Interpreting syndepositional sediment remobilization and deformation beneath submarine gravity flows; a kinematic boundary layer approach

Butler, Robert W.; Eggenhuisen, Joris T.; Haughton, Peter D. W.; McCaffrey, William D.

doi:10.1144/jgs2014-150

Cited by 31 publications

(18 citation statements)

References 41 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Indeed, the lack of mixing between the soft superficial sediment (F1) and the upper layer (F3) implies that the upper sediment layer was highly cohesive. Similar deformation structures can be found at the base of hyperpycnal flows such as turbidites, when the underlying superficial sediment is very fine and cohesive 49,50 . The higher terrestrial signature of these layers suggests a strong land-to-sea hyperpycnal flow coming from the inundated area into the bay.…”

Section: Discussionsupporting

confidence: 61%

“…The layer boundaries show asymmetric flame structures with rip-up clasts (F1, buckling) at the base of both layer 46,47 . These observed structures indicate syn-depositional reworking with shearing of superficial soft and cohesive sediment beneath a dense and cohesive gravity flow 48,49 . Indeed, the lack of mixing between the soft superficial sediment (F1) and the upper layer (F3) implies that the upper sediment layer was highly cohesive.…”

Section: Discussionmentioning

confidence: 93%

See 1 more Smart Citation

Backwash sediment record of the 2009 South Pacific Tsunami and 1960 Great Chilean Earthquake Tsunami

Riou

Chaumillon

Sabatier

et al. 2020

Sci Rep

View full text Add to dashboard Cite

Following recent tsunamis, most studies have focused on the onshore deposits, while the offshore backwash deposits, crucial for a better understanding of the hydrodynamic processes during such events and offering an opportunity for sedimentary archives of past tsunamis, have mostly been omitted. Here, we present a unique sedimentary record of the backwash from two historical tsunamis sampled in a sheltered bay in American Samoa, namely the 2009 South Pacific Tsunami and the 1960 Great Chilean Earthquake Tsunami. Although not always concomitant with a marked grain size change, backwash deposits are identified by terrestrial geochemical and mineralogical signatures, associated with basal soft sediment micro-deformations. These micro-deformations, including asymmetric flame structures, are described for the first time in historic shallow marine backwash deposits and lead us to propose an improved depositional mechanism for tsunami backflow based on hyperpycnal currents. Moreover, this study brings a potential new criterion to the proxy toolkit for identifying tsunami backwash deposits, namely the basal soft sediment micro-deformations. We suggest that further studies focus on these micro-deformations in order to test the representability of this criterion for tsunami backwash deposits. Sheltered shallow marine environments in areas repeatedly impacted by tsunamis have a higher potential for the reconstruction of paleo-tsunami catalogs and should be preferentially investigated for coastal risk assessment. Over the last two decades, interest in tsunami-related research has increased significantly, with peaks in the number of published articles following the 2004 Indian Ocean Tsunami (IOT), the 2009 South Pacific Tsunami (SPT) and the 2011 Tohoku-Oki Tsunami (TOT) 1. However, most studies have focused on onshore deposits, with only a few tackling the issue of backwash depositional processes 2-16. Unlike onshore deposits, offshore deposits are not subject to subaerial erosion and less to anthropic reworking, but can be altered by waves, currents, mixing and bioturbation 1,16. Most of the studies of historic tsunami backwash were carried out in open beach environments following the 2004 IOT and 2011 TOT 5,13,14,16-18. However, such environments have a poor preservation potential due to their exposure to waves. In contrast, sheltered bays may provide a higher preservation potential due to less reworking by waves. Thus, the choice of the study zone is key when looking for marine backwash deposits. We suggest that in shallow marine sheltered environments characterized by a low hydrodynamic setting, a complete and uninterrupted record is more likely to be preserved. Most studies of backwash deposits are based on grain size, geochemical data and microfossils 1. Shallow marine tsunami deposits are usually characterized by an increase of the mean grain size within usually fine marine mud, due to the inclusion of coarse terrestrial sediment originating from the onshore-inundated or beach areas 5,6,12,15,16 , often accompanied by...

show abstract

Section: Discussionsupporting

confidence: 61%

Section: Discussionmentioning

confidence: 93%

Backwash sediment record of the 2009 South Pacific Tsunami and 1960 Great Chilean Earthquake Tsunami

Riou

Chaumillon

Sabatier

et al. 2020

Sci Rep

View full text Add to dashboard Cite

show abstract

“…The studied MTC is dominated by low‐amplitude, chaotic seismic reflections, with a high‐amplitude, semi‐continuous basal reflection that caps a sequence of older‐MTCs and polygonally faulted mudstones (Figure ). The high‐amplitude basal reflection is interpreted as a basal shear surface, representing a kinematic boundary layer (sensu Butler, Eggenhuisen, Haughton, & McCaffrey, ) or zone, upon which the MTC was translated and ultimately deposited (Martinsen, ; Varnes, ). The basal shear surface connects updip to a headwall scarp and downdip to a frontal ramp, which define the limit of the extensional and contractional domains, respectively.…”

