Abstract:Diferentes métodos de estudo foram desenvolvidos para definir os padrões de transporte de sedimentos, sendo um deles o modelo de tendência direcional de transporte de sedimentos (GSTA), que se baseia na análise da variabilidade espacial dos parâmetros granulométricos – média (μ), desvio-padrão (σ) e assimetria (Sk). Neste trabalho, o complemento GisedTrend, que opera em ambiente de Sistema de Informações Geográficas (SIG), foi implementado para analisar a dinâmica sedimentar da margem interna da restinga da Ma… Show more
“…Previous studies of surficial sediment distribution along Marambaia Barrier Island, presented by Ponçano (1976) and Borges (1990), and revisited by Carvalho and Guerra (2020), show the predominance of moderately well-sorted medium sands (Fig. 1c).…”
Section: Study Areamentioning
confidence: 68%
“…10; Table 3). Figure 10.( a ) Geochronology of beach ridge sets; ( b ) inset, showing modern sediment transport patterns near/at Marambaia Barrier Island inferred from grain-size trend analysis (Carvalho and Guerra, 2020). A = sediment accumulation area; R = sediment removal area.…”
Section: Resultsmentioning
confidence: 99%
“…Tidal currents and secondary wind-generated currents were possibly responsible for sand transport along the bayshore by reworking and redistributing older deposits of the barrier itself. Carvalho and Guerra (2020) applied a grain-size trend model to surface sediments collected along the barrier's shoreline and nearby submersed area (<2 m depth) and identified an area of divergence of sediment transport that occurs both towards Ponta da Pombeba and eastwards (Fig. 9b).…”
Barrier islands are sedimentary bodies susceptible to changes in sediment supply, dominant physical processes, and sea level. The aim of this work was to study the sedimentary processes that established Marambaia Barrier Island (SE Brazil) as an elongated sandy body that created Sepetiba Bay. For this purpose, barrier and back-barrier bay environments were analyzed using high-resolution satellite imagery, geophysical and topographic surveys, surface sediment samples and short cores, and radiocarbon and optically stimulated luminescence (OSL) dating techniques. Seven morpho-sedimentary domains were identified: coastal beach ridges, overland flow features, inter-ridge paleo lagoon, bayside beach ridges, marshlands, dune field and tidal wetlands. The results show that Marambaia Barrier Island evolved throughout the Holocene, first under normal regression conditions during sea-level rise, and then by forced regression as sea level lowered to its present position. Concurrent processes related to longshore drift, onshore transport, reworked barrier deposits, eolian transport, bay circulation, and pedogenesis influenced its morpho-sedimentary evolution. Morphological features such as truncated beach ridges, flying spits, and filled channels attest to the occurrence of alternating periods of erosion and accretion, evincing how the morphology of barrier island systems preserves an important archive of environmental changes.
“…Previous studies of surficial sediment distribution along Marambaia Barrier Island, presented by Ponçano (1976) and Borges (1990), and revisited by Carvalho and Guerra (2020), show the predominance of moderately well-sorted medium sands (Fig. 1c).…”
Section: Study Areamentioning
confidence: 68%
“…10; Table 3). Figure 10.( a ) Geochronology of beach ridge sets; ( b ) inset, showing modern sediment transport patterns near/at Marambaia Barrier Island inferred from grain-size trend analysis (Carvalho and Guerra, 2020). A = sediment accumulation area; R = sediment removal area.…”
Section: Resultsmentioning
confidence: 99%
“…Tidal currents and secondary wind-generated currents were possibly responsible for sand transport along the bayshore by reworking and redistributing older deposits of the barrier itself. Carvalho and Guerra (2020) applied a grain-size trend model to surface sediments collected along the barrier's shoreline and nearby submersed area (<2 m depth) and identified an area of divergence of sediment transport that occurs both towards Ponta da Pombeba and eastwards (Fig. 9b).…”
Barrier islands are sedimentary bodies susceptible to changes in sediment supply, dominant physical processes, and sea level. The aim of this work was to study the sedimentary processes that established Marambaia Barrier Island (SE Brazil) as an elongated sandy body that created Sepetiba Bay. For this purpose, barrier and back-barrier bay environments were analyzed using high-resolution satellite imagery, geophysical and topographic surveys, surface sediment samples and short cores, and radiocarbon and optically stimulated luminescence (OSL) dating techniques. Seven morpho-sedimentary domains were identified: coastal beach ridges, overland flow features, inter-ridge paleo lagoon, bayside beach ridges, marshlands, dune field and tidal wetlands. The results show that Marambaia Barrier Island evolved throughout the Holocene, first under normal regression conditions during sea-level rise, and then by forced regression as sea level lowered to its present position. Concurrent processes related to longshore drift, onshore transport, reworked barrier deposits, eolian transport, bay circulation, and pedogenesis influenced its morpho-sedimentary evolution. Morphological features such as truncated beach ridges, flying spits, and filled channels attest to the occurrence of alternating periods of erosion and accretion, evincing how the morphology of barrier island systems preserves an important archive of environmental changes.
