Dinocyst Zones Research Articles

Paleomagnetism and integrated stratigraphy of the Upper Berriasian hemipelagic succession in the Barlya section Western Balkan, Bulgaria: Implications for lithogenic input and paleoredox variations

A continuous Late Berriasian sedimentary and stratigraphic record is here presented from a hemipelagic succession from the Western Balkan (Barlya section, Bulgaria). The section, 39-m-thick, was stratigraphically calibrated using a variety of methods: biostratigraphy (calpionellids, calcareous nannofossils and calcareous dinocysts), magnetostratigraphy and carbon isotope stratigraphy. Additionally, chemostratigraphy and rock magnetic stratigraphy were applied in order to identify major paleoenvironmental changes: lithogenic input and paleoredox variations. Polarity zones from M17r to M14r were identified from the uppermost Lower Berriasian up to the Berriasian/Valanginian boundary (Elliptica to Darderi calpionellid subzones and NK-1 to NK-3 nannofossil zones). Late Berriasian calcareous dinocyst zones of Stomiosphaerina proxima, Stomiosphaera wanneri and Colomisphaera conferta were correlated with magnetostratigraphy for the first time. A carbon isotope profile correlates very well with the δ13C records from SE France and the Western Atlantic, documenting some well-resolved minima and maxima in a generally decreasing trend. Magnetic susceptibility (MS) reveals a very good positive correlation with lithogenic elements (e.g., Al, Ti, Zr, Th and others) and is regarded as a reliable proxy of detrital input. Influx of fine grained terrigenous material increases in the Upper Berriasian up to the Berriasian/Valanginian boundary. A prominent MS increase takes place in the lowermost part of polarity zone M16n (close to the Simplex/Oblonga subzonal boundary). The MS event can be traced in the Central Carpathian, Apennine and SE France sections, exactly in the same stratigraphic position. It is coeval with an important climatic turnover in Western Tethys; however, it might have been strengthened by a general regression and regional tectonic events in the Carpatho–Balkan area. Two oxygen deficient intervals were documented: the first in the Lower Berriasian (M17r to M16r); the second one in the uppermost Upper Berriasian up to the boundary with Valanginian (M15r to M14r). Both intervals correlate with an elevated sea-level in the Western Tethys.

Assemblages of organic-walled phytoplankton, pollen, and spores from the Solenovian Horizon (lower Oligocene) of Western Eurasia

The analysis of organic-walled phytoplankton, pollen, and spores in sections of the Solenovian Horizon (second half of the lower Oligocene) in the Western Carpathians, Crimea-Caucasus region, and Scythian and Turan plates revealed that facies of a more desalinated basin (lower, Polbian Subhorizon) are characterized by a more impoverished assemblage of dinocysts, prasinophytes, and acritarchs numbering up to 20–30 taxa. Depending on facies properties, they are dominated by representatives of Batiacasphaera accompanied by thin-walled Hystrichokolpoma morphotypes or cysts of the Adnatosphaeridium-Glaphyrocysta Group, which allows facies to be defined as bed-ranked units within the single lower Oligocene Wetzeliella gochtii dinocyst zone. The organic-walled phytoplankton assemblage from the upper (Ikiburulian) subhorizon implies the frequently alternating salinity regime for this inner basin. The palynological assemblages of the Solenovian Horizon are characterized by a high share of Pinus pollen accompanied by pollen of Fagaceae (particularly in southern areas), Juglandaceae, and diverse thermophilic plants including evergreen taxa. The Solenovian climate was subtropical in western and southern areas and moderately warm seasonal with hot summers in others. The dominant arid climate was interrupted by brief humid episodes.

