Calcareous Dinoflagellate Cysts Research Articles

Octahedronoides tethysianus n.gen., n.sp., enigmatic clusters of microspheres at the Jurassic-Cretaceous transition

In the literature, numerous accounts exist of microspheres scattered in the pelagic environments of the Tethys realm at the Jurassic-Cretaceous transition. These microspheres are commonly associated with genera such as Cadosina, Colomisphaera, or Stomiosphaera, and attributed to calcareous dinocysts. On the other hand, there are few records of the microsphere, initially described as Cadosina minuta BORZA, 1980, which are arranged in small clusters, likely comprising six cells. This distinctive grouping and its architecture preclude attribution to the calcareous dinocysts. A new genus and a new species (as Octahedronoides tethysianus n.gen., n.sp.) are introduced to define these clusters of leiospheres, which are here reascribed to the acritarchs.

A re-description of the historical stratotype for the Berriasian Stage (Cretaceous System): Biostratigraphy and magnetostratigraphy

The historical stratotype for the Berriasian Stage (Cretaceous System) at Berrias (Ardèche, France) is here re-assessed. It shows a sedimentary record of early to late Berriasian age, part of the pelagic limestone succession of the western Vocontian Basin. We describe a studied section, circa 30 m in thickness, which yields calpionellids, calcareous dinocysts, calcareous nannofossils, and ammonites. The magnetostratigraphy of the section is revised, and calibrated with the biostratigraphy of these fossil groups. Magnetozones M19n to M15r (including M16n.1r) are identified and matched to the calpionellid zonation, with the Alpina to Oblonga biozones represented.

New physical and biological evidence of lateral transport affecting dinoflagellate cyst distribution in the benthic nepheloid layer along a land-sea transect off Figueira da Foz (Atlantic Iberian margin)

IntroductionThe production of resting cysts is a key dispersal and survival strategy of many dinoflagellate species. However, little is known about the role of suspended cysts in the benthic nepheloid layer (BNL) in the initiation and decline of planktonic populations.MethodsIn September 2019, sampling of the dinoflagellate cyst community at different water depths in the water column and in the bottom sediments, and studies of spatio-temporal changes in physical properties (temperature, salinity, density and suspended sediment concentration), were carried out along a land-sea transect off Figueira da Foz (NW Portugal) to investigate the dinoflagellate cyst distribution and the factors (physical and biological) affecting it. A clustering analysis was used to compare the BNL and sediment cyst records with the cyst rain recorded by a sediment trap at a fixed station. Furthermore, Lagrangian particle experiments enabled simulating cyst trajectories in the BNL 5 and 10 days before sampling and assessing cross-shore, vertical and alongshore transport within the studied region.ResultsA well-developed BNL was present during the survey, which covered a change from active (14th of September) to relaxed (19th of September) upwelling conditions. Organic-walled dinoflagellate cysts were dominant in all samples, although calcareous dinoflagellate cysts consistently occurred (at low abundances). High proportions of full cysts were observed in the BNL, of which a significant portion was viable as shown by excystment experiments. Moreover, BNL cyst records collected on the 19th of September along the land-sea transect were similar to the sediment trap cyst record but greatly differed from sediment cyst records. The heterotrophic small spiny brown cysts (SBC) and cysts of the autotrophic yessotoxin-producer Protoceratium reticulatum notably increased during the survey, in the BNL and in the water column above.DiscussionThe comparison of the BNL, surface sediment and sediment trap cyst records supported that the main origin of cysts in the BNL was the recent production in the water column. The spatial coincidences in the distribution of cysts and vegetative cells of Protoceratium reticulatum also supported that full cysts in the water column were being produced in surface waters. New data evidenced the presence of a significant reservoir of viable cysts in the BNL that have the potential to seed new planktonic blooms. Furthermore, back-track particle modelling evidenced that alongshore advection was the main physical mechanism controlling cyst dynamics in the BNL during most part of the survey period, being particularly intense in coastal stations (<100 m depth). Consequently, the sediment cyst signal is a mixture of locally and regionally produced cysts. We provide multi-disciplinary data evidencing that cysts recently formed in the photic zone can be laterally advected within the studied region through the BNL, contributing to a better understanding of the role of the BNL in cyst dynamics and tracing the seed sources of the new blooms.

