The influence of basin settings and flow properties on the dimensions of submarine lobe elements

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Authors

Yvonne Spychala , Joris Eggenhuisen , Mike Tilston, Florian Pohl 

Abstract

Submarine lobes have been identified within various deep-water settings, including the basin-floor, the base of slope and the continental slope. Their dimensions and geometries are postulated to be controlled by the topographical configuration of the seabed, sediment supply system and slope maturity. While confinement has been suggested as a main control factor for lobe dimensions, it does not explain the spread of lobe dimensions within individual systems.
Ten experiments were conducted in a 3D-flume to study the depositional characteristics of lobe associated with 1) different basin floor dipping angles (0-4°), 2) different sediment concentration of the parent turbidity current (11-19 % Vol), and 3) varying discharge (25 - 40 m3/h). Most runs produced lobate deposits that onlapped onto the lower slope independent of basin floor-dip and concentration. We determined that the deposits best describe the hierarchical level of lobe elements. Lobe element length is proportional to basin-floor angle and sediment volume concentration. A higher amount of bypass is observed in the proximal area as the basin-floor angles get steeper and concentrations higher. Deposits of runs with lower discharge could be traced higher upslope while runs with higher discharge produced an area of low deposition behind the channel mouth, i.e. discharge controls whether lobe deposits are attached or detached from their channel-levee systems. Integration of measured lobe element dimensions and particle advection length-scale analysis shows that latter can be used as a first order estimation of lobe element length. However, the estimations are strongly depended on the used average grain size (e.g. silt is still actively transported after all sand has been deposited) and the method cannot be used to locate the main depocentre. Furthermore, attempted reconstruction of turbidity current velocities from natural systems suggest that the method is not appropriate for use on more complex composite bodies as lobes.

DOI

https://doi.org/10.31223/osf.io/sk8v3

Subjects

Earth Sciences, Physical Sciences and Mathematics, Sedimentology

Keywords

advection length, dimensions, experimental study, sand vs silt deposition, submarine lobes

Dates

Published: 2019-05-22 23:37

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License

Academic Free License (AFL) 3.0

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