Browsing by Author "Descamps, Gabrielle Sofia"
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- Paleoenvironmental and paleoceanographic changes recorded in the marine and nearshore sediments in the Lower Cretaceous Arrifes sequence, Albufeira, Algarve Basin, PortugalPublication . Descamps, Gabrielle Sofia; Fernandes, Paulo; Gilda, LopesThis project focuses on the Late Hauterivian to Late Barremian sedimentary succession that outcrops at Arrifes, southwest of Albufeira (southern Portugal). The aim is to study the forcing mechanisms (sedimentological, climaBc, oceanographic and biological) that are recorded in the straBgraphic succession of Arrifes. A detailed straBgraphic log of the sequence was established to interpret the different sedimentary facies, their relaBons and evoluBon. This task was necessary to guide the sampling used for geochemical and palynological studies, including the study of palynofacies, and the biostraBgraphic studies of dinoflagellate cysts. The laGer study allowed daBng of the Arrifes succession of Late Hauterivian to Late Barremian age. The deposiBonal age constrained also the paleoenvironmental, paleoceanographic (including eustasy) and paleoclimaBc changes observed in the Arrifes sequence. Geochemical analysis of whole-rock and carbon stable isotopes was also used to characterise paleoenvironmental and paleoclimaBc condiBons. During Lower Cretaceous Bmes, the Arrifes succession experienced shiMs between wet climates in the Late Hauterivian, increasing aridity in the Early Barremian and again wet climates during the Late Barremian. MulBple sea-level fluctuaBons occurred during this Bme interval, but overall the deposiBonal environments were of Bde dominated nearshore carbonate environments. During the peak of transgressive phases, deep water offshore facies were also established. The δ13Corg curve indicates the presence of several moderate negaBve excursions during Barremian Bmes. These excursions are tentaBvely related to the deposiBon of marine organic-rich sediments, mainly induced by oceanographic condiBons of sea-level rises or induced by climaBc consequences such as density straBficaBon or increased conBnental flows to the ocean, rather than deposiBon influenced by an Oceanic Anoxia Event (OAE), since no such event has been idenBfied for Barremian age. However, the Late Hauterivian shows a strong negaBve values of δ13Corg, at the base of the straBgraphic succession, it could be tentaBvely related to the Faraoni OAE (F-OAE). Moreover, the sedimentology, age and geochemical features of the Arrifes succession are similar to the Salema and the Barrancão formaBons located in the western Algarve Basin, and can therefore be correlated which each other.