Hydrodynamic and geomorphological controls on surface sedimentation at the Subtropical Shelf Front / Brazil–Malvinas Confluence transition off Uruguay (Southwestern Atlantic Continental Margin)

Franco-Fraguas, Paula; Burone, Letícia; Mahiques, Michel Michaelovitch de; Ortega, Leonardo; Urien, Carlos M.; Muñoz, Araceli; López, Guzmán; Marín, Yamandú; Carranza, Alvar; Lahuerta, Nuria; Mello, Camila de

doi:10.1016/j.margeo.2013.12.010

Cited by 32 publications

(28 citation statements)

References 24 publications

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“…In line with the general geomorphology off SESA, the upper continental slope off Uruguay is steep (Urien and Ewing, 1974) and hosts a series of shelf-cutting gullies and channels (Franco-Fraguas et al, 2014). The contour-parallel bottom currents, that have dominate the regional and local sediment transport and depositional pattern at the continental slope off northern Argentina and Uruguay over Late Paleogene and Neogene, have formed a huge contouritic terrace-channel succession (Hernández-Molina et al, 2009;Preu et al, 2012).…”

Section: Study Areamentioning

confidence: 77%

“…The western South Atlantic margin is dominated by the encounter of the poleward-flowing Brazil Current (BC) and the equatorward-flowing Malvinas Current (MC), forming the Brazil-Malvinas Confluence (BMC) at intermediate water depths (500-1000 m; Peterson and Stramma, 1991;Stramma and England, 1999). Along the upper slope, BC transports the superficial Tropical Water (TW) and underlying South Atlantic Central Water (SACW) in southward direction, whilst MC moves the near-surface Sub-Antarctic Water (SAW) and the underlying upper part of the Antarctic Intermediate Water (AAIW) to the north (for references see Franco-Fraguas et al, 2014).…”

Section: Study Areamentioning

confidence: 99%

“…It discontinuously extends from northern Argentina to the Campos Basin off southeastern Brazil (Viana and Faugéres, 1998;Hernández-Molina et al, 2016). The terrace section in the study area is latitudinally bounded by two major canyons to its north and south (Franco-Fraguas et al, 2014; the Piriápolis and José Ignacio canyon systems: Hernández-Molina et al, 2016).…”

Section: Study Areamentioning

confidence: 99%

“…While Points b-d likewise apply to our study area, an explicit overall along-slope convex seafloor topography is not given. Instead, the upper slope is intersected by canyon structures, which occur at a lateral spacing of about 60 km (Franco-Fraguas et al, 2014;Hernández-Molina et al, 2016). These structures, each about 15 km wide, probably lead to an intense turbulent interaction with the slope-parallel bottom flow (Viana and Faugéres, 1998;Preu et al, 2012;Voigt et al, 2013) of the southward-directed BC.…”

Section: Deposition On the Terrace: Shelf Sediment Export Dynamics Vementioning

confidence: 99%

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Sediment Export Dynamics Reflecting the Holocene Hydrodynamic Variability of a High-Energy Continental Shelf System (Southeastern South America)

