New biostratigraphic investigations based on palynomorphs (mainly dinoflagellate cysts), foraminifera and calcareous nannoplankton recovered from eight geological sections indicate that the Hangu ...Formation near the Pluton-Pipirig area (Tarcău Nappe, Eastern Carpathians, Romania), previously assigned to the Senonian–Paleocene interval, includes only uppermost Cretaceous deposits. The palynological assemblages are moderately rich, with a total of 167 well-preserved taxa. The marine palynomorphs – essentially consisting of dinoflagellate cysts (dinocysts) – are dominated by peridinioid taxa, mainly recorded in upper Upper Campanian–lower Maastrichtian deposits, and by a high-diversity assemblage of gonyaulacoid taxa during the late Maastrichtian. Marine algae and dinogymnioid dinocysts were less common. The terrestrial palynoflora is dominated by fern spores and angiosperm pollen, with subordinate gymnosperm pollen. The foraminiferal assemblages include an assortment of well-preserved agglutinated forms, present mainly in the upper Maastrichtian deposits, whereas calcareous benthics and planktonic foraminifera are rare and poorly preserved. Calcareous nannoplankton assemblages are also rare, often represented by two taxa (Micula staurophora and Watznaueria barnesiae); certain important biostratigraphic markers were found to be reworked in the analyzed deposits. Age assignments for the studied sections were mainly provided by dinocysts, through the identification of significant marker taxa and comparisons with well-calibrated Campanian–Maastrichtian dinocyst assemblages from well-dated sections and stratotypes, located mostly in the Northern Hemisphere.
Indices such as particulate organic matter (POM) composition, the relative abundance of dinocyst eco-groups, as well as agglutinated foraminiferal morphogroups, were used to reconstruct the depositional environments of the Hangu Formation from the studied area. The upper Upper Campanian–lower Maastrichtian deposits from the Pluton-Pipirig sections were mainly deposited in neritic marine conditions, although occasional redeposition of the sediments transported by turbidity currents towards deeper water settings is not excluded, either. The depositional environments evolve towards outer neritic to distal (bathyal) during the late Maastrichtian, as indicated by palynofacies constituents and by high frequencies of gonyaulacoid dinocysts and deep-water benthic foraminifera.
•Upper Campanian–Maastrichtian microfossils, Eastern Carpathians, Romania, are studied.•Palaeoenvironmental and palaeoecological conditions are discussed.•A new detailed geological map for the studied area was proposed.
Microfacies analyses of twenty-five samples collected from three outcrops located in the northwestern part of the Transylvanian Basin offered new insights into the structural architecture and ...diagenetic features of the nummultic accumulations in this region. The data from thin-section observations revealed the fact that diagenetic processes (mainly pressure dissolutions) played a crucial role in the fabric development, porosity evolution and general morphology of these build-ups. A high degree of compaction was observed with respect to the abundance of stylolitic structures, fissure sets, and numerous fragmented nummulitic particles within the matrix. Such features allowed the identification of several phases of stylolitization which affected the nummulitic accumulations during burial diagenesis. Moreover, these compactional traits can provide clues for understanding the ratio variations between
N. perforatus
A (microspheric) and B (macrospheric) forms in such deposits. Combining our results with previous data we better constrained the autochthonous and/or para-autochthonous provenance of the nummulithoclasts. Our results offer a new perspective into the development and preservation of nummulitic accumulations deposited in the Eocene tropical/sub-tropical shallow-marine settings of the central Neotethyan realm.
The dataset presents quantitative information on the taxa distribution of calcareous nannoplankton and smaller benthic foraminifera retrieved from the nummulitic accumulation in the Transylvanian ...Basin (Romania). Until now, only the larger benthic foraminifera and bryozoans were systematically studied, data on calcareous nannoplankton and smaller benthic foraminifera are scares. Our data comprise of quantitative information on the calcareous nannoplankton and smaller benthic foraminifera (raw individuals counts, relative abundance), diversity indices, benthic foraminifera dissolved oxygen index – BFOI and normalised data (ARCSIN values) used for clustering and principal component analysis. These data provide information on paleoenvironmental changes in the north-western part of the Transylvanian Basin during the middle Eocene (Bartonian) and can be used in any comparative study on the reconstruction and paleoenvironmental interpretation of the nummulitic carbonate reservoirs from Tethyan regions. The present data article is associated with the research paper “In the shadow of giants: Calcareous nannoplankton and smaller benthic foraminifera from an Eocene nummulitic accumulation (Transylvanian Basin, Romania)” by Bindiu-Haitonic et al. 2021 1.
