Onset of an Aptian carbonate platform overlying a Middle-Late Jurassic radiolaritic-ophiolithic mélange in the Mirdita Zone of Albania

Abstract

Late Jurassic and Early Cretaceous carbonate sediments of different age and facies, form the post-emplacement settings on top of the Mirdita Ophiolite Zone in northern Albania. They seal the early Late Jurassic emplacement of the ophiolite knappes, are the only datable relics overlying the ophiolites in the Late Jurassic - Early Cretaceous, aiding the evaluation of the different tectonic movements associated with uplift and erosion as well as sea-level fluctuations during that time span. These carbonates overlie ophiolite-derived clastics very often as shallowing-upward sequences. One of the largest shallow-water platforms is the Mali I Shenjtit platform, previously assigned to the Barremian-Aptian. A well-preserved section at the base of the platform can be ascribed to the Early-Late Aptian based on orbitolinid foraminifera together with dasycladalean algae. This carbonate platform is the youngest preserved Early Cretaceous platform in Albania, but was largely eroded away. Late Cretaceous shallow-water rudist limestones are widespread and preserved in the Dinaride-Albanide-Hellenide realm directly above an eroded older basement. Therefore, this Aptian platform is very important for the reconstruction of the Early Cretaceous palaeogeography in the northwestern Neotethyan realm. In addition, the stratigraphic ranges of characteristic Aptian orbitolinid foraminifera, Rectodictyoconus giganteus SCHROEDER and Mesorbitolina texana (ROEMER), are discussed on the basis of these results.