New Tithonian-Berriasian morphospecies of the genus Stomiosphaera Wanner (calcareous dinoflagellate cysts) from the Vaca Muerta Formation, Neuquén Basin, Argentina

Five new morphospecies of calcareous dinoflagellate cysts belonging to the genus Stomiosphaera Wanner, are described from the Tithonian–Berriasian Vaca Muerta Formation, in the Neuquén Basin, Western Argentina: Stomiosphaera triangulata sp. nov., Stomiosphaera quadrata sp. nov., Stomiosphaera subechinata sp. nov., Stomiosphaera subspinosa sp. nov., and Stomiosphaera gracilis sp. nov. Their stratigraphic distribution is discussed, particularly that of Stomiosphaera subechinata sp. nov. (Tithonian – lower Berriasian), which was previously assigned to Stomiosphaera echinata Nowak, a species that in the Tethys domain appears for the first time in the upper Valanginian. Likewise, possible assignments to the genera defined from three-dimensional observations are proposed, and eutrophic neritic conditions are interpreted for the time in which these species appear in the Neuquén Basin.

Stomiosphaerina bakae sp. nov., a new calcareous dinocyst of the Upper Cretaceous of the Central European Basin.

In this work the new species of Stomiosphaerina bakae sp. nov. is described. This is the third species of the genus Stomiosphaerina. Several dozen specimens of the newly described species were found within the Upper Cretaceous (upper Turonian) white chalk at Dubivtsi section near Halych in western Ukraine (south-eastern margin of Central European Basin). Stomiosphaerina bakae sp. nov. has an asymmetrical oval (pear-like shape) test, as it is wider in one side, and sharp in the opposite side, ranging from 55 to 67 μm in length and from 42 to 56.5 μm in width. It has a two-layered calcareous test. The outer layer, with thickness ranging from 4.5 to 6.5 μm, is built of long and wide plate-shaped calcite crystals and is white in plain-polarized light with a dark cross in crossed-polarized light. The inner layer, with thickness ranging from 1.5 to 4.5 μm, is yellowish, goldish to brownish color in plain-polarized light, with proximal and distal side smooth and even, and is built of short fibrous calcite crystals, without preferential orientation. One narrow (6 to 8 μm width) aperture is observed. Stomiosphaerina bakae sp. nov. differs from other species of Stomiosphaerina, i.e. Stomiosphaerina biedai Nowak 1974 and Stomiosphaerina proxima Řehánek 1987, by its cyst-shape, cyst-size, layers thickness, structure of outer layer and width of aperture. Stomiosphaerina bakae sp. nov. most likely corresponds to the non-defined species of Stomiosphaerina sp. described by Nowak 1974.

Calcareous dinoflagellate blooms during the Late Cretaceous 'greenhouse' world-a case study from western Ukraine.

The Late Cretaceous was a unique period in the history of the Earth characterized by elevated sea levels, reduced land area, and significantly high concentrations of atmospheric CO2 resulting in increased temperatures across the globe-a 'Greenhouse World'. During this period, calcareous dinoflagellate cysts (c-dinocysts) flourished and became a ubiquitous constituent of calcifying plankton around the world. An acme in calcareous dinocysts during the Albian to the Turonian coincided with the highest recorded seawater surface temperatures and was possibly linked to conditions that favored calcification and a highly oligotrophic system in European shelf seas. This study examines the potential applicability of c-dinocysts as a proxy for paleoenvironmental conditions based on their assemblage changes plotted against foraminiferal occurrences and microfacies analysis. The material was extracted from the upper Turonian chalk of the Dubivtsi region in western Ukraine. An inverse correlation was observed between species diversity and the number of c-dinocyst specimens. Nutrient availability gradients apparently determined important changes in the calcareous dinocysts distribution. These trophic changes were likely caused by the interplay of eustatic sea-level fluctuations and Subhercynian tectonic activity leading to changeable nutrient inputs from the nearby land.