Purpose
Some marine organisms can be used as Biological Quality Elements to estimate the degree of environmental impact and to monitor the health of benthic habitats. Organisms with mineralized protections, such as benthic foraminifera, can provide helpful information on the evolution of the coastal system over a long period and determine the Paleo-Ecological Quality Status (Paleo-EcoQS). This work aims at reconstructing the Paleo-EcoQS in the heavily anthropized Sepetiba Bay (SB; Rio de Janeiro State, SE Brazil).
Materials and methods
This work is based on a multiproxy approach, including textural, geochemical, and foraminiferal data along the core SP11 retrieved near the Pico da Marambaia (a mountain on the tip of the Marambaia Barrier Island). Geochemical analyses encompassing total organic carbon (TOC), total sulfur (S), total nitrogen (N), calcium carbonate (CaCO3), stable isotopes in organic matter (OMδ13C, and OMδ15N) and elemental concentrations as well as 201Pb, 137Cs, and radiocarbon dating were performed to characterize the Paleo-EcoQS in the bay.
Results
The values of the Paleo-EcoQS.st (standardized Paleo-EcoQS) index in core SP11 indicate that the paleoenvironmental quality varied from moderate to good between ≈50 AD and ≈1500 AD and from good to high between the ~ 1920s and ~ 1990s. Since the 1990s, the Paleo-EcoQS.st has deteriorated considerably, probably due to the deposition of contaminated dredging material in nearby areas. Ballast water discharge may have introduced alien species, such as Ammonia buzasi, into the SB.
Conclusions
The results obtained in core SP11, compared to those of another core (i.e., SP8) from a nearby area, suggest that the reference level of maximum environmental quality is not always reached in a period before industrialization in coastal ecosystems with significant interaction with the ocean; natural factors, related, for example, to sedimentary dynamic processes or geomorphological changes, can lead to unexpected results.
Barrier islands are low-lying elongated, narrow sandy deposits, usually parallel to the coastline, separated from the continent by a lagoon. Due to their low elevation above sea level, barrier islands are environments susceptible to drastic morphological changes depending on the meteo-oceanographic conditions to which they are subjected. This work presents the morphological changes between 1985 and 2021 in “Restinga da Marambaia”—a 40 km long barrier island on Brazil’s Southeastern coast. One hundred thirty-four scenes from the Landsat collection were processed, enabling the quantification of the barrier island area. Additionally, the rates of change in the position of the shorelines facing the Atlantic Ocean, Sepetiba Bay, and Marambaia Bay were computed. The barrier island’s total area and the central sector’s width present significant seasonal variability, which is maximum during the austral fall and winter seasons. On the shores facing the Atlantic Ocean and Sepetiba Bay, it is noted that the central and far eastern sectors show an erosional trend. In contrast, the coastline is more stable on the shore facing Marambaia Bay. The seasonal variations of the barrier island area occur during a period of low rainfall and more energetic waves associated with local winds, which produce coastal currents, transporting the available sediments.
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