Occurrence of storm-generated bedforms along the inner continental shelf: Southeastern Brazil

Moscon, Daphnne Moraes Costa; Bastos, Alex Cardoso

Abstracts

Side-scan sonar surveys were carried out in two different areas on the inner continental shelf off the state of Espírito Santo (southeastern Brazil, Area 1- Guarapari Inner shelf -GUA and Area 2- Espirito Santo Bay - BES) and revealed bedforms much like those known as storm-generated bedforms. These bedforms are characterized by bands of fine sand deposited alternately over a coarse sand bottom, generating a deposit pattern of bands of fine sand intercalated with bands of coarse sand occurring between water depths of 25 to 30 m and five to eight m in GUA and ESB, respectively. In both areas, patches of coarse sand reveal the occurrence of wave-generated ripples, with crests that tend to be parallel to the coastline. The facies composition consists of very fine to fine muddy carbonate sands with siliciclastic fine gravel in GUA and coarse to medium sand with bioclastic gravel in BES. Thus, the influence of storm currents and waves in the formation and maintenance of these storm-generated bedforms is clear. However, the classification of the hydrodynamics and sediment transportation is required for estimating the formation, transportation and maintenance of these bedforms.

Storm events; Bedform; Tempestites; Inner Continental shelf; Brazil

Levantamentos sonográficos desenvolvidos em duas áreas da plataforma interna adjacente ao estado do Espírito Santo revelam formas de fundo cuja origem é fortemente relacionada a eventos de tempestades. Estas são caracterizadas por alternâncias de bandas de areias finas sobrepostas, de forma alternada, a um fundo de areias grossas, gerando manchas de areias grossas intercaladas abruptamente com faixas de areias finas a profundidades de 25-30 m para GUA e de 05-08 m para BES. Em ambas as áreas as faixas de areias grossas apresentam marcas de ondulação geradas por ondas com orientação levemente paralela a linha de costa. A sedimentologia de GUA é composta por areias finas a muito finas lamosas carbonáticas com cascalhos siliciclásticos e a de BES por areias grossas e médias com cascalhos biodetríticos. Desta forma, é clara a ação de correntes/ondas de tempestade no fundo marinho de GUA e de BES; porém, a classificação quanto ao comportamento hidrodinâmico e ao transporte de sedimento é necessária para as estimativas sobre a formação, transporte e manutenção das feições encontradas.

