The Toarcian oceanic anoxic event (ca 183 Ma) coincides with a global perturbation marked by enhanced organic carbon burial and a general decrease in calcium carbonate production, probably triggered by changes in the composition of marine plankton and elevated carbon dioxide levels in the atmosphere. This study is based on high‐resolution sampling of two stratigraphic successions, located in Valdorbia (Umbria–Marche Apennines) and Monte Mangart (Julian Alps), Italy, which represent expressions of the Toarcian oceanic anoxic event in deep‐water pelagic sediments. These successions are characterized by the occurrence of black shales showing relatively low total organic carbon concentrations (compared with coeval strata in Northern Europe), generally < 2%, and low hydrogen indices. On this basis, they are similar to other Toarcian black shales described from the Tethyan region. The positive and negative carbon‐isotope records from the two localities permit a high‐resolution correlation such that ammonite biostratigraphy information from Valdorbia can be transferred to those parts of the Monte Mangart section that lack these fossils. Spectral analyses of δ13Corg values and of CaCO3 percentages from the sedimentary records of both the Valdorbia and Monte Mangart sections reveal a strong cyclic pattern, best interpreted as an eccentricity signal which hence implies a duration of ca 500 kyr for the negative carbon‐isotope excursion. Based on the carbon‐isotope curves obtained, the high‐resolution correlation between the Italian successions and a section in Yorkshire (Northern Europe) confirms the supposition that the apparent mismatch between the dating of the Toarcian oceanic anoxic event in the Boreal and Tethyan realms is an artefact of biostratigraphy.

A revision of the calpionellid bio-chronostratigraphy in Western Sicily (Italy) was carried out, in order to update the taxonomy of this group, through the identification of some genera (Borziella, Longicollaria, Chitinoidella, Dobeniella, Sturiella, Borzaiella and Praecalpionellites) and species (Remaniella catalanoi POP, Remaniella duranddelgai POP, Remaniella colomi POP, Remaniella borzai POP, Remaniella filipescui POP) recorded for the first time in the area. The studied sections, belonging to the Trapanese and Saccense Domains (Western Sicily), include at the base the upper portion of the Rosso Ammonitico Unit (Upper Tithonian), followed by the Lattimusa Formation (Lower Cretaceous). The quantitative and biostratigraphic analysis of the calpionellid assemblages allowed us to identify 13 assemblages and to define some important bioevents for the Upper Tithonian-Valangianian interval. The recorded calpionellid bioevents allowed us to recognize Zone/Subzone schema, which have been correlated with the bio-chronostratigraphy previously proposed for the Western Tethys. RIASSUNTOUna revisione della biostratigrafia a Calpionellidi in sezioni della Sicilia Occidentale ha permesso di aggiornare la tassonomia di questo gruppo, con l'identificazione di generi (Borziella, Longicollaria, Chitinoidella, Dobeniella, Sturiella, Borzaiella e Praecalpionellites) e delle specie (Remaniella catalanoi Pop, Remaniella duranddelgai Pop, Remaniella colomi Pop, Remaniella borzai Pop, Remaniella filipescui Pop) rinvenuti per la prima volta in Sicilia Occidentale. Le sezioni studiate appartengono ai Domini Saccense e Trapanese. Tali sezioni sono caratterizzate alla base dell' Unità Rosso Ammonitico e successivamente dalla Formazione della Lattimusa. L'analisi biostratigrafica e quantitativa delle associazioni a Calpionellidi ha permesso di identificare 13 associazioni e di caratterizzare alcuni eventi principali, nell'intervallo Titoniano superiore-Valanginiano.

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