An Experimental Study of Turbidite Channel Deposits: Implications for Channel Evolution and Sandstone Deposits

Gaining a detailed understanding of turbidite bed sequences is important for the characterization of sandstone reservoir properties, correlation of well cores, and geological interpretation. Many factors influence the internal structure of sandstone reservoirs: source material, source location in time, transport processes, basin geometry, fan channel development and evolution to name a few. Sandstone deposits associated with channel complexes are easy to find but difficult to develop. Here, we conduct tank experiments of scaled sediment-laden turbidity currents traversing a submerged channel to: (1) establish a state-of-the-art data collection and data processing system that has the potential to gain a unique understanding of the processes and deposits that build submarine fan environments; and (2) to use the facility to demonstrate how the interaction of a depositive turbidity current with a sinuous channel may influence the geometry, spatial relationships and grain size sorting of sandstone deposits. Our data shows the construction of prominent levees, asymmetric levee growth, continuous channel overspill, enhanced channel overspill downstream of bend corners, and lobate-shaped lobe deposits. Our preliminary results are qualitative, but indicate that channel wavelength, bend curvature, and bend peak-to-peak amplitude may have strong controls on down-channel and cross-channel depositional patterns, deposit thickness and grain size sorting.ChevronTexaco (Firm

Flow-Substrate Interactions in Aggrading and Degrading Submarine Channels

Connecting real time measurements of current-bed interactions to the temporal evolution of submarine channels can be extremely challenging in natural settings. We present a suite of physical experiments that offer insight into the spectrum of interactions between turbidity currents and their channels, from (i) detachment-limited erosion to (ii) transport-limited erosion to (iii) pure deposition. In all three cases channel sinuosity influenced patterns of erosion and deposition; the outsides of bends displayed the highest erosion rates in the first two cases, whereas the outsides of bends were associated with the highest deposition rates the third. We connect the evolution of these channels to the turbulence of the near-bed boundary layer. In the erosional experiments both channel beds roughened through time, developing erosional bedforms or trains of ripples. Reynolds estimates of boundary layer roughness indicate that, in both erosional cases, the near-bed boundary layer roughened from smooth or transitionally rough to rough, whereas the depositional channel appears to have remained consistently smooth. Our results suggest that, in the absence of any changes from upstream, erosion in submarine channels is a self-reinforcing mechanism whereby developing bed roughness increases turbulence at the boundary layer, thereby inhibiting deposition, promoting sediment entrainment and enhancing channel relief; deposition occurs in submarine channels when the boundary layer remains smooth, promoting aggradation and loss of channel relief