Glacial-interglacial trench supply variation, spreading-ridge subduction, and feedback controls on the Andean margin development at the Chile triple junction area (45-48°S)

• Published in: Journal of Geophysical Research: Solid Earth
• Main Authors: Bourgois, Jacques, Guivel, Christèle, Lagabrielle, Yves, Calmus, Thierry, Boulègue, Jacques, Daux, Valérie
• Other Authors: Institut des Sciences de la Terre de Paris (iSTeP), Institut national des sciences de l'Univers (INSU - CNRS)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Laboratoire de Planétologie et Géodynamique de Nantes UMR 6112 (LPGN), Université de Nantes (UN)-Centre National de la Recherche Scientifique (CNRS), Institut de Recherche pour le Développement (IRD Nouvelle-Calédonie ), Instituto de Geologia, Universidad Nacional Autónoma de México = National Autonomous University of Mexico (UNAM), Laboratoire de Géochimie et Métallogénie, Université Pierre et Marie Curie - Paris 6 (UPMC), Laboratoire des Sciences du Climat et de l'Environnement Gif-sur-Yvette (LSCE), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Direction de Recherche Fondamentale (CEA) (DRF (CEA)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA), Géochrononologie Traceurs Archéométrie (GEOTRAC), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Direction de Recherche Fondamentale (CEA) (DRF (CEA)), Glaces et Continents, Climats et Isotopes Stables (GLACCIOS)
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2000
• Subjects: [SDU.STU.TE]Sciences of the Universe [physics]/Earth Sciences/Tectonics; Chile Trench; Antarc*; Antarctica; Ice cap
• Online Access: https://hal.science/hal-02497069; https://hal.science/hal-02497069/document; https://hal.science/hal-02497069/file/1999JB900400.pdf; https://doi.org/10.1029/1999JB900400

International audience During the Chile triple junction (CTJ) cruise (March–April 1997), EM12 bathymetry and seismic reflection data were collected in the vicinity of the Chile triple junction (45‐480S), where an active spreading ridge is being subducted beneath the Andean continental margin. Results show a continental margin development shaped by tectonic processes spanning a spectrum from subduction‐erosion to subduction‐accretion. The Andean continental margin and the Chile trench exhibit a strong segmentation which reflects the slab segmentation and the Chile triple junction migration. Three segments were identified along the Andean continental margin: the presubduction, the synsubduction, and the postsubduction segments, from north to south. Both climate‐induced variations of the sediment supply to the trench and the tectonic reorganization at the Nazca‐Antarctica plate boundary involving postsubduction ridge jump are the two main factors that control the tectonic regime of this continental margin. Along the survey area we infer the succession of two different periods during the last glacial‐interglacial cycle: a glacial period with ice‐rafted detrital discharges restricted to the shoreline area and low river output and a warmer period during which the Andean ice cap retreat allowed the Andes to be drained off. During these warm periods, rapid increase in trench deposition caused the margin to switch from subductionerosion or nonaccretion to subduction‐accretion: (1) along the presubduction segment after the last deglaciation and (2) along the postsubduction segment after the interglacial episode at 130–117 ka. Conversely, a nonaccretion or subduction‐érosion mode characterized the presubduction and postsubduction segments during glacial maximums. The major effects of subduction of the buoyant Chile ridge include a shallow trench which diverts trench sediment supply and tectonic instabilities at the Nazca‐Antarctica plate boundary. We suggest that a postsubduction westward jump of the Chile ridge occurred ...