| Popis: |
The Pindos isopic zone of western mainland Greece consists of a series of imbricate thrust slices that contain Mesozoic 'deep-water' sediments and Cenozoic flysch deposits. The thrust stack is overthrust to the west over the Mesozoic platform carbonates of the Gavrovo-Tripolitza zone and is, in turn, overthrust on its eastern edge by the continental margin deposits of the Othris zone and the platform carbonates of the Parnassos zone. Basalts of a probable mid-Triassic age, intercalated at the base of the thrust sequence, are petrographically and geochemically similar to alkaline basalts found in modern rifting environments. The oldest sediments in the zone consist of Late Triassic, white to dark grey, locally pyritic, Halobia limestones and clastic turbidites of terriginous and volcanic provenance. In central parts of the zone these sediments are overlain by latest Triassic to Liassic radiolarian cherts and shales, while in marginal thrust slices they are succeeded by allodapic calcirudites and calcarenites deposited in a system of fans and aprons. These Triassic and Liassic volcanics and sediments (Karpenision Fmn.) are interpreted to reflect the rifting and subsidence of the Pindos basin. The Middle to Late Jurassic sediments (Trikhonis and Athamnos Fmns.) consist of radiolarian cherts and shales deposited both by pelagic settling and by turbidity currents which were generated along the subsiding basin margins and from intrabasinal highs. During the latest Jurassic time central parts of the basin were characterised by pelagic, calpionellid limestones, while allodapic carbonate deposition was restablished along some parts of the basin margins. Radiolarian cherts and shales deposition occurred throughout the zone during the Lower Cretaceous period (Platanos Fmn.), probably in response to renewed subsidence of the basin floor. Volcaniclastic turbidites ocourring within these shales are correalated with melanges of a similar provenance in the Othris zone. These sediments may represent a unique interval of deposition associated with the emplacement of ophiolite over the eastern continental margin (Othris zone) of the Pindos zone. The Late Cretaceous sedimentary facies (Evritania Formation) consist of prograding calciturbidite fans in marginal areas of the basin, and distal turbidites, pelagic limestones and marlstones in central parts of the basin. This facies distribution was disrupted during the Maastrichtian period when tectonic activity in the adjoining zones, and along the basin margins, led first to the deposition of allodapic carbonate in cantral parts of the basin and later to the incursion of siliciclastic 'flysch' turbidites throughout the basin. The sedimentary facies and subsidence patterns of the Pindos sequence suggest that it may have originally been deposited on a mafic, oceanic-type crust, intruded during Triassic rifting. This basement may have been partially consumed during ophiolite emplacement in Lower Cretaceous time, and was completely removed during the accretion and deformation of the Pindos zone sediments in Late Eocene time. |
