Application of the Principles of Seismic Geomorphology to Continental Slope and Base-of-Slope Systems: Case Studies from SeaFloor and Near-Sea Floor Analogues

The study of near-seafloor deepwater landscapes and the processes that form them are as important to the understanding of deeply buried marine depositional systems as the study of modern fluvial environments is to our understanding of ancient terrestrial depositional systems. In fact, these near-seafloor studies follow in the great tradition established by earlier clastic sedimentologists in the use of modern systems to understand ancient environments. The acquisition and mapping of exploration 3D seismic surveys over the last few decades allows for the study of seafloor geomorphology with a spatial resolution comparable to most deepwater multibeam bathymetric tools, and represents a significant advancement that can be used to push forward general understanding of slope and base-of-slope depositional systems through the application of the emerging science of seismic geomorphology. The papers assembled for this volume demonstrate the utility of seafloor-to-shallow subsurface data sets in studying the development of submarine landscapes and their affiliated sedimentary deposits. These contributions highlight the controls of slope morphology on patterns of both sedimentation and erosion. Many of the papers also highlight the influence of pre-existing seafloor relief on confining sediment-gravity flows specific transport pathways, thereby affecting subsequent evolution of the seafloor. The understanding of depositional processes that comes from studying deepwater analogue systems remains the best way take to knowledge from one basin or system and apply confidently to another for prediction and characterization of reservoirs for exploration and production of hydrocarbons.
3D Seismic Stratigraphy and Evolution of Upper Pleistocene Deepwater Depositional Systems, Alaminos Canyon, Northwestern Deep Gulf Of Mexico
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Published:January 01, 2012
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CiteCitation
Shu Jiang, Paul Weimer, Sverre Henriksen, William S. Hammon, III, 2012. "3D Seismic Stratigraphy and Evolution of Upper Pleistocene Deepwater Depositional Systems, Alaminos Canyon, Northwestern Deep Gulf Of Mexico", Application of the Principles of Seismic Geomorphology to Continental Slope and Base-of-Slope Systems: Case Studies from SeaFloor and Near-Sea Floor Analogues, Bradford E. Prather, Mark E. Deptuck, David Mohrig, Berend Van Hoorn, Russell B. Wynn
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Abstract
The Pleistocene Alaminos Fan in the northwestern deep Gulf of Mexico is a large submarine fan located at the base of the continental slope. High-resolution, near-seafloor 3D seismic data were interpreted to study the evolution of two Pleistocene shallow sequences. Results indicate that there can be considerable variability in the evolution of deepwater systems in the same overall setting, and the significance that seafloor topography and gradient changes can make in the overall development of different architectural elements. Seismic facies indicate that the sequence consists primarily of mass-transport deposits (MTDs), channel-fill sediments, and sheet deposits in the lower sequence, whereas the upper sequence consists of a single channel.
The older sequence consists of two distinctly different deepwater systems. To the east, a prominent channel system overlies basal MTDs. The channel system consists of one upfan channel that bifurcates downfan to at least six discrete channels flanked by levees. The evolution of the downdip distributary channel system is the result of deposition in the unconfined setting. To the west, an updip channel fed sheet deposits that developed in the back limb of a fold in a confined setting. The sheet, in turn, is overlain by a channel–levee system. This vertical change is likely the results of the fill-and-spill of sediments in the area.
In the near-floor sequence, a single deepwater channel is flanked by low-amplitude levee reflections. Quantifying the dimensions of this younger channel shows that it evolved from a wider, straight channel at the base of the sequence to a relatively narrow sinuous channel with increasing sinuosity upward.