The middle/late Eocene transition in the Eastern Carpathians (Romania) based on foraminifera and calcareous nannofossil assemblages

Foraminiferal and calcareous nannofossil assemblages from the Eastern Carpathians (northern part of the Tarcău Nappe, Romania) were documented and correlated in order to reconstruct the palaeonvironmental settings and provide a biostratigraphic framework of the Plopu Formation. The benthic foraminiferal assemblages are dominated by flysch-type agglutinated taxa, suggesting a bathyal palaeodepth with frequent oscillations of the carbon compensation depth. The agglutinated foraminifera morphogroup analyses suggest different levels of organic matter influx and oxygenation. Both the foraminifera and calcareous nannofossil assemblages suggest a shift between the warm mid Eocene to the cooler late Eocene climate. Biostratigraphic data based on calcareous nannofossils (NP15–NP19/NNTe8–NNTe12 biozones) helped to establish the age of the formation. Four assemblages of benthic agglutinated foraminifera (Psammosiphonella cylindrica – Nothia excelsa; Paratrochamminoides spp. – Trochamminoides spp.; Karrerulina spp.– Reticulophragmium amplectens; Spiroplectammina spectabilis) correlated with calcareous nannofossil bioevents supported the placement of the mid to late Eocene transition within the Plopu Formation

Upper Cretaceous Deep-Water Agglutinated Foraminifera from the Contessa Highway Section, Umbria-Marche basin, Italy: Taxonomy and Biostratigraphy

The taxonomy and biostratigraphy of deep-water agglutinated foraminifera (DWAF) are documented in a 299 m thick section collected from the Upper Cretaceous (Turonian to Maastrichtian) of the Scaglia Bianca and Scaglia Rossa Formations in the Contessa Highway section of Italy. A total of 94 species belonging to 48 genera are documented from the section, including two new species: Subreophax longicameratus n.sp., and Hormosinella fusiformis n.sp.. The DWAF assemblages display a general trend of increasing abundance and diversity from the Cenomanian/Turonian boundary to the Cretaceous/Paleogene boundary. The biostratigraphy of DWAF in the Upper Cretaceous part of the Contessa Highway section is calibrated to the 2008 ICS timescale by means of the calcareous nannofossil biostratigraphy. Nine calcareous nannofossil biozones are determined in the interval CC10 to CC26, but some of the Upper Cretaceous nannofossil biozones could not be determined owing to poor preservation or the absence of index taxa. The first occurrences of biostratigraphically important DWAF species are compared with the first occurrences in the Upper Cretaceous of the Carpathians and the North Atlantic. The agglutinated foraminiferal biozones of the Carpathian schemes of Geroch & Nowak (1984) and Neagu et al. (1992) and the North Atlantic zonation of Kuhnt et al. (1992) cannot be applied in their entirety to the Contessa Highway section owing to the scarcity of some index taxa. Four Upper Cretaceous DWAF biozones described from the Atlantic and Western Tethys are recognised in the Scaglia formations at Contessa: the lower Turonian Bulbobaculites problematicus Zone, the upper Turonian to Coniacian Uvigerinammina jankoi Zone, the Santonian to Campanian Caudammina gigantea Zone, and the Maastrichtian Remesella varians Zone. However, some of the cosmopolitan index taxa, such as Bulbobaculites problematicus and Uvigerinammina jankoi have truncated stratigraphic ranges. The oligotrophic palaeoenvironmental conditions represented by the red deep-water Scaglia Rossa limestones cause flysch-type species such as Uvigerinammina jankoi and Caudammina gigantea to be rare, and in the case of Rectoprotomarssonella rugosa, an index species for the Lower Campanian, to be absent. Nevertheless, the Uvigerinammina jankoi Zone in Contessa can be correlated with the Carpathian Basins and the North Atlantic. Agglutinated foraminiferal assemblages are similar in taxonomic composition to those of the Carpathian Basins but in addition, a series of small abyssal type Haplophragmoides species known from the North Atlantic DSDP/ODP sites are present in the Contessa Highway section, probably as a result of oligotrophic conditions in the central Tethys. The abundance of agglutinated foraminifera at Contessa displays mimima during sea level high stands in the late Turonian, late Coniacian, late Santonian, early Campanian. These low abundance assemblages likely indicate enhanced oligotrophy as result of sediment starvation. The foraminiferal abundance and diversity values generally increase upsection, and typical "flysch-type" species appear in the record, indicating more detrital influx and a change to more mesotrophic conditions in the Campanian

Geochemistry of Upper Cretaceous of the Bozeş Formation (Apuseni Mts., Romania) : provenance implications

A whole-rock geochemical study was carried out on sandstones from the Upper Cretaceous Bozeş Formation in the southeastern part of the Apuseni Mountains (Romania) in order to constrain their provenance and depositional setting. The geochemical results were compared and integrated with previously reported provenance indicators, such as framework composition and heavy mineral assemblages. The chemical composition is similar for all samples investigated, with limited ranges for both major oxides and trace elements. The sandstones are potassic (Na2O/K2O < 1) and can be classified mainly as arenites with a few greywackes. Their immature to relatively mature character is revealed by the SiO2/Al2O3 ratios, ranging between 3.90 and 11.25, as well as their high Sr/Rb ratios. The source rocks were affected by weak to moderate chemical alteration, as indicated by the specific index (CIA), with values between 47 and 71. The detrital material was influenced by a little hydraulic sorting during transportation, while post-depositional eftects were limited to K-metasomatism. Two major potential source types were identified based on the chemical composition of the samples studied: a felsic magmatic arc and a recycled, quartzose metasedimentary basement. Our data indicate that the depositional setting is likely to be on a convergent margin. The results are consistent with uplifted and exhumed Transylvanian basement as the major source area