Growth Patterns of Subaqueous Depositional Channel Lobe Systems Developed Over A Basement With A Downdip Break In Slope: Laboratory Experiments

Abstract

A series of large-scale experiments on nonchannelized, depositional turbidity currents show the evolution and complex stratigraphy of channel-lobe systems developed updip and downdip of a break in slope. Two different sets of experimental turbidity currents with different sediment concentrations were run. The results provided a comparative picture of the gross structure of the fans, with information on their surfaces, growth sequences, and times of activity of the incised channels and lobed features. In particular, data analysis focused on: (a) velocity and suspended-sediment concentration of the flows themselves; (b) time and spatial sequences of channel and lobe construction and modification, and (c) spatial trends in grain-size distribution along the deposit. Significantly, the floor geometry employed in this study allowed investigation of adjustments in deep-sea fan deposition associated with natural changes in bed slope. We show here that the break in slope played a very important role in governing channel aggradation and lobe architecture over the deposit. More specifically, the slope break tended to break up the formation of long channels and enhance the formation of lobate features. A comparison with field submarine lobe analogs demonstrates that the morphodynamics and stratigraphy associated with lobed fans can indeed be modeled, within limits, at laboratory scale.

Hydraulic and sediment transport properties of autogenic avulsion cycles on submarine fans with supercritical distributaries

“…Hydraulic jumps have been considered important features on submarine fans, particularly at dramatic breaks in slope [e.g., Komar , ; Garcia and Parker , ; García , ; Gray et al , ]. External slope breaks certainly have an important impact on the evolution of submarine fan systems [e.g., Fernandez et al , ]. However, they were unnecessary in these experiments as hydraulic jumps formed upstream of the imposed basin slope break.…”

“…Experiments are a convenient way to observe morphodynamic processes since the timescales for change are drastically shortened compared to their natural counterparts, boundary conditions can be dictated, and the environment can be carefully instrumented. In studying the spatial distribution of sedimentary bodies, submarine fan experimentalists have generally taken one of two approaches: (1) experimentally created turbidity currents with a range of sediment sizes [ Luthi , ; Parsons et al , ; Yu et al , ; Cantelli et al , ; Fernandez et al , ] or (2) saline underflows and plastic sediment [ Metivier et al , ; Hoyal and Sheets , ; Weill et al , ]. Turbidity current experiments have the advantage of using the same materials as their natural counterparts and as such can replicate grain size patterns and deposition from suspension.…”

Quantification of the Bed-scale Architecture of Submarine Depositional Environments and Application to Lobe Deposits of the Point Loma Formation, California

“…Using the understanding that compensation decreases from proximal-to-distal (Sullivan et al,2000;Fernandez et al, 2014), the fairly abrupt outcrop expression of the contact between Element One and Two over approximately 50 m indicates a more proximal or axial lobe position than previously interpreted by Fleming (2010). This is supported by the relatively coarse-grained nature of the lobe deposits at Cabrillo National Monument (Figure 15).…”

“…Compensational stacking is the tendency to for a deposit to preferentially fill topographic lows, with the magnitude of compensation typically decreasing from proximal-distal (Mutti and Sonnino, 1981;Sullivan et al, 2000;Cantelli et al, 2011;Fernandez et al, 2014). There have been two proposed methods, fractal and hierarchical, for compensational stacking, which depend on either consistent compensation or variable compensation at the different hierarchical scales, respectively (Mutti and Sonnino, 1981;Mutti and Normark, 1987;Deptuck et al, 2008;Prélat et al, 2009;Straub and Pyles, 2012).…”

Submarine Mass Movements and their Consequences

“…Recent experimental fan and field studies suggest that sub-and supercritical turbidity currents each have a characteristic architecture (Cantelli et al 2011;Fernandez et al 2014;Hoyal and Sheets 2009;Hamilton et al 2015) and facies associations . Recent experimental fan and field studies suggest that sub-and supercritical turbidity currents each have a characteristic architecture (Cantelli et al 2011;Fernandez et al 2014;Hoyal and Sheets 2009;Hamilton et al 2015) and facies associations .…”