Deep Marine Processes
Deep marine clastic deposits are formed when large volumes of sediment are transported into deep water from an original shallow-water setting (after Einsele, 1991)1. They include a complex suite between the end-members of dilute turbidity currents and subaqueous slides (Nardin et al., 1979)2. All resedimentation depends upon the downslope component of gravity acting upon material stored on or moving down a slope. All the processes may be classified as a subaqueous mass movement and most of them as sediment gravity flows. Only rock falls and slides fall outside such a classification.
Sediment gravity flows may be subdivided on their rheological behaviour or on the nature of their clast-support mechanism. Sediment gravity flows are all mixtures, in varying proportions, of water and sedimentary particles. In order for these mixtures to move and deform internally, particles must be dilated to move relative to one another and the various clast-support mechanisms provide a further basis for subdivision (Middleton and Hampton, 1976)3.
Most downslope movements result from general or local loss of shear strength so that the sediment-water mass or some particular layer within it is no longer able to resist the downslope gravitational shear. Such instability is favoured by high slope gradients, high rates of sedimentation, repeated cyclical stress, and high biological productivity leading to gas generation due to decomposition.
Deep marine processes and deposits are described under the following sub-headings:
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| Olistolith avalanche deposit | Creep deposit | Slide/slump deposit | Debrite |
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| Grainflow deposit | Fluidisation deposit | High density turbidite | Low density turbidite |
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| Contourite |
A brief overview of the most commonly recorded sediment gravity flows within deep marine environments is to be found in the section entitled Deep marine concepts.
References
- Einsele, G., 1991. Submarine mass flow deposits. Cycles and events in stratigraphy. Springer-Verlag, Berlin.
- Nardin, T.R., Hein, F.J., Gorsline, D.S. and Edwards, B.D., 1979. A review of mass movement processes, sediment and acoustic characteristics in slope and base-of-slope systems versus canyon-fan-basin floor systems. In: Doyle, L.J. and Pilkey, O.H. (eds.), Geology of continental slopes. SEPM, Spec. Publ., no. 27, p. 61-73.
- Middleton, G.V. and Hampton, M.A., 1976. Subaqueous sediment transport and deposition by sediment gravity flows. In: Stanley, D.J. and Swift, D.J.P. (eds.), Marine sediment transport and environmental management. Wiley, New York, p. 197-218.
A comprehensive reference list for the Deep Marine section can be found here.