Tempestades; Formas de fundo; Tempestitos; Plataforma continental; Brasil

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AMOS, C. L.; LI, M. Z.; CHOUNG, K. ûS. Storm-generated, hummocky stratification on the outer-Scotian Shelf. Geo-Marineá Letts, áv. 16, p. 85-94, 1996.
BELDERSON, áR. H.; JOHNSON, M. A.; KENYON, N. H. In: STRIDE, A áH. (Ed.). Offshore tide sands: processes and deposits. áLondon: Chapman and Hall, 1982. cap. 3, p. 27-57.
CACCHIONE, D. A.; DRAKE, D. E.; GRANT, W. D.; WILIAMS, A. J.; TATE, G. B. Variability of sea-floor roughness áwithin áthe coastal ocean dynamics experiment (CODE) region.á Woods Hole oceanogr. Inst., Tech. Rept, n.á 25-83, 183, á44 p., á1983.
CACCHIONE, D. A.; GRANT, W. D.; TATE, G. B. Rippled scour depressions on the inner continental shelf off central California. J. sediment.á Petrology v. 54, p. 1280û1291, 1984.
CETTO, P. H.; BASTOS, A. C. Padr§es de reflexÒo sonogrßficos associados a dep¾sitos sedimentares biodetrÝticos em um trecho da plataforma continental interna ao largo de Guarapari û ES. In: SIMPËSIO BRASILEIRO DE GEOF═SICA (SBGF), 2006,á Natal, RN.áAnais ... 2006.á CD-ROM.
CETTO, P. H.; BASTOS, A. C. Faciologia de sedimentos carbonßticos biogÛnicos, plataforma continental interna de Guarapari, ES - Brasil. In: Congresso Latino-Americano de CiÛncias do mar û COLACMAR, 12. áFlorian¾polis, SC, 2007. Anais à 2007. CD-ROM.
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EITTREM, S. L.; ANIMA, R. J.; STEVENSON, A. J. Seafloor geology of the Monterey Bay area continental shelf. Mar. Geol, v. 181, p. á3û34, 2002.
GOFF, J. A.; MAYER, L. A.; TRAYKOVSKI, P.; BUYNEVICH, I.; WILKENS, R.; RAYMOND, R.; GLANG, G.; EVANS, R. L.; OLSON, H.; JENKINS, C. Detailed investigation of sorted bedforms, or "rippled scour depressions", within the Martha's Vineyard Coastal Observatory, Massachusetts. Continent Shelf Res, áv. 25, p. 461-484, 2005.
GREENWOOD, B.; SHERMAN, D. J. Hummocky cross-stratification in the surf zone: flow parameters and bedding genesis. Sedimentology,áv. 33, p. 33-45, 1986.
HUNTER, R. E.; THORN, D. R.; SWISHER, M. L. Depositional and erosional features of the inner shelf, northeastern Bering Sea.áGeologie Mijnb, v. 61, p. 49-62, 1982.
KENYON, N. H. The origin of some transverse sand patches in the Celtic Sea. Geologic Magaz., áv. 102, p. 389-394, 1970.
KLEINHANS, M. G.; PASSCHIER, S.; VAN DIJK, T. A. G. P. áThe origin of megaripples, long wave ripples and Hummocky Cross-Stratification in the North Sea in mixed flows, p. á142-151. In: HULSCHER, S.; GARLAN, T.; IDIER, D. ááWORKSHOP áINTERNATIONAL, MARINE SANDWAVE AND RIVER DUNE DYNAMICS, 2, University of áTwente, Netherlands, á2004. 352 p.
LI, M. Z.; AMOS, C. L. Sheet flow and large wave ripples under combined waves and currents: Field observations, model predictions and effects on boundary layer dynamics. Continent Shelf Research v. 19, p. 637-663, 1999.
LOPES, A. L. M.; SILVA, C. G.; DIAS, G. T. M. CaracterizaþÒo sonogrßfica das feiþ§es arenosas de fundo da plataforma continental interna e mÚdia a sul da Bacia de Campos. In: CONGRESSO INTERNACIONAL DA SOCIEDADE BRASILEIRA DE GEOF═SICA, 8., 2003. Anais ... 2003.
MURRAY, A. B.; THIELER, E. R. A new hypothesis for the formation of large-scale inner-shelf sediment sorting and 'rippled scour depressions'. Continent.á Shelf Res, áv. 24, p. 295û315, 2004.
NITTROUER, C. A.; WRIGHT, L. D. Transport of particles across continental shelves. Revs Geophys, áv. 32, n. 1, p. 85-113, 1994.
SOUTHARD, J. B.; BOGUCHWAL, A. Bed configurations in steady unidirectional water flows. Part 2. Synthesis of flume data. J. sedim. áPetrology, áv. 60, n. 5, p. 658-679, 1990.
SWIFT, D. J. P. Response of the shelf floor to flow. In: TILLMAN, R. W.; SWIFT, D. J. P.; WALKER, R. G. (Ed.).á Shelf sands and sandstone reservoirs. SEPM Short Course, áv. 13, p. 135-241, 1985.
SWIFT, D. J. P.; FREELAND, G. L. Sand waves and current lineation on the inner shelf, Middle Atlantic Bight of North America. Mar. Geol, v. 48, p. 1257-1266, 1978.
SWIFT, D. J. P.; FIGUEIREDO, A. G.; FREELAND, G. L.; OERTEL, G. F. Hummocky cross-stratification and megaripples: A geological double-standard?, J. Sedim. Petrology, v. 53, p. 1295-1317, 1982.
VAN DE MEENE, J. W. H.; BOERSMA, J. R.; TERWINDT, J. H. J. áSedimentary structures of combined flow deposits from the shoreface connected ridges along the central Dutch coast. Mar.á Geol, v. 131, p. 151-175, 1996.
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Publication Dates

Publication in this collection
27 Aug 2010
Date of issue
2010

History

Reviewed
14 Dec 2009
Received
06 July 2009
Accepted
05 Mar 2010

This work is licensed under a Creative Commons Attribution 4.0 International License.

[1] ALBINO, J. Processos de sedimentaþÒo atual e morfodinÔmica das praias de Bicanga a PovoaþÒo, ES 1999.182 p. Tese de Doutorado, Programa de P¾s-GraduaþÒo Geologia Sedimentar. áSÒo Paulo: USP, 1999.

[2] AMOS, C. L.; LI, M. Z.; CHOUNG, K. ûS. Storm-generated, hummocky stratification on the outer-Scotian Shelf. Geo-Marineá Letts, áv. 16, p. 85-94, 1996.

[3] BELDERSON, áR. H.; JOHNSON, M. A.; KENYON, N. H. In: STRIDE, A áH. (Ed.). Offshore tide sands: processes and deposits. áLondon: Chapman and Hall, 1982. cap. 3, p. 27-57.

[4] CACCHIONE, D. A.; DRAKE, D. E.; GRANT, W. D.; WILIAMS, A. J.; TATE, G. B. Variability of sea-floor roughness áwithin áthe coastal ocean dynamics experiment (CODE) region.á Woods Hole oceanogr. Inst., Tech. Rept, n.á 25-83, 183, á44 p., á1983.

[5] CACCHIONE, D. A.; GRANT, W. D.; TATE, G. B. Rippled scour depressions on the inner continental shelf off central California. J. sediment.á Petrology v. 54, p. 1280û1291, 1984.

[6] CETTO, P. H.; BASTOS, A. C. Padr§es de reflexÒo sonogrßficos associados a dep¾sitos sedimentares biodetrÝticos em um trecho da plataforma continental interna ao largo de Guarapari û ES. In: SIMPËSIO BRASILEIRO DE GEOF═SICA (SBGF), 2006,á Natal, RN.áAnais ... 2006.á CD-ROM.

