Dinâmica espacial e temporal do ravinamento na margem esquerda da bacia do Baixo Tejo : formas, processos e factores

Tese de doutoramento, Geografia (Geografia Física), Universidade de Lisboa, Instituto de Geografia e Ordenamento do Território, 2014

Caracterização de ambientes de transição do SW Alentejano a distintas escalas temporais

Tese de doutoramento, Geologia (Geologia Económica e do Ambiente), Universidade de Lisboa, Faculdade de Ciências, 2016

Beryllium-7 sorption to inorganic particles in Tahsis Inlet, Nootka Sound, B.C.

Senior thesis written for Oceanography 445

Análise do transporte ferroviário de mercadorias associado à problemática da diferença de bitola entre linhas da rede ferroviária: estudo do caso prático: ligação do porto de Aveiro ao corredor internacional de mercadorias E-80

Trabalho Final de Mestrado para obtenção do grau de Mestre em Engenharia Civil

Estudo geotécnico dos solos do vale do Leça no âmbito de uma obra de requalificação portuária

A expansão da área ocupada pelo Porto de Leixões (Matosinhos e Leça da Palmeira), sobre solos muito compressíveis, de origem fluvial e marinha, leva a que seja necessário recorrer à engenharia para encontrar soluções adequadas à utilização de obras dos fins em vista. Assim, na zona do porto são muitos os projectos de engenharia civil/geotécnica executados nestes solos. Como exemplo, podem citar-se a Consolidação do Terrapleno e Construção dos Caminhos de Rolamento do Terminal de Contentores TC4S, a Reabilitação de um troço com 110m, do Cais Sul e do Cais Nascente da Doca nº 4 e a Construção da Portaria Principal do Porto de Leixões, todos no vale fóssil do rio Leça. São vastos os métodos a usar para o melhoramento destes solos, a colocação de colunas de brita, com o objectivo de reforçar o solo, aumentando a sua capacidade de carga e funcionando como drenos verticais, para solucionar o problema das deformações excessivas durante e após o final da obra, uma alternativa consiste em induzir a aceleração da consolidação da camada de solo mole, o uso de pré-carregamento e drenos verticais são usuais. Quando o tempo de concretização da obra exige que o aterro seja utilizado de imediato, uma solução viável é a colocação de estacas, que transferem o peso do aterro, ou parte dele, para camadas mais competentes. Também se pode proceder à retirada do solo original e substituí-lo por outro de qualidade superior. A mais recente técnica de melhoria de solos por injecção - jet grouting - é utilizada em diversas situações, incluindo obras provisórias e definitivas. O presente trabalho visa descrever, em função dos diversos factores, o comportamento do solo face aos vários métodos utilizados e os objectivos pretendidos que serão abordados no enquadramento empírico do trabalho.

Synthesis of the Piacenzian onshore record between the Aveiro and Setubal parallels (Western portuguese margin)

Onshore, the Piacenzianof the Mondego and Lower Tagus Tertiary basins comprises siliciclastic sediments deposited in shallow marine to continental environments. The outcrops of the deposits are relatively widespread in the Aveiro and Seuibal region. A lithostratigraphic synthesis based on the correlation of geological sections, is presented for the two basins. In general, the Piacenzian sediments display a regressive sucession. The Late Tortonian-Zanclean (?) confined drainage pattern changed at the beginning of Piazencian, to fluvial systems draining to the Atlantic, and capturing the drainage of the inner parts of the Hesperic Meseta. The Piacenzian sedimentary sequence post-dates one of the uprising phases during Neogene compression, recorded by a strong regional unconformity. Some local active faulting - as in Lousa, Rio Maior and Senibal- Pinhal Novo - allowed the local thickening of the sedimentary record. Later compressive tectonism continues to generate reverse faulting and diapiric reactivation, affecting those sediments. Currently, the Piacenzian deposits culminates the marginal piedmonts, widely eroded by the Quaternary fluvial dissection.

