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  • Characterization of the sedimentary environment of the Gilão River Mouth, based on sedimentological and mineralogical analysis
    Publication . Rocha, F.; Boski, T.; Gomes, Celso; Moura, Delminda; Veiga-Pires, C.
    The main objective of this paper is to use the mineralogical composition of the fine and clay fractions of the sediments from the studied borehole to a better characterization of the Gilão Estuary sedimentary environment.
  • Chronology of the sedimentary processes during the postglacial sea level rise in two estuaries of the Algarve coast, Southern Portugal
    Publication . Boski, T.; Camacho, Sarita; Moura, Delminda; Fletcher, William; Wilamowski, A.; Veiga-Pires, C.; Correia, Victor; Loureiro, C.; Santana, Paulo
    Four profiles of estuarine sediments obtained from boreholes drilled in the Algarve, Southern Portugal were studied in order to reconstruct the process of sediment accumulation driven by the postglacial sea level rise. In addition to the sedimentological analysis, the Foraminifera Index of Marine Influence (FIMI) permitted assessment of the nature and organization of sedimentary facies in the BelicheeGuadiana and Gilão-Almargem estuaries. The Beliche- Guadiana CM5 and Almargem G2 profiles accumulated in a sheltered environment, with the former presenting an almost continuous record of the sea level rise since ca 13 000 cal yr BP. The G1 and G3 profiles from the Gilão-Almargem area represent a more discontinuous record of the last 8000 years, which accumulated in the more dynamic environment of an outer estuary. The integration of all radiocarbon ages of dated levels, led to an estimate of sediment accumulation rates. Assuming a constant position of the sediment surface with respect to the tidal range and a negligible compaction of sediment, the sea level rose at the rate of 7 mm yr ^-1 in the period from 13 000 to 7500 cal yr BP. This process slowed down to ca 0.9 mm yr 1 from 7500 cal yr BP until the present. The marked historical change in the rate of sediment accumulation in these estuaries also occurred with the accumulation of organic matter and is, therefore, important data for global biogeochemical models of carbon. The main obstacle to obtain higher temporal resolution of the sedimentary processes was the intense anaerobic respiration of organic matter via sulphate reduction, which did not allow any accumulation of peat and, furthermore, led to erasure of the palaeontological record by acid formed from the subsequent oxidation of sulphides.
  • Variação do nível do mar na costa algarvia durante o Plistocénico
    Publication . Albardeiro, L.; Moura, Delminda; Veiga-Pires, C.; Boski, T.
    São objectivos do presente trabalho, o estudo da evolução da morfologia costeira durante o Plistocénico Superior, a correlação de plataformas de abrasão marinha com a estratigrafia isotópica marinha e a utilização da informação recolhida como uma ferramenta de gestão costeira.
  • Ensaio de caracterização do meio sedimentar do estuário do Rio Gilão, com base em análises de parâmetros mineralógicos e sedimentológicos
    Publication . Rocha, F.; Boski, T.; Gomes, Celso; Moura, Delminda; Veiga-Pires, C.
    Foram realizadas análises sedimentológicas e mineralógicas ao sedimento recolhido numa sondagem realizada no estuário do Rio Gilão próximo do Arraial Ferreira Neto. A sondagem atingiu o substrato rochoso pré-holocénico aos 18 m de profundidade.
  • Fronteira Pliocénico-Plistocénico: estudo de caso nas formações detríticas do Algarve
    Publication . Moura, Delminda; Boski, T.; Veiga-Pires, C.; Mariano, J.
    Na região do Algarve, a sedimentação pós Miocénico foi quase exclusivamente detrítica e a escassez de horizontes cronológicos torna muito difícil posicionar a fronteira Neogénico-Quaternário (FNQ). Com base na magnetostratigrafia e na interpretação das fácies sedimentares, propõe-se no presente trabalho que seja considerada como FNQ a inversão de polaridade Gauss-Matuyama, uma vez que ocorre no seio de um sistema regressivo que poderá corresponder à instalação de condições de glacial no Hemisfério Norte.
  • Caracterização da evolução do perfil longitudinal das ribeiras do oeste do Algarve - dados preliminares
    Publication . Rodrigues, Bruno; Veiga-Pires, C.; Moura, Delminda; Fernandes, Paulo; Boski, T.
    A actual rede hidrográfica na região do Algarve, devido à proximidade do mar e ao seu contexto tectónico, teve ao longo da sua formação uma forte influência dos efeitos eustáticos, tendo também o clima regional um papel fulcral na incisão do vales actuais a diferentes escalas temporais.
  • Working with spectrophotometry on sedimentary cores from estuaries of south Portugal
    Publication . Veiga-Pires, C.; Mestre, Nélia; Moura, Delminda; Boski, T.
    The study of estuarine sediments to document Late Quatemary coastal changes had always benn of extreme importance, as they reflect the combination of sea-level and sedimentary changes, either at a local, regional or global scale.(...)
  • Downwearing rates on shore platforms of different calcareous lithotypes
    Publication . Moura, Delminda; Gabriel, Selma; Ramos-Pereira, Ana; Neves, Mário; Trindade, Jorge; Viegas, José; Veiga-Pires, C.; Ferreira, Óscar; Matias, Ana; Jacob, J.; Boski, T.; Santana, Paulo
    Vertical lowering (downwearing) of shore platform surfaces is a very important mechanism in their morphological evolution albeit much remains incompletely understood. The efficacy of mechanical and chemical weathering acting on a given substrate, together with erosional processes, influences downwearing rates. In order to determine the relationship between lithotypes and downwearing rates, data collected from a Transverse Micro-erosion Meter were obtained for shore platforms of three different calcareous lithotypes (biocalcarenite, calcarenite and carbonated siltstone) along the central Algarve coast (Southern Portugal). Downwearing rates ranged between 0.096 mm year−1 and 1.676 mm year−1 in biocalcarenite and weakly cemented calcarenite, respectively. In addition, physical properties of the rocks comprising the platforms were measured, including uniaxial compressive strength (as determined by the Point Load Test), porosity, and calcium carbonate content. The results show that downwearing depends primarily on the intrinsic properties of the substrate. Porosity, in particular, acts in two ways: (i) it tends to weaken the substrate; and, (ii) it controls the downward extent of the water percolation and therefore the depth of the weathering mantle subject to erosion by waves and currents.
  • Does the glacial/interglacial sea-level changes modulate the atmospheric CO2 variations?
    Publication . Boski, T.; Moura, Delminda; Veiga-Pires, C.; Fletcher, William; Correia, Victor
    It is postulated the rate of the terrestrial organic carbon (OC) retention around the moving ocean/continent interface is strongly affected by the sea-level.
  • Evolução da linha de costa durante a transgressão holocénica: Baía de Armação de Pêra (Sul de Portugal)
    Publication . Moura, Delminda; Albardeiro, L.; Veiga-Pires, C.; Boski, T.
    As zona costeiras são importantes zona húmidas, suporte de ecossistemas cuja conservação depende da estabilidade dos ambientes geológicos litorais. Estes respondem a numerosos factores, entre os quais a variação do nível médio do mar (nmm).(...)