The Pointe-Du-Fort Mass Movement Deposits, Upper Saguenay Fjord, Canada: A Multiphase Build-Up

Duchesne, Mathieu J.; Long, Bernard; Locat, Pascal; Locat, Jacques; Masse, Mélanie

doi:10.1007/978-94-010-0093-2_55

Cited by 4 publications

(4 citation statements)

References 18 publications

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“…Density flows can transform from coherent mass movements (e.g. Hampton, 1972; Mohrig & Marr, 2003; Piper & Normark, 2009) and originate from small‐scale failures in gullies, as the slopes attain equilibrium (Duchesne et al ., 2003). Debris originating from these slope failures can directly reach the flat fjord floor or temporarily accumulate on the stepped cross‐sectional morphology of the fjord.…”

Section: Resultsmentioning

confidence: 99%

“…Subaqueous fjord‐side debrites in modern fjords show that the overall fjord basin dimensions do not play an important role in flow confinement, because their runout distances are often on the order of 10 3 m and the deposits concentrate at the fjord sides (Ilstad et al ., 2004; Forwick & Vorren, 2012). The build‐up of each debrite bedset can be explained by retrogressive slope failures and by a stable position of the mouths of the feeding gullies, which allows for the aggradation of debrites derived from multiple debris‐flow events (Duchesne et al ., 2003; Longva et al ., 2003). In addition, the multiple bedsets indicate multiple point sources of debris flows, probably due to being fed by multiple gullies.…”

Section: Resultsmentioning

confidence: 99%

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Gravitational resedimentation as a fundamental process in filling fjords: Lessons from outcrops from a late Palaeozoic fjord in Namibia

Menozzo da Rosa,

Isbell,

McNall

et al. 2023

Sedimentology

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The stratigraphic architecture of fjords is complicated due to the delicate interplay between ice dynamics, sediment supply, relative sea‐level fluctuations and slope failures. Glaciogenic sediment is prone to failure and to be carried downslope to the fjord floor through the entire spectrum of mass movements and subaqueous density flows, as the unstable paraglacial submarine landscape moves toward stability. Palaeofjords formed by Gondwanan glaciers during the late Palaeozoic Ice Age contain a compelling record of gravitational resedimentation in fjord depositional systems. This paper showcases the geomorphology and depositional history of a glacial cycle in the Orutanda fjord in north‐western Namibia as an example of an overdeepened fjord basin fill dominated by products of subaqueous gravitational processes. During glaciation, the Orutanda glacier carved a 20 km long by 3.7 km wide glacial trough that embodies an overdeepened basin. Ice thickness during terminal glacial occupation of the fjord is estimated to had been up to 200 m based on the fjord geomorphology. The progressive retreat of the tidewater glacier, concomitant with marine flooding, increased accommodation space in the overdeepened basin during deglaciation. During this stage, proglacial sedimentation through iceberg rafting and settling of turbid plumes was outpaced by intense paraglacial downslope resedimentation of glacially‐transported debris. Successive failures from the fjord walls and downslope resedimentation resulted in coalescing debrite–turbidite lobes on the fjord floor. Slide deposits, composed entirely of deformed debrites and turbidites, indicate these resedimented facies were prone to renewed mass wasting. As the Orutanda glacier melted, the fjord experienced the axial progradation of a fjord‐head delta registered only by turbidites and slide deposits derived from its collapse. The Orutanda fjord sheds light on the relevance of paraglacial mass wasting in overprinting glaciogenic deposits. This insight is key to understanding the role of glaciers versus non‐glacial processes in producing the glacial deep‐time record.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Gravitational resedimentation as a fundamental process in filling fjords: Lessons from outcrops from a late Palaeozoic fjord in Namibia

Menozzo da Rosa,

Isbell,

McNall

et al. 2023

Sedimentology

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“…Horizontally laminated structures cover a wide range of flow states [Boggs, 1995]. In the present geological context, i.e., a mass wasting dominated environment, these structures might be the product of a high-density flow or a phase of a upper flow regime transport following a debris flow sedimentation episode [Bouma, 1963;Duchesne et al, 2003;Ò Cofaigh et al, 2004].…”

Section: Genesis Of the Seismic Faciesmentioning

confidence: 99%

“…In many cases the formation of mass movement deposits includes several phases of erosion and deposition of various amplitudes. For example, Duchesne et al [2003] showed on CT scan images that some sedimentological features observed in the Upper Saguenay Fjord basin result from multiple depositional phases which have signatures as thin as 1 mm. If these small-scale phases are numerous on a profile, they can mask largerscale phases which are approaching the resolution of the seismic data and which can thus be correlated with the seismic (Figures 3 and 4).…”

Section: Presence Of Noise In the Sedimentary Columnmentioning

confidence: 99%

On the use of computerized tomography scan analysis to determine the genesis of very high resolution seismic reflection facies

Duchesne¹,

Long²,

Labrie³

et al. 2006

J. Geophys. Res.

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[1] Computerized tomography scanner (CT scanner) is a powerful tool that can reveal millimeter-scale stratigraphy from cores. The coupling of very high resolution (VHR) seismic data with CT scan data represents a new approach to determine with more confidence the genesis of seismic facies. However, prior to the application of such a method, a clear understanding of the relationship between these two types of data (e.g., physical parameters in common) is necessary. The application of CT scan analysis along with VHR seismic data showed that seismic and CT scan signals respond to different physical properties of the sediments. Results suggest that similar seismic facies may correspond to different CT scan facies and, conversely, that different CT scan facies may have the same acoustic response. Sedimentary structures observed on the CT scan imagery suggest that a seismic response should be linked to a synthesis of lithological variations instead of a single and unique lithology change/contrast. Furthermore, this study points toward the fact that the geometry of the reflections does not always correspond to the geometry of sedimentary structures but rather to the anisotropy of the physical properties of the deposit. Consequently, to give a genetic connotation to the internal reflection pattern of a seismic facies can be misleading in some cases. Finally, the fine-scale sedimentological analysis based on very high resolution CT scan data is useful to determine very fine seismic analogs and thus to better explain the seismic expression of a deposit.Citation: Duchesne, M. J., B. F. Long, J. Labrie, and P. G. Simpkin (2006), On the use of computerized tomography scan analysis to determine the genesis of very high resolution seismic reflection facies,

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Submarine Mass Movements in the Upper Saguenay Fjord, (Québec, Canada), Triggered by the 1663 Earthquake

Locat

Martin

Levesque

et al. 2003

Submarine Mass Movements and Their Consequences

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The Pointe-Du-Fort Mass Movement Deposits, Upper Saguenay Fjord, Canada: A Multiphase Build-Up

Cited by 4 publications

References 18 publications

Gravitational resedimentation as a fundamental process in filling fjords: Lessons from outcrops from a late Palaeozoic fjord in Namibia

Gravitational resedimentation as a fundamental process in filling fjords: Lessons from outcrops from a late Palaeozoic fjord in Namibia

On the use of computerized tomography scan analysis to determine the genesis of very high resolution seismic reflection facies

Submarine Mass Movements in the Upper Saguenay Fjord, (Québec, Canada), Triggered by the 1663 Earthquake

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