Disentangling environmental and diagenetic δ18O and δ13C signals from marine carbonates deposited under warm climate conditions during the early Danian

Paleoceanographic reconstructions are usually based on the chemical composition of foraminiferal tests, and pristine calcite preservation is crucial to support reliable interpretations. Therefore, prior knowledge about the structure and chemical composition of microfossils calcite is important to assess whether geochemical results reflect environmental and/or post-burial signals. Here, we present the first microstructural study of early Danian benthic foraminiferal calcite, and evaluate environmental signals and post depositional biases in benthic and planktonic foraminiferal and bulk carbon (δ13C) and oxygen (δ18O) isotope records at Ocean Drilling Program (ODP) Site 1262 (South Atlantic Ocean). We focused our study on the first ∼350 kyr that followed the Cretaceous-Paleogene (K-Pg) boundary, encompassing the Dan-C2 carbon cycle perturbation. Benthic and planktonic δ13C records show the expected surface-to-bottom gradient, suggesting the preservation of original environmental signals. However, benthic and planktonic δ18O records show strongly overlapping and scattered values, suggesting diagenetic alteration of isotopic signals. We identified the occurrence of authigenic carbonates, such as girvasite and siderite, in benthic foraminiferal tests, which increased Mg, Mn, Ba and Fe contents of tests calcite. Our results support that thermodynamic changes occurred in tandem with the decrease of bottom and pore water oxygenation to favor precipitation of authigenic carbonate phases, which altered isotopic fractionation of δ18O. Nevertheless, bulk sediments clearly depict the negative δ13C and δ18O excursions characteristic of the DanC2, with remarkably low values, characterizing the record of a surface ocean environmental signal. This low δ13C and δ18O were mostly recorded by highly-abundant calcispheres (calcareous dinocysts), suggesting that this group of microfossils has a high potential for surface ocean paleoceanographic reconstructions.

Upper Valanginian – Hauterivian calcareous dinoflagellate cyst and calpionellid zones from the Agrio Formation (Neuquén Basin), Argentina

In this paper we describe for the first time the calcareous dinoflagellate cysts and calpionellid associations from upper Valanginian-Hauterivian orbital-driven rhythmic distal ramp deposits (Agrio Formation) in the Neuquén Basin, Argentina. Three stratigraphic sections from the northern Neuquén province (Loma La Torre and El Portón) and southern Mendoza province (Arroyo Loncoche) were studied. The Agrio Formation contains a low diverse association of these microfossils, among which ten calcareous dinoflagellate cyst species and five calpionellid species were recognized, all of them known from the Lower Cretaceous pelagic sediments of the Tethyan region. Two calcareous dinoflagellate cyst zones (Carpistomiosphaera valanginiana, and Stomiosphaera echinata), as well one calpionellid zone (Tintinnopsella), previously proposed for the Tethyan realm, are confirmed for the Agrio Formation. These zones are consistent to late Valanginian - Hauterivian age assignments previously established based on ammonites, nannofossils, and organic-walled dinoflagellate cysts.

Tithonian–Berriasian calcisphere (calcareous dinoflagellate cysts) zones in the Neuquén Basin, Argentina: correlation between Southern Andes and Tethyan regions

Tithonian–Berriasian calcisphere (calcareous dinoflagellate cysts) zones in the Neuquén Basin, Argentina: correlation between Southern Andes and Tethyan regions

