Evolution of a Fan Channel on the Surface of the Outer Mississippi Fan: Evidence from Side-Looking Sonar
A deep-towed, side-looking sonar survey of an outer fan, distributary channel near DSDP Sites 614 and 615 on the Mississippi Fan defined three distinct morphologic zones: (1) a relatively “straight” channel zone (sinuosity of 1.1), (2) a channel termination zone, and (3) a splay and “finger-shaped distributary” zone. Boundaries between zones are gradual with no direct connection observed between this channel and the leveed channel that was mapped and drilled farther upfan during DSDP Leg 96.
In the “straight” channel zone, a clearly defined, shallow (10 m, 33 feet), incised channel exists within a broader area of surficial erosional features. Locally, the inner walls and floor of the channel area are marked by very low-acoustic backscatter on the side-looking sonar images. In some reaches, the channel path is parallel to the alignment of several distinct north-northeast lineations in the backscatter intensity. Low-relief levees (less than 5 m, 15 feet) are discontinuous along the margins of the straight channel zone and die out before the channel terminates. Detached splay and “finger-shaped distributaries” consist of branching lobate-like features with low relief that extend beyond the termination of the single, relatively straight channel.
The side-looking sonar images record at least five stages of development, each of which may have consisted of more than one event or series of depositional events. In order from oldest to youngest: (1) channeled erosion during which the broad area of finger-shaped distributaries was created, (2) erosion causing lineation or grooving on the fan surface, (3) formation of the “straight” channel and the broader erosional area in which it lies, (4) both development of and destruction of levees on parts of the channel, and (5) blanketing the sea floor with fine-grained sediment that returns low acoustic backscatter. The erosional events that sculpted the fan surface were probably initiated by an unconfined sediment gravity-flow event, whose source was either in the main channel-levee region farther upfan or on the continental slope. These data suggest that the area was not part of the most recently active depositional lobe on the outer Mississippi Fan.
KeywordsDebris Flow Sonar Image Acoustic Backscatter High Backscatter Turbidite System
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- Barnes, N.E., and Normark, W.R., 1985: Diagnostic parameters for comparing modern submarine fans and ancient turbidite systems, in A.H. Bouma, W.R. Normark, and N.E. Barnes, eds., Submarine fans and related turbidite systems; Springer-Verlag, New York p. 13–14 and chart.Google Scholar
- Chayes, D.N., 1983: Evolution of SeaMARC I, in Proceedings of Third Working Symposium on Oceanographic Data Systems; Maryland, IEEE Computer Society Press, p. 103–108.Google Scholar
- EEZ Scan 85 Scientific Staff, 1987: Atlas of the U.S. Exclusive Economic zone, Gulf of Mexico and Eastern Caribbean Areas; U.S. Geol. Surv., Reston, Virginia, p. 162.Google Scholar
- Howell, D.G., and Normark, W.R., 1982: Sedimentology of submarine fans, in P.A. Scholle and D.R. Spearing, eds., Sandstone depositional environments; Am. Assoc. Petrol. Geol. Memoir 31, p. 365–404.Google Scholar
- Huang, T.L., and Goodell, H.G., 1970: Sediments and sedimentary processes of the eastern Mississippi Cone, Gulf of Mexico; Am. Assoc. Petrol. Geol. Bull., v. 54, p. 2070–2100.Google Scholar
- Kastens, K.A., and Shor, A.N., 1985: Depositional processes of a meandering channel on the Mississippi Fan; Am. Assoc. Petrol. Geol. Bull., v. 69, p. 190202.Google Scholar
- Kastens, K.A., and Shor, A.N., 1986: Evolution of a channel meander on the Mississippi Deep-sea Fan; Marine Geol., v. 71, p. 165–175.Google Scholar
- Menard, H.W., 1964: Marine geology at the Pacific. McGraw-Hill, New York, p. 71.Google Scholar