Assinatura tectono-sedimentar do auge da compressão bética em Portugal: a descontinuidade sedimentar Valesiano terminal-Turoliano

An Upper Miocene important sedimentary break can be accurately recognised in the Portuguese basins and is reflected by a drastic palaeogeographic change in relation to a large-scale tectonic event of probable uppermost Vallesian-Turolian (9,5 Ma; middle Tortonian) age. The characterisation of the sedimentary record of this tectonic event, as well as its relations with interpreted active faults is made for different situations: Douro (NW border), Mondego, Lower-Tagus and Sado Tertiary basins. The sedimentary record, considered upper Tortonian-Messinian ? (uppermost Vallesian-Turolian ?) is interpreted mainly as endorheic alluvial fans (internal drainage), developed along active NNE-SSW indent-linked strike-slip faults and NE-SW reverse faults. At NE Portugal, proximal fluvial systems of an endorheic hydrographic network drained eastwards to the Spanish Duero interior Basin. The main evidences of the betic compression clímax in Portugal mainland are presented; the interpreted active tectonic structures are in accordance with an intense NNW-SSE crustal shortening, but some regional differences are also documented.

Estratigrafia e interpretação paleogeográfica do Cenozóico continental do norte de Portugal

Palaeogeographic and tectono-sedimentary interpretation of northern Portugal, in which previous studies (geomorphology, lithostratigraphy, mineralogy, sedimentology, palaeontology, etc.) were considered, is here proposed. Cenozoic shows different features according to its morphotectonic setting in the eestern region (Trás-os-Montes) or near to the Atlantic coast (western region, Minho and Douro Litoral areas). Although in the eastern region the sedimentary record is considered late Neogene, in some places Paleogene (?) was identified. This oldest record, represented by alluvial deposits, was preserved from complete erosion because of its position inside Bragança-Vilariça-Manteigas fault zone grabens. Later sedimentary episodes (upper Tortonian-Zanclean ?), represented by two allostratigraphical units, were interpreted as proximal fluvial braided systems of an endorheic hydrographic network, draining to the Spanish Duero Basin (eastwards); nowadays, they still remained in tectonic depressions and incised-valleys. Later on, eastern sedimentation becomes scarcer because Atlantic fluvial systems (e.g. the pre-Douro), successively, captured previous endorheic drainages. The proximal reaches of the allostratigraphic unit considered Placencian is recorded in Mirandela (western Trás-os-Montes) but the following fluvial episode (Gelasian-early Pleistocene ?) was already documented in east Trás-os-Montes, preserved in high platforms and in tectonic depressions. Placencian and Quaternary sedimentary records in the western coastal zone, mainly represented by terraces, are located in the Minho, Lima, Alverães, Cávado and Ave large fluvial valleys and in the Oporto littoral platform. In conclusion, northern Portugal Tertiary sedimentary episodes were mainly controlled by tectonics, but later on (Placencian-Quaternary) also by eustasy.

Paleoalterações e cimentações nos depósitos continentais terciários de Portugal central: importância na interpretação de processos antigos

This paper describes the palaeoweathering, cementation, clay minerals association and other closely related characteristics of central Portugal allostratigraphic Tertiary units (SLD's), that can be used for palaeoclimatic interpretation and palaeoenvironmental reconstruction. Lateral and vertical changes in palaeosols are of value for improving our understanding of the autocyclic and allocyclic controls on sediment acumulation in an alluvial basin, but they can also have stratigraphic importance. In some cases it is concluded that the geomorphological setting may have been more decisive than climatic conditions to the production of the palaeoweathering. During late Palaeogene (SLD7-8), surface and near-surface silicification were developed on tectonically stable land surfaces of minimal local relief under a semi-arid climate; groundwater flow was responsible for some eodiagenesis calcareous accumulations, with the neoformation of palygorskite. Conditions during the Miocene (SLD9-11) were favourable for the smectization of the metamorphic basement and arenization of granites. Intense rubefaction associated with basement conversion into clay (illite and kaolinite), is ascribed to internal drainage during late Messinian-Zanclean (SLD12). During Piacenzian (SLD13) intense kaolinization and hydromorphism are typical, reflecting a more humid and hot temperate climate and important Atlantic fluvial drainage. Later on (Gelasian-early Pleistocene ?; SLD14). more cold and dry conditicns are interpreted, at the beginning of the fluvial incision sage. Silica cementation is identified in the upper Eocence-Oligocene ? (SLD18; the major period of silicification), middle to upper Miocene (SLD10)and upper Tortonian-Messinian (SLD11); these occurrences are compatible with either arid or semi-arid conditions and the establishment of a flat landscape upon which a silcrete was developed.

