On the termination of deep-sea fan channels: Examples from the Rhône Fan (Gulf of Lion, Western Mediterranean Sea)

Droz, Laurence; Jégou, Isabelle; Gillet, Hervé; Dennielou, Bernard; Bez, M.; Canals, Miquel; Amblàs, David; Lastras, Galderic; Rabineau, Marina

doi:10.1016/j.geomorph.2020.107368

Cited by 12 publications

(26 citation statements)

References 92 publications

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“…Additionally, because of resolution limitations, imaging of submarine lobes often reveals few details of architectural features within the lobe or even on the lobe surface. These fine-scale features are best revealed by high resolution bathymetric surveys (Maier et al, 2011;Carvajal et al, 2017;Maier et al, 2018;Droz et al, 2020;Maier et al, 2020). Such high resolution surveys illustrate the diversity of deep-water depositional systems but these surveys are rare.…”

Section: Seismicly Imaged Subsurface and Modern Analogsmentioning

confidence: 99%

Architectural Diversity of Submarine Lobate Deposits

2021

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Lobate deposits in deep-water settings are diverse in their depositional architecture but this diversity is under-represented in the literature. Diverse architectures result from multiple factors including source material, basin margin physiography, transport pathway, and depositional setting. In this contribution, we emphasize the impact of differing source materials related to differing delivery mechanisms and their influence on architecture, which is an important consideration in source-to-sink studies. Three well imaged subsurface lobate deposits are described that display three markedly different morphologies. All three lobate examples, two from intraslope settings offshore Nigeria and one from a basin-floor setting offshore Indonesia, are buried by less than 150 m of muddy sediment and are imaged with high resolution 3D reflection seismic data of similar quality and resolution. Distinctively different distributary channel patterns are present in two of the examples, and no comparable distributaries are imaged in a third example. Distributary channels are emphasized because they are objectively recognized and because they often represent elements of elevated fluid content within buried lobate deposits and thus influence permeability structure. We speculate that the different distributary channel patterns documented here resulted from different processes linked to source materials: 1) a lobate deposit that is pervasively channelized by many distributaries that have branched at numerous points is interpreted to result from comparatively mud-rich, stratified, turbulent flows; 2) an absence of distributaries in a lobate deposit is interpreted to result from collapse of mud-poor, turbulent flows remobilized from littoral drift; and 3) a lobate deposit with only a few, long, straight distributaries with few branching points is interpreted to be dominated by highly viscous flows (i.e., debris flows). We propose a conceptual model that illustrates the relationship between the proportion of mud in contributing flows and the relative size and runout distance of lobate deposits. We conclude that reconciling 3D seismic morphologies with outcrop observations of channels, scours, and amalgamation zones, and simple application of hierarchical schemes, is problematic. Furthermore, when characterizing unconfined deep-water deposits in the subsurface, multiple models with significant differences in predicted permeability structure should be considered.

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Section: Seismicly Imaged Subsurface and Modern Analogsmentioning

confidence: 99%

Architectural Diversity of Submarine Lobate Deposits

2021

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“…Dakin et al, 2013;Lee et al, 2004;Moscardelli et al, 2006;Pickering and Hilton, 1998). Alternatively, scours are commonly concentrated in channel-lobe-transition-zones (CLTZs) (Brooks et al, 2018a;Hofstra et al, 2015), in channel mouth settings (Carvajal et al, 2017;Droz et al, 2020;Maier et al, 2020;Pohl et al, 2020Pohl et al, , 2019, or have a multi-event origin.…”

Section: Origin Of the Erosion Surfacementioning

confidence: 99%

“…Scouring of channel margins is shown to be extensive especially in areas with higher slope gradients (>1°) (Carvajal et al, 2017). Scour concatenation is likely a major driver for channel avulsion, inception and propagation resulting in further turbidity current confinement (Droz et al, 2020). In the La Jolla channel, these scours form laterally extensive erosion surfaces that can extend for kilometres beyond the channel (Maier et al, 2020), however their high aspect ratio make them difficult to identify in outcrop.…”

Section: Origin Of the Erosion Surfacementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

“…Scours are readily recognized erosional bedforms on modern seafloor datasets in deep-marine systems (Bonnel et al, 2005;Carvajal et al, 2017;Covault et al, 2014;Droz et al, 2020;Fildani et al, 2006;Macdonald et al, 2011;Maier et al, 2011Maier et al, , 2020Wynn et al, 2002) and have been imaged in many high resolution seafloor data, providing more detail about their distribution and geometry (Carvajal et al, 2017;Droz et al, 2020;Maier et al, 2020Maier et al, , 2018. Scours are associated with slide scars (Dakin et al, 2013;Lee et al, 2004;Moscardelli et al, 2006;Pickering and Hilton, 1998), or located in channel-lobe-transition-zones (CLTZs) (Brooks et al, 2018a;Hofstra et al, 2015), or channel mouths settings prior to channel propagation (Carvajal et al, 2017;Droz et al, 2020;Maier et al, 2020;Pohl et al, 2020Pohl et al, , 2019. Abundant examples of interpreted ancient small-scale scour-fills include the Ross Formation, Ireland (Elliott, 2000;Lien et al, 2003;Pyles et al, 2014), the Albian Black Flysch, Spain (Vicente Bravo and Robles, 1995), the Annot sandstone, France (Morris and Normark, 2000), the Windermere Group, Canada (Terlaky et al, 2016), the Karoo Basin, South Africa (Brooks et al, 2018), the Macigno Costiero Formation, Italy (Eggenhuisen et al, 2011), and the Boso Peninsula, Japan (Ito et al, 2014).…”

