Orbital cyclostratigraphy and sequence stratigraphy of Upper Cretaceous platform carbonates at Monte Sant'Erasmo, southern Apennines, Italy

Microstratigraphic (cm-scale) analysis of a Cretaceous (Santonian) carbonate platform succession (59 m thick) at Monte Sant'Erasmo (southern Apennines) reveals the recurrence of textures and sedimentary structures hierarchically organized in m-thick elementary cycles and groups of cycles (bundles and superbundles); such organization suggests environmental fluctuations of differing rank. A high-frequency climatic and eustatic control related to the orbital perturbations of the Earth can explain the hierarchy of these cycles that compares well with the organization of a slightly older succession (Turonian-Coniacian) outcropping at Monte Tobenna, some 70 ion to the south-east. In the latter case, as well as in several Lower Cretaceous carbonate platform successions of the southern Apennines, hierarchy of cycles as well as numerical analysis of the thickness of every stacked interval, each characterised by specific textural properties (lithofacies), has allowed us to infer specific time values to the various orders of cycles, based on the Earth's orbital periodicities. We suggest that the elementary cycles of Monte Sant'Erasmo were controlled by the precession of the equinoxes, while the bundles and superbundles were forced by the short and long orbital eccentricity, respectively. Moreover, applying sequence stratigraphic concepts, we discuss, at the superbundle level, the sedimentary dynamics of the studied succession in terms of depositional sequences and system tracts. Based on the inferred cycle durations, the Monte Sant'Erasmo section required not less than 2400 ky to form, the average accumulation rate (present day thickness) being c. 21 mm/ky. (C) 1999 Academic Press.