Nicola Perilli

Late Cretaceous flysch deposits of the Northern Apennines, Italy: age of inception of orogenesis-controlled sedimentation

Abstract Calcareous nannofossils have proved to be very effective in determining the age of Cretaceous flysch sequences of the Northern Apennines. Here, we focus on the beginning of flysch sedimentation, which replaced previous pelagic deposition during the Late Cretaceous convergence stage. In all the examined sequences an early to late Campanian age has been determined for the bases of the flysch formations, implying an essentially synchronous start of orogenesis-controlled sedimentation within the Ligurian Apenninic (Ligurian) Ocean Basin. Data obtained from the siliciclastic turbidite sequence (Vat Lavagna/Mt. Gottero Sandstones) overlying Jurassic ophiolites and sedimentary cover, indicate continuous sedimentation from earliest Campanian to early Paleocene. Thus, either a forearc or ‘dormant trench’ tectonic setting seems to be required for this sequence. Regarding the calcareous Helminthoid Flysch, a minor diachrony in the basal ages suggest a general younging from south to north. The onset ages of flysch sedimentation range from early Campanian (Southern Tuscany Flysch), to early-middle Campanian (Mt. Caio/Ottone Flysch), to latest Campanian (S. Remo, Mt. Antola, Mt. Cassio, Mt. Caio/Orocco Flysch). This diachrony could be the consequence of Late Cretaceous-early Tertiary transcurrent tectonics in the Apenninic Basin and/or of multiple source areas (from both the European/Iberian and Adriatic margins). These tectonic implications are in agreement with the kinematic evidence of a transpressional regime along the Iberian/Adriatic plate boundary (Apenninic sector) during the Late Cretaceous.

STRATIGRAPHY OF THE CAPORALINO-SANT’ANGELO UNIT: A FAKE JURASSIC-EOCENE SUCCESSION OF THE “ALPINE” CORSICA

This paper aims to provide new insights on the Caporalino-Sant’Angelo Unit outcropping north of Corte, in the Caporalino-Omessa area (NE Corsica). It belongs to the stack of the units from the “Alpine” Corsica, which overlies the “Hercynian” Corsica basement and its sedimentary cover. Based on a geological mapping, a refined lithostratigraphy and new datings, the Caporalino-Sant’Angelo Unit is a fake Middle Jurassic-Middle Eocene succession, sedimented on the European continental margin, because it is a Middle Eocene clastic wedge, accumulated in a synorogenic compressive basin located between the European distal continental margin and the deforming “Corsican” accretionary wedge. This basin received the siliciclastic input from the “Hercynian” Corsica basement, and the carbonatic input derived from the sedimentary cover of tectonic units, subsequently involved into the complex “Corsican” accretionary wedge.

CHRONOSTRATIGRAPHIC FRAMEWORK OF THE EXTERNAL LIGURIAN UNITS (LATE CRETACEOUS, NORTHERN APENNINES, ITALY) BASED ON CALCAREOUS NANNOFOSSILS

The study of calcareous nannofossil assemblages recovered from the External Ligurian Units allows us (1) to reconstruct the distribution patterns of selected Late Cretaceous taxa; (2) to identify the biohorizons helpful in recognizing and characterizing the standard zones of Sissingh (1977); some of which have been grouped; and (3) to propose a synthesis of the ages achieved until now for the External Ligurian Units. According to the available dataset; rooted on published and unpublished data; the here proposed biostratigraphic scheme is based on 24 age-indicative taxa and 16 first occurrences; and its biostratigraphic resolution is comparable with the resolution of the scheme of Sissingh (1977); only considering FOs. Calcareous nannofossils are hence a fossil group useful to furnish a new and more complete chronostratigraphic framework of the main External Ligurian Units; helpful to better constrain the tectono-sedimentary and the geodynamic evolution of the Western Tethys Domain.

CALCAREOUS NANNOFOSSIL BIOSTRATIGRAPHY OF PALEOCENE TO MIDDLE EOCENE SUCCESSIONS (TERTIARY FLYSCH AUCTT.) OF THE NORTHERN APENNINES

An accurate biostratigraphic study of the Paleocene-middle Eocene calcareous nannofossils was performed on the turbiditic successions that characterize the Northern Apennines Mt. Caio, Farini d’Olmo, Mt. Sporno and Mt. Penice Units, belonging to the “Tertiary Flysch Auctt .” and referable to the External Ligurides. This geologic complex accumulated in a link key area, located between the oceanic Ligure-Piedmontese domain and the Adria continental margin. The reference biostratigraphic scheme used in the study is the recently published calcareous nannofossil biozonation proposed for the Paleogene by Agnini et al. (2014). The obtained biostratigraphic and chronostratigraphic data suggest that further investigation is needed to clarify the tectono-sedimentary evolution and to unravel the complex architecture of the External Ligurides.