Palynology of late-glacial and postglacial sediments in Georgian Bay, Ontario, Canada, as related to the Great Lakes history /

This investigation comprises three parts: (1) the source, mechanism of transport, and distribution of pollen, spores and other palynomorphs in Georgian Bay bottom sediments and a comparison of these data with the contemporary vegetation, (2) the relative significance of fluvial transportation of pollen and spores, and (3) the late- and postglacial history of vegetational and climatic changes in the Georgicin Bay region. Modem pollen and spore assemblages in Georgian Bay do reflect the surrovinding vegetation when preservation and pollen production by the different species are considered and accounted for. Relative pollen percentage and concentration isopoll patterns indicate that rivers contribute large quantities of pollen and spores to Georgian Bay. This is further substantiated by large amounts of pollen and spores which were caught in traps in the Moon, Muskoka, and Nottawasaga Rivers which flow into Georgian Bay. The majority of pollen and spores caught in these traps were washed into the rivers by surface water runoff and so reflect the vegetation of the watershed in a regional sense. In a 12.9 metre long sediment core from northeastern Georgian Bay the relative percentage and absolute pollen concentrations allow correlation of Georgian Bay Lake phases with climatic and forest history. Four distinct pollen zones are distinguished: zone GB IV which is the oldest, reflects the succession from open spruce woodland to boreal forest; zone GB III represents a period of pine-mixed hardwoods forests from about 10,000 to 7,500 years ago. A pine-maplehemlock association dominated in zone GB II, although during the culmination of postglacial warming about 4,000 to 5,000 years ago the Georgian Bay forests had a more deciduous character. Zone GB I clearly shows European man's disturbance of the forest by logging activities.

Sedimentology and stratigraphy of the Lower Silurian Grimsby formation, in subsurface, Lake Erie and Southwestern Ontario

Since the first offshore Lake Erie well was drilled in 1941, the Grimsby and Thorold formations of the Cataract Group have been economically important to the oil and gas industry of Ontario. The Cataract Group provides a significant amount of Ontario's gas production primarily from wells located on Lake Erie. The Grimsby - Thorold formations are the result of nearshore estuarine processes influenced by tides on a prograding shelf and are composed of subtidal channel complexes, discrete tidal channels, mud flats and non-marine deposits. Deposition was related to a regressive - transgressive cycle associated with eustatic sea level changes caused by the melting and resurgence of continental glaciation centred in Africa in the Late Ordovician/Early Silurian. Grimsby deposition began during a regression with the deposition of subtidal channel complexes incised into the marine deposits of the Cabot Head Formation. The presence of mud drapes and mud couplets suggest that these deposits were influenced by tides. These deposits dominate the lower half of the Grimsby. Deposition continued with a change from these subtidal channel complexes to laterally migrating, discrete, shallow tidal channels and mud flats. These were in turn overlain by the non-marine deposits of the Thorold Formation. Grimsby - Thorold deposition ended with a major transgression replacing siliciclastic deposition with primarily carbonate deposition. Sediment was sourced from the east and southeast and associated with a continuation of the Taconic Orogeny into the Early Silurian. The fluvial head of the estuary prograded from a shoreline that was located in western New York and western Pennsylvania running NNE-SSW and then turning NW-SE and paralleling the present day Lake Erie shoreline. iii The facies attributed to the Grimsby - Thorold formations can be ascribed to the three zones within the tripartite zonation suggested by Dalrymple et ale (1992) for estuaries, that is, a marine-dominated facies, a mixed energy facies, and a facies that is dominated by fluvial processes. Also, sediments within the Grimsby - Thorold are commonly fining upwards sequences which are common in estuarine settings whereas deltaic deposits are normally composed of coarsening upwards sequences in a vertical wedge shape with coarser material near the head. The only coarsening observed was in the Thorold Formation and attributed to non-marine deposition by palynological evidence. The presence of a lag deposit at the base of the sediments of the Grimsby Thorold formations suggests that they were incised into the Cabot Head Formation. Further, the thickness of Early Silurian sediments located between the top of the Queenston Formation, where Early Silurian sedimentation began, to the top of the Reynales - Irondequoit formation are constant whether the Grimsby - Thorold formations are present or not. Also, cross-sections using a sand body located in the Cabot Head Formation for correlation further imply that the Grimsby Formation has been incised into the previous deposits of the Cabot Head.

