Sediment mass-flow processes on a depositional lobe, outer Mississippi Fan
- Geological Survey, Woods Hole, MA (United States)
- Geological Survey, Menlo Park, CA (United States)
- Laval Univ., Saint-Foy, Quebec (Canada). Dept. of Geology and Geological Engineering
- Inst. of Oceanographic Sciences, Wormley, Surrey (United Kingdom). Deacon Lab.
As exploration for hydrocarbons moves toward subtler traps, channel-end sand deposits of deep-sea fans and related turbidite systems are among the key targets. SeaMARC 1A sidescan-sonar imagery and cores from the distal reaches of a depositional lobe on the Mississippi Fan show that channelized mass flow as the dominant mechanism for transport of silt and sand during the formation of this part of the fan. Sediments in these flows were rapidly deposited once outside of their confining channels. The depositional lobe is formed of a series of long, narrow sublobes composed of thin-bedded turbidites (normally graded siliciclastic sand and silt, 20 cm thick on average), debris-flow deposits (soft clay clasts up to 5 cm in diameter in a siliciclastic silt matrix, 48 cm thick on average), and background-sedimentation hemipelagic muds. The mass flows most likely originated from slope failure at the head of the Mississippi Canyon or on the outer continental shelf and flowed approximately 500 km to the distal reaches of the fan, with debris flow being the dominant flow type. An analysis that uses the geometry of the confining channels and strength properties of the debris-flow material shows that these thin debris flows could have traveled hundreds of kilometers on extremely small sea-floor slopes at low velocities if the flowing medium behaved as Bingham fluids and were steady-state phenomena.
- OSTI ID:
- 445628
- Journal Information:
- Journal of Sedimentary Research, Section A: Sedimentary Petrology and Processes, Vol. 66, Issue 5; Other Information: PBD: Sep 1996
- Country of Publication:
- United States
- Language:
- English
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