Sediment deposition and erosion at the Argentine continental slope: evidence for an intensification of deep ocean circulation during the Late Neogene

• Main Authors: Gruetzner, Jens, Uenzelmann-Neben, Gabriele, Franke, Dieter
• Format: Conference Object
• Language: unknown
• Published: 2013
• Subjects: Antarc*; Antarctic
• Online Access: https://epic.awi.de/id/eprint/33908/; https://hdl.handle.net/10013/epic.42266

A complex history of sediment deposition at the Argentine continental margin during the Plio-Pleistocene is indicated by the presence of a canyon system, submarine channels, sediment drifts and sediment waves. We use a dense grid of seismic reflection profiles together with bathymetric data to identify sedimentary units, map depocenter geometries, separate along-slope from down-slope processes and relate depositional stages to past changes in climate, oceanography and tectonics. The topmost seismic unit in the working area (40 to 48°S) exhibits a variety of co-occurring seismic and morphological features that are diagnostic for both down-slope and along-slope sediment redistribution. In general, current controlled sedimentation is more obvious south of 45°S (“terraces sector”) while in the northern part (“canyons sector”) of the working area contouritic features are reshaped by cross-slope erosion through canyons. Within the canyons sector an extensive field of migrating sediment waves is observed at a water depth of 2500 to 3500 m. The waves are 1.5 to 4 km wide and 30 to 100 m high. Buried waves overlying reflector AR7 (~6 Ma) indicate that the field has been active since the Early Pliocene. Seaward of the 3500 m isobaths a slope plastered drift with a thickness of ~400 - 600 m and a width of ~10 - 20 km and can be traced for ~100 km within the working area. These features likely are northward extensions of a current derived unit identified in the terraces sector and indicate that during the Plio-Pleistocene strong current controlled sedimentation occurred close to the interface between Circumpolar Deep Water (CDW) and Antarctic Bottom Water (AABW). Erosion via slope cutting canyons is most extensive in ~3000 m water depth at the central Argentine margin (43.5°S, 57.5°W) where multiple branches of the Ameghino canyon system join. None of the canyons in the working area cut into reflectors AR5/AR6 (~14 – 17 Ma), and only the main branches of the Ameghino canyon cut into reflector AR7 (~6 Ma) on the upper slope. ...