A revised northern European Turonian (Upper Cretaceous) dinoflagellate cyst biostratigraphy: Integrating palynology and carbon isotope events

Organic walled dinoflagellate cyst (dinocyst) assemblage data are presented for a new Turonian regional reference core (Bch-1) drilled at Běchary in the Bohemian Cretaceous Basin, east-central Czech Republic. The detailed stratigraphic framework for the section is summarised based on calcareous nannofossil and macrofossil biostratigraphy, regional e-log correlation, sequence stratigraphy and carbon isotope chemostratigraphy. Dinocyst results obtained for 196 samples from the 405m long core offer the highest resolution (~22kyr) stratigraphically well-constrained data set available to date for the Turonian Stage, 93.9–89.8Ma. A dinocyst biostratigraphic framework is presented based on the evolutionary first and last occurrence, first common occurrence, and acmes of key species. Published dinocyst data from English Turonian Chalk successions in East Sussex, Berkshire, Kent and Norfolk are reviewed within a stratigraphic framework provided by macrofossil records and carbon isotope event (CIE) chemostratigraphy. Critical analysis of existing published Turonian dinocyst zonation schemes shows them to be untenable. Correlation of the English Chalk data to Bch-1 provides a basis for defining a regional dinocyst event stratigraphy with 22 datum levels, and a revised dinocyst zonation scheme constrained within a chemostratigraphic framework of 10 major CIEs. The new zones consist of a Cenomanian Litosphaeridium siphoniphorum Zone, followed by the Cauveridinium membraniphorum Zone spanning the uppermost Cenomanian to Lower Coniacian. This is subdivided into: Senoniasphaera turonica (Lower–mid-Middle Turonian); and Raetiaedinium truncigerum (mid-Middle Turonian–mid-Lower Coniacian) subzones. The Oligosphaeridium pulcherrimum Zone (Senonisphaera rotundata Subzone) characterises the Lower Coniacian. The new stratigraphy offers a basis for improved correlation and dating of Upper Cretaceous successions.

A revised Paleocene (Teurian) dinoflagellate cyst zonation from eastern New Zealand

Organic-walled dinoflagellate cyst (dinocyst) assemblages are documented from Paleocene (New Zealand Teurian Stage) sediments in five sections from eastern New Zealand: Tawanui, Angora Road and Toi Flat-1 core in the East Coast Basin, mid-Waipara River in the Canterbury Basin, and ODP Site 1121 on the eastern margin of Campbell Plateau. Based on dinocyst results from these sections, along with published earliest Paleocene records from the East Coast, Canterbury and Great South Basins, a revised Paleocene (Teurian) dinocyst zonation is proposed. The zones are labelled as NZDP — New Zealand Dinocyst Paleocene — and are all interval zones. The eight zones, NZDP1 to NZDP8, encompass the entire Paleocene, from the Cretaceous–Paleogene boundary at 66.04Ma to the Paleocene–Eocene boundary at 55.96Ma. Correlation of the NZDP zones with the International and New Zealand Time Scales is provided, and is primarily based on correlation with calcareous nannofossil biostratigraphy. Three new dinocyst species are described: Leptodinium? pustulatum sp. nov., Cerodinium angulatum sp. nov., and Vozzhennikovia tawanuiensis sp. nov.

Microbiota and stratigraphy of lower Paleogene deposits of the Urma Plateau, Central Dagestan

The study of nannofossils, dinocysts, and foraminifera from Paleogene deposits of the Urma Plateau of Central Dagestan revealed the Paleocene-Eocene age of the Gray Formation, to apply zonations based on of all three groups of microplankton, and to correlate the regional dinocyst and planktonic foraminifer zonations to the standard nannofossil scale. Nannofossil zonation of O. Varol’s (1989) is shown to be successfully applied for subdivision of Danian deposits. The large foraminifer assemblage found in the lower Eocene deposits is correlated to the NP12-NP13 zones of the nannofossil scale.

Quantitative palynostratigraphy and palaeoecology of Tethyan Paleocene–Eocene red beds in north of Zagros sedimentary basin, Iran

