Submarine canyon formation and evolution in the Argentine Continental Margin between 43º 30´ S and 48º S

• Published in: Geomorphology
• Main Authors: Lastras, Galderic, Acosta-Yepes, Juan, Pereiro-Muñoz, José Antonio, Canals i Artigas, Miquel
• Format: Article in Journal/Newspaper
• Language: unknown
• Published: 2011
• Subjects: Medio Marino; Sede Central IEO; Antarctic; Argentine; Moreno; Patagonia; Piedra Buena; Antarc*
• Online Access: http://hdl.handle.net/10508/8210; http://hdl.handle.net/10261/319932; https://doi.org/10.1016/j.geomorph.2010.12.027

In the framework of the Vulnerable Marine Ecosystems (VME) of the High Seas of the South West Atlantic, large areas of the Argentine Continental Margin (ACM) between 44°30'S and 48°S have been swath-mapped for the first time, obtaining full data coverage of the seafloor in this region between the outermost continental shelf and the middle slope down to 1600 m water depth. The slope is characterized by the presence of smooth terraces (Nagera, Perito Moreno and Piedra Buena) that widen towards the south, limited by morphological steps with evident signs of erosion in the form of scours. These terraces form part of the Argentine contourite depositional systems, generated by the interaction of the northwards flowing Antarctic water masses with the seafloor. Within the studied area, seven canyons and their multiple branches dissect the upper and middle continental slopes, from west to east, across the terraces and the steps. These canyons, which belong to the Patagonia submarine canyon system and are collected at a depth of ~ 3.5 km by a slope-parallel, SSW–NNE-oriented channel known as the Almirante Brown transverse canyon, display a large variety of morphologies. These include incisions from just a dozen of metres to 650 m, straight to highly meandering sections with sharp bends, well-developed levees and walls that reach 35° in slope gradient, hanging branches, conspicuous axial incisions and multiple knickpoints. Only the northernmost canyon indents in the continental shelf, whereas the others start at the limit between the upper and middle slopes, and are often fed by small, straight, leveed gullies. The action of both across-slope processes represented by submarine canyons and along-slope processes represented by terracing and scouring conform the ACM as a peculiar mixed margin, with the presence of both contour and gravity currents at the same place at the same time. We propose that at present, along-slope erosion and transport mainly occurs along the Perito Moreno terrace, whereas across-slope processes are ...