603-pp14 - UNIVERSITY OF SOUTH ALABAMA Last Time Shelves...

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1 MAS 603: Geological Oceanography MAS 603: Geological Oceanography Lecture 14: Submarine Fans Lecture 14: Submarine Fans UNIVERSITY OF SOUTH ALABAMA Last Time Last Time Shelves Definition and a bit of history Factors controlling shelf sedimentation •T h e B a h a m a s Continental Shelves Continental Shelves By definition: shelves are: “oceanic environments characterized by moderate water depths (10m to 150/200m) in which a variety of shallow marine and moderate depth facies occur” ht p:/ faculty.gg.uwyo.edu/hel er/Sed%20Strat%20Class/SedStrat%207/SedStrat7.html Factors influencing shelf sedimentation Factors influencing shelf sedimentation Six factors are recognized as influencing shelf sedimentation. The last three are designated as “biggie” factors. 1) Sea level fluctuations (controls distribution of relict sediments, barrier reefs etc.) 2) Animal-sediment interactions (modifies the substrate) 3) Chemistry (produces authigenic minerals) 4) Type and rate of sedimentation 5) Climate 6) Type and intensity of shelf hydraulic regime (“energy”) Biggies Factors influencing shelf sedimentation Factors influencing shelf sedimentation Type and rate of sedimentation River Shelf break Relict Sediment Wedge Modified from McCave (1972) Shelf break Relict Relict? Shelf break High-energy shoreline very-high sedimentation Normal Continental Shelves Continental Shelves Climate Controls shelf sedimentation by its effects on the surrounding land mass (siliciclastic source area). • Wet and hot (tropical) = intense chemical weathering and clay production • Cold and dry (temperate) = physical weathering and sand/gravel production Rainfall (cm) Temperature ( ° C) 40 0 250 0 15% + gravel 45% + sand content 40% + mud content Modified from Hayes (1967) F w
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2 Continental Shelves Continental Shelves Hydraulic regime Three dominant processes are responsible for transporting, reworking and sorting sediment on shelves (including relict areas). 1) Tide-dominated shelves (17% of pericontinental shelf areas)
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603-pp14 - UNIVERSITY OF SOUTH ALABAMA Last Time Shelves...

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