Late Miocene reef complexes in the Eastern Mediterranean Basin: cyclicity, sequence stratigraphy and palaeoenvironmental changes in the Messarà Basin (Crete island, Greece)

Late Miocene reefs have been mainly investigated from the western and central Mediterranean Basin (Esteban, 1979; Rouchy et al., 1986; Moissette and Saint Martin, 1992; Pedley and Grasso, 1994; Franseen et al., 1996; Bosellini et al., 2002). The Late Miocene reef complexes from the Mediterranean Basin are characterized by a low diversity with the dominance of the genus Porites. A coral reef complex dominated by Porites has been recently discovered in the Neogene Messarà Basin (Crete Island, Greece). This basin developed as a consequence of the extensional tectonics that, starting from the Serravallian, affected the Cretan mobile-belt and gave rise to the formation of the Aegean Basin. The Porites reef complex of the Messarà Basin provides new data to improve the palaeogeographic distribution map of the Mediterranean reefs during the Late Miocene.The coral reef complex of the Neogene Messarà Basin developed in a siliciclastic-dominated depositional system and represents the first occurrence of marine deposits in the Neogene succession of southern Crete. The coral reef complex overlies continental deposits consisting of coarse- and fine-grained alluvial sediments with hydromorphic soils and rests below fine- to medium-grained Late Miocene shelf deposits with molluscs, scaphopods, spicule of sponges, planktonic and benthonic foraminifers.The coral reef complex of the Messarà Basin starts with a reef-building assemblage that consists of subspherical colonies of Siderastrea and Tarbellastraea, together with Porites in massive colonies and some columnar morphs. Above this first bioherm, at least nine low diversity coral reefs have been observed. These latter are mainly characterized by branching Porites colonies and are cyclically separated by coarse-grained fan delta deposits. As a consequence of relative sea-level changes, the coral reef complex of the Messarà Basin developed in a mixed sedimentation system with marked partitioning in the siliciclastic and carbonate deposition. A well-developed cyclicity and a long-term aggradational stacking pattern characterize this coral reef complex. Each elementary cycle starts with coarse-grained delta deposits, which are related to lowstand conditions, and passes upsection to a Porites reef building. The coral reefs grew during relative sea-level rises and highstands, whereas during the subsequent relative sea-level drop the coral reef underwent erosional processes responsible of their truncation. The relative sea-level lowstand condition controls both the genesis of the erosion surface at the top of each cycle and the distribution of the siliciclastic sediments into the basin, advancing the delta front basinwards. In the observed cyclicity of the coral reef complex of the Messarà Basin, lowstand, transgressive and highstand conditions revealed by each cycle show relative proportions that seem to be mainly tectonically controlled. In some cases, the vertical facies distribution within the reef-building assemblages shows higher-frequency cycles (parasequences?) induced by low relative sea-level fluctuations