Sedimentology of the Sixteen Mile Creek Lagoon, Niagara Peninsula, Ontario, Canada

The effec s of relative water level changes in Lake Ontario were detected in the ysical, chemical and biological characteristics of the sediments of the Fifteen, Sixteen and Twenty Mile Creek lagoonal complexes. Regional environmental changes have occurred resulting in the following sequence of sediments in the three lagoons and marsh. From the base up they are; (I) Till,(2) Pink Clay, (3) Bottom Sand, (4) Gyttja, (5) Orange Sandy Silt, (6) Brown Clay and (7) Gray Clay. The till was only encountered in the marsh and channel; however, it is presumed to occur throughout the entire area. The presence of diatoms and sponge spicules, the vertical and ongitudinal uniformity of the sediment and the stratigr ic position of the Pink Clay indicate that it has a glacial or post-glacial lacustrine origin. Overl ng the Pink Clay or Till is a clayey, silty sand to gravel. The downstream fining and unsorted nature of this material indicate that it has a fluvial/deltaic origin. Water levels began rising in the lagoon 3,250 years ago resulting in the deposition of the Gyttja, a brown, organic-rich silty clay probably deposited in a shallow, stagnant environment as shown by the presence of pyrite in the organic material and relatively high proportions of benthic diatoms and grass pollen. Increase in the rate of deposition of the Gyttja on Twenty Mile Creek and a decrease in the same unit on Sixteen Mile Creek is possibly the result of a capture of the Sixteen Mile Creek by the Twenty Mile Creek. The rise in lake level responsible for the onset and transgression of this III unit may have been produced by isostatic rebound; however, the deposition also corresponds closely to a drop in the level of Lake Huron and increased flow through the lower lakes. The o ange Sandy Silt, present only in the marsh, appears to be a buried soil horizon as shown by oxidized roots, and may be the upland equivalant to the Gyttja. Additional deepening resulted in the deposition of Brown Clay, a unit which only occurs at the lakeward end of the three lagoons. The decrease in grass pollen and the relatively high proportion of pelagic diatoms are evidence for this. The deepening may be the result of isostatic rebound; however, the onset of its deposition at 1640 years B.P. is synchronous in the three lagoons and corresponds to the end of the subAtlantic climatic episode. The effects of the climatic change in southern Ontario is uncertain. Average deposition rates of the Brown Clay are similar to those in the upper Gyttja on Sixteen Mile Creek; however, Twenty Mile Creek shows lower rates of the Brown Clay than those in the upper Gyttja. The Gray Clay covers the present bottom of the three lagoons and also occurs in the marsh It is inter1aminated wi sand in the channels. Increases in the rates of deposi ion, high concentrations of Ca and Zn, an Ambrosia rise, and an increase in bioturbation possibly due to the activities of the carp, indicate th this unit is a recent deposit resulting from the activities of man.

The sedimentology of the lower Silurian whirlpool sandstone in subsurface Lake Erie, Ontario

The lower Silurian Whirlpool Sandstone is composed of two main units: a fluvial unit and an estuarine to transitional marine unit. The lowermost unit is made up of sandy braided fluvial deposits, in shallow valleys, that flowed towards the northwest. The fluvial channels are largely filled by cross-bedded, well sorted, quartzose sands, with little ripple crosslaminated or overbank shales. Erosionally overlying this lower unit are brackish water to marine deposits. In the east, this unit consists of estuarine channels and tidal flat deposits. The channels consist of fluvial sands at the base, changing upwards into brackish and tidally influenced channelized sandstones and shales. The estuarine channels flowed to the southwest. Westwards, the unit contains backbarrier facies with extensive washover deposits. Separating the backbarrier facies from shoreface sandstone facies to the west, are barrier island sands represented by barrier-foreshore facies. The barrier islands are dissected by tidal inlets characterized by fining upward abandonment sequences. Inlet deposits are also present west of the barrier island, abandoned by transgression on the shoreface. The sandy marine deposits are replaced to the west by carbonates of the Manitoulin Limestone. During the latest Ordovician, a hiatus in crustal loading during the Taconic Orogeny led to erosional offloading and crustal rebound, the eroded material distributed towards the west, northwest and north as the terrestrial deposits of the fluvial Whirlpool. The "anti-peripheral bulge" of the rebound interfered with the peripheral bulge of the Michigan Basin, nulling the Algonquin Arch, and allowing the detritus of the fluvial Whirlpool to spread onto the Algonquin Arch. The Taconic Orogeny resumed in the earliest Silurian with crustal loading to the south and southeast, and causing tilting of the surface slope in subsurface Lake Erie towards the ii southwest. Lowstand terrestrial deposits were scoured into the new slope. The new crustal loading also reactivated the peripheral bulge of the Appalachian Basin, allowing it to interact with the bulge of the Michigan Basin, raising the Algonquin Arch. The crustal loading depressed the Appalachian basin and allowed transgression to occur. The renewed Algonquin Arch allowed the early Silurian transgression to proceed up two slopes, one to the east and one to the west. The transgression to the east entered the lowstand valleys and created the estuarine Whirlpool. The rising arch caused progradation of the Manitoulin carbonates upon shoreface facies of the Whirlpool Sandstone and upon offshore facies of the Cabot Head Formation. Further crustal loading caused basin subsidence and rapid transgression, abandoning the Whirlpool estuary in an offshore setting.