2019

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This study reconstructs Holocene hydrodynamic changes on the outer shelf off Uruguay by examining deposits from a morphological terrace on the uppermost continental slope (250 m water depth). Seismo-acoustics, litho- and chronostratigraphy, granulometry, and Neodymium isotopy were applied to three sediment cores. The 9.5-m thick terrace sediment record, documenting the past 11.5 cal ka BP, provides exceptional insight into the transport and settling mechanisms of the sand injected from the shelf into the open ocean. The sandy outer shelf is identified as the principal sediment origin. Contouritic bottom currents do not significantly affect deposition on the terrace. Instead, the sandy sediment gets spilled over the shelf edge in the form of suspension clouds, spreading uniformly over the whole terrace. The suspended sand does not transform into high-concentration gravity-driven bottom flows but rains down onto the terrace as a quasi-permanent material supply. This observation suggests that the formation of turbidite beds, as frequently found at the deeper slope in this region, requires first a temporary storage of sediment at deposition-favoring locations on the uppermost continental slope (terraces, canyon heads), before a secondary and episodic process can mobilize the mass.An overall fining-upward trend in silty sand shelf export over Holocene times reflects the deglacial sea-level rise dynamics, leading to overall less effective material mobilization on and transfer across the shelf due to water deepening. The pronounced vertical hydrographic shelf front, as a shallow expression of the regional oceanic confluence zone, acted temporarily as main sediment exporting conveyer, before it shifted further north. The water depth of the terrace coincides with the transition zone between Central Water and Intermediate Water. The pronounced water density gradient might influence sediment distribution twofold, acting as a barrier for sand suspension cloud spreading as well as a medium for incoming internal waves bringing sediment remobilization. DINÂMICA DE EXPORTAÇÃO DE SEDIMENTOS EM FUNÇÃO DA VARIABILIDADE HIDRODINÂMICA DURANTE O HOLOCENO NUM SISTEMA DE PLATAFORMA CONTINENTAL DE ELEVADA ENERGIA (SE DA AMÉRICA DO SUL) ResumoEste estudo pretende ser uma contribuição para a reconstrução das alterações hidrodinâmicas Holocénicas, da plataforma continental externa do Uruguai, a partir de depósitos sedimentares de um terraço do talude continental superior (250 m de profundidade). Três testemunhos de sedimentos foram submetidos a análises geofísicas, lito e cronostratigráficas e granulométricas, tendo também sido obtidos resultados de isótopos de neodímio. O registro sedimentar com 9,5 m de espessura no terraço, documentando os últimos 11,5 ka cal BP, fornece importantes informações sobre os mecanismos de transporte e sedimentação da areia remobilizada da plataforma continental e transportada para o oceano profundo.Os dados obtidos na área de estudo revelaram que o substrato arenoso da plataforma continental externa foi a principal fonte de sedimento para o talude continental superior. As correntes de fundo de contorno não afetaram significativamente a deposição de sedimentos no referido terraço. Em vez disso, o sedimento arenoso remobilizado da plataforma formou nuvens de partículas em suspensão que se espalharam uniformemente por todo o terraço. A areia, uma vez em suspensão, não deu ludar a fluxos gravitacionais de fundo concentrados, mas “choveu” de modo quase continuo por todo o terraço. Esta constatação sugere que a formação de camadas turbidíticas, tais como as que freqüentemente são encontradas no talude continental inferior da região, requerem que primeiramente haja um armazenamento temporário de sedimentos em locais favoráveis à sua deposição na plataforma continental superior (terraços, cabeceiras de cânions), antes da ocorrência de um processo secundário e episódico poder mobilizar os materiais acumulados.Verifica-se, na área de estudo, uma tendência geral de redução da granulometria da areia siltosa ao longo do Holoceno devido à subida do nível do mar após a deglaciação; esta terá levado a uma menor remobilização e a uma transferência menos eficaz de sedimentos da plataforma continental para o talude devido ao aumento da profundidade da coluna de água.A pronunciada frente hidrográfica vertical da plataforma, expressão da zona de confluência oceânica regional, atuou temporariamente como principal processo de transporte e exportação de sedimentos, para norte. A profundidade da água do terraço coincide com a zona de transição entre a Água Central e a Água Intermediária. O pronunciado gradiente de densidade da água poderá ter influenciado de duas maneiras a distribuição de sedimentos, atuando como uma barreira para a propagação da nuvem de areia em suspensão e como meio de propagação de ondas internas que chegam, remobilizando e exportando sedimentos. Palavras-chave: Exportação de sedimentos de plataforma. Margem oceânica de elevada energia. Sudeste da América do Sul. Holoceno.

