Sedimentology and high-resolution sequence stratigraphy of a lower Cretaceous shallow-water carbonate succession from the western Gargano Promontory (Apulia, Southern Italy)

Detailed facies analysis of a lower Cretaceous inner-shelf carbonate succession cropping out in the western Gargano Promontory reveals a complex stacking of depositional sequences. The organization of lithofacies associations in beds and bedsets allowed to identify 43 elementary sequences (41 completely outcropping) grouped in 12 small-scale sequences (10 completely outcropping) forming 4 medium-scale sequences (2 completely outcropping). This hierarchical organization of the sequences has been interpreted as related to composite relative sea-level changes probably driven by the Earth’s orbital perturbations in the Milankovitch frequency band. Sequence stratigraphy concepts have been applied to all hierarchy of sequences; transgressive and regressive trends in vertical stacking of lithofacies and groups of lithofacies as well as the repetition of some diagnostic surfaces or intervals interpreted as sequence boundaries, transgressive surfaces and maximum flooding zones allowed the identification of depositional sequences and related systems tracts. The superposition of relative sea-level changes occurring with different frequencies and amplitudes has been described in terms of accommodation changing through time. It emerges that this interaction leads to the internal variability observed in all orders of sequences. The bulk of the observed succession is made up of deposits formed during medium-scale late transgressive/early highstand periods. During these times, thicker small-scale sequences formed by an higher number of elementary sequences are recorded in the succession suggesting a general gain in accommodation. On the contrary, during medium-scale early transgressive and late highstand periods small-scale sequences are thinner and show a lower number of elementary sequences suggesting a general loss in accommodation.