Integrated biostratigraphy (Ammonoidea, Foraminiferida) of the Aalenian of the Lusitanian Basin (Portugal): A synthesis

Abstract

This work reports a synthesis of biostratigraphic outputs resulting from over two decades of comprehensive analysis on the expressive stratigraphic record of the Aalenian of the Lusitanian Basin (Western Iberian Margin; Portugal). The rich and diverse ammonite record studied from ten marly and marlylimestones sections, outcropping in different sectors of the basin ranging from distal to proximal facies, has enabled the establishment of a detailed ammonite-based biostratigraphical framework correlated with other basins located around the Iberian Plate. The study of the benthic foraminiferal assemblages occurring in the basin at the same time interval has allowed the establishment of a biostratigraphic scale based on microfossils accurately calibrated with the ammonite record, an important tool in log interpretation in the context of hydrocarbon exploration activities in sedimentary basins of Jurassic age. The corresponding biostratigraphic units are characterized, as well as the bioevents recognized in the benthic foraminiferal record, which represent another additional proxy of local and/or regional rank that can be used to determine both the age and depositional environment assigned to core samples.