Microfacies analysis of deep-water breccia clasts: a tool for interpreting shallow- vs. deep-ramp Paleogene sedimentation in Cephalonia and Zakynthos (Ionian Islands, Greece)

The tectono-sedimentary evolution of the western Pre-Apulian zone of the Hellenides is investigated through comparison of the microfacies of clasts from breccia beds within gravity-flow successions of Zakynthos with those of the carbonate ramp of the westernmost part of Cephalonia. After the demise of a Late Cretaceous rimmed platform, the Paleogene successions of the Ionian Islands represent different facies patterns of a carbonate ramp. In western Cephalonia (Lixouri peninsula), different successions suggest the existence of five juxtaposed tectono-sedimentary sectors, remnants of a larger carbonate ramp. In Zakynthos, six distinct sectors with different toe of slope-proximal basin stratigraphic successions were recognized, all affected by a Paleocene-Lower Eocene hiatus, which can be grouped into two tectono-sedimentary units. Through the analysis of successions of the Lixouri peninsula and breccia clasts from Zakynthos, 24 age-constrained and spatially related Upper Cretaceous–Oligocene microfacies types were recognized, illustrating a variety of sedimentary environments. These microfacies were allocated to five different stages in the evolution of a tectono-sedimentary model from down-faulting, through backstepping, uplift and dismantling, to fault-controlled subsidence and finally complete drowning. Various microfacies of the clasts can be correlated to the stratigraphic record of the Lixouri peninsula, whereas others are absent there. Thus an inferred adjacent source terrain, now tectonically obliterated, was likely located west of the present-day Ionian Islands.