Integrated stratigraphy of shallow marine Albian strata from the southern Lusitanian Basin of Portugal
Horikx, Maurits; Heimhofer, Ulrich; Dinis, Jorge; Huck, Stefan
published: Apr 1, 2014
ArtNo. ESP026004701004, Price: 29.00 €
Stratigraphic age assignment of Cretaceous shoal-water deposits is notoriously difficult and often hampered by the lack of typical index fossils and the prevalence of sedimentary gaps. Here, we present new bio- and chemostratigraphic data for three sections located in the Lusitanian Basin, Portugal, composed of Albian strata. Sections are correlated and dated using dinoflagellate cyst biostratigraphy, strontium-isotope stratigraphy based on oyster and rudist shells and carbon-isotope stratigraphy. The measured Sr-isotope values from pristine shells are in line with global open marine 87Sr/86Sr values from the Albian. Correlation of the Portuguese C-isotope curve with hemipelagic Albian reference records and the presence of typical Albian dinoflagellate cysts further constrain the age of the different sections. The proximal-marine and thick (∼ 190 m) Sao Julião section serves hereby as reference curve. Correlation with the independently well-dated and more distal Guincho section in the Lusitanian Basin slightly revise the age of the Sao Julião and Magoito sections compared to previously published results. Furthermore, our findings demonstrate the time-transgressive nature of marine deposition in the southern Lusitanian Basin. The onset of marine conditions in the Água Doce Member and the deposition of rudist bearing carbonates of the Ponta da Galé Member are diachronous and started significantly earlier in the southernmost part of the basin compared to the north. In summary, the combined geochemical and biostratigraphic results provide an enhanced time control and slightly revise the age of the sections in comparison to previously published studies while providing lithological descriptions, Sr-isotope derived ages and carbon-isotope records. Furthermore, the carbon-isotope record of Sao Julião can be correlated with Italian (Umbria-Marche Basin) and French (Vocontian Trough) sections and highlights the applicability of shallow marine deposits as chemostratigraphic archives.