Maria Conceição Freitas

University of Lisbon | UL · Center of Geology (CEGUL)

Laksar is a small river near the village of Ksar Seghir, located between Tangier and Ceuta (Morocco), strategic points to control the Strait of Gibraltar over centuries. The river outlets at the western part of a sandy beach that can block the fluvial discharge in years of low precipitation/river flow. The area is densely occupied since the 5th cen...

This study analyses land use changes in the Sado Estuary (West-Central Portugal) based on a multi-temporal analysis of 19th century cartographic data and 21st century remote sensing land use maps, updated by fieldwork. A GIS plot of land use evolution is summarized in a quantitative table. The comparison shows the changes in land use, with increasi...

In this paper, sedimentological, geochemical, palaeontological and radiocarbon dating results from Holocene cores are presented to infer the palaeoenvironmental evolution of the Thyna coast in the Gulf of Gabes (Tunisia). Based on detailed faunal, sedimentological and geochemical analyses, the evolution of the coastline and the impact of a high-ene...

This study analyses the changes in land use in the Sado estuary (West-Central Portugal) based on a multitemporal analysis of cartographic data from the 19th century and remote sensing land use maps from the 21st century, updated by field work. A GIS plotting of land-use evolution is summarized in a quantitative table. The comparison shows the chang...

O projeto “Lisbon Stories” tem como objetivo o estudo da evolução paleoambiental da margem norte do estuário do Tejo, para compreender a sua evolução natural, a contribuição antrópica e como foi utilizada em diferentes períodos históricos, desde a Idade do Ferro até aos nossos dias. Neste trabalho, apresentam-se os resultados das análises realizada...

Entre os séculos XV e XIX, mais de 12 milhões de pessoas foram escravizadas no continente africano e transportadas, na sua maioria, para as Américas. As condições ambientais dos locais de origem e destino dessas pessoas foram alteradas devido ao abandono de terras no interior africano, ao incremento da produção agrícola nas regiões de destino, e ao...

Started in 2022, the project “Ecologies of Feedom: Materialities of Slavery and Post-emancipation in the Atlantic World” (ECOFREEDOM) is an archaeological, interdisciplinary research project about the formation of the Atlantic world since the 16th century, with a focus on the social and environmental impacts of slavery and colonialism in Cacheu,...

Coastal ecosystems like mangroves, seagrasses, and tidal salt marshes are known as Blue Carbon storage places. These places work as carbon sinks by trapping atmospheric carbon in the biomass (Leaving Aboveground biomass (LAB), Non leaving Aboveground biomass (NLAB) (litter-death plant) and Leaving belowground biomass (LBB) (root and rhizome)) and o...

Neste trabalho apresentam-se os resultados de uma análise icnológica preliminar, obtida a partir da observação de tocas, e de outros traços de actividade, da mesofauna presente nos rasos de maré do estuário do rio Mira, entre a superfície e ~1 m de profundidade, em zonas situadas a 2 km e a 14 km a montante da desembocadura. Além da medição in-situ...

Anthropogenic modifications are changes in the landscape resulting from interventions on natural elements, usually related to the types of land use and coverage. This article analyzes the main biophysical components of the estuarine municipalities of the Sado River - emphasizing geology, geomorphology and anthropogenic derivations of the landscape....

Texture (coarse vs. fine fraction), magnetic susceptibility (MS), organic matter content and organic chemistry data (%Corg, %N, δ13C, δ15N) performed for Arez3, a 13.5 m-long sediment core collected in the Sado valley (Portugal).

Texture (coarse vs. fine fraction), organic matter content and organic chemistry data (%Corg, %N, δ13C, δ15N) performed for Laxique, a 10.5 m-long sediment core collected in the Sado valley (Portugal).

This report summarizes current threats to the Tagus estuary and adjacent ecosystems, presented in Lisbon in June 2021, and prioritizes actions to maintain or improve ecosystem services for a densely populated area close to the deep ocean.

The infilling of coastal incised river valleys is an important sedimentary record that holds imprinting's of depositional environments and sea-level variations. Notwithstanding, the stratigraphic record is difficult to interpret once: i) incised valley coastal areas preserve information both from marine and fluvial processes; ii) the morphology of...

Salt marshes are highly valued coastal environments for different services: coastline protection, biodiversity, and blue carbon. They are vulnerable to climate changes, particularly to sea-level rise. For this reason, it is essential to project the evolution of marsh areas until the end of the century. This work presents a reduced complexity model...