Stratigrafie sedimentů doprovázejících vulkanity těšínitové asociace u Bruzovic

The rocks of the teschenite association form smaller scattered occurrences in the upper part of the Hradiště Formation of the Silesian Unit. The age of the igneous rocks corresponds to Berriasian to Barremian (Menčík et al. 1983). The teschenite association includes a relatively heterogeneous group of rocks with variable abundances of felsic and mafic minerals. Three outcrops of the teschenite association rocks (both typical teschenites and strongly altered ultramafic types) embedded in non- volcanic sediments were studied in the bed of the Pazderůvka River between Bruzovice and Žermanice (Bz1, Bz2, and Bz3; Fig. 1). At Bz1 and Bz2 outcrops, bodies of teschenite are hosted by sedimentary rocks affected by caustic metamorphism. The volcanic rocks at Bz3 are represented by strongly altered, markedly clayey dark green rocks with a macroscopically apparent high proportion of dark micas and pyroxenes. The bedrock of the outcrop is composed of calcareous claystone, limestone, and sandy limestone, likely representing Těšín Limestones. The phase composition of the volcanic rocks from the Bz1 and Bz2 localities is to a certain extent similar, which indicates that the same body was observed at both localities. Macroscopically, the rocks are medium- to coarse-grained with a variable proportion of dark minerals, indicating internal differentiation of the body. The very high proportions of natrolite (up to about 35 %, up to 54 % in the leucocratic type) are particularly notable. The volcanic rocks from the Bz3 locality are quite different. Their composition corresponds to strongly argilitised mafic rocks (and their volcaniclastic derivates), containing more than 50 % of clay component with a dominance of smectite, as documented by X-ray diffraction data. As for the primary components, pyroxene, biotite, plagioclase, and accessory amphibole were detected. Calcareous dinoflagellate cysts Cadosina semiradiata fusca, Colomisphaera vogleri, and Cadosina semiradiata representing the lower Valanginian to upper Barremian were identified in polished sections of the calcareous rock. Non-calcareous dinoflagellate cysts in Bz1 and Bz2 samples are almost black, reflecting the strong thermal effects of the teschenite intrusion at the contact with with the sediments. The dinoflagellate cysts in the Bz3 outcrop are very well preserved with no evidence of thermal alteration. The overlying body of the volcanic rock can be therefore considered as effusive. Circulodinium vermiculatum, Cymososphaeridium validum, Muderongia tabulata, Oligosphaeridium albertense, Oligosphaeridium asterigerum, Pseudoceratium pelliferum, Systematophora palmula from the Bz3 outcrop can be considered as stratigraphically significant. Based on the first occurrence of C. validum and the last occurrences of Circulodinium vermiculatum and Systematophora palmula, Leereveld (1995) delineates a dinoflagellate zone of Cymososphaeridium validum which represents the upper Valanginian to the lowermost Hauterivian. The composition of palynofacies, in which palynomorphs predominate, is characteristic of a distal well-oxygenated shelf.

New microbiostratigraphic data (calpionellids and calcispheres) from the tithonian of central Chile, type section (Río Tinguiririca) of the baños del Flaco Formation

This work presents new biostratigraphic data based on calpionellids and calcareous dinoflagellate cysts for the Tithonian in Central Chile. This stratigraphic interval is mostly represented by a thick marine succession of limestone and sandstone known as Baños del Flaco Formation. This formation originated in the shallow-water setting of a carbonate ramp and correlates with other well-studied units in the Neuquén basin of Argentina. Calpionellids and calcareous dinogflagellate cysts are studied on the Chilean side of the Andes for the first time. The recognition of several calpionellids and calcareous dinogflagellate cyst species within the lower Baños del Flaco Formation allowed the identification of a preliminary microbiostratigraphic zonation. Calcareous dinoflagellate cysts include eleven species that defines the Colomisphaera tenuis, and Colomisphaera fortis zones, whereas six chitinoidellid species allowed the identification of the Chitinoidella and Crassicollaria zones, with the Slovenica, Boneti and Remanei subzones. These new microbiostratigraphic data suggest a latest early to earliest late Tithonian age for the studied interval.

Calcareous dinoflagellate cyst distribution across the K/Pg boundary at DSDP site 577, Shatsky Rise, western North Pacific Ocean

An analysis of calcareous dinoflagellate cysts has been carried out on sixteen samples from across the K/Pg boundary interval from Deep Sea Drilling Project Site 577 situated on Shatsky Rise in the western North Pacific. This is the first time that a detailed study of this microfossil group has been undertaken from deep sea sediments of Late Cretaceous–early Paleocene age in the North Pacific realm. Eight species of calcareous dinoflagellate cysts were found to comprise low diversity assemblages of which half are representative of extant taxa. The most pronounced bioevent is that of Cervisiella operculata reaching its highest proportions at the K/Pg boundary transition underscoring the utility and cosmopolitan distribution of the species with its acme as a marker for the earliest Danian. We also identify an indirect sea surface paleotemperature signal as represented by variance in wall thickness in two distinct morphotypes of Thoracosphaera heimii (morphotypes A and B). The cyst concentrations and relative abundances of these taxa are interpreted to reflect the late Maastrichtian warming event and subsequent late Maastrichtian cooling phase prior to the interval of gradual warming in the early Danian marked by the opportunistic capitalization of Cervisiella operculata during a time of ocean recovery following the terminal Cretaceous.

