An interdisciplinary investigation of a recent submarine mass transport deposit at the continental margin off Uruguay.

Henkel, Susann, Strasser, Michael, Schwenk, Tilmann, Hanebuth, Till J. J., Hüsener, Johannes, Arnold, Gail L., Winkelmann, Daniel, Formolo, Michael, Tomasini, Juan, Krastel, Sebastian and Kasten, Sabine (2011) An interdisciplinary investigation of a recent submarine mass transport deposit at the continental margin off Uruguay. Open Access Geochemistry, Geophysics, Geosystems, 12 (8). Q08009. DOI 10.1029/2011GC003669.

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Assessing frequency and extent of mass movement at continental margins is crucial to evaluate risks for offshore constructions and coastal areas. A multidisciplinary approach including geophysical, sedimentological, geotechnical, and geochemical methods was applied to investigate multistage mass transport deposits (MTDs) off Uruguay, on top of which no surficial hemipelagic drape was detected based on echosounder data. Nonsteady state pore water conditions are evidenced by a distinct gradient change in the sulfate (SO42−) profile at 2.8 m depth. A sharp sedimentological contact at 2.43 m coincides with an abrupt downward increase in shear strength from ∼10 to >20 kPa. This boundary is interpreted as a paleosurface (and top of an older MTD) that has recently been covered by a sediment package during a younger landslide event. This youngest MTD supposedly originated from an upslope position and carried its initial pore water signature downward. The kink in the SO42− profile ∼35 cm below the sedimentological and geotechnical contact indicates that bioirrigation affected the paleosurface before deposition of the youngest MTD. Based on modeling of the diffusive re-equilibration of SO42− the age of the most recent MTD is estimated to be <30 years. The mass movement was possibly related to an earthquake in 1988 (∼70 km southwest of the core location). Probabilistic slope stability back analysis of general landslide structures in the study area reveals that slope failure initiation requires additional ground accelerations. Therefore, we consider the earthquake as a reasonable trigger if additional weakening processes (e.g., erosion by previous retrogressive failure events or excess pore pressures) preconditioned the slope for failure. Our study reveals the necessity of multidisciplinary approaches to accurately recognize and date recent slope failures in complex settings such as the investigated area.

Document Type: Article
Keywords: Meeresgeologie; Continental margin ; pore water geochemistry ; slope stability ; submarine mass transport
Research affiliation: MARUM
Kiel University > Kiel Marine Science
OceanRep > The Future Ocean - Cluster of Excellence
OceanRep > The Future Ocean - Cluster of Excellence > FO-R06
OceanRep > GEOMAR > FB4 Dynamics of the Ocean Floor > FB4-GDY Marine Geodynamics
OceanRep > GEOMAR > FB4 Dynamics of the Ocean Floor > FB4-JRG-B4 Submarine Hazards
Refereed: Yes
Open Access Journal?: No
DOI etc.: 10.1029/2011GC003669
ISSN: 1525-2027
Projects: Future Ocean, EUROPROX, Excellence Cluster 'The Ocean in the Earth System'
Date Deposited: 15 Aug 2011 08:45
Last Modified: 23 Sep 2019 23:42

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