Cretaceous anoxic events in the argilliti e radiolariti di Campomaggiore unit (Lagonegro-Molise basin, southern Italy)

In the Basilicata region (southern Apennines) a Cretaceous clayey succession, intensely tectonized, outcrops. This succession, here named argilliti e radiolariti di Campomaggiore, has a thickness of about 200 metres, is part of a tectonic unit, here named Vaglio di Basilicata tectonic unit, and belongs to the paleogeographic domain of the Lagonegro-Molise basin. A detailed stratigraphy and a preliminary facies analysis have been carried out, and several samples have been collected along two stratigraphie sections in order to obtain biostratigraphic, sedimentological and geochemical informations. The succession has an age ranging from Late Valanginian (?) to Turanian, and can be correlated partly to the Flysch rosso formation. The succession, made up of varicoloured siliceous clayshales/claystones and mudstones, is characterized by the occurrence at different heights of at least five organic carbon-rich blackish horizons. The latter contain several layers of black shales/oil shales with a TOC (Total Organic Carbon) content ranging from 20% up to about 42% w.t. All these horizons could be related to Oceanic Anoxic Events (OAE) that occurred in these very time intervals. In particular, the first horizon (CAE1) belongs to the lower part of the succession which has an age variable from Late Valanginian (?) to Early Aptian, the second horizon (CAE2) is Aptian-Early Albian in age, whilst the successive two horizons (CAE3, CAE4) are dated Early-Middle Albian. Unfortunately, these data are insufficient to establish to which of the already known anoxic events the studied horizons could be equivalent (i.e. Selli Level-Early Aptian=OAE1a; 113 Level-Late Aptian, Urbino and Monte Nerone levels-Early Albian=OAE1b). Finally, the last horizon, Cenomanian-Turonian in age, and occurring in the upper part of the succession, is confirmed to be equivalent to the Bonarelli Horizon, corresponding to the worldwide Second Oceanic Anoxic Event (OAE2). The entire succession is coeval with Maiolica, Marne a Fucoidi and Scaglia Bianca formations, outcropping in central and northern Apennines and southern Alps, in which Selli, 113, Urbino, Monte Nerone and Bonarelli horizons were recognized. All the data allow us to hypothesize that the Lagonegro-Molise basin, the Umbria-Marche basin and the Lombardy basin experienced a similar palaeogeographic and palaeoceanographic setting.