Coastal environments like tidal marshes and flats are very important as they support enormous biodiversity and provide several services such as coastline protection, retention of pollutants, and organic carbon sequestration, having considerable potential to mitigate climate change. The study of these ecosystems is of huge importance to know their d...

Marshes are one of the three (mangroves, marshes, and seagrasses) most critical coastal ecosystems for carbon sequestration and storage. They are essential for coastal preservation as they provide numerous ecosystem services that support coastal communities worldwide and have considerable potential to mitigate climate change. Organic carbon sequest...

In this paper we present the results of a multidisciplinary study performed in the Carrasqueira valley, a tributary of the River Sado (SW Portugal), aimed at characterising the Holocene environmental conditions during the late Mesolithic occupation of this valley. Our findings are based on a 13.5 m long sediment core (Arez3) collected on the alluvi...

The Cabo Verde Archipelago holds a remarkable sedimentary record of tsunami inundations, as highlighted by recent finds on Santiago and Maio Islands. Santiago, in particular, constitutes an exceptional site to study in detail the proximal impacts of the megatsunami(s) triggered by the well-known catastrophic flank collapse of Fogo volcano (~60 km t...

Apresentamos uma primeira abordagem sobre a paisagem submersa do porto de Olisipo e a sua evolução durante o período de ocupação romana, nomeadamente nas zonas actualmente correspondentes ao Terreiro do Paço e Ribeira das Naus. Este modelo da paisagem é construído com base na análise de vários indicadores ambientais obtidos em sondagens de sediment...

The aims of this work are to characterize the palaeoenvironmental evolution and the sedimentary fluvial responses to climate and river flow changes of the upstream reaches of the Sado estuary since the Mid-Late Holocene. By combining the previous information, we also intent to define the limit of the fluvial-estuarine boundary and maximum limit of...

No âmbito do projecto Lisbon Stories recolheram-se em contexto de obra amostras de sedimento da antiga margem estuarina do Tejo. Os sedimentos foram analisados para diversos proxies e a interpretação dos resultados contribuiu para melhor compreender a evolução desta zona ribeirinha nos últimos milénios. Nas áreas de amostragem encontraram-se testem...

The chronological framework for Neanderthal occupation and demise across Europe continues to be debated. In particular, there is still uncertainty regarding the nature, timing and regional expressions of the Middle to Upper Palaeolithic transition associated with the disappearance of Neanderthals and the broader expansion of modern human population...

Evidence for frequent, large landslides on the flanks of the volcanic edifices forming the Canary Islands include outstanding landslide scars and their correlative submarine and subaerial rock and debris avalanche deposits. These landslides involved volumes ranging from tens to hundreds of km3. The sudden entry of large volumes of rock masses in th...

Aim: Temperate forests are currently facing multiple stresses due to climate change, biological invasions, habitat fragmentation and fire regime change. How these stressors interact with each other influences how, when and whether ecosystems recover, or whether they adapt or transition to a different ecological state. Because forest recovery or col...

Nearshore upwelling along the eastern North Atlantic margin regulates regional marine ecosystem productivity and thus impacts blue economies. While most global circulation models show an increase in the intensity and duration of seasonal upwelling at high latitudes under future human-induced warmer conditions, projections for the North Atlantic are...

Pollen and NPP analysis performed on the sedimentary deposits accumulated in the inter-tidal banks of the Tagus Estuary allow for the reconstruction of vegetation history and landscape changes that occurred in Lisbon from the 1st to the 6th century cal AD. The high chronological resolution of this investigation makes it possible to identify changes...

O estuário do Tejo é um dos maiores estuários da Europa ocidental cobrindo uma área de cerca de 325 km2 de extensão. A incisão do vale onde se desenvolve ocorreu durante os vários períodos glaciares do Quaternário e finalmente durante o Último Máximo Glacial, dando origem a um vale que atinge profundidades superiores a 80 m. Esta depressão morfológ...

Tsunamis and storms cause considerable coastal flooding, numerous fatalities, destruction of structures, and erosion. The characterization of energy and frequency associated with each wave contribute to the risk assessment in coastal regions. Coastal boulder deposits represent a physical proof of extreme inundation and allow us to study the effects...

The study of coastal boulder accumulations generated by extreme marine events, and of the energy and frequency involved in boulder transport, is of paramount importance in understanding the risk associated with extreme marine inundations. One of the frequently asked questions is whether the deposits are storm or tsunami-related, both events being c...

Between ca.8400-7000 cal BP Late Mesolithic communities occupied the Sado valley embankments, upstream Alcácer do Sal, Portugal. The consumption of marine resources is attested by the shell waste abandoned in several sites (known as shell middens) and later confirmed by isotopic analyses on bone collagen from individuals buried in these locations....