Export flux succession of dinoflagellate cysts and planktonic foraminifera in an active upwelling cell off Cape Blanc (NW Africa)

To better understand production, succession, excystment and transport of dinoflagellate cysts (dinocysts) and planktonic foraminifera in the upper water column, we investigated their fluxes during a 7-day survey in the active upwelling off Cape Blanc (NW Africa) in November 2018 with drifting traps at 100 m, 200 m and 400 m water depth. The survey covered a change from active upwelling to stratified conditions. Highest production of organic dinocysts and planktonic foraminifera was observed during active upwelling conditions and decreased drastically towards the end of the survey. Calcareous dinocysts appeared later during upwelling relaxation. Cytoplasm-bearing (full) dinocysts and foraminifera were produced in the water column above the traps (<100 m depth). Some of the empty dinocysts were resuspended, implying that sediments below the survey site contain both local and allochthonous cyst assemblages. This is the first demonstration that excystment in the upper water column is species-specific. Brigantedinium excysted in the upper water column before reaching deeper depths, whereas no upper water column excystment was observed for the other dinoflagellate species. Dinoflagellate and planktonic foraminifera associations showed a clear succession. During active upwelling, Echinidinium zonneveldiae, Brigantedinium spp., other peridinioids, Echinidinium spp., cysts of Pentapharsodinium dalei, ‘other photosynthetic organic-walled dinocysts‘, Neogloboquadrina incompta and Globigerinella calida were collected. During upwelling relaxation, Lingulodinium machaerophorum was produced; and under stratified conditions Gymnodiniaceae cysts (G. microreticulatum, G. catenatum) and the foraminifera Globigerina bulloides and Orbulina universa were sampled. Apart from enhancing knowledge of these species, our observations allow more detailed reconstructions of upwelling history in the Cape Blanc region based on sedimentary archives using fossilized dinoflagellate and planktonic foraminifera assemblages.

Cadosinopsis rehakovii sp. nov., a new calcareous dinocyst from the Jurassic-Cretaceous transitional interval of the Western Tethys.

Variegated limestones, a transitional series between red, Upper Jurassic radiolarite and whitish, Lower Cretaceous Maiolica limestone in the Pieniny Klippen Belt deposits in the Polish part of the Western Carpathians, have yielded rich microfossil assemblages with common calcareous dinoflagellate resting stages, hereafter, dinocysts. We found an undescribed dinocyst species in red-greenish limestone of a deep water, pelagic habitat in the Branisko succession of the Pieniny Klippen Basin and named it Cadosinopsis rehakovii sp. nov. The new species has a spherical to oval calcareous test ranging from 34 to 59 μm in length and 30 to 50 μm in width, with two layered wall. The inner layer is built of coarse–thick, plate-shaped calcite crystals and is white in transmitted light. The outer layer is built of fibrous crystals, vitreous (transparent) in transmitted light. The aperture is wide and seen only in the inner layer. We compared the detailed morphological characteristics of the new species with another species from the same genus in the Jurassic and Cretaceous Tethyan deposits. Specimens have been measured, grouped and interpreted using cluster analysis, principal component analysis (PCA) and canonical variate analysis (CVA). Among them, the new species shows a resemblance in cross-section to other species of Cadosinopsis, C. nowaki Borza, 1984, and C. andrusovi Scheibner 1967, previously described in literature. However, the two species are easily distinguishable by some features. Cadosinopsis. nowaki is bigger in size (length from 50 to76 μm and width from 43 to 67 μm), its inner layer is thicker and consists of vitreous-sparite calcite, and it has less centrically located chamber. C. andrusovi is much bigger in size as its length ranges from 68 to 108 μm and width ranges from 60 to 80 μm, and the cyst is more oval and its chamber less spherical. The new species is the third Cadosinopsis species described in the Tethyan realm and about two hundred and sixty-first fossil species (morphotype) described in the world so far.