- Middleton, G.V., and Southard, J.B., 1984: Mechanics of sediment movement: Soc. Econ. Paleon. Mineral., Eastern Section Short Course Notes Number 3, second edition, p. 401.Google Scholar
- Moore, G.T., Starke, G.E., Bonham, L.C., and Woodbury, H.O., 1978: Mississippi Fan, Gulf of Mexico-physiography, stratigraphy, and sedimentation patterns, in A.H. Bouma, G.T. Moore, and J.M. Coleman, eds., Framework, facies, and oil-trapping characteristics of the Upper Continental Margin; Am. Assoc. Petrol. Geol. Studies Geol., v. 7, p. 155–191.Google Scholar
- Normark, W.R., 1970: Growth patterns of deep-sea fans; Am. Assoc. Petrol. Geol. Bull., v. 54, p. 2170–2195.Google Scholar
- Normark, W.R., 1978: Fan valleys, channels and depositional lobes on modern submarine fans: Characters for recognition of sandy turbidite environments; Am. Assoc. Petrol. Geol. Bull., v. 62, p. 912–931.Google Scholar
- Normark, W.R., Meyer, A.W., Cremer, M., Droz, L., O’Connell, S., Pickering, K.T., Stelting, C.E., Stow, D.A.V., Brooks, G.R., Mazzullo, J., Roberts, H., and Thayer, P., 1986: Summary of drilling results for the Mississippi Fan and considerations for application to other turbidite systems, in A.H. Bouma, J.M. Coleman, and A.W. Meyer, et al., Init. Repts. DSDP, 96: U.S. Government Printing Office, Washington, D.C., p. 425–436.Google Scholar
- O’Connell, S., 1986: Anatomy of modern submarine depositional and distributary systems. Ph.D. dissertation, Columbia University, New York, p. 302. O’Connell, S., and Normark, W.R., 1986: Acoustic facies and sediment composition of the Mississippi Fan drill sites, DSDP Leg 96, in A.H. Bouma, J.M. Coleman, and A.W. Meyer, et al., Init. Repts. DSDP, 96: U.S. Government Printing Office, Washington, D.C., p. 457–473.Google Scholar
- Pequegnat, W.E., 1972: A deep bottom current on the Mississippi Cone, in L.R.A. Capurro and J.L. Reid, eds., Contributions on the Physical Oceanography of the Gulf of Mexico; Houston, Gulf Publishing Company, p. 65–87.Google Scholar
- Pequegnat, W.E., Bryant, W.R., Fredericks, A.D., McKee, T., and Spalding, T., 1972: Deep-sea ironstone deposits in the Gulf of Mexico; J. Sediment. Petrol., v. 42, p. 700–710.Google Scholar
- Shepard, R.G., and Dill, R.F., 1966: Submarine canyons and other sea valleys: Rand McNally, Chicago, p. 381.Google Scholar
- Singer, J.K., and Anderson, J.B., 1984: Use of total grain size distributions to define bedload erosion and transport for poorly sorted sediment undergoing simulated bioturbation; Marine Geol., v. 62, p. 335–359.Google Scholar
- Stelting, C.E., and DSDP Leg 96 Shipboard Scientists, 1985a: Migratory Characteristics of a mid-fan meander belt, Mississippi Fan, in A.H. Bouma, W.E. Normark, and N.E. Barnes, eds., Submarine fans and related-turbidite systems; Springer-Verlag, New York, p. 283–290.Google Scholar
- Stelting, C.E., Pickering, K.T., Bouma, A.H., Coleman, J.M., Cremer, M., Droz, L., Meyer-Wright, A.A., Normark, W.R., O’Connell, S., Stow, D.A.V., and DSDP Leg 96 Shipboard Scientist, 1985b: Drilling results on the middle Mississippi Fan, in A.H. Bouma, W.R. Normark, and N.E. Barnes, eds., Submarine fans and related turbidite systems, Springer-Verlag, New York, p. 275–283.Google Scholar
- Stelting, C.E., Droz, L., Cremer, M., Meyer-Wright, A.A., Normark, W.R., O’Connell, S., Pickering, K.T., and Stow, D.A.V., 1986: Late Pleistocene seismic stratigraphy of the Mississippi Fan, 1986. in A.H. Bouma, J.M. Coleman, A.W. Meyer, et al., Init. Repts. DSDP, 96: U.S. Government Printing Office, Washington, D.C., p. 437–456.Google Scholar
- Stow, D.A.V., Cremer, M., Droz, L., Meyer, A.W., Normark, W.R., O’Connell, S., Pickering K.T., Stelting, C.C., Angell, S.A., and Chaplin, C., 1986: Facies composition and texture of Mississippi Fan sediments, Deep Sea Drilling Project, 96, Gulf of Mexico, in A.H. Bouma, J.M. Coleman, and A.W. Meyer, et al., Init. Repts. DSDP, 96: U.S. Government Printing Office, Washington, D.C., p. 475–488.Google Scholar