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SHOREFACE PROCESSES IN ONSLOW BAYsediment cover. Many rippled scour depressions have beencovered completely by fine to medium sand, and there isabundant evidence for strong, seaward-directed currents.These currents deposited large, lobe-like sand bodies at thebase of the shoreface. This is particularly apparent wherestorm overwash did not occur; large dunes appear to haveintensified downwelling currents and seaward sedimenttransport.A number of studies (e.g., Hayes, 1967; Aigner, 1985)have documented the presence of tempestites (graded stormlayers) in shelf sediments. The areal extent of individualevent layers, however, is not well known. Hurricane Berthaproduced a distinct and mappable tempestite layer on theinner shelf. While we do not have post-Fran vibracores, thesidescan-sonar data suggests that the post-Bertha imprintwas probably replaced by a more regional and deeper (in thesedimentary section) event layer.Recent studies of the shoreface geologic framework(e.g., Riggs, et al., 1995; Thieler et al., 1995) and age- mixingof the shell fraction on modern beaches (Wehmiller etal., 1995) indicate that shoreface bypassing, particularly thataccomplished during storms, is an important process on theNorth Carolina coast. Both hurricanes have created new orfresh exposures of ancient sediments and rocks on the shorefaceand inner shelf. Marine hardbottoms produce much ofthe residual sediment cover in Onslow Bay as they are biologicallyand physically eroded. Many of the areas in oursurveys have been buried, eroded or otherwise ”modified" asa sediment source. Our previous work has also identified theimportance of sedimentary texture and geologic control onshoreface sediment transport pathways. Have previouslyidentified transport pathways been opened or closed? If so,what is the nature of that change? Will these events have anysignificant impact on the longer-term evolution of the shoreface?These questions await further study.REFERENCESAigner, T., 1985. Storm depositional systems: Dynamic stratigraphyin modern and ancient shallow- marine sequences. LectureNotes in Earth Sciences Number 3. Springer-Verlag, New York,174 pp.Bijker, E.W., 1967. Some considerations about scales for coastalmodels with moveable beds. Delft Hydraulics Research LaboratoryTechnical Report No.50. Delft, The Netherlands.Blackwelder, B.W., Macintyre, I.G., and Pilkey, O.H., 1982. Geologyof the continental shelf, Onslow Bay, North Carolina, asrevealed by submarine outcrops. American Association ofPetroleum Geologists Bulletin, 66: 44-56.Bruun, P., 1954. Coast erosion and development of beach profiles.U.S. Army Corps of Engineers, Beach Erosion Board, TechnicalMemorandum 44.Bruun, P., 1962. Sea-Ievel rise as a cause of shore erosion. Proceedings,Journal of the Waterways and Harbors Division. ASCE,New York, 88: 117- 130.Cacchione, D.A. and Drake, D.E., 1982. Measurements of stormgenerated bottom stresses on the continental shelf, Journal ofGeophysical Research, 87: 1952-1960.Cacchione, D.A., Drake, D.E., Ferreira, J. T., and Tate, G.B., 1994.Bottom stress estimates and sand transport on the northern Californiainner continental shelf. In: J.H. Trowbridge and A.R:M.Nowell (Editors), Continental Shelf Research (Special volume,Sediment Transport Events on the Shelf and Slope -STRESS),14: 1271-1289.Cacchione, D.A., Grant, W.D., Drake, D.E., and Glenn, S., 1987.Storm-dominated bottom boundary layer dynamics on thenorthern California continental shelf: Measurements and predictions.Journal of Geophysical Research, 92: 1817-1827.Cacchione, D.A., Drake, D.E., Grant, W.D., and Tate, G.B. 1984.Rippled scour depressions on the inner continental shelf offcentral California. Journal of Sedimentary Petrology, 54: 1280-1291.Cleary, W.J., and Pilkey, O.H., 1968. Sedimentation in Onslow Bay.In: Guidebook for field excursions, Geological Society ofAmerica, Southeastern Section, Southeastern Geology SpecialPublication 1, Durham, North Carolina, 17 pp.Curray, J.R., 1969. Shore zone sand bodies - Barriers, cheniers, andbeach ridges. In: D.J. Stanley {Editor), The New Concepts ofContinental Margin Sedimentation. American Geological Institute,Washington, p. JCII-1-JCII-18.Dean, R.G., 1977. Equilibrium beach profiles: U.S. Atlantic andGulf Coasts. Department of Civil Engineering, University ofDelaware, Newark, Ocean Engineering Technical Report 12, 46pp.Dean, R.G., 1983. Principles of beach nourishment. In: P.D. Komar{Editor), Handbook of Coastal Processes and Erosion: CRCPress, Boca Raton, pp.217-231.Dean, R.G., 1987. Coastal sediment processes: Toward engineeringsolutions. Proceedings, Coastal Sediments '87, New York,ASCE, pp. 1- 24.Dean, R.G., 1991. Equilibrium beach profiles: Characteristics andapplications. Journal of Coastal Research, 7: 53-84.Dean, R.G., and Perlin, M., 1986. Intercomparison of near-bottomkinematics by several wave theories and field and laboratorydata. Coastal Engineering, 9: 399-437.Dyer, K.R., and Soulsby, R.L., 1988. Sand transport on the continentalshelf. Annual Review of Fluid Mechanics, 20: 295-324.Ekman, V.W., 1905. On the influence of the Earth's rotation onocean currents. Ark. fur Math. Astron. Och Fysik., 2: 1-53.Gadd, P.E., Lavelle, J.W., and Swift, D.J.P., 1978, Estimates of sandtransport on the New York Shelf using near-bottom currentmeter observations. Journal of Sedimentary Petrology, 48: 239-252.Glenn, S.M., and Grant, W.D., 1987. A suspended sediment stratificationcorrection for combined wave and current flows. Journalof Geophysical Research, 92: 8244-8464.Grant, W.D., and Madsen, O.S., 1979. Combined wave and currentinteraction with a rough bottom. Journal of GeophysicalResearch, 84: 1797-1808.Hansen, M., and Lillycrop, W.J., 1988. Evaluation of closure depthand its role in estimating beach fill volumes. In: L.S. Tait (Editor),Beach Preservation Technology '88. Florida Shore andBeach Preservation Association, Tallahassee, pp. 107- 114.25