Extensive high-resolution palaeontological, stratigraphic and sedimentological data offer a new and comprehensive view of the genesis and evolution of the most extended Eocene nummulitic accumulation ...in the northern Neotethyan realm. The preserved Bartonian (SBZ 17) Nummulites assemblages consist of large, granulate Nummulites perforatus and/or small, radiate Nummulites beaumonti. The assemblages differ in taxonomic content and/or in the relative abundance of test type (A- versus B-forms): Assemblage 1 is dominated by N. beaumonti A-forms, N. perforatus A-forms are sporadic, while B-forms are rare or missing; Assemblage 2 consists of N. perforatus A- and B-forms; and Assemblage 3 consists essentially of N. perforatus A- and B-forms with only rare N. beaumonti A- and B-forms. These assemblages are interpreted as autochthonous and autochthonous to para-autochthonous, deposited on a low-angle inner shelf. Their distribution in space and time reflects the interplay between the palaeoenvironment and the ability of N. perforatus and N. beaumonti to colonize new habitats. Thus the genesis and development of the studied nummulitic accumulations mirrors the ecological preferences of the two Nummulites species, the relative sea-level, the sediment supply and possibly the climate history. The shelf around the storm wave base was first colonized by N. beaumonti and rare N. perforatus, then the mass nummulitic accumulation was formed by the accumulation of N. perforatus tests between the storm wave base and the fair weather wave base. The accumulation of abundant N. perforatus and rare N. beaumonti around the fair weather wave base occurred in the last phase.
•Detailed description of a unique Eocene nummulitic accumulation.•Distribution of the assemblages are related to the relative sea-level changes.•Composition of the Nummulites assemblages are linked to the ecological preferences.•Development of the nummulitic accumulation is the result of biotic and abiotic factors.
Nummulitic accumulations are an important component of the Eocene sedimentary record in the Neotethyan realm. Their age, paleoenvironmental significance and depositional model are almost exclusively ...based on the interpretation of the larger benthic foraminiferal assemblages. We show here, however, that the high-resolution study of the other, often neglected, microfossils (calcareous nannoplankton and benthic foraminifera) is crucial to better constrain the diversity and paleoenvironmental gradient along the nummulitic accumulation(s). The studied micropaleontological assemblages, recovered from the large Eocene (Bartonian) nummulitic accumulation in the northwestern Transylvanian Basin (Romania), suggest an inner shelf depositional environment. A depth and nutrient gradient along the nummulitic accumulation from the south to the north could be recognized. In the southern part of the study area the environment was shallow and oligotrophic with Zygrablithus bijugatus, Blackites inflatus, Neococcolithes dubius, Ericsonia spp., larger sized reticulofenestrids and epiphytic foraminifera taxa (Pararotalia, Lobatula and Cibicides) on a sandy substrate. The progressive deepening toward the north led to an increase in clay content and more nutrient-rich marine waters in which calcareous nannoplankton (especially Reticulofenestra minuta), agglutinated foraminifera and calcareous infaunal foraminifera (Nonion, Protelphidium and Reusella) proliferated. The calcareous nannoplankton and smaller benthic foraminiferal assemblages confirm and further constrain the Bartonian age of the studied nummulitic accumulation, previously based on the larger benthic foraminiferal SBZ 17 zone.
•Detailed micropaleontological study of a nummulitic accumulation•Multivariate data analyses were performed.•Abiotic factors are the main control on the distribution of the assemblages.•Paleoecological parameters reflect a preference for shallow water.
The Călata site (north-west of Transilvanian Basin, Romania) includes the Ciuleni Member of the middle Eocene-age Mortănușa Formation, a marine deposit in an outer, open marine facies, from where ...fossil vertebrates were very poorly known. In the last four years, nearly 150 remains of fish (mostly teeth) were recovered from the Călata site. We identified 21 taxa representing 20 genera that belong to 12 orders of chondrichthys and teleostei fishes. This study is the first to report Rostroraja and Palaeocybium from Romania, and we report seven additional genera from the Bartonian of Romania for the first time. We performed analysis of calcareous nannoplankton and foraminifera which allowed us to refine the age of the deposits and corroborate palaeoecological data. The combined data from the microfossils and fishes document the first middle-late Bartonian (NP17) marine fish fauna from Romania. This fauna was deposited in tropical waters with relatively shallow depths and with increased terrigenous input from a probable close-by shoreline.
Eocene foraminiferal assemblages from the Moldova Valley area in the Eastern Carpathians have been investigated with a focus on biostratigraphy and paleoenvironmental changes under the influence of ...Eocene tectonics. Paleoenvironmental investigations have been carried on two sections using foraminiferal morphogroups, clusters, and diversity analyses. The Eocene assemblages are highly diversified and dominated by deep-water agglutinated foraminifera; rare calcareous benthic and planktonic foraminifera were indentified only in one section. Agglutinated foraminiferal morphogroups are differently represented in the studied sections: while in the first section (GHP) M2c (elongate keeled) and M3b (flattened irregular) morphotypes are lacking, the second section (GHE) includes all the agglutinated foraminifera morphogroups. Bathyal paleoenvironments are indicated by typical deep-water agglutinated foraminifera together with Ammolagena clavata (Jones and Parker). Based on the presence of the agglutinated species Bulbobaculites gorlicensis Wakowska, Reticulophragmium amplectens (Grzybowski), Spiroplectammina spectabilis (Grzybowski) emend Kaminski, and calcareous nannofossils, the age of the deposits has been assigned to the Bartonian (the GHP section) and the Priabonian (the GHE section).
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