Browsing by Author "Pais, João"
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- Geochemistry and mineralogy of the Lower Cretaceous of the Lusitanian Basin (western Portugal): Deciphering palaeoclimates from weathering indices and integrated vegetational dataPublication . Dinis, Pedro A.; Dinis, Jorge L.; Mendes, Mário Miguel; Rey, Jacques; Pais, JoãoThe present study investigates the climatic influence on the geochemistry and mineralogy of the Lower Cretaceous succession of the Ericeira region (Lusitanian Basin, western Portugal). Palaeoclimatic conditions are inferred from a combination of weathering indices and independent palynological and palaeobotanical data. A composite weathering intensity index is computed from selected geochemical and mineralogical data. The concentrations of some elements (Co, Ni, Sc, Th, V, Y, Zn, Zr) indicate variable contributions of sediments from the Lusitanian Basin margin and Iberian hinterland. It is demonstrated that the weathering intensity values are largely influenced by source area geology. The increases in weathering intensity following major unconformities (Late Barremian and Late Aptian) are partially attributed to the arrival of detritus from an evolved regolith sequence in the Iberian hinterland. A combined analysis of independent proxies is found necessary to conveniently discern the roles played by distinct processes on the weathering intensity and investigate the palaeoclimatic conditions. (C) 2015 Academie des sciences. Published by Elsevier Masson SAS. All rights reserved.
- Miocene dinoflagellate cyst assemblages: preliminary correlation between the Lower Tagus and Algarve Basins (Portugal)Publication . Castro, Lígia; Borges, Marisa; Pereira, Zélia; Fernandes, Paulo; Pais, JoãoBiostratigraphic studies of several sections and a borehole (Belverde) of the Lower Tagus Basin, based on Miocene dinoflagellate cyst assemblages, have allowed a detailed stratigraphic investigation to be conducted. Assemblages are very diverse and abundant and can be used as important biostratigraphic guides. Recently, a palynostratigraphic study based on dinoflagellate cysts was conducted in two offshore wells, Ruivo-1 and Corvina, located in the Algarve Basin (southern Portugal). The recovered dinoflagellate assemblages are less abundant and diverse than those obtained in the Lower Tagus Basin. New inferences are made regarding the correlation between the dinoflagellate cysts known from the Lower Tagus Basin with the assemblages recently recovered from the Algarve Basin. Species of selected dinoflagellate cyst assemblages recovered are similar in both basins. Continuing progress with these new palynological studies and biostratigraphic data will help to refine knowledge of and correlations between Portuguese Miocene deposits.