Cyclostratigraphy of a carbonate platform as a tool for high-precision correlation

Mesozoic Carbonate Platforms of Southern Italy are thick (> 3000 m) and well-stratified bodies, uplifted by the Late Tertiary-Quaternary deformation of the Northern Gondwanian Continental Margin. They formed mostly in the shallow ramp, open to restricted lagoon and peritidal/supratidal settings, and show a prevailingly cyclic organization, consisting of m-scale shallowing upward units. We think that this cyclicity is demonstrably controlled by the Earth's orbital perturbations (individual cycle duration, hierarchical organization, numerical analysis of their sedimentological and petrophysical features). The genetic mechanisms of the cyclicity have a climatic dictator (allocyclicity), that is coupled with eustatic oscillations evidenced by features related to subaerial exposure, ranging from microkarst to more mature karst and paleosoils. Exposure features are widespread at the top of the cycles, even when these units are formed by only subtidal deposits, suggesting eustatic control. This paper presents a study of three sections of the Aptian in the Campania region of Southern Italy. Here, a total of congruent to 250 m has been studied at a cm scale. Sections include Serra Sbregavitelli (Central Matese Mountains, congruent to 160 m, Upper Aptian-Lower Albian); Monte Faito (Sorrento Peninsula, congruent to 55 m, Upper Aptian-Lower Albian), and Monte Tobenna (Picentini Mountains, congruent to 35 m, Upper Aptian), the latter two outcropping congruent to 100 km SSE of the former. The three sections have a hierarchical organization composed of elementary cycles in turn grouped in bundles and superbundles, that have been related respectively to the Earth's short and long orbital eccentricity oscillation, while the elementary cycles mostly appear to correspond to the precession or to a combination of precession and obliquity periodicities. In these successions, the stratal pattern shows a dominant aggradational configuration. The thickness of the cycles and their groups appears environmentally controlled, the thicker cycles being those formed in more open marine settings and vice versa. If analysed in terms of sequence stratigraphy, we may recognize in the superbundles a transgressive and a highstand system tract that, together with maximum flooding surfaces and sequence boundaries, was used to develop chronostratigraphic diagrams and to identify cycle omissions at the bundle and superbundle level. The number and amplitude of omissions in the successions appear proportional to the environmental conditions: the more restricted the water circulation in their original depositional sites, the more prone they were to cycle omissions. The sections of Monte Tobenna and Monte Faito were punctuated by omissions tone of them at the superbundle level), while in Serra Sbregavitelli, we recognize a smaller number of gaps, not reaching the superbundle level. Lower-frequency oscillations (800-2000 k.y,) are also evident and suggest a long-term eustatic oscillation of the same periodicity during the lower Cretaceous. Based on the hierarchical organization of the cyclic successions analysed and taking into account the recognized omissions, we have correlated the Serra Sbregavitelli Section (SSS) with the two distant sections of Monte Tobenna (corresponding to the lower SSS) and of Monte Faito (corresponding to the upper SSS). Using appropriate biostratigraphic markers. a correlation appears possible at the scale of bundles of cycles (congruent to 100 k.y. and sometimes also at the elementary cycle level (less than or equal to 50 k.y.). (C) 1999 Elsevier Science B.V. All rights reserved.