Section: Seismic Characterisation Of the Mtcmentioning

confidence: 99%

Strain analysis of a seismically imaged mass‐transport complex, offshore Uruguay

et al. 2019

View full text Add to dashboard Cite

Strain style, magnitude and distribution within mass‐transport complexes (MTCs) are important for understanding the process evolution of submarine mass flows and for estimating their runout distances. Structural restoration and quantification of strain in gravitationally driven passive margins have been shown to approximately balance between updip extensional and downdip contractional domains; such an exercise has not yet been attempted for MTCs. We here interpret and structurally restore a shallowly buried (c. 1,500 mbsf) and well‐imaged MTC, offshore Uruguay using a high‐resolution (12.5 m vertical and 15 × 12.5 m horizontal resolution) three‐dimensional seismic‐reflection survey. This allows us to characterise and quantify vertical and lateral strain distribution within the deposit. Detailed seismic mapping and attribute analysis shows that the MTC is characterised by a complicated array of kinematic indicators, which vary spatially in style and concentration. Seismic‐attribute extractions reveal several previously undocumented fabrics preserved in the MTC, including internal shearing in the form of sub‐orthogonal shear zones, and fold‐thrust systems within the basal shear zone beneath rafted‐blocks. These features suggest multiple transport directions and phases of flow during emplacement. The MTC is characterised by a broadly tripartite strain distribution, with extensional (e.g. normal faults), translational and contractional (e.g. folds and thrusts) domains, along with a radial frontally emergent zone. We also show how strain is preferentially concentrated around intra‐MTC rafted‐blocks due to their kinematic interactions with the underlying basal shear zone. Overall, and even when volume loss within the frontally emergent zone is included, a strain difference between extension (1.6–1.9 km) and contraction (6.7–7.3 km) is calculated. We attribute this to a combination of distributed, sub‐seismic, ‘cryptic’ strain, likely related to de‐watering, grain‐scale deformation and related changes in bulk sediment volume. This work has implications for assessing MTCs strain distribution and provides a practical approach for evaluating structural interpretations within such deposits.

show abstract

“…We interpret SF10 to represent mass-transport complexes (MTCs) emplaced by debris, slump or slide processes during shelf-margin failure (Dott 1963;Nardin 1979;Nemec 1990). The highamplitude basal surfaces likely represent kinematic boundary zones upon which the MTCs were transported (sensu Butler et al 2016). The frontal ramps (Fig.…”

Section: Discussionmentioning

confidence: 99%

Lateral variability of shelf-edge, slope and basin-floor deposits, Santos Basin, offshore Brazil

Steventon¹,

Jackson²,

Hodgson³

et al. 2022

Preprint

View full text Add to dashboard Cite

Construction of continental margins is driven by sediment transported across the shelf to the shelf-edge, where it is reworked by wave-, tide- and river-influenced processes within deltas and flanking clastic shorelines. Stalling of continental margin progradation often results in degradation of the outer shelf to upper slope, with re-sedimentation to the lower slope and basin-floor via a range of sediment gravity-flows and mass-movement processes. Our understanding of how these processes contribute to the long-term development of continental margins has typically been limited to observations from broadly two-dimensional, subsurface and outcrop datasets. Consequently, the three-dimensional, particularly along-strike variability in process regime and margin evolution is poorly constrained and often underappreciated. We use a large (90 km by 30 km, parallel to depositional strike and dip, respectively) post-stack time-migrated 3D seismic-reflection dataset to investigate along-strike variations in shelf margin progradation and outer-shelf to upper-slope collapse in the Santos Basin, offshore SE Brazil. Early Palaeogene to Eocene progradation of the shelf margin is recorded by spectacularly imaged, SE-dipping clinoforms. Periodic failure of the outer-shelf and upper slope formed c.30 km-wide (parallel to shelf margin strike) slump scars, which resulted in a strongly scalloped upper slope. Margin collapse caused (1) the emplacement of slope-attached mass-transport complexes (MTCs) (up to ca. 375 m thick, 12+ km long, 20 km wide) on the proximal basin-floor, and (2) accommodation creation on the outer shelf to upper slope. This newly formed accommodation was infilled by shelf-edge-delta clinoforms (up to 685 m thick), that nucleated and prograded basinward from the margin-collapse headwall scarp, downlapping onto the underlying slump scar and/or MTCs. Trajectory analysis of the shelf-edge deltas suggests that slope degradation-created accommodation was generated mainly during times of base-level rise rather than, as would be predicted by most sequence-stratigraphic models, during base-level fall. Our results highlight the significant along-strike variability in depositional style, geometry and evolution of that can occur on this and other continental margins. Coeval strata, separated by only a few kilometres, display strikingly different stratigraphic architectures; this variability could be missed in 2D datasets and is not currently captured in conventional 2D sequence stratigraphic models.

show abstract

Interpreting syndepositional sediment remobilization and deformation beneath submarine gravity flows; a kinematic boundary layer approach

Cited by 31 publications

References 41 publications

Backwash sediment record of the 2009 South Pacific Tsunami and 1960 Great Chilean Earthquake Tsunami

Backwash sediment record of the 2009 South Pacific Tsunami and 1960 Great Chilean Earthquake Tsunami

Strain analysis of a seismically imaged mass‐transport complex, offshore Uruguay

Lateral variability of shelf-edge, slope and basin-floor deposits, Santos Basin, offshore Brazil

Contact Info

Product

Resources

About