Biostratigraphic and quantitative characteristics of dinocyst assemblages and palynofacies have been used to interpret the paleoecology and sea level changes of Paleocene–Eocene red beds in north of Zagros sedimentary basin, Iran. One hundred forty-eight species and 69 genera of dinoflagellate cysts are recorded from 32 rock samples collected from the 153-m-thick outcrop section. Three dinocyst zones comparable to North Hemisphere mid-latitude zonation are established and described. Three palynofacies differentiated—VI: proximal suboxic–anoxic shelf, VIII: distal dysoxic–anoxic shelf, and IX: distal suboxic–anoxic basin—suggest a suboxic–anoxic proximal–distal shelf and distal basin for the strata under investigation. The sequence stratigraphy events have been documented on the basis of palynological asset recorded such as palynofacies, SOM/MP ratio, dinocyst abundance and diversity, peridinioid/gonyaulacoid (P/G) ratio, proximochorate and cavate cysts ratio, and specific inner neritic, outer neritic, and oceanic taxa trends). The record of sea level changes for the Paleocene–Eocene red beds shows a third-order sequence with one sequence boundary (type II). The P/G ratio shows increasing upward trend of paleoproductivity in this sequence.

Biostratigraphy and microfacies of the pelagic carbonates across the Jurassic/Cretaceous boundary in eastern Serbia (Stara Planina–Poreč Zone)

Integrated micropaleontological and microfacies studies on Tithonian and Berriasian pelagic carbonates of the Stara Planina–Poreč Zone (eastern Serbia) provided a new knowledge on the stratigraphic ages, depositional settings and lateral correlation with the Western Balkan Unit in Bulgaria. A total of forty calpionellid species, nineteen benthic foraminiferal species, and fourteen species of calcareous dinoflagellates have been identified in the Rosomač section in eastern Serbia. Calpionellid zones Chitinoidella, Crassicollaria, Calpionella, and Calpionellopsis have been recorded. Calcareous dinoflagellate zonation consists of Parastomiosphaera malmica, Colomisphaera fortis, and Stomiosphaerina proxima zones. The Rosomač Limestones are assigned to the Upper Tithonian and Lower Berriasian and the Ržana Clayey Limestone Beds to the Upper Berriasian. Seven distinct microfacies have been identified at the Rosomač section in eastern Serbia. Two of them, MF 1 calpionellid mudstones and MF 2 calpionellid wackestones, characterize the basinal depositional zone. Five microfacies belong to the slope facial zone, including the toe of the slope. These are: MF 3 Saccocoma wackestones, MF 4 wackestones with bioclasts, MF 5 intraclast-bioclastic grainstones, MF 6 bioclast-intraclastic floatstones, and MF 7 bioclast-intraclastic rudstones. Vertical microfacies distributions are directly correlated with the calpionellid and calcareous dinocyst zonations in sections in Serbia and Bulgaria. The pelagic carbonates in the Tithonian/Berriasian boundary interval were deposited under slope conditions at Rosomač section, and under basinal conditions at Barlya section in western Bulgaria.

Bio- and magnetostratigraphy of Rupelian–mid Chattian deposits from the Danish land area

The age of the lithostratigraphic units in the Oligocene succession of Denmark is not well known. In order to remedy this situation, an integrated bio-magnetostratigraphical study of the Rupelian–mid Chattian deposits was carried out on six key sections situated in central Jutland. The studied sections include all previously known lithostratigraphical units (i.e., the Grundfør and Viborg Clay Members of the Viborg Formation, Linde Clay, Hvorslev Clay, Branden Clay) and a new, informal Unit X.The biostratigraphical part of the paper critically discusses the differences in ranges of some dinoflagellate cysts in relation to the two most commonly applied dinocyst zonations, the D- and NSO-zonation. The local calcareous nannofossil zonation of the upper NP23–lower NP25 interval in the studied sections is correlated to the standard NP zonation via the Contessa Barbetti Road section in central Italy. The correlation shows that an interval of the range of the dinoflagellate cyst Svalbardella recognized within the lower Chattian Asterigerina guerichi guerichi Zone in Denmark and Belgium is coeval with the global Oi2b cooling event.The identified magnetic polarity intervals have been correlated with the global polarity time scale on the basis of the biostratigraphy. The Viborg Formation is thus referred to Chron C13n and the lowermost part of C12r; the Linde Clay is referred to lower Chron C12r; and the Hvorslev Clay is referred to Chron C11n, C10 and C9r, or only the C11n.1n–C10r interval. The Branden Clay is referred to Chron C9r, C9n and C8r. Unit X is referred to Chron C8n.

