Deep-Marine Pseudo Dune Cross-Stratification—Similar, But Completely Different

Arnott, R. W. C.; Al-Mufti, Omar N.

doi:10.2110/jsr.2017.21

Cited by 18 publications

(14 citation statements)

References 49 publications

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“…Noteworthy is the occurrence of dune-like cross-stratification at the top of the antidune bed of Fig. 6B and the abundance of Tb2, Tb1 and Tc layers in very thin (cm) beds occasionally enveloped in muds, indicating deposition from low-density subcritical flows (cf., Arnott and Al-Mufti, 2017). Although some of these occurrences could represent the waning tail of the flow episode, stacks of beds that are enveloped in mud represent events on their own.…”

Section: Discussionmentioning

confidence: 99%

Supercritical flows and their control on the architecture and facies of small-radius sand-rich fan lobes

Postma

Kleverlaan²

2018

Sedimentary Geology

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Section: Discussionmentioning

confidence: 99%

Supercritical flows and their control on the architecture and facies of small-radius sand-rich fan lobes

Postma

Kleverlaan²

2018

Sedimentary Geology

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“…Mounded bed tops suggest a bedform-related origin, particularly in beds containing planar or hummocky cross stratification (Lf4b-c). In beds with concave-up bases these bedforms may have formed in relation to the infilling of depressions (sensu Arnott and Al-Mufti, 2017); however, this process does not account for those with flat bed bases. Another possible formative mechanism is deposition and tractional reworking of sediment forming dunes (Mutti, 1977) or megaripples (Tinterri, 2011).…”

Section: Facies Association 2 (Fa2) -Laterally Variable Thin Bedsmentioning

confidence: 99%

Syndepositional tectonics and mass-transport deposits control channelized, bathymetrically complex deep-water systems (Aínsa depocenter, Spain)

Tek

Poyatos‐Moré

Patacci

et al. 2020

Journal of Sedimentary Research

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The inception and evolution of channels in deep-water systems is controlled by the axial gradient and lateral confinement experienced by their formative flows. These parameters are often shaped by the action of tectonic structures and/or the emplacement of mass-transport deposits (MTDs). The Arro turbidite system (Aínsa depocenter, Spanish Pyrenees) is an ancient example of a deep-water channelized system from a bathymetrically complex basin, deposited in an active tectonic setting. Sedimentologic fieldwork and geologic mapping of the Arro system has been undertaken to provide context for a detailed study of three of the best-exposed outcrops: Sierra de Soto Gully, Barranco de la Caxigosa, and Muro de Bellos. These locations exemplify the role of confinement in controlling the facies and architecture in the system. Sedimentologic characterization of the deposits has allowed the identification of fifteen facies and eight facies associations; these form a continuum and are non-unique to any depositional environment. However, architectural characterization allowed the grouping of facies associations into four depositional elements: i) weakly confined, increasing-to-decreasing energy deposits; ii) progradational, weakly confined to overbank deposits; iii) alternations of MTDs and turbidites; iv) channel fills. Different styles of channel architecture are observed. In Barranco de la Caxigosa, a master surface which was cut and subsequently filled hosts three channel stories with erosional bases; channelization was enhanced by quasi-instantaneous imposition of lateral confinement by the emplacement of MTDs. In Muro de Bellos, the inception of partially levee-confined channel stories was enhanced by progressive narrowing of the depositional fairway by tectonic structures, which also controlled their migration. Results of this study suggest that deep-water channelization in active tectonic settings may be enhanced or hindered due to: 1) flow interaction with MTD-margin topography or; 2) MTD-top topography; 3) differential compaction of MTDs and/or sediment being loaded into MTDs; 4) formation of megascours by erosive MTDs; 5) basin-floor topography being reset by MTDs. Therefore, the Arro system can be used as an analog for ancient subsurface or outcrop of channelized deposits in bathymetrically complex basins, or as an ancient record of deposits left by flow types observed in modern confined systems.

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“…Many scours were later filled with coarse‐grained sandstone/conglomerate (F2a and F1a) suggesting local net sedimentation from high‐concentration sediment suspensions that deposited most of their sediment load further downflow. Some scours are filled with planar‐laminated sandstone (F2c) or a prograding wedge of planar‐stratified transitioning to high‐angle, cross‐stratified sandstone of F2d (Arnott & Al‐Mufti, ), suggesting local preservation of traction‐transport sediment beneath bypassing flows. Less common small scours filled with sandstone–mudstone couplets of F3 were deposited from the fine‐grained tails of complete bypassing flows, or by clast‐rich debris flows (F1d) possibly related to local instability on the lower slope.…”

Section: Resultsmentioning

confidence: 99%

Stratigraphic record in the transition from basin floor to continental slope sedimentation in the ancient passive‐margin Windermere turbidite system

Navarro

Arnott

2020

Sedimentology

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Well-exposed, vertically dipping, glacially polished outcrops of the Neoproterozoic Windermere Supergroup in the southern Canadian Cordillera include basin-floor deposits of the Upper Kaza Group overlain by slope channel complexes of the Isaac Formation. Within the 2Á5 km thick Kaza and Isaac succession is an up to 360 m thick interval composed of diverse deep-water stratal elements including scour and interscour deposits, distributary channels, finegrained turbidites, terminal splays, mass-transport deposits, erosional and lev eed channels and avulsion splays, which collectively were formed during the development of an ancient passive-margin channel-lobe system. The proportion and vertical and lateral arrangement of stratal elements reveal three distinct complexes. The lower complex, consisting mostly of distributary channels and small and large scours, is interpreted to represent the detachment of lobes from an upflow lev eed channel, wherein a well-developed channel-lobe transition zone was formed by efficient, siliciclastic flows during a period of sustained transport bypass and limited deposition coincident with the onset of falling relative sea level. The middle, comparatively thicker and more sandstone-rich complex, comprises distributary channel fills, fine-grained turbidites and lesser terminal splays that are interspersed with small scours, capped by a slope lev eed channel filled with coarser-grained siliciclastic sediment. The abundance of basin-floor elements suggests negligible separation between the lev eed channel and lobe, and therefore a poorly-developed channel-lobe transition zone, resulting from inefficient, siliciclastic-rich depositional flows that became dominant during lowstand and/or ensuing transgression. The stratal makeup of the upper complex resembles the lower detached complex, suggesting a return to efficient flows, and an abrupt change to mixed carbonate-siliciclastic sediments associated with highstand conditions. Accordingly, the stratigraphic architecture and stacking pattern of the Kaza-Isaac interval, which relate to the formation of multiple channel-lobe transition zones, were controlled by temporal changes in sediment supply and flow characteristics during the long-term progradation of the Laurentian continental margin.

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Deep-Marine Pseudo Dune Cross-Stratification—Similar, But Completely Different

Cited by 18 publications

References 49 publications

Supercritical flows and their control on the architecture and facies of small-radius sand-rich fan lobes

Supercritical flows and their control on the architecture and facies of small-radius sand-rich fan lobes

Syndepositional tectonics and mass-transport deposits control channelized, bathymetrically complex deep-water systems (Aínsa depocenter, Spain)

Stratigraphic record in the transition from basin floor to continental slope sedimentation in the ancient passive‐margin Windermere turbidite system

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