The reconstruction of the upper Palaeozoic sedimentary evolution of Western Mediterranean area is suffering for scarce age documentation of its stratigraphic units. This is also the consequence of the metamorphism and deformation they experienced during the Alpine tectonic events. Based on palynology and thermal maturity assessment, we contribute to this issue reporting biostratigraphic and sedimentological results in key-outcrops of the upper Palaeozoic successions of southern Tuscany (Italy), thus offering new data for the Palaeozoic units of the inner Northern Apennines, as well as for their palaeogeographic and palaeotectonic evolution predating the opening of the Alpine Neo-Tethys. This study is focused on the Falsacqua Formation mainly consisting of quartzitic phyllite, sandstone and carbonate, representing the basal succession of two tectonic units exposed in the Middle Tuscan Ridge, and which age attribution was strongly debated in literature and referred either to late Carboniferous-early Permian or Devonian. Palynological data document the first finding of a microflora of middle-late Permian age adding key chronological constraints. This age assignment permits to correlate the Falsacqua Formation with the coeval deposits of southern Tuscany (i.e., Farma and Poggio al Carpino formations) and Elba Island (Rio Marina Formation) that are all characterized by a similar microfloral content. Optical thermal maturity index as Spore Colour Index is around 9 to 10 and suggests a T peak of about 300–350 °C while the Raman spectroscopy on carbonaceous material indicates a T peak around 375 °C for both tectonic units. These data provide new constraints for the maximum T values occurred during syn-collisional metamorphism developed in this sector of the Northern Apennines.
Bibliographical noteFunding Information:
This work was supported by the Research Project of the Department of Physics and Geology ( University of Perugia ) Fondo Ricerca di Base 2017 ( CAPEZBASE2017 ; 2017–2019), Fondo Ricerca di Base 2018 ( SPIRICBAS2018 ) (E.C., Am.Sp.) and PRIN 2017RX9XXXY (S.C.). M.Z. received funding from the Italian Ministry of University and Research (MIUR), through the program PON-AIM (Attraction and International Mobility) – project no. 1815472, Activity 1, line 1. The Raman laboratory analyses (G.V.) at the Department of Earth and Geoenvironmental Sciences, University of Bari (Italy), was funded by Potenziamento Strutturale PONa3_00369 “Laboratorio per lo Sviluppo Integrato delle Scienze e delle TEcnologie dei Materiali Avanzati e per dispositivi innovativi (SISTEMA)”.
The Editor-in Chief of Sedimentary Geology Dr. Catherine Chague (UNSW, Sydney, Australia), Prof. Ausonio Ronchi (University of Pavia, Italy) and an anonymous reviewer are warmly thanked for their constructive remarks that contribute to improving this paper. Mr. Andrea Speziali (Department of Physics and Geology, University of Perugia) is thanked for processing samples for organic matter analysis.
- Northern Apennines
- Organic matter analyses
- Raman spectroscopy