Patrons de distribution des crustacés planctoniques dans le fleuve Saint-Laurent

La recherche porte sur les patrons de distribution longitudinale (amont-aval) et transversale (rive nord - rive sud) des communautés de crustacés planctoniques qui ont été analysés le long du fleuve Saint-Laurent entre le lac Saint-François et la zone de transition estuarienne, à deux hydropériodes en mai (crue) et en août (étiage). Les données zooplanctoniques et environnementales ont été récoltées à 52 stations réparties sur 16 transects transversaux en 2006. Au chapitre 1, nous présentons les principaux modèles écosystémiques en rivière, une synthèse des facteurs influençant le zooplancton en rivières et les objectifs et hypothèses de recherche. Au chapitre 2, nous décrivons la structure des communautés de zooplancton dans trois zones biogéographiques du fleuve et 6 habitats longitudinaux, ainsi que les relations entre la structure du zooplancton et la distribution spatiale des masses d’eau et les variables environnementales. Au chapitre 3, nous réalisons une partition de la variation des variables spatiales AEM (basées sur la distribution des masses d’eau) et des variables environnementales pour évaluer quelle part de la variation du zooplancton est expliquée par les processus hydrologiques (variables AEM) et les conditions locales (facteurs environnementaux). Le gradient salinité-conductivité relié à la discontinuité fleuve-estuaire a déterminé la distribution à grande échelle du zooplancton. Dans les zones fluviales, la distribution du zooplancton est davantage influencée par la distribution des masses d’eau que par les facteurs environnementaux locaux. La distribution des masses d’eau explique une plus grande partie de la variation dans la distribution du zooplancton en août qu’en mai.

Évidence génétique de populations sympatriques de la perchaude (Perca flavescens) dans le Lac Saint-Pierre

La perchaude (Perca flavescens) constitue une ressource socioéconomique de grande importance dans le Lac Saint-Pierre (Québec, Canada). Bien que ce lac fluvial soit désigné réserve de la biosphère par l’UNESCO, le statut de la perchaude est préoccupant. Afin de permettre à l’espèce de persister en fonction des diverses pressions anthropiques, il est important de comprendre sa dynamique populationnelle et les mécanismes qui en sont responsables. La perchaude est connue pour sa philopatrie ; le fait de toujours se reproduire à son site de naissance peut entraîner la subdivision d’une espèce en de multiples populations, où chacune pourra être pourvue d’adaptations locales distinctes. Il est possible d’étudier ces processus à l’aide des signaux génétiques associés à la reproduction des individus. Toutefois, une faible différentiation génétique entre les populations du Lac Saint-Pierre est envisagée en raison de la colonisation récente du système (moins de 8000 ans). L’objectif de cette étude est de déterminer s’il existe plusieurs populations de perchaude dans le Lac Saint-Pierre. Les simulations réalisées ont révélé que l’utilisation de marqueurs AFLP (amplified fragment length polymorphism), permettant une analyse globale du génome, affiche une meilleure détection de la différentiation des populations que celle des marqueurs microsatellites. Afin d’associer les individus à leur site de naissance, la méthode d’AFLP et des microsatellites ont été utilisées sur des larves capturées suite à l’éclosion des oeufs. Trois analyses distinctes d’AFLP ont indiqué une corrélation entre la composition génétique des individus et des sites géographiques, confirmant ainsi la présence de plusieurs populations sympatriques dans le Lac Saint-Pierre, découlant vraisemblablement de la philopatrie de l’espèce. L’absence de différentiation génétique relatée par les marqueurs microsatellites vient confirmer l’importance du choix des marqueurs génétiques. Bien que la différentiation génétique observée soit relativement faible, la gestion de la perchaude devrait tenir compte de la dynamique des populations distinctes dans ce système.