Since written information exists, river floods were recorded in local and regional archives in the entire world. These are specially constituted by documents in churches about pilgrimages to ask for rain, people perished in floods, chronicles of the kings, documents in libraries, autarchies, old magazines, newspapers, etc. For thousands of years ag...

Naturally and artificially breached tidal inlets can promote fast morphological changes along the adjacent detrital barriers, as they evolve in response to the contemporaneous wave regime. Inlet migration results in downdrift barrier erosion, while updrift sand accumulation and concomitant barrier extension are commonly observed. This study address...

Estuaries are sensitive to changes in global to regional sea level, to climate-driven variation in rainfall and to fluvial discharge. In this study, we use source and environmentally sensitive proxies together with radiocarbon dating to examine a 7-m-thick sedimentary record from the Sado estuary accumulated throughout the last 3.6 kyr. The lithofa...

A paleoclimatic reconstruction for the west coast of Portugal spanning the last six centuries is presented. This is based on the foraminiferal records of two dated sediment cores retrieved from the high marsh settings of Casa Branca (southwest coast, Mira estuary) and Caminha (northwest coast, Minho estuary), and supported by geochemical-sedimentol...

The obligatory adaptation of Organizations to the General Data Protection Regulation (EU) 2016/679 (GDPR), will imply a set of legal, technological and functional changes, with a direct impact on the daily life of Organizations as a result of their increased responsibility with data protection subjects that has been reinforced by the new legislatio...

A multiproxy study combining paleomagnetic, rock magnetic (magnetic susceptibility; anhysteretic remanent magnetization, ARM; isothermal remanent magnetization, IRM, anisotropy of magnetic susceptibility, AMS) and geochemical (XRF) data was carried out on trench sediments collected in the area of Boca do Rio (Algarve, South Portugal) known to have...

We examine the Holocene environmental changes in a wet dune slack of the Portuguese coast, Poço do Barbarroxa de Baixo. Lithology, organic matter, biological proxies and high-resolution chronology provide estimations of sediment accumulation rates and changes in environmental conditions in relation to sea-level change and climate variability during...

The fluvio‑estuarine beaches of downtown Lisbon during the Iron Age and Roman Period. In the aim of the Lisbon Stories project several sediment samples, both sediment cores and discrete samples, were recovered in the riverine Lisbon area. The analyses of those sediments will allow rebuilding the palaeoenvironmental evolution of the northern Tagus m...

São apresentados neste trabalho os resultados do estudo de quatro sondagens recolhidas na margem Norte do Tejo. A análise destes sedimentos permite reconstruir a paisagem e compreender a evolução paleoambiental da margem antes da construção dos grandes aterros. A sua interpretação permitiu concluir que: a sedimentação na zona subtidal mais proximal...

The maintenance of salt marsh areas in context of climate change depends on the balance between the salt marsh sedimentation rates and the sea level rise rates. This abstract presents a methodology to quantify the evolution of these areas until the end of the century, considering both parameters. The obtained result allows pointing out that the sal...

In the study of palaeotsunamis it is crucial to decipher the sedimentological record, to derive intensity of past events and to infer different inundation phases. To achieve this goal, it is important to apply high-resolution techniques that allow magnifying intra-deposit details (at a sub-centimetric scale) that otherwise would not be perceived; c...

The resilience of salt marshes to climate change and sea level rise mainly depends on the balance between sedimentation rates and sea level rise rates. A model was developed to forecast how Caldeira de Tróia salt marsh will respond to that global forcing factor. The results indicate that the salt marsh can tolerate the projected rise in sea level f...

Although research focus mostly on high marshes the understanding of sedimentation rates and patterns along the whole intertidal environment is key to improve projection models in different scenarios of sea level rise (SLR). This study presents the results from the analysis of a sediment core collected in a low marsh on the North bank of Caldeira de...

Saltmarshes are essential ecosystems both from an ecological and biological point of view. Furthermore, they constitute an important social niche, providing valuable economic and protection functions. Thus, understanding their rates and patterns of sedimentation is critical for functional management and rehabilitation, especially in an SLR scenario...

Recent work has applied microtextural and heavy mineral analyses to sandy storm and tsunami deposits from Portugal, Scotland, Indonesia and the USA. We looked at the interpretation of microtextural imagery (scanning electron microscopy) of quartz grains and heavy mineral compositions. We consider inundation events of different chronologies and sour...

Beach sand can harbour pathogenic and opportunistic microorganisms, as well as faecal indicator bacteria that influence directly the bathing water quality. Pathogenic and opportunistic microorganisms often raise concern of exposure during beach related recreational activities. In this work, three different types of sandy beaches (natural basaltic,...