Late Holocene paleoceanography and climate variability over the Mackenzie Slope (Beaufort Sea, Canadian Arctic)

Late Holocene paleoceanography and climate variability of the Southeastern Beaufort Sea (Canadian Arctic) have been investigated on the basis of sedimentary cores collected over the Mackenzie Slope. Piston, trigger and box cores were sampled at station 803 in 2004 aboard the CCGS Amundsen at 218m water depth. The chronology of the piston core is constrained by 4 AMS-14C dates, as the sedimentation rate in the box core is assessed from 210Pb data. We obtain a continuous composite sequence covering the last 4600years, with a sedimentation rate of ~140cm.kyr−1. Transfer functions (modern analogue technique) based on dinoflagellate cyst (dinocyst) assemblages were used to reconstruct the evolution of sea-surface conditions over the time period covered by the cores.Palynological data reveal that dinocyst assemblages are dominated by Operculodinium centrocarpum sensu lato (mean of 43.3%) throughout the core, with the accompanying taxa Brigantedinium spp. (19.6%), Islandinium minutum (15.6%) and cysts of Pentapharsodinium dalei (13.7%). Four zones have been established on the basis of dinocyst relative abundances. Dinocyst assemblage zone 1 (D1), from 4600 to 2700cal years BP, is dominated by O. centrocarpum (mean of 49.0%). In zone D2 (2700–1500cal years BP), the relative abundances of O. centrocarpum decrease (34.4%) in favour of the opportunistic, heterotrophic taxa Brigantedinium spp. (28.8%) and cysts of Polykrikos sp. var. arctic/quadratus (2.8%). Dinocyst zone D3 (1500–30cal years BP or 450–1920AD) is characterised by the high relative abundance of the peridinioid taxa I. minutum (19.9%). The last zone (D4), spanning from 1920 to 2004AD, is again dominated by O. centrocarpum (44.5%), and shows low relative abundances of Brigantedinium spp. and cf. Echinidinium karaense.Quantitative reconstructions of past sea-surface parameters (August sea-surface temperature: SST, August sea-surface salinity: SSS, and duration of sea-ice cover) indicate relatively stable conditions over the last 4.6kyr, with episodic cooling events (SST of ~1.5°C below the modern value of 6°C) that took place between 700 and 1820AD. We associate the last and the longest of these cooling events (1560–1820AD) with the Little Ice Age. Reconstructed SSS shows decadal oscillations since 1920AD that we tentatively associate with the accumulation of freshwater by the Beaufort Gyre and the subsequent Great Salinity Anomalies. Our data suggest that similar salinity anomalies could have occurred ca. 1860 and 1790AD.Stable isotopic data show a slight increase in δ13C values (from ~−27.1‰ at the base to ~−25.8‰ at the top) over the last 4.6kyr that we associate with the gradual increase in atmospheric CO2 concentration as recorded by Antarctic ice cores. Variations in the δ15N profile suggest variations in Pacific water influence from 4600 to ~1300cal years BP, associated with centennial scale shifts of the Arctic Oscillation phases.

Micropaleontological data (dinocysts, nannoplankton, spores and pollen) and biostratigraphy of the Alkun Formation, North Ossetia

The initially obtained data characterize organic-walled phytoplankton (dinocysts), nannoplankton, spores, and pollen from the Upper Argun, Alkun, and Lower Assa deposits of the Fiagdon and Mairamadag sections situated on the southeast of North Ossetia (North Caucasus) in the Alkun Formation stratotype area. The lithology of the formation is described, and its position in the Oligocene-Miocene succession is considered. According to the analyzed data on organic-walled phytoplankton from the Fiagdon and Mairamadag sections, the transitional late Oligocene-early Miocene dinoflora from the top of the Argun Formation and the lower part of the Alkun Formation is in general of the Miocene aspect. Based on the dinocysts, deposits from the upper part of the Alkun Formation coupled with the Assa Formation are attributed to the lower Miocene. The entire interval of the studied deposits corresponds to the acme subzone Def of the Ebu Zone in the Mediterranean dinocyst zonation by D. Zevenboom, where it spans the top of the Chattian and lower part of the Aquitanian Stage. Nannoplankton assemblages from the Alkun deposits are tentatively correlated with the nannoplankton assemblage of Zone NN1 in the standard zonation by E. Martini. It is impossible to date precisely the Alkun Formation based on nannoplankton, as the respective deposits are lacking index species and characteristic taxa of the standard zonation. The dominance of the cosmopolitan species Cyclicargolithus floridanus is a peculiar feature of nannoplankton assemblages from the Alkun Formation. Palynological data are used to consider the dynamics of the evolution of the vegetation cover and climate. Four episodes of relative cooling are distinguished against a background of warm-temperate climatic conditions in general. The most significant episodes occurred in the mid-Alkun time and during the early phase of the Assa time.

