Mesozoic early Tertiary passive margin evolution of the Pindos ocean (NW Peloponnese, Greece)

Sediment-starved deep-water slope/basin facies of passive margins are of particular interest as they record an interplay of processes, including plate tectonic evolution, elastic sediment input, pelagic deposition and relative sea-level change. In the past, insights have come from deep-sea drilling of non-emplaced passive margins (e.g. eastern U.S.A.), and from preserved sequences within sutured units, e.g. the Tethyan and Iapetus orogenic belts. Deep-water passive margin successions discussed here represent an excellent example of a relatively sediment-starved slope/basin setting related to the margin of a microcontinent within the Neotethyan ocean in the eastern Mediterranean region. Lithologies are preserved as a series of thrust sheets formed during suturing of the Neotethys ocean. Thrusting resulted in regular in-sequence thrusting, such that the original slope-margin setting can be restored with confidence. Compared to other Tethyan passive continental margin/abyssal successions (e.g. Oman), these sedimentary rocks retain remarkable structural coherence, allowing exceptionally detailed three-dimensional reconstructions of facies patterns and palaeoceanographic conditions. The sedimentary successions belong to the Pindos Zone of western Greece (Pindos Group) and comprise deep-water carbonate, siliciclastic and siliceous rocks, ranging in age from Late Triassic to Eocene. These rocks accumulated along the western margin of a small Neotethyan oceanic basin (i.e. Pindos ocean), separating the continental blocks of Adria (Apulia) and Pelagonia. The oldest sediments comprise disrupted siliciclastic turbidites, largely derived from a metamorphic source to the west and deposited on young oceanic basement. From the Late Triassic to latest Maastrichtian, variable thicknesses of hemipelagic carbonate and proximal carbonate debris flows accumulated in westerly areas, while mainly hemipelagic carbonate and more distal calciturbidite were deposited further east. This pattern was interrupted by an extended period of siliceous, radiolarian-dominated sedimentation during the Aalenian to Tithonian (Jurassic). From latest Maastrichtian onwards, progressive closure of the Pindos oceanic basin is recorded by a gradual change in sediment composition from dominantly carbonate deposition, supplied from the Gavrovo-Tripolitza carbonate platform to the west, to siliciclastic sediment derived from the north and east. During the Eocene/Oligocene, eastward subduction of the Pindos ocean resulted in deep-sea sedimentary lithologies being detached from their oceanic igneous basement as an accretionary prism and emplaced westwards onto the adjacent carbonate platform, ending up as a series of thin-skinned thrust sheets. (C) 1998 Elsevier Science B.V. All rights reserved.