Strontium stratigraphy of the Burdigalian transgression in the Western Mediterranean

摘要

A ~(87)Sr/ ~(86)Sr analysis of selected pectinid shells has been performed to refine the stratigraphical framework of the Burdigalian transgressive event. Samples were collected from shallow water successions of the Western Mediterranean area (North-Eastern Sardinia, Southern Corsica, Central Apennines). The Western Mediterranean is the result of the interaction between the European and the African plates. Sardinia and Corsica were extended and rifted apart from the Iberian Peninsula during the opening of the Liguro-Provencal basin, between 30 and 15Ma. In the outcrops of Northern Sardinia and Southern Corsica, Burdigalian deposits nonconformably overlie Varisican granites. In the central Apennines the Burdigalian deposits paraconformably overlie the Cretaceous platform. These are transgressive deposits, characterized by the presence of Miogypsina globulina, which points out early to middle Burdigalian age. The Sr isotope ages indicate that marine transgression in Northern Sardina and Southern Corsica took place between 18.6 and 18.3Ma, which could correspond to the eustatic sea level rise of the Bur3 third-order sequence. In the Central Apennines the Burdigalian transgression was anticipated (18.8Ma) by subsidence input linked to the eastward migration of the orogenic system. This input allowed the Miocene carbonate ramp to develop on the Cretaceous platform substrate, while successive eustatic rise controlled the evolution of the stratigraphical architecture. The following regressive phase is recorded in both the Apennine and Corsica successions. The end of this phase is dated between 17.6 and 17.5Ma and corresponds to sea level drop corresponding to the occurrence of the Mi 1b event. □Burdigalian, pectinids, strontium stratigraphy, transgression, Western Mediterranean.