Neogene dinocyst zonation for the eastern North Sea Basin, Denmark

A dinocyst zonation for the Neogene succession in the eastern part of the North Sea Basin (Denmark) is presented. The zonation is based on an extensive database comprising data from more than fifty onshore and offshore boreholes and about twenty five outcrops. Most of the nineteen dinocyst zones described and defined herein, are new. The zonation is correlated with previously published dinocyst zonations within the North Sea Basin, in the North Atlantic and with the revised Northwest European zonation. The presented zonation gives a detailed subdivision of the Oligocene–Miocene transition, of the Lower Miocene, and of the Upper Miocene and Pliocene successions. The previous zonation of the onshore Danish Middle Miocene is reconsidered and partly redefined. The zonation is correlated with other biostratigraphic subdivisions of the Neogene succession in the Danish region in addition to litho- and sequence stratigraphy. The dinocyst zonation and the foraminifer zonation of the Danish Miocene (based upon analysis of the same boreholes) were independently calibrated with the established nannoplankton zonation. This correlation revealed a mismatch generally corresponding to one nannoplankton zone. Absolute ages of the new dinocyst zones are proposed based on correlation from the studied succession within the North Sea Basin with the international zonations and stratigraphic schemes. In addition, parts of the succession have been dated by strontium isotope analysis of mollusc shells. Inconsistencies due to first and last occurrences of some dinocyst species in previous studies and the present study, especially within the Lower Miocene, implied that new Sr-isotope datings from mollusc shells from the cored Sdr. Vium borehole and other localities in this study would be invaluable. Indeed, this method allowed the previous last occurrence of Cordosphaeridium cantharellus (one of the zonal index fossils) dated as between 17.95 My and 19.5 My in previous studies, to be assigned a new dating of 18.4 My. The timespan of the zones range from 2.6 My for the Amiculospharea umbraculum Zone to 0.4 My for the Achomosphaera andalousiensis Zone. Neogene biostratigraphy in the North Sea Basin has been problematic due to the periodically limited connection between the North Sea Basin and the North Atlantic Ocean, especially with respect to stratigraphy based on foraminifers and calcareous nannoplankton. Many of the stratigraphically most important taxa, e.g. those defining stratigraphic boundaries in type sections, have not been found within the North Sea Basin. This problem seems to be solved by correlation based on the new dinocyst stratigraphy, because stratigraphically significant taxa do occur in the North Sea deposits, even in marginal marine settings.

Paleogene biostratigraphy of the North Circum-Caspian region (implication of the dinocysts and nannoplankton from the Novouzensk reference borehole), Part 1: Age substantiation and correlation of deposits