Facies analysis and stratigraphy across the Jurassic-Cretaceous boundary in a new basinal Tithonian–Berriasian section of the Vaca Muerta Formation, Las Tapaderas, Southern Mendoza Andes, Argentina

This paper presents a multidisciplinary study of a new basinal section of Tithonian-Berriasian the Vaca Muerta Formation at Las Tapaderas area, including detailed, biostratigraphic, sedimentologic, sequence stratigraphic and cyclostratigraphic analysis. Biostratigraphy based on ammonite, calpionellids and calcareous dinoflagellate cysts indicate that Las Tapaderas section spans through the Lower Tithonian - lowermost Upper Berriasian, however, its upper part is covered through an erosive unconformity by Pleistocene volcaniclastic deposits, and therefore Las Tapaderas section could reach the Lower Valanginian. Two facies associations were identified, corresponding to basinal and distal outer ramp subenvironments. Recognition of flooding surfaces allowed the identification of three composite depositional sequences and eight high-frequency depositional sequences, which can be correlated with other sections throughout the basin. Cyclostratigraphic analysis based on the recognition of marlstone/limestone couples (elementary cycles) allowed to build a time series based on bed thickness. Fourier analysis indicates the characteristic mid latitude precession-eccentricity syndrome, with 220 precessional cycles (~20.4 and ~23 kyr), 53 low frequency eccentricity cycles (~79, ~90 and ~140 kyr) and 11 high frequency eccentricity cycles (~400 kyr). Spectral analysis also allowed to recognize the presence of the obliquity cycle (38.5 kyr), which has been erratically recorded in the Vaca Muerta Formation. Our data allowed the construction of an orbital scale, calibrated by cosmopolitan markers (calpionellids and calcareous dinoflagellate cysts), for this section. The precise bio- and cyclostratigraphic location of the Jurassic-Cretaceous boundary was established for this section. The sedimentation rate was studied at the scale of the precession cycle, showing values between 0.6 and 3 cm/kyr, while at the low-frequency eccentricity scale it shows values between 1 and 2 cm/kyr.

Rise of calcispheres during the Carnian Pluvial Episode (Late Triassic)

It has been argued that the beginning of significant pelagic calcification could have been linked to the Carnian Pluvial Episode (CPE), a climate change in the Late Triassic (~234–232 Ma) that was marked by C-cycle disruption and global warming. Nevertheless, abundant calcareous nannofossils have been described so far only in post-CPE rocks, and therefore no conclusive hypotheses can be drawn on possible causal links with it. Here we show that in deep-water successions of the Western Tethys, Orthopithonella calcispheres interpreted as calcareous dinocysts became an important component of carbonate sedimentation from the onset of the CPE, and could constitute up to 8% of hemipelagic limestones. Before the CPE, in similar depositional environments, calcispheres are rare or absent, and never constitute a significant part of the sediment. This change in the deep-water carbonate sedimentation, is mirrored in the shallow water environments by the rise of the reefs built by Scleractinia corals. These important innovations in Earth's carbonate systems may indicate a deep modification in the ocean biogeochemistry during the CPE. • Calcispheres were studied in successions across the Carnian Pluvial Episode (CPE). • In Western Tethys Calcispheres are abundant from the onset of the CPE. • They belong to the genus Orthopithonella. • They were a significant component of CPE hemipelagic–pelagic limestones.