Coastal overwash is one of the most important hazards affecting the coastal zone and therefore has been the focus of several studies related to the establishment of setback lines. However, studies of extreme overwash (EO) events along urban beaches backed by a seawall or structure are scarce, and reveal the difficulties associated with its assessme...

This work presents results of sedimentological and paleoecological analysis performed in EDP1 core taken at the Tagus North margin in Lisbon (Cais do Sodré), where four units were defined. Sedimentation of bottom unit 1 occurred in an estuarine environment, in low energy conditions. Unit 2 corresponds to deposition in a high-energy environment, cha...

The geological record of the 1755 tsunami is widespread along Algarve lowlands but no other unequivocal signature of tsunami inundation was found in onshore sediments deposited since Roman times. This chapter addresses the research undertaken on the documentary and geological evidences of destructive tsunamis in the south-facing Algarve coast of Po...

The Western Massif of the Picos de Europa (43°N – 4‐5°W) includes some of the highest peaks in the Cantabrian Mountains. This massif was heavily glaciated during the Last Glaciation, though the post‐glacial environmental evolution is still poorly understood. Using a geomorphological and sedimentological approach, we have reconstructed the environme...

Tsunamis are highly energetic events that may destructively impact the coast. Resolving the degree of coastal resilience to tsunamis is extremely difficult and sometimes impossible. In part, our understanding is constrained by the limited number of contemporaneous examples and by the high dynamism of coastal systems. In fact, long-term changes of c...

The distribution of Recent and Holocene Cyprideis torosa (Jones, 1850) from brackish estuaries and lagoons of mainland Portugal is presented; older Cenozoic C. torosa are also briefly mentioned. Around 550 specimens were found alive, in Melides lagoon (456) and salt marshes from large estuaries (90). Thousands of empty valves and carapaces, with di...

An assessment of tsunami hazard posed to oceanic volcanic archipelagos in the Central Atlantic (Macaronesia) is here presented. The tsunami risk is generally regarded as low in this region. However, accounts of historical tsunami inundation events and geological evidence of past historical and pre-historical tsunami-related inundations affecting th...

Beach sand can harbour pathogenic and opportunistic microorganisms, as well as faecal indicator bacteria that influence directly the bathing water quality. Pathogenic and opportunistic microorganisms often raise concern of exposure during beach related recreational activities. In this work, three different types of sandy beaches (natural basaltic,...

A 5.4 m long sediment core was collected from Belbín, a karstic depression dammed by a moraine in a mid-altitude environment in the Western Massif of the Picos de Europa of the Cantabrian Mountains, northern Spain. 14C AMS dating of the basal sediments in the core suggests that the maximum glacier advance during the last glacial cycle preceded the...

In this work we present preliminary results of the study of one sediment core (EDP1), collected near Cais do Sodré, Lisbon downtown, close to the present day Tagus riverfront. The results allowed differentiation of 4 major sediment units that present a signature of increasing anthropic influence over time. The lowermost unit (Unit 1) corresponds to...

The Western Massif of the Picos de Europa (latitude 43° N, longitude 4-5° W) includes some of the highest peaks in the Cantabrian Mountains. This massif was heavily glaciated during the Last Glaciation, though the post-glacial environmental evolution is still poorly understood. Using a complementary geomorphological and sedimentological approach, w...

In this contribution we present data from a 182 cm-long sedimentary sequence collected in the mid-altitude area of Belbín, a depression dammed by a moraine during the Last Glaciation in the Western Massif of the Picos de Europa (Cantabrian Mountains, NW Spain), in order to reconstruct the environmental changes and the conditioning factors of these...

The AD 1755 tsunami was the most devastating tsunami that affected Atlantic Europe in historical times. In this work we summarize its sedimentological signatures in lowlands (Martinhal, Barranco, Furnas, Boca do Rio, Salgados-Alcantarilha) of the Algarve coast that contrast in geologic and geomorphological settings and sediment abundance. We found...

Tsunamis are amongst the most catastrophic natural hazards affecting worldwide coastal areas. Their impacts are recorded in the geological archives and its study provides crucial insights into the dynamics and intensity of these events. Moreover, the accurate establishment of return periods can also be derived using sedimentological data. In fact,...

Geoindicators are used to describe reference situations and measure changes and trends in physical environment over time. They provide a simplified form to communicate complex data and information, and constitute a facilitator mechanism in the dialog among stakeholders. In this work, a review on the use of geoindicators in sandy coastal environment...