Eight zonal dinocyst assemblages and three bio stratigraphic units ranked as “beds with flora” are first distinguished in the Danian—lower Lutetian interval of the Paleogene succession, penetrated by the reference borehole Novousensk no. 1, where eight standard and one local nannoplankton zones are simultaneously recognized. The direct correlation of nannoplankton and dinocyst zones is used to refine the paleon-tological substantiation and stratigraphic position of regional lithostratigraphic units, ranges of hiatuses, and the correlation with the general stratigraphie scale. The nannoplankton of the Danian NP2 Cruciplacolithus tenuis and NP3 Chiasmolithus danicus zones is characteristic of the Algai Formation (Fm). The nannoplankton of the NP4 Coccolithus robustus Zone and dinocysts of the D3a Alterbidinium circulum Zone from the Tsyganovo Fm characterizes the Danian top. The Lower Syzran Subformation (Subfm) corresponds to the upper part of the NP4 Coccolithus robustus Zone (Neochiastizygus junctus local zone) and to the D3b (part) Cerodinium depressum Zone of the Selandian dinocysts. The latter spans part of the Upper Syzran Subformation, whose characteristic nannofossils are the nannoplankton of the NP5 Fasciculithus tympaniformis Zone and the dinocysts of the D3b (part) Isabelidinium? viborgense Zone of the Selandian. The Novouzensk Fm is represented by a succession of the dinocyst Cerodinium markovae Beds and the standard D4c Apectodinium hyperacanthum Zone of the upper Thanetian. The coccolitophorids of the lower Thanetian NP6 Heliolithus kleinpelli Zone occur at the formation base. The Bostandyk Fm includes successive bio stratigraphie units of the Ypresian. In the dinocyst scale, these are the D5a Apectodinium augustum Zone, the Pterospermella Beds (DEla Zone of the North Sea scale), and zones DBlb-c Deflandrea oebisfeldensis, D7c Dracodinium varielon-gitudum, and D8 Dracodinium politum—Charlesdowniea coleothrypta, while units of the nannoplankton scale correspond to the NP12 Martasterites tribrachiatus and NP13 Discoaster lodoensis zones. The Kopterek Fm yields Lutetian nannofossils: the nannoplankton of the NP14 Discoaster sublodoensis Zone and the dinocysts of the Wetzeliella coronata—Areosphaeridium diktyoplokum Beds. Three meaningful hiatuses are established at the Danian base, Selandian top, and in the lower Ypresian.

LITHOLOGY AND DATING OF THE MIDDLE-UPPER EOCENE DEPOSITS IN THE JUNCTION ZONE OF THE DNIEPER-DONETS DEPRESSION AND THE DONETS BASIN

A lithologic and biostratigraphic study of the Kiev and Obukhov regional stages in the junction zone of the Dnieper-Donets Depression, Voronezh anteclise and northwest margin of the Donets Basin has confirmed two-component structure of the Kiev regional stage, with chertification being typical of the upper part of the Kiev and lower part of the Obukhov regional stages. Foraminiferal layers with Acarinina kiewensis and layers with Pseudoclavulina subbotinae-Robulus dimorphus, nannoplankton Zone NP16, dinocyst Zone DP9 and diatom layers with Stictodiscus kossutii have been recognized in the lower carbonaceous part of Kiev deposits. Layers with agglutinated foraminifers, dinocyst Zone DP10 and the diatom Cristodiscus succinctus Zone have been recognized in the non-carbonate part of Kiev deposits. Diatomes of the Plagiogramma paleоgena Zone have been identified in the lower part of Obukhov deposits. According to the identified microfossil assemblages, the Kiev and Obukhov regional stages in the region under study are dated to be Bartonian and Priabonian, respectively. This study reveals difficulties connected with the recognition of standard oceanic zones in epicontinental basins and points to the necessity of creating regional biostratigraphic schemes.

Palynology of the Palaeogene and Neogene from the Warmia and Mazury areas (NE Poland)

Palynology of the Palaeogene and Neogene from the Warmia and Mazury areas (NE Poland)Pollen, phytoplankton and microfauna from the Palaeogene and Neogene of two boreholes in NE Poland have been studied. Borehole Klucznik 1 is located in the Warmia area, and borehole Sąpłaty 3 borehole in the Mazury area. The oldest palynomorph assemblage comes from the Klucznik sediments; it consists of phytoplankton from the Early Palaeocene (Danian) D1 and D2 dinocyst zone, and from the Selandian D3 zone. The Eocene is present in the both the Klucznik and the Sąpłaty successions. The Middle Eocene assemblage has been dated as late Bartonian and belongs to the D11 dinocyst zone. The Late Eocene (Priabonian) D12 dinocyst zone is also present in both boreholes. Sporomorphs of a Late Eocene palynomorph assemblage point on the proximity of land and on terrestrial vegetation. The dinocyst zone D13, characteristic for the earliest Oligocene ('Latdorfian') has been found in both profiles as well. A Neogene sporomorph assemblage dating from the Middle Miocene (Early Serravallian) occurs only in the Sąpłaty profile. This sporomorph assemblage is correlated with pollen zone VIII. Pollen zone IX is present in the uppermost part of the Middle Miocene (Middle Serravallian). Late Miocene deposits

