Podstawy ekostratygrafii ichtiofaunistycznej osadów oligocenu-wczesnego miocenu basenu zewnętrznych Karpat Polskich

The paper presents the results of an analysis of ichthyofaunal variability throughout the section of the Menilite-Krosno Series (MKS) in the Outer Carpathians of Poland. The studied tanathocoenoses were formed at the bottom of a more than 2,000 m deep northern basin of the Tethys, being largely represented by the continental rise and bottoms of its narrow furrows, and - to a lesser degree - the continental slope and slopes of a submarine high. Lateral variability of statististically representative assemblages of tanathocoenoses hosted in thin, isochro- nous horizons is interpreted as a result of both local changes of ichthyocoenoses and the influence of post-mortem relocation of fishes that mainly dwelled the shelf and upper continental slope. Vertical variability, in turn, is considered as a resulting from changeable conditions of the ecological environment, the input and outflow of taxa whose evolution proceeded in the Indo-Pacific area, and the species extinction. Changeability of ichthyofauna within a ca. 16-m.y.-long interval made it possible to document and formally describe 9 zones and 4 subzones of ichthyofauna of ecostratigraphic character. These zones comprise index, representative and accompanying taxa that belong to different ecological groups. Conceptual models of the origin of ichthyofaunal assemblages of individual zones are presented. It is suggested that the origin of assemblage differentiation resulted from the appearance and disappearance of the oxygen minimum zone in the water column, global and local sea level changes, topography of the basin bottom, as well as final basin infilling by sediments of submarine fans. The described and preserved collection of fossil Carpathian fishes, housed at the Department of Palaeozoology of the University of Wrocław, requires further specialized palaeontological studies in order to reconstruct a more complete composition of the Oligocene-Early Miocene ichthyofauna

Insights into the Cenozoic geology of North Beirut (harbour area): biostratigraphy, sedimentology and structural history

The biostratigraphy and sedimentology of the outcrops and bedrock recently exposed in archaeological excavations around the harbour area of Beirut (~5 km²) unlock the geological and structural history of that area, which in turn are key to understanding the hydrocarbon and hydrogeological potential of the region. A key location (Site 2) of a studied outcrop section and newly uncovered bedrock is on the northern foothill cliff of East Beirut (Achrafieh). The outcrop section of carbonates is of Eocene beds overlain by conformable Miocene beds. The excavation of the slope bordering the outcrop uncovered a bedrock section of an early Pliocene shoreline of carbonate/siliciclastic sands at its base and topped by a beach-rock structure. The early Pliocene age of the shoreline section is dated by an assemblage of planktonic foraminifera that includes Sphaeroidinellopsis subdehiscens, Sphaeroidinella dehiscens and Orbulina universa. The Eocene carbonates of Site 2 extend the coverage of the previously reported Eocene outcrops in the harbour area. They form a parasequence of thin-bedded, chalky white limestones that includes the youngest fossil fish deposits in Lebanon ( Bregmaceros filamentosus). The deposits are dated as early Priabonian by their association with the planktonic foraminiferal assemblage of Porticulasphaera tropicalis, Globigerinatheka barri, Dentoglobigerina venezuelana, Globigerina praebulloides, Turborotalia centralis and Borelis sp. The Middle Miocene carbonates that conformably overlie the early Priabonian, parasequence include a planktonic foraminiferal assemblage of Globigerinoides trilobus, Orbulina universa and Borelis melo. Elsewhere, in the harbour area, the preserved Eocene limestones are also overlain by conformable Miocene carbonate parasequences of Langhian–Serravallian age. Younger argillaceous limestone beds of the Mio/Pliocene age occur in the eastern central part of the harbour area and enclose an assemblage of Truncorotalia crassaformis, Globorotalia inflata and Orbulina universa. The three markers of old and recently raised structural blocks in the harbour area are a Lutetian/Bartonian marine terrace in the south west corner, a lower Pliocene shoreline carbonate section in the north east side and a Holocene raised beach of marine conglomerates in the north east corner of the area. The locations of these paleo-shorelines, less than 2 km apart, indicate a progressive platform narrowing of North Beirut since the Paleogene. This study underpins the geological complexity of the region and contributes to understanding the underlying geology, which will be needed for future regional archaeological, hydrocarbon and hydrogeological exploration