Provenance of the Bosnian Flysch

Sandwiched between the Adriatic Carbonate Platform and the Dinaride Ophiolite Zone, the Bosnian Flysch forms a c. 3000 in thick, intensely folded stack of Upper Jurassic to Cretaceous mixed carbonate and siliciclastic sediments in the Dinarides. New petrographic, heavy mineral, zircon U/Pb and fission-track data as well as biostratigraphic evidence allow us to reconstruct the palaeogeology of the source areas of the Bosnian Flysch basin in late Mesozoic times. Middle Jurassic intraoceanic subduction of the Neotethys was shortly followed by exhumation of the overriding oceanic plate. Trench sedimentation was controlled by a dual sediment Supply from the sub-ophiolitic high-grade metamorphic soles and from the distal continental margin of the Adriatic plate. Following obduction onto Adria, from the Jurassic-Cretaceous transition onward, a vast elastic wedge (Vranduk Formation) was developed in front of the leading edge, fed by continental basement units of Adria that experienced Early Cretaceous synsedimentary cooling, by the overlying ophiolitic thrust sheets and by redeposited elements of coeval Urgonian facies reefs grown oil the thrust wedge complex. Following mid-Cretaceous deformation and thermal overprint of the Vranduk Formation, the depozoile migrated further towards SW and received increasing amounts of redeposited carbonate detritus released from the Adriatic Carbonate Platform margin (Ugar Formation). Subordinate siliciclastic source components indicate changing source rocks on the upper plate, with ophiolites becoming subordinate. The zone of the continental basement previously affected by the Late Jurassic-Early Cretaceous thermal imprint has been removed: instead, the basement mostly Supplied detritus with a wide range of pre-Jurassic cooling ages. However, a c. 80 Ma, largely synsedimentary cooling event is also recorded by the Ugar Formation, that contrasts the predominantly Early Cretaceous cooling of the Adriatic basement and suggests, at least locally,a fast exhumation

Calcareous nannofossil age constraints on Miocene flysch sedimentation in the Outer Dinarides (Slovenia, Croatia, Bosnia-Herzegovina and Montenegro)

Flysch deposits are associated with the Outer Dinaride nappe front. They overlie Eocene platform carbonate to bathyal marl successions that subsequently cover Cretaceous platform carbonates of Apulia and the Dinaride nappes. Planktonic foraminifer biostratigraphy indicates Eocene age of flysch sedimentation. New calcareous nannofossil data reveal that several assemblages are present; besides the dominant Mid-Eocene species, Cretaceous, Paleocene, Oligocene and Miocene taxa were also identified throughout the entire flysch belt. Widespread occurrence of nannofossil species of zone NN4-6 indicates that flysch deposition lasted up to at least the Mid-Miocene. Ubiquitous occurrence of various pre-Miocene taxa demonstrates that extensive, possibly submarine, sediment recycling has occurred in the Cenozoic. As flysch remnants are typically sandwiched between thrust sheets, these new stratigraphic ages give a lower bracket on deformation age of the coastal range. The data provide a link between Cretaceous compression in the Bosnian Flysch and recent deformation in the Adriatic offshore area

THANETIAN AND EARLY YPRESIAN ORTHOPHRAGMINES (FORAMINIFERA: DISCOCYCLINIDAE AND ORBITOCLYPEIDAE) FROM THE CENTRAL WESTERN TETHYS (TURKEY, ITALY AND BULGARIA) AND THEIR REVISED TAXONOMY AND BIOSTRATIGRAPHY

The rich orthophragminid assemblages from the upper Thanetian and lower Ypresian of Turkey are discussed together with the coeval faunas from Spilecco (N Italy) and Beloslav (Bulgaria). Their taxonomy, evolution and biozonation in the Western Tethys are revised. Our biometric study is based mainly on a large number of equatorial sections of megalospheric individuals. We present the emended description of Discocyclina seunesi, D. tenuis, Orbitoclypeus multiplicatus, O. bayani and Asterocyclina taramellii. A new species, Nemkovella stockari is introduced. The evolutionary lineages of Discocyclina seunesi, Orbitoclypeus multiplicatus and O. bayani are restored for the first time by using the consistent size-increase of the megalospheric embryon that also allowed introducing some new subspecies (Discocyclina seunesi beloslavensis, D. s. karabuekensis, Orbitoclypeus multiplicatus kastamonuensis, O. bayani kurucasileensis and O. munieri ponticus). By owing the most complete record of Thanetian and early Ypresian orthophragmines from the Western Tethys (using also data from SW France and the Crimean Peninsula) we could reconstruct their early evolution. The chronostratigraphical position of some localities was ascertained from planktic and larger benthic foraminifera, as well as calcareous nannoplankton. In the updated orthophragminid zonation (zones are marked by OZ), OZ 1a corresponds to the early Thanetian, OZ 1b to the middle Thanetian. They are distinguished on the base of the evolution of Discocyclina seunesi. In these zones, only two unribbed species of Discocyclina and Orbitoclypeus each are present. Ribbed Orbitoclypeus, genus Asterocyclina and Nemkovella appeared in the redefined OZ 2 zone belonging to the late Thanetian. Discocyclina archiaci and D. dispansa substituted D. seunesi at about the Paleocene/Eocene boundary. The early Ypresian can be subdivided into the OZ 3 and 4 zones that can be distinguished from each other by the different developmental stages of the simultaneously running evolutionary lineages such as Discocyclina archiaci, Orbitoclypeus schopeni and O. multiplicatus.