The upper Volgian Substage in Northeast Siberia (Nordvik Peninsula) and its Panboreal correlation based on ammonites

Section of the middle and upper Volgian substages and basal Boreal Berriasian in the Cape Urdyuk-Khaya (Nordvik Peninsula) is largely composed of dark argillites substantially enriched in Corg. Characteristic of the section is a continuous succession of ammonite, foraminiferal, ostracode, and dinocyst zones known also in the other Arctic areas. Boundaries of the upper Volgian Substage are recognizable only based on biostratigraphic criteria. The succession of the middle Volgian Taimyrosphinctes excentricus to basal Ryazanian Hectoroceras kochi zones is characterized. The range of the substage is revised. The lower Exoticus Zone, where ammonites characteristic of the Nikitini Zone upper part in the East European platform have been found, is referred to the middle Volgian Substage. Newly found ammonites are figured. Two possible positions of the Jurassic-Cretaceous boundary in the Arctic region, i.e., at the lower and upper boundaries of the Chetae Zone at the top of the upper Volgian Substage, are discussed.

Discussion on the Eocene–Oligocene boundary in the UK Journal , Vol. 163, 2006, pp. 401–415

Jerry Hooker, Margaret Collinson, Stephen Grimes, Nick Sille & David Mattey write: Recognition of the Eocene–Oligocene boundary in the Hampshire Basin, UK, has been debated since naming of the Oligocene Epoch in 1854. Previously, this was because the boundary itself had not been stabilized and because the strata concerned are largely non-marine. A Global Boundary Stratotype and Stratigraphic Point (GSSP) was established at Massignano, Italy, in 1993 in marine strata. Recognition of the boundary on extinction of the planktonic foraminiferan family Hantkeninidae made boundary identification difficult in the continental realm. Correlation to marginal marine and non-marine strata is nevertheless possible via magnetostratigraphic and sequence stratigraphic studies and, importantly, biostratigraphically via dinocyst zones at Massignano (Brinkhuis & Biffi 1993; Brinkhuis & Visscher 1995). Therefore, recent publication of the magnetostratigraphy, sequence stratigraphy and orbital cyclicity of much of the Hampshire Basin Solent Group (Gale et al . 2006) is welcomed and substantially increases the number of correlation tools available in this area. Such cyclical phenomena, however, rely on absolute dating or biostratigraphy for calibration. No radiometric dates exist for the Solent Group, so biostratigraphy remains the best means of dating the succession. There are, however, problems with the way Gale et al . (2006) have interpreted biostratigraphic markers and therefore with their placement of the Eocene–Oligocene boundary and associated events. The organisms concerned are calcareous nannoplankton (NP zones) and mammals (MP reference levels). Thus, the record by Aubry (1985) of NP22 in the Argiles Vertes de Romainville, Paris Basin, was subsequently qualified by her (Aubry 1986, p. 307) as ‘zone NP22 (not younger; possibly older: NP21?)’. This dating was based solely on the presence of rare Isthmolithus recurvus , which ranges from NP19/20 to NP22 (Aubry 1992), this being the real level of dating for the Argiles Vertes de Romainville …

Organic-walled dinoflagellate cyst stratigraphy in an expanded Oligocene–Miocene boundary section in the eastern North Sea Basin (Frida-1 Well, Denmark) and correlation from basinal to marginal areas