Uppermost Berriasian macro- and microfossil assemblages from the Ticha Formation of the Eastern Fore-Balkan Mts (Bulgaria)

Late Berriasian macro- and microfossil assemblages from the Ticha Formation (Eastern Fore-Balkan Mts, Bulgaria) were studied. Eight ammonite taxa, including coiled and straight forms, were described. In addition, 23 calpionellid, 12 calcareous dinocyst and 4 foraminiferal taxa were identified. The “Thurmanniceras” otopeta ammonite Subzone of the Tirnovella alpillensis Zone, the calpionellid Oblonga Subzone of the Calpionellopsis Zone and the Stomiosphaera wanneri calcareous dinocyst Zone were indicated. The advent of Bochianites neocomiensis, the late occurrence of Bochianites (?) ambiguus and the earliest appearance of Phylloceras (Hypophylloceras) tethys tethys was documented in the Eastern Fore-Balkan Mts area. The calpionellid-spicule microfacies was also recognized. The fossil data allow a correlation with similar coeval localities of the European Tethyan Realm. Pelagic macro- and microfossils and the microfacies are indicative of deeper-water basin depositional settings.

Slump/Slide facies and biostratigraphy at the transition of the Cieszyn and Hradiste formations in the Cieszyn (Tesin) Section (Outer Flysch Carpathians)

ABSTRACT: New sedimentological observations in the Lower Cretaceous of the Silesian Unit and integrated biostratigraphy based on calcareous nannofossils, dinoflagellate cysts, calpionellids and foraminifers have brought new insight to the stratigraphy of the Cieszyn section. The oldest exposed strata of themudstone facies of the Cieszyn Limestone Formation are of early Berriasian age, based on calcareous nannofossil evidence. This work proposes that the Jurassic-Cretaceous boundary reported by previous authors was based on reworked microfossils. The detritic facies of the Cieszyn Limestone Formation, typically dominated by detritic-limestone turbidites, appears to be completely missing. Instead, a thick body with combined slump and slide features, of Berriasian–Valanginian age, forms the transition with the overlying lower Valanginian strata of the Hradiste Formation. The slump/slide body represents a local facies, deposited on a fault scarp related to fault-controlled extension of the Proto-Silesian Basin floor.

Biostratigraphy and Paleogeography of the Bazhenovo Formation (Upper Jurassic and Lower Cretaceous) Based on Radiolarians, Nannoplankton and Calcareous Dinocysts

Biostratigraphy and Paleogeography of the Bazhenovo Formation (Upper Jurassic and Lower Cretaceous) Based on Radiolarians, Nannoplankton and Calcareous Dinocysts

Biostratigraphy and microfacies of the pelagic carbonate formations in the Yavorets section (Tithonian–Berriasian), Western Balkan Mts, Bulgaria

Calpionellid study has provided new evidence of early and late Tithonian age of the top of the Gintsi Formation, and of late Tithonian and early Berriasian age of the Glozhene Formation in the Yavorets section (Western Balkan Mts, Bulgaria). The calpionellid Chitinoidella, Praetintinnopsella, Crassicollaria, and Calpionella zones have been documented in successive order. Three calcareous dinocyst zones – Colomisphaera tenuis, Colomisphaera fortis and Stomiosphaerina proxima, have been determined in this lower Tithonian to lower Berriasian interval. From the base upwards, the following microfacies have been recognized: Saccocoma (Gintsi Formation, lower and upper Tithonian), Globochaete alpina, and calpionellid (Glozhene Formation, upper Tithonian and lower Berriasian). The base of the Berriasian has been traced at the explosion of the uniformly shaped spherical variety of Calpionella alpina. Evolutionary lineages of species of the genus Calpionella are discussed, as well as the vertical distributions and abundance peaks of crassicollarians. The calpionellid zones described herein are correlated with coeval zonations from the Western, Central and Eastern Tethyan domains. The regional correlation with previously studied sections of Tithonian/Berriasian pelagic carbonates in the Western Balkan Mts revealed a transition to hemipelagic deposition of the limestone-marl succession of the Salash Formation and/or sandstone accumulation during the middle to late Berriasian (Elliptica and Simplex calpionellid subzones) due to unstable conditions of the sedimentary environment. From the west to the east in the Western Balkan Unit (i.e., from the Rosomač section in eastern Serbia to the Sarbenitsa, Bov and Yavorets sections in the Iskar River Valley area), there is a trend of slight progressive deepening of the basin. This is manifested in the occurrence of redeposited shallow-carbonate-platform microfossils in the west to greater thickenesses of the Gintsi and Glozhene formations and occurrence of sandstone channel deposits in the east.