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- Downwearing rates on shore platforms of different calcareous lithotypesPublication . 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, PauloVertical 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.
- Morphological features and processes in the central Algarve rocky coast (South Portugal)Publication . Moura, Delminda; Albardeiro, L.; Veiga-Pires, C.; Boski, T.; Tigano, EsterMorphological features along the Algarve rocky coast, South Portugal, are identified and described, with an emphasis on shore platforms and notches. The contributions of processes, such as wave attack, chemical weathering and bioerosion, to sculpting the shore platforms are discussed. The preferential localization of shore platforms on sites exposed to waves, and the lack of significant chemical weathering, point to wave erosion as the first-order factor in platform formation, whilst bioerosion/bioprotection, lithology and geological structure determine platform morphological variations. In addition, platforms above the present intertidal zone appear to have a polygenetic evolution, being inherited from former sea-level highstands and currently undergoing chemical weathering. The occurrence of notch features is independent of the degree of exposure to waves, but they mostly occur where the substratum is sand. Hydrostatic pressure appears to be an important factor in the formation of marine caves in the more sheltered sites.
- Quaternary sea level highstands in the Algarve (South Portugal)Publication . Moura, Delminda; Albardeiro, L.; Veiga-Pires, C.; Boski, T.Algarve is the Portuguese southernmost region in which we can distinguish three main domains in the coastal zone. In the west coast, abrupt cliffs are cutting mainly Paleozoic schists and graywackes, prevailing small enclosed beaches with the largest sandy beaches being developed adjacently to the river mouths. In the windward side (west) of the south coast, cliffs were formed essentially into the Mesozoic and Miocene limestones.