Abstract. The organic-walled dinoflagellate cyst (dinocyst) assemblages in an unusually thick (>800m) Oligocene–Miocene boundary succession from the eastern North Sea Basin (the Frida-1 Well) were studied. Six successive dinocyst assemblages are described: the Wetzeliella gochtii Assemblage (early Chattian), the Distatodinium biffii Assemblage (Chattian), the Deflandrea phosphoritica Assemblage (latest Chattian), the Homotryblium spp. Assemblage (early Aquitanian), the Caligodinium amiculum Assemblage (Aquitanian) and the Cordosphaeridium cantharellus Assemblage (latest Aquitanian to early Burdigalian). The dinocyst assemblages are compared with informal dinocyst zonations proposed for the southern North Sea Basin (Germany, Belgium and the Netherlands).A correlation of the expanded basinal succession in Frida-1 with the marginal marine succession found onshore Jylland, based on the dinocyst stratigraphy combined with well logs and seismic data, is proposed. This correlation confirms earlier proposed datings of the onshore deposits and the presence of several hiati. Furthermore, the correlation made it possible to subdivide the succession in Frida-1 into the sequences A–C, as defined onshore. The Mi-1 glaciation event and thus the Oligocene–Miocene boundary are proposed to correlate to the boundary between sequences A and B.

Terminal paleocene of the Volga middle reaches: Biostratigraphy and paleosettings

Diatoms and marine palynomorphs from several sections of the Kamyshin Formation (Sengilei-1, Sengilei-2, Balasheika, Kuz’kino, boreholes 38 and 50) are jointly studied for the first time in the Volga middle reaches. According to results, the formation lower part corresponds here to Viborg Zone 4-Viborg Zone 5 (Heilmann-Clausen, 1985)/Alisocysta margarita (part)-Apectodinium hyperacanthum (Powell, 1992) diatom zones of Northern Europe. Higher levels of the formation are correlative with Trinacria ventriculosa and Hemiaulus proteus dinocyst zones (Strelnikova, 1992). Thus, the Kamyshin sedimentary cycle in the Volga middle reaches corresponds to the interval of NP8 (part) and NP9 zones of the general scale. As is established, different terrigenous to siliceous facies of that cycle (sands, diatomites, opokas and clay) are mostly confined to eastern and southeastern areas of the study region. Judging from taxonomic composition, assemblages of diatoms and marine palynomorphs originated in coastal paleosettings with active hydrodynamics and high productivity of water mass. Diatom assemblages from different facies are dissimilar. Three phases of Thanetian transgression are distinguished based on quantitative proportions of different ecologic groups (Paralia/Pyxidicula ratio variations). Within transition from the Trinacria ventriculosa to Hemiaulus proteus Zone, there are recorded considerable changes in composition of diatom assemblages: the appearance of new genera with considerable morphologic innovations (Podosira, Craspedodiscus, Fenestrella, Moisseevia, Solium, Gyrocylindrus) and compositional renewals of genera Pyxidicula, Trinacria, and Hemiaulus. These changes are indicative of a global biotic crisis in the Paleocene-Eocene transition related with thermal maximum and negative C-isotope excursion and extinction of benthic fauna groups.

Early cretaceous dinocysts of northern Siberia and their stratigraphic significance

The palynological analysis of the Berriasian-Barremian of northern Siberia has once again demonstrated the great stratigraphic value of dinocysts. A succession of ten dinocyst zones has been established. Most of their boundaries may be considered as important stratigraphic marks, which can be traced, apart from in Siberia, in northern Europe, Greenland, and China. Groups of characteristic species, in common for these territories, are determined for certain intervals. Dinocysts of the suborders Rhaetogonyaulacineae and Cladopixiineae (including two new morphotypes), four species of Dingodinium and four species of Aprobolocysta are described, among them new species Dingodinium subtile and Aprobolocysta cornuta. The genus Horologinella is revised, and the diagnosis of Aprobolocysta is emended.

Oligocene dinoflagellate cyst biostratigraphy of the southern North Sea Basin

The Rupelian (Lower Oligocene) and Chattian (Upper Oligocene) stratotype sections are both defined on the basis of the southern North Sea Basin sedimentary successions. The characterisation of biotic events occurring within the stratotypes (and equivalents) is vital for the recognition of these stages outside the North Sea Basin. Although the restricted marine setting of the North Sea Basin during most of the Paleogene clearly hampers ‘traditional’ calcareous