is supported by the existence of freshwater diatom‐rich deposits in the Galician outer shelf at depths of 150 to 160 m (Bao et al ., ). These data indicate that the sea‐level was below this depth range and was probably close to the shelf break at a depth of 180 m (Rey et al ., ).…”

“…The continental shelf of north‐west Iberia forms a gently dipping, north‐bearing, 30 to 50 km wide geomorphological structure with a shelf break located at water depths of 160 to 180 m. Sediments are dominated by continental inputs via riverine discharges, and they accumulate in the continental margin at rates of up to 1·5 mm yr −1 (Rey et al ., ). The shelf has been subjected to high sediment supply during the Holocene, as corroborated by the presence of prograding sandy sedimentary bodies (Martínez‐Carreño et al ., ).…”

Chapter 1 An overview of the continental shelves of the world

“…Rey et al (2014) present a detailed overview of the most distinct features and processes on the shelf, among which waves and tides, seasonal upwelling, and coast-parallel currents are recognized.…”