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Multidirectional, synchronously-triggered seismo-turbidites and debrites revealed by X-ray computed tomography (CT)

(2014) SEDIMENTOLOGY. 61(4). p.861-880
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Abstract
On 21 April 2007, a Mw 6.2 earthquake struck Aysén fjord (Chilean Patagonia) and caused onshore and offshore mass movements which triggered tsunamis and density flows in the fjord. To better understand the facies successions in, and the intercalation of, the density-flow deposits, a study was made of the 2007 deposits in 22 short sediment cores taken in the inner Aysén fjord. By combining grain-size analysis with X-ray computed tomography scanning, it was possible to demonstrate that the encountered facies correspond to classical divisions of debrites and turbidites. The single-event deposits consist of a succession of several sub-deposits deposited under different flow directions and can be interpreted as stacked turbidites. Orientations of: (i) folds; (ii) imbricated mud clasts; iii) backsets and foresets of climbing ripples; and (iv) asymmetrical convolute lamination, were used to determine relative flow directions at the location of the cores. By assigning the basal flow of the stacked debrites and turbidites to the closest principal mass-flow, the absolute flow directions of the sub-deposits were determined which, in combination with multibeam basin-floor morphology, allowed reconstruction of the 2007 density-flow successions in Aysén fjord. Furthermore, alternating flow directions provide evidence for a seiche induced by the density flows. It was concluded that X-ray computed tomography scans provide crucial information for reconstructing palaeoflows and can be a useful tool in marine and lacustrine sedimentology and palaeoseismology. The multidirectionality of sub-deposits in turbidites is, next to differences in mineralogy, a new criterion to identify stacked turbidites. These multidirectional, stacked turbidites are an indication of simultaneous triggering of density flows and can therefore, in most cases, be attributed to earthquakes, ruling out other triggers, such as floods, storms or other sediment failures. This article is protected by copyright. All rights reserved.
Keywords
2007 earthquake, density flow, Aysén, fjord, stacked, flow direction, OFQUI FAULT ZONE, SEDIMENT TRANSPORT, SLOPE FAILURES, AYSEN FJORD, EARTHQUAKES, DEPOSITS, CURRENTS, SEA, MARGIN, CHILE

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MLA
Van Daele, Maarten, Veerle Cnudde, Philippe Duyck, et al. “Multidirectional, Synchronously-triggered Seismo-turbidites and Debrites Revealed by X-ray Computed Tomography (CT).” SEDIMENTOLOGY 61.4 (2014): 861–880. Print.
APA
Van Daele, Maarten, Cnudde, V., Duyck, P., Pino, M., Urrutia, R., & De Batist, M. (2014). Multidirectional, synchronously-triggered seismo-turbidites and debrites revealed by X-ray computed tomography (CT). SEDIMENTOLOGY, 61(4), 861–880.
Chicago author-date
Van Daele, Maarten, Veerle Cnudde, Philippe Duyck, Mario Pino, Roberto Urrutia, and Marc De Batist. 2014. “Multidirectional, Synchronously-triggered Seismo-turbidites and Debrites Revealed by X-ray Computed Tomography (CT).” Sedimentology 61 (4): 861–880.
Chicago author-date (all authors)
Van Daele, Maarten, Veerle Cnudde, Philippe Duyck, Mario Pino, Roberto Urrutia, and Marc De Batist. 2014. “Multidirectional, Synchronously-triggered Seismo-turbidites and Debrites Revealed by X-ray Computed Tomography (CT).” Sedimentology 61 (4): 861–880.
Vancouver
1.
Van Daele M, Cnudde V, Duyck P, Pino M, Urrutia R, De Batist M. Multidirectional, synchronously-triggered seismo-turbidites and debrites revealed by X-ray computed tomography (CT). SEDIMENTOLOGY. 2014;61(4):861–80.
IEEE
[1]
M. Van Daele, V. Cnudde, P. Duyck, M. Pino, R. Urrutia, and M. De Batist, “Multidirectional, synchronously-triggered seismo-turbidites and debrites revealed by X-ray computed tomography (CT),” SEDIMENTOLOGY, vol. 61, no. 4, pp. 861–880, 2014.
@article{4240699,
  abstract     = {On 21 April 2007, a Mw 6.2 earthquake struck Aysén fjord (Chilean Patagonia) and caused onshore and offshore mass movements which triggered tsunamis and density flows in the fjord. To better understand the facies successions in, and the intercalation of, the density-flow deposits, a study was made of the 2007 deposits in 22 short sediment cores taken in the inner Aysén fjord. By combining grain-size analysis with X-ray computed tomography scanning, it was possible to demonstrate that the encountered facies correspond to classical divisions of debrites and turbidites. The single-event deposits consist of a succession of several sub-deposits deposited under different flow directions and can be interpreted as stacked turbidites. Orientations of: (i) folds; (ii) imbricated mud clasts; iii) backsets and foresets of climbing ripples; and (iv) asymmetrical convolute lamination, were used to determine relative flow directions at the location of the cores. By assigning the basal flow of the stacked debrites and turbidites to the closest principal mass-flow, the absolute flow directions of the sub-deposits were determined which, in combination with multibeam basin-floor morphology, allowed reconstruction of the 2007 density-flow successions in Aysén fjord. Furthermore, alternating flow directions provide evidence for a seiche induced by the density flows. It was concluded that X-ray computed tomography scans provide crucial information for reconstructing palaeoflows and can be a useful tool in marine and lacustrine sedimentology and palaeoseismology. The multidirectionality of sub-deposits in turbidites is, next to differences in mineralogy, a new criterion to identify stacked turbidites. These multidirectional, stacked turbidites are an indication of simultaneous triggering of density flows and can therefore, in most cases, be attributed to earthquakes, ruling out other triggers, such as floods, storms or other sediment failures. This article is protected by copyright. All rights reserved.},
  author       = {Van Daele, Maarten and Cnudde, Veerle and Duyck, Philippe and Pino, Mario and Urrutia, Roberto and De Batist, Marc},
  issn         = {0037-0746},
  journal      = {SEDIMENTOLOGY},
  keywords     = {2007 earthquake,density flow,Aysén,fjord,stacked,flow direction,OFQUI FAULT ZONE,SEDIMENT TRANSPORT,SLOPE FAILURES,AYSEN FJORD,EARTHQUAKES,DEPOSITS,CURRENTS,SEA,MARGIN,CHILE},
  language     = {eng},
  number       = {4},
  pages        = {861--880},
  title        = {Multidirectional, synchronously-triggered seismo-turbidites and debrites revealed by X-ray computed tomography (CT)},
  url          = {http://dx.doi.org/10.1111/sed.12070},
  volume       = {61},
  year         = {2014},
}

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