Diversity of sediment deposition at the Argentine continental margin during the Cenozoic


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Jens.Gruetzner [ at ] awi.de

Abstract

Based on distinct along-margin variations in architecture, volume, and width of seaward dipping reflector sequences the Argentine passive margin can be divided in four segments, which are numbered I-IV from South to North and are bounded by transfer zones. We investigate how these margin segments are reflected in the distribution and thickness of the sediments contained in the Argentine basin, which documents tectonic, climatic and oceanographic events. Our analysis of five Cenozoic time slices is based on the identification of regional reflectors in an extensive net of seismic reflection profiles (> 11000 km) and resolves spatial and temporal variations in the relative importance of downslope versus along-slope sediment transport processes. Seismic features diagnostic of current or gravity controlled sedimentation are identified and compared along the margin from 38°S to 50°S. Mapped changes in depocenter locations and sedimentation rates already published for segments I and II (> 42°S) are augmented with newest results for segment III (38-42°S) characterized by a much narrower shelf, the proximity to the Rio de la Plata and the influence of North Atlantic Deep water (NADW). During the Paleocene and Eocene the whole margin was characterized by steady pelagic sedimentation with little evidence for the influence of bottom current activity and/or gravitational sediment transport. From the Oligocene to the middle Miocene a giant elongated detached drift developed in segments I and II in a deep marine environment that was strongly current dominated by northward directed flow of Antarctic water masses. Strong variations of down-slope versus along-slope sediment transport from one segment to the next mainly developed from ~17 Ma onward. Current controlled sediment transport and deposition shaped the terraces of segment I, while in segment II down-slope transport possibly triggered by tectonic uplift in South America became dominant between ~17 Ma and ~6 Ma. Since ~6 Ma an interplay of down- slope and along-slope sediment transport is indicated for segments II to IV by the presence of slope plastered sediment drifts, channel-levee systems, canyons, and extensive mudwave fields. Although the Argentine margin lies beneath a key portion of the global thermohaline circulation it has not been investigated using scientific drilling. The results presented here currently help to develop an IODP drill proposal for the region which will be submitted in 2015.



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Conference (Talk)
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Primary Division
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Not peer-reviewed
Publication Status
Published
Event Details
75. Jahrestagung der Deutschen Geophysikalischen Gesellschaft (DGG), 23 Mar 2015 - 26 Mar 2015, Hannover.
Eprint ID
37342
Cite as
Gruetzner, J. , Uenzelmann-Neben, G. and Franke, D. (2015): Diversity of sediment deposition at the Argentine continental margin during the Cenozoic , 75. Jahrestagung der Deutschen Geophysikalischen Gesellschaft (DGG), Hannover, 23 March 2015 - 26 March 2015 .


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