Section: Introductionmentioning

confidence: 99%

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The origin and 3D architecture of a km-scale deep-water scour-fill: example from the Skoorsteenberg Fm., Karoo Basin, South Africa

Hansen¹,

Healy²,

Cartesio³

et al. 2021

Preprint

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Scours, and scour fields, are common features on the modern seafloor of deep-marine systems, particularly downstream of submarine channels, and in channel-lobe-transitions-zones. High-resolution images of the seafloor have improved the documentation of the large scale, coalescence, and distribution of these scours in deep-marine systems. However, their scale and high aspect ratio mean they can be challenging to identify in outcrop. Here, we document a large-scale, composite erosion surface from the exhumed deep-marine stratigraphy of Unit 5 from the Permian Karoo Basin succession in South Africa, which is interpreted to be present at the end of a submarine channel.This study utilizes 24 sedimentary logs, 2 cored boreholes, and extensive palaeocurrent and thickness data across a 126 km2 study area. Sedimentary facies analysis, thickness variations and correlation panels allowed identification of a lower heterolithic-dominated part (up to 70 m thick) and an upper sandstone-dominated part (10-40 m thick) separated by an extensive erosion surface. The lower part comprises heterolithics with abundant current and sinusoidal ripples, which due to palaeocurrents, thickness trends and adjacent depositional environments is interpreted as the aggradational lobe complex fringes. The base of the upper part comprises 2-3 medium-bedded sandstone beds interpreted as precursor lobes cut by a 3-4 km wide, 1-2 km long, and up to 28 m deep, high aspect ratio (1:100) composite scour surface. The abrupt change from heterolithics to thick-bedded sandstones marks the establishment of a new sediment delivery system, which may have been triggered by an updip channel avulsion. The composite scour and subsequent sandstone fill support a change from erosion- and bypass-dominated flows to depositional flows, which might reflect increasingly sand-rich flows as a new sediment route matured. This study provides a unique outcrop example with 3D stratigraphic control of the record of a new sediment conduit, and development and fill of a large-scale composite scour surface at the channel mouth, providing a rare insight into how scours imaged on seafloor data can be preserved in the rock record.

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Channel‐lobe transition zone development in tectonically active settings: Implications for hybrid bed development

Brooks

Itô

Zuchuat

et al. 2022

The Depositional Record

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Channel‐lobe transition zones are dynamic areas located between deepwater channels and lobes. Presented here is a rare example of an exhumed channel‐lobe transition zone from an active‐margin setting, in the Kazusa forearc Basin, Boso Peninsula, Japan. This Plio‐Pleistocene outcrop exposes a thick (tens of metres) channel‐lobe transition zone succession with excellent dating control, in contrast to existing poorly dated studies of thinner (metres) deposits in tectonically quiescent settings. This high‐resolution outcrop permits the roles of climate and associated relative sea‐level changes on stratigraphic architecture to be assessed. Three development stages are recognised with an overall coarsening‐upward then fining‐upwards trend. Each stage is interpreted to record one obliquity‐driven glacioeustatic sea‐level fall‐then‐rise cycle, based on comparison with published data. Deposition of the thickest and coarsest strata, Stage 2, is interpreted to record the end of a period of relative sea‐level fall. The thinner and finer strata of Stages 1 and 3 formed during interglacial periods where the stronger Kuroshio Oceanic Current, coupled to increased monsoonally driven tropical cyclone frequency and intensity, likely resulted in inhibited downslope sediment transfer. A key aspect of channel‐lobe transition zone deposits in this case is the presence of a diverse range of hybrid beds, in contrast to previous work where they have primarily been associated with lobe fringes. Here hybrid bed characteristics, and grain‐size variations, are used to assess the relative importance of longitudinal and vertical segregation processes, and compared to existing models. Compared to channel‐lobe transition zones in tectonically quiescent basin‐fills, this channel‐lobe transition zone shows less evidence of bypassing flows (i.e. thicker stratigraphy, more isolated scour‐fills, fewer bypass lags) and has significantly more hybrid beds. These features may be common in active basin channel‐lobe transition zones due to: high subsidence rates; high sedimentation rates; and disequilibrium of tectonically active slopes. This disequilibrium could rejuvenate erodible mud‐rich substrate, leading to mud‐rich flows arriving at the channel‐lobe transition zone, and decelerating rapidly, forming hybrid beds.

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On the termination of deep-sea fan channels: Examples from the Rhône Fan (Gulf of Lion, Western Mediterranean Sea)

Cited by 12 publications

References 92 publications

Architectural Diversity of Submarine Lobate Deposits

Architectural Diversity of Submarine Lobate Deposits

The origin and 3D architecture of a km-scale deep-water scour-fill: example from the Skoorsteenberg Fm., Karoo Basin, South Africa

Channel‐lobe transition zone development in tectonically active settings: Implications for hybrid bed development

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