Abstract
On the continental shelves off large deltas, rapid progradation and deposition result in highly underconsolidated marine sediments. These deposits, which are often also rich in interstitial methane gas, can be subject to widespread and active mass movement downslope. For example, the submarine slopes of the Mississippi River delta are affected by a variety of sediment instability processes. Geologic and geophysical surveys using side-scan sonar, subbottom profilers, and precision depth recorders have been completed for the entire subaqueous delta. Survey lines were spaced at 240-m intervals, and water depths ranged from 5 m to 20 m. Bottom morphology, including sediment deformations indicative of instability, has been mapped at a scale of 1:12,000, and large-area, scale-corrected sonar mosaics have been constructed. The features identified include collapse depressions, bottleneck slides, shallow rotational slides, mudflow gullies, overlapping mudflow lobes, and a wide variety of faults. The slides and mudflows are extremely active, and movement rates of several hundred metres per year have been recorded. Damage to offshore oil and gas pipelines and platforms has occurred. Also, the concept of slow, continuous deltaic progradation must be modified to include the effects of these processes. For example, on the shelf, normal settling of suspended clays averages only a few millimetres per year, whereas at the front of the delta slope more than 30 m of sediment has been deposited by mudflows and slides since 1875.
These deltaic processes are the result of complex temporal and spatial combinations of different factors, including the generation of excess pore pressures by rapid sedimentation, methane gas within the sediments, wave-induced stresses, and localized slope oversteepening. These conditions are not unique to the Mississippi Delta, and indeed similar processes, which affect geologic deposition models and provide design constraints for offshore engineering, appear to be common in many deltaic environments.
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References
Bea, R. G., and Audibert, J. M. E., 1980, Offshore platforms and pipelines in Mississippi River delta, J. Geotech. Engr. Div., Proc. Am. Soc. Civil Engr., 106(GT8):853–869 (Paper 15645 ).
Coleman, J. M., 1976, Deltas: Processes of Deposition and Models for Exploration, Burgess Publishing Co., 7108 Ohms Lane, Minneapolis, Minn. 55435.
Coleman, J. M., and Prior, D. B., 1981, Resurveys of active mudslides, Mississippi Delta, Geomarine Letters (in press).
Coleman, J. M., and Garrison, L. E., 1977, Geologic aspects of marine slope instability, northwestern Gulf of Mexico, Mar. Geotech., 2: 9–44.
Coleman, J. M., Suhayda, J. N., Whelan, T., III, and Wright, L. D., 1974, Mass movements of Mississippi River delta sediments, Proc. 24th Conf. of Gulf Assoc. Geol. Soc., Lafayette, La., pp. 49–68.
Coleman, J. M., Prior, D. B., and Garrison, L. E., 1980, “Sub-aqueous Sediment Instabilities in the Offshore Mississippi River Delta,” Bureau of Land Management Open-File Rept. 80– 01, New Orleans, La.
Denk, E., Milburger, L. J., Dunlap, W. A., and Bryant, W. R., 1981, A pressurized core barrel for sampling gassy marine sediments, Proc., Offshore Tech. Conf., Houston, Texas (1981).
Dunlap, W. A., and Prior, D. B., 1981, Factors contributing to the initiation of slope instability, Mississippi Delta, Proc., Offshore Tech. Conf., Houston, Texas (in press).
Dunlap, W. A., Bryant, W. R., Williams, G. N., and Suhayda, J. N., 1979, Storm wave effects on deltaic sediments—results of SEASWAB I and II, Proc., Port and Ocean Engr. under Arctic Conditions, 2: 899–920.
Fisk, H. N., and McClelland, B., 1959, Geology of continental shelf off Louisiana: its influence on offshore foundation design, Bull. Geol. Soc. Amer., 70: 1369–1394.
Fisk, H. N., McFarlan, E., Jr., Kolb, C. R., and Wilbert, L. G., 1954, Sedimentary framework of the modern Mississippi Delta, Jour. Sediment. Petrol., 24: 76–99.
Forristall, G. Z., Reece, A. M., Thro, M. E., Ward, E. G., Doyle, E. H., and Hamilton, R. C., 1980, Measurements of sea wave attenuation due to deformable bottoms, Proc., Amer. Soc. Civil Engr., Miami, Florida (in press).
Garrison, L. E., 1974, “The Instability of Surface Sediments on Parts of the Mississippi Delta Front,” U.S. Geol. Survey Open-File Rept., Corpus Christi, Texas, 18 pp.
Henkel, D. J., 1970, The role of waves in causing submarine landslides, Geotechnique, 20: 75–80.
