Calibration of early-middle Toarcian nannofossil events based on high-resolution ammonite biostratigraphy in two expanded sections from the Iberian Range (East Spain)

This work deals with refined nannofossil biostratigraphy in two well-docume nted lower-middle Toarcian sections, in the Iberian Range. The sampled shal low carbonate ramp deposits belong to the Turmiel Fm. and consist of an alt ernation of marls and limestones. Both lithologies yield common and well-pr eserved ammonite assemblages, which provide a refined ammonite biostratigra phic framework. A significant calcareous nannofossil composition change has been recognized within the Serpentinus Zone, and a useful succession of na nnofossil events has been calibrated to the ammonite biostratigraphy. This succession includes: FO of Lotharingus sigillatus (Mirabile Subzone); LO of Mitrolithus jansae (Semicelatum Subzone); FO of Cavinolithus cantaluppii ( Strangewaysi Subzone); LOs of Biscutum grande and Biscutum finchii (lower p art of the Serpentinus Zone); FO of Carinolithus superbus (Strangewaysi-Fal ciferum boundary); FO of Lotharingius velatus (Falciferum Subzone); FOs of Discorhabdus striatus and Discorhabdus ignotus (Serpentinus-Bifrons boundar y) and "acme end" of Lotharingius hauffii (Variabilis-Illustris boundary). In the studied sections, the composition changes, the biohorizons recognize d and their succession are closely comparable with other early-middle Toarc ian Boreal sections. (C) 2000 Elsevier Science B.V. All rights reserved.