[7] CETTO, P. H.; BASTOS, A. C. Faciologia de sedimentos carbonßticos biogÛnicos, plataforma continental interna de Guarapari, ES - Brasil. In: Congresso Latino-Americano de CiÛncias do mar û COLACMAR, 12. áFlorian¾polis, SC, 2007. Anais à 2007. CD-ROM.

[8] CHEEL, R. J.; LECKIE, D. A. Coarse-grained storm beds of the Upper Cretaceous Chungo Member (Wapiabi Formation), southern Alberta, Canada: J. sedim. Petrology, v. 62, p. 933-945, 1992.

[9] EITTREM, S. L.; ANIMA, R. J.; STEVENSON, A. J. Seafloor geology of the Monterey Bay area continental shelf. Mar. Geol, v. 181, p. á3û34, 2002.

[10] GOFF, J. A.; MAYER, L. A.; TRAYKOVSKI, P.; BUYNEVICH, I.; WILKENS, R.; RAYMOND, R.; GLANG, G.; EVANS, R. L.; OLSON, H.; JENKINS, C. Detailed investigation of sorted bedforms, or "rippled scour depressions", within the Martha's Vineyard Coastal Observatory, Massachusetts. Continent Shelf Res, áv. 25, p. 461-484, 2005.

[11] GREENWOOD, B.; SHERMAN, D. J. Hummocky cross-stratification in the surf zone: flow parameters and bedding genesis. Sedimentology,áv. 33, p. 33-45, 1986.

[12] HUNTER, R. E.; THORN, D. R.; SWISHER, M. L. Depositional and erosional features of the inner shelf, northeastern Bering Sea.áGeologie Mijnb, v. 61, p. 49-62, 1982.

[13] KENYON, N. H. The origin of some transverse sand patches in the Celtic Sea. Geologic Magaz., áv. 102, p. 389-394, 1970.

[14] KLEINHANS, M. G.; PASSCHIER, S.; VAN DIJK, T. A. G. P. áThe origin of megaripples, long wave ripples and Hummocky Cross-Stratification in the North Sea in mixed flows, p. á142-151. In: HULSCHER, S.; GARLAN, T.; IDIER, D. ááWORKSHOP áINTERNATIONAL, MARINE SANDWAVE AND RIVER DUNE DYNAMICS, 2, University of áTwente, Netherlands, á2004. 352 p.

[15] LI, M. Z.; AMOS, C. L. Sheet flow and large wave ripples under combined waves and currents: Field observations, model predictions and effects on boundary layer dynamics. Continent Shelf Research v. 19, p. 637-663, 1999.

[16] LOPES, A. L. M.; SILVA, C. G.; DIAS, G. T. M. CaracterizaþÒo sonogrßfica das feiþ§es arenosas de fundo da plataforma continental interna e mÚdia a sul da Bacia de Campos. In: CONGRESSO INTERNACIONAL DA SOCIEDADE BRASILEIRA DE GEOF═SICA, 8., 2003. Anais ... 2003.

[17] MURRAY, A. B.; THIELER, E. R. A new hypothesis for the formation of large-scale inner-shelf sediment sorting and 'rippled scour depressions'. Continent.á Shelf Res, áv. 24, p. 295û315, 2004.

[18] NITTROUER, C. A.; WRIGHT, L. D. Transport of particles across continental shelves. Revs Geophys, áv. 32, n. 1, p. 85-113, 1994.

[19] SOUTHARD, J. B.; BOGUCHWAL, A. Bed configurations in steady unidirectional water flows. Part 2. Synthesis of flume data. J. sedim. áPetrology, áv. 60, n. 5, p. 658-679, 1990.

[20] SWIFT, D. J. P. Response of the shelf floor to flow. In: TILLMAN, R. W.; SWIFT, D. J. P.; WALKER, R. G. (Ed.).á Shelf sands and sandstone reservoirs. SEPM Short Course, áv. 13, p. 135-241, 1985.

[21] SWIFT, D. J. P.; FREELAND, G. L. Sand waves and current lineation on the inner shelf, Middle Atlantic Bight of North America. Mar. Geol, v. 48, p. 1257-1266, 1978.

[22] SWIFT, D. J. P.; FIGUEIREDO, A. G.; FREELAND, G. L.; OERTEL, G. F. Hummocky cross-stratification and megaripples: A geological double-standard?, J. Sedim. Petrology, v. 53, p. 1295-1317, 1982.

[23] VAN DE MEENE, J. W. H.; BOERSMA, J. R.; TERWINDT, J. H. J. áSedimentary structures of combined flow deposits from the shoreface connected ridges along the central Dutch coast. Mar.á Geol, v. 131, p. 151-175, 1996.

[24] WALKER, R. G.; JAMES, N. P. Facies Models: Response to sea level change. Canada: GEOText1, 1992. 454 p.