Depositional processes of a meandering channel on Mississippi fan
A continuous, meandering, leveed channel traverses the Mississippi fan from the continental slope to the abyssal plain. Using water-gun seismic reflection profiling, 3.5- and 4.5-kHz profiling, and SeaMARC I side-scan sonar, the authors surveyed a 30-km (16-nmi) long channel segment midway between the slope break and channel terminus, where the channel bends through a tight meander with a 2.8-km (1.5-nmi) radius of curvature. At the entrance to each meander bend, the outer levee is unusually low, similar to the crevasses observed in rivers. The levees are constructed of an acoustically opaque unit and draped with an acoustically laminated unit; these are interpreted as coarser and finer grained overbank deposits, respectively. A series of high-amplitude seismic reflectors underlying the channel axis are interpreted as coarse sediments deposited from the base of turbidity currents. When last active, the channel was more than 100 m (300 ft) deep, but it has been filled to the brim by acoustically transparent units, leaving a levee crest/thalweg relief of as little as 5 m (16 ft). These channel-filling units are interpreted as debris flows. The upper surface of the debris flows is sculpted by flowline-parallel, side-scan lineations where the flow was unimpeded and by arcuate ridges transverse to the flow where bathymetric obstacles constrained the flow. 10 figures.
- Research Organization:
- Columbia Univ., Palisades, NY
- OSTI ID:
- 5701799
- Journal Information:
- Am. Assoc. Pet. Geol., Bull.; (United States), Vol. 69:2
- Country of Publication:
- United States
- Language:
- English
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