Hooper, J. R., 1980, Crustal layers in Mississippi Delta mudflows, Proc., Offshore Tech. Conf., Houston, Texas, Paper 3770, pp. 277–287.
Morgan, J. P., 1961, Mudlumps at the mouths of the Mississippi River, in: “Genesis and Paleontology of the Mississippi River Mudlumps,” Louisiana Dept. of Conservation Geol. Bull. 35, pp. 1–116.
Morgan, J. P., Coleman, J. M., and Gagliano, S. M., 1963, “Mudlumps at the Mouth of South Pass, Mississippi River: Sedimentology, Paleontology, Structure, Origin, and Relation to Deltaic Processes,” Coastal Studies Series No. 10, Coastal Studies Inst., Louisiana State Univ., Baton Rouge, 190 pp.
Morgan, J. P., Coleman, J. M., and Gagliano, S. M., 1968, Mudlumps: diapiric structures in Mississippi Delta sediments, in: “Diapirism and Diapirs,” Amer. Assoc. Petrol. Geologists Memoir 8, pp. 145–161.
Prior, D. B., and J. M. Coleman, 1978a, Disintegrating, retrogressive landslides on very low angle subaqueous slopes, Mississippi Delta, Mar. Geotech., 2: 37–60.
Prior, D. B., and Coleman, J. M., 1978b, Submarine landslides on the Mississippi delta front slope, in: “Geoscience and Man,” XIX:41–53, School of Geosciences, Louisiana State Univ., Baton Rouge.
Prior, D. B., and Coleman, J. M., 1980, Sonograph mosaics of submarine slope instabilities, Mississippi River delta, Mar. Geol., 36: 227–239.
Prior, D. B., and Suhayda, J. N., 1979a, Application of infinite slope analysis to subaqueous sediment instability, Mississippi Delta, Engr. Geol., 14: 1–10.
Prior, D. B., and Suhayda, J. N., 1979b, Submarine mudslide morphology and development mechanisms, Mississippi Delta, Proc., Offshore Tech. Conf., Houston, Texas, Paper 3482, pp. 1055–1061.
Prior, D. B., Coleman, J. M., and Garrison, L. E., 1979a, Digitally acquired undistorted side scan sonar images of submarine landslides, Mississippi Delta, Geology, 7: 423–425.
Prior, D. B., Coleman, J. M., and Caron, R. L., 1979b, Sea floor mapping using micro-computer assisted side-scan sonar, Proc., 13th Internat. Remote Sensing Symposium, Ann Arbor, Mich.
Reece, E. W., Ryerson, D. E., Kestly, J. D., and McNeill, R. L., 1979, The development of in situ marine seismic and geotechnical instrumentation systems, Proc., Conf. on Port and Ocean Engr. under Arctic Conditions, Trondheim, Norway.
Roberts, H. H., 1980, Sediment characteristics of Mississippi River delta-front deposits, Trans., Gulf Coast Assoc. Geol. Soc. (in press).
Schapery, R. A., and Dunlap, W. A., 1978, Prediction of storm-induced sea bottom movement and platform forces, Proc. Offshore Tech. Conf., Houston, Texas, Paper 3259, pp. 1789–1796.
Shepard, F. P., 1955, Delta front valleys bordering the Mississippi distributaries, Bull. Geol. Soc. Amer., 66: 1489–1498.
Suhayda, J. N., Whelan, T., III, Coleman, J. M., Booth, J. S., and Garrison, L. E., 1976, Marine sediment instability: interaction of hydrodynamic forces and bottom sediments, Proc., Offshore Tech. Conf., Houston, Texas, Paper 2426, pp. 29–40.
Terzaghi, K., 1956, Varieties of submarine slope failures, Proc., 8th Texas Oil Mech. and Engr. Conf., pp. 1–41.
Whelan, T., III, Coleman, J. M., Roberts, H. H., and Suhayda, J. N., 1976, The occurrence of methane in recent deltaic sediments and its effects on soil stability, Internat. Assoc. Engr. Geol. Bull., 14: 55–64.
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© 1982 Plenum Press, New York
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Prior, D.B., Coleman, J.M. (1982). Active Slides and Flows in Underconsolidated Marine Sediments on the Slopes of the Mississippi Delta. In: Saxov, S., Nieuwenhuis, J.K. (eds) Marine Slides and Other Mass Movements. NATO Conference Series, vol 6. Springer, Boston, MA. https://doi.org/10.1007/978-1-4613-3362-3_3
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DOI: https://doi.org/10.1007/978-1-4613-3362-3_3
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