Turbidites deposited on Southern Central Chilean seamounts: Evidence for energetic turbidity currents.

Völker, David, Reichel, T., Wiedicke, M. and Heubeck, C. (2008) Turbidites deposited on Southern Central Chilean seamounts: Evidence for energetic turbidity currents. Marine Geology, 251 . pp. 15-31. DOI 10.1016/j.margeo.2008.01.008.

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Gravity cores obtained from isolated seamounts located within, and rising up to 300 m from the sediment-filled Peru–Chile Trench off Southern Central Chile (36°S–39°S) contain numerous turbidite layers which are much coarser than the hemipelagic background sedimentation. The mineralogical composition of some of the beds indicates a mixed origin from various source terrains while the faunal assemblage of benthic foraminifera in one of the turbidite layers shows a mixed origin from upper shelfal to middle-lower bathyal depths which could indicate a multi-source origin and therefore indicate an earthquake triggering of the causing turbidity currents. The bathymetric setting and the grain size distribution of the sampled layers, together with swath echosounder and sediment echosounder data which monitor the distribution of turbidites on the elevated Nazca Plate allow some estimates on the flow direction, flow velocity and height of the causing turbidity currents. We discuss two alternative models of deposition, both of which imply high (175–450 m) turbidity currents and we suggest a channelized transport process as the general mode of turbidite deposition. Whether these turbidites are suspension fallout products of thick turbiditic flows or bedload deposits from sheet-like turbidity currents overwhelming elevated structures cannot be decided upon using our sedimentological data, but the specific morphology of the seamounts rather argues for the first option. Oxygen isotope stratigraphy of one of the cores indicates that the turbiditic sequences were deposited during the last Glacial period and during the following transition period and turbiditic deposition stopped during the Holocene. This climatic coupling seems to be dominant, while the occurrence of megathrust earthquakes provides a trigger mechanism. This seismic triggering takes effect only during times of very high sediment supply to the shelf and slope.

Document Type: Article
Keywords: turbidity current; suspension fallout; bedload deposit; Peru–Chile Trench; perched turbidite beds; turbidity current runup; mass wasting
Research affiliation: OceanRep > SFB 574
OceanRep > SFB 574 > A1
OceanRep > GEOMAR > FB4 Dynamics of the Ocean Floor > FB4-GDY Marine Geodynamics
Refereed: Yes
Open Access Journal?: No
DOI etc.: 10.1016/j.margeo.2008.01.008
ISSN: 0025-3227
Projects: SPOC, TIPTEQ, SFB267, SFB574
Contribution Number:
SFB 574144
Date Deposited: 03 Dec 2008 16:51
Last Modified: 23 Sep 2019 21:22
URI: http://oceanrep.geomar.de/id/eprint/1727

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