A multidisciplinary approach to global correlation and geochronology. The Cretaceous shallow-water carbonates of southern Apennines, Italy

Detailed sedimentological and carbon-isotope data have allowed us to propose a high-resolution regional correlation between four Lower Cretaceous carbonate-platform successions, Early Aptian to Early Albian in age cropping out in the southern Apennines. These successions, formed in open to restricted lagoonal and peritidal/supratidal settings, reveal a high-frequency cyclic recurrence of depositional and early meteoric (karstic and/or pedogenetic) features. The latter are normally superimposed on subtidal deposits, suggesting that the above cyclicity may be linked to sea-level changes. In the studied sections, elementary cycles are grouped into bundles which in turn are grouped into superbundles. While bundles and superbundles appear to be related to the Earth's orbital short- and long-eccentricity signal respectively, elementary cycles seem to record either the precession or a combination of the precession and obliquity periodicity. Moreover, the stacking pattern of the orbitally controlled cycles suggests that they are superimposed on lower-frequency sea-level fluctuations (Transgressive/Regressive Facies Trends). The delta 13C curves, established throughout the sections, show the same carbon-isotope pattern as the time-equivalent pelagic strata (two positive carbon-isotope episodes separated by an interval with lower carbon-isotope values). On the basis of this correspondence, and integrating the cyclostratigraphy and the carbon-isotope stratigraphy with the sequence-stratigraphy, we propose a high-precision regional correlation and a chronostratigraphic chart and suggest a time-duration of 7.8 my for the studied interval. Moreover, on the basis of sequence-stratigraphy and isotope geochemical criteria, and using our orbital chronostratigraphy as a reference-frame, a correlation with current global scales is here proposed.