The Eocene-Oligocene climate transition in the Central Paratethys

Abstract We studied two boreholes (Cserépváralja-1 and Kiscell-1) with continuous sedimentary records across the Eocene-Oligocene climate transition from the Central Paratethyan area. Assemblages of benthic foraminifera display a shift in dominance by epifaunal taxa in the late Eocene to shallow and deep infaunal taxa in the early Oligocene. Using the benthic foraminiferal oxygen index (BFOI), a decreasing trend of bottom-water oxygen levels is established across the Eocene-Oligocene transition (EOT), leading to the development of dysoxic conditions later in the early Oligocene. Trends in δ18O and δ13C values measured on tests of selected benthic and planktic foraminifera roughly parallel those of the global record of stepped EOT δ18O increase and deviate only later in the early Oligocene, related to the isolation of the Paratethys. The overall similarity of the isotope curves and the presence of a planktic-benthic ecological offset suggest that the original isotope trends are preserved, despite the systematically more negative δ18O values. Of different scenarios, a quasi-uniform diagenetic overprint by fluids with low δ18O values, during burial or uplift, appears best supported. We conclude that the globally established isotopic expression of Antarctic ice sheet growth across the EOT may be recognizable in the Paratethys. Deviations from the global trends after the EOT were caused by regional paleoceanographic changes induced by the progressing Alpine orogeny and sea-level change, which led to a restricted connection with the open ocean, freshwater influx from increased precipitation, and gradual development of bottom-water oxygen depletion

Changes in Calcareous Nannoplankton Assemblages Around the Eocene-Oligocene Climate Transition in the Hungarian Palaeogene Basin (Central Paratethys)

The Eocene-Oligocene climate transition (EOT) is the last major greenhouse-icehouse climate state shift in Earth history, ending the warm, ice-free early Palaeogene world and ushering in the Antarctic glaciation. This study is focused on the Hungarian Palaeogene Basin within the Central Paratethys, aiming to characterise the effect of the global cooling event in the calcareous nannoplankton assemblages and to reconstruct the palaeoenvironmental evolution of the region. Calcareous nannoplankton biostratigraphy is focused on documenting the NP21 Zone. Hierarchical cluster analysis allowed us to distinguish five successive assemblages. Thereby defined phases are compared with recently published trends in δ18O values and foraminiferal changes. Taxa with a preference for oligotrophic and warm surface waters dominate the lowest assemblage. The next assemblage contains taxa that indicate oligotrophic conditions but temperate surface water at the onset of the EOT. Nannoplankton abundance drops to a minimum in the third phase, when taxa adapted to cool surface waters gradually became dominant. A gradual rebound of nannoplankton abundance is observed in the fourth phase, possibly reflecting regional climate change related to the uplifting Alpine chain. After the end of the EOT, the youngest assemblage includes mostly eurytopic taxa which could tolerate an increased rate of freshwater and terrestrial influx

Provenance of the Bosnian Flysch

Sandwiched between the Adriatic Carbonate Platform and the Dinaride Ophiolite Zone, the Bosnian Flysch forms a c. 3000 m thick, intensely folded stack of Upper Jurassic to Cretaceous mixed carbonate and siliciclastic sediments in the Dinarides. New petrographic, heavy mineral, zircon U/Pb and fission-track data as well as biostratigraphic evidence allow us to reconstruct the palaeogeology of the source areas of the Bosnian Flysch basin in late Mesozoic times. Middle Jurassic intraoceanic subduction of the Neotethys was shortly followed by exhumation of the overriding oceanic plate. Trench sedimentation was controlled by a dual sediment supply from the sub-ophiolitic high-grade metamorphic soles and from the distal continental margin of the Adriatic plate. Following obduction onto Adria, from the Jurassic–Cretaceous transition onwards a vast clastic wedge (Vranduk Formation) was developed in front of the leading edge, fed by continental basement units of Adria that experienced Early Cretaceous synsedimentary cooling, by the overlying ophiolitic thrust sheets and by redeposited elements of coeval Urgonian facies reefs grown on the thrust wedge complex. Following mid-Cretaceous deformation and thermal overprint of the Vranduk Formation, the depozone migrated further towards SW and received increasing amounts of redeposited carbonate detritus released from the Adriatic Carbonate Platform margin (Ugar Formation). Subordinate siliciclastic source components indicate changing source rocks on the upper plate, with ophiolites becoming subordinate. The zone of the continental basement previously affected by the Late Jurassic–Early Cretaceous thermal imprint has been removed; instead, the basement mostly supplied detritus with a wide range of pre-Jurassic cooling ages. However, a c. 80 Ma, largely synsedimentary cooling event is also recorded by the Ugar Formation, that contrasts the predominantly Early Cretaceous cooling of the Adriatic basement and suggests, at least locally, a fast exhumation