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Section: Study Areamentioning

confidence: 77%

Section: Study Areamentioning

confidence: 99%

Section: Study Areamentioning

confidence: 99%

Section: Deposition On the Terrace: Shelf Sediment Export Dynamics Vementioning

confidence: 99%

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Sediment Export Dynamics Reflecting the Holocene Hydrodynamic Variability of a High-Energy Continental Shelf System (Southeastern South America)

2019

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“…The South-western Atlantic Margin (SAM, Atlantic Ocean) is recognized as one of the most productive regions in the world, and this is mainly due to the Brazil-Malvinas Confluence (BMC), resulting from the convergence of the Southward-flowing Brazil Current (BC) and the northward flowing Malvinas Current (MC) (Ortega & Martínez, 2007;Schmid & Garzoli, 2009). This large- Chacarita (34°49'59.83"S,56°5'23.27"W) scale oceanographic process presumably traps floating items and may enhance sedimentation rates (e.g., Franco-Fraguas et al 2014).…”

Section: B) Waterwaysmentioning

confidence: 99%

Management and research on plastic debris in Uruguayan Aquatic Systems: update and perspectives

Lozoya

Carranza

Lenzi³

et al. 2015

RGCI

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Synthetic plastics have become an indispensable component of modern life, and the amount of plastics disposal has increased dramatically as a result. With human population increasing, it is expected that the prevalence of plastic debris in the environment will also increase, unless sustainable daily habits are incorporated, waste management improved, and new alternative materials are discovered and popularized. To date, several reports show negative effects of plastic debris on marine and freshwater fauna (e.g. invertebrates, birds, turtles, marine mammals). Plastic are ubiquitous in the water column, deposited Lozoya et al. (2015) 378 in fine sediments and enter the guts, respiratory structures and tissues of different aquatic species, and are incorporated into food webs via ingestion. This global problem also affects beach and near-shore activities (e.g. tourism, fisheries, and aquaculture) with negative social and economic consequences. The research of plastics effect on aquatic environments in Uruguay is only incipient. With the aim of contributing to scientific knowledge, decision-making and the management of plastic debris, here we reviewed the available information on plastic debris sources, their impacts on biodiversity, and policy issues in Uruguayan aquatic systems. Moreover, we reviewed and systematized community outreach initiatives, and examined national policies and management initiatives. We found that Uruguayan aquatic systems (freshwater, coastal marine and benthic) are affected by plastic pollution, both from land-based and sea-based activities, although national-level policies are modern and well suited for minimizing the impacts of plastic pollution. We reviewed biota-plastic debris interactions, and found evidence for impacts on a number of aquatic taxa, including the poorly reported ingestion of microplastics in freshwaters fishes and the association with plastic benthic debris. Global and regional hydrographic settings (Río de la Plata Estuary), as well as idiosyncratic ecological, socio-economic and cultural issues, make Uruguay a valuable test-site for this topic. Our ultimate goal is to minimize the effects of this widespread environmental, economic, health and aesthetic problem. Resumo Pesquisas e manejo de descartes plásticos em sistemas aquáticos uruguaios: atualização e perspectivasProdutos plásticos tem se tornado um componente indispensável na vida moderna, como conseqüência disso a quantidade de plásticos descartados tem dramaticamente aumentado. É esperado que com o aumento da população de seres humanos a prevalência de descartes plásticos também aumente, a menos que hábitos cotidianos sustentáveis sejam incorporados, e novos materiais alternativos sejam descobertos e popularizados. Até o momento, diversas pesquisas têm mostrado os efeitos negativos de descartes plásticos sobre a fauna marinha e dulcícola (p. ex.: invertebrados, aves, tartarugas e mamíferos marinhos). Em ambientes aquáticos, plásticos estão em toda parte: na coluna de água, depositados em sedimento fino e dent...

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Morphosedimentary Configuration of the Argentina Continental Margin

Violante

Laprida

Chapori

2017

The Argentina Continental Margin

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Hydrodynamic and geomorphological controls on surface sedimentation at the Subtropical Shelf Front / Brazil–Malvinas Confluence transition off Uruguay (Southwestern Atlantic Continental Margin)

Cited by 32 publications

References 24 publications

Sediment Export Dynamics Reflecting the Holocene Hydrodynamic Variability of a High-Energy Continental Shelf System (Southeastern South America)

Sediment Export Dynamics Reflecting the Holocene Hydrodynamic Variability of a High-Energy Continental Shelf System (Southeastern South America)

Management and research on plastic debris in Uruguayan Aquatic Systems: update and perspectives

Morphosedimentary Configuration of the Argentina Continental Margin

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