The Project PTDC/CTE-GIX/098968/2008 - High resolution stratigraphy of the Lower Jurassic organic-rich marine series in the Lusitanian Basin (Portugal): Initial expectations and results

Abstract

Apresenta-se neste trabalho uma caracterização e os principais resultados do Projecto “Estratigrafia de alta resolução das séries marinhas ricas em matéria orgânica do Jurássico Inferior da Bacia Lusitânica”, financiado pela Fundação para a Ciência e Tecnologia (Portugal). Este projecto centrou-se numa análise estratigráfica multidisciplinar baseada num vasto conjunto de parâmetros bióticos e abióticos da sucessão margo-calcária rica em matéria orgânica do Jurássico Inferior da bacia, envolvendo sete objetivos principais: 1. Análise sedimentológica (mineralógica, textural e composicional) e sequencial da sucessão hemipelágica do Jurássico Inferior (Sinemuriano superior–Toarciano); 2. Precisões biostratigráficas a partir do registo de amonóides do intervalo compreendido entre o Sinemuriano superior e o Pliensbaquiano superior; 3. Análise paleontológica e paleoecológica da macrofauna bentónica (fundamentalmente braquiópodes e bivalves); 4. Análise biostratigráfica, taxonómica e paleoecológica da fauna de ostracodos (Sinemuriano–Toarciano); 5. Análise quimiostratigráfica baseada principalmente nos isótopos estáveis de carbono (Sinemuriano–Pliensbaquiano); 6. Análise geoquímica e de petrografia orgânica (carbono orgânico total, pirólise Rock-Eval e biomarcadores) do Sinemuriano–Pliensbaquiano; 7. Análise dos padrões de variação dos raios gama (Sinemuriano–Toarciano.This work presents the main results of the Project ”High resolution stratigraphy of the Lower Jurassic organic-rich marine series in the Lusitanian Basin (Portugal)”, supported by the Portuguese Foundation for Science and Technology. This project was focused on a multidisciplinary stratigraphic analysis based on the study of a range of biotic and abiotic parameters of the Lower Jurassic marl–limestone succession rich in organic matter, embracing seven main objectives: 1. Sedimentological (mineralogical, textural and compositional) and sequential analysis of the whole Lower Jurassic hemipelagic succession (Upper Sinemurian–Toarcian); 2. Ammonite biostratigraphic precisions of the Upper Sinemurian and Upper Pliensbachian; 3. Palaeontological and palaeoecological analysis of the benthic macrofauna (especially brachiopods and bivalves); 4. Biostratigraphical, taxonomic and palaeoecological analysis of the ostracod fauna (Sinemurian–Toarcian); 5. Chemostratigraphic analysis based mainly on carbon stable isotopes (Sinemurian–Pliensbachian); 6. Organic geochemical and petrographic analysis (total organic carbon, palynofacies, Rock-Eval pyrolysis and biomarkers) of the Sinemurian–Pliensbachian; 7. Vertical variation patterns of gamma-ray analysis (Sinemurian–Toarcian). Besides the new results in each specific scientific domain (for example, biostratigraphy, palaeoecology, sedimentology, sequence stratigraphy and cyclicity, chemostratigraphy and organic geochemistry), the integration of all data, in several cases at highresolution level, allows emphasizing the achievement of two main transverse goals: the improvement of the stratigraphy and sedimentary knowledge of the Lower Jurassic series of western Iberia margin, with implications in the palaoenvironmental and palaeoceanographic interpretations of the Tethyan pre-Atlantic basins dynamics and global correlation; taking into consideration the huge number of organic geochemical parameters analyzed, the results of this research contributed significantly to understand the role of the different Sinemurian and Pliensbachian organic-rich intervals as potential hydrocarbon generation sources (quality of organic matter and maturation).Depto. de Geodinámica, Estratigrafía y PaleontologíaFac. de Ciencias GeológicasTRUEFondo Europeo de Desarrollo Regional (COMPETE- FEDER)Fundação para a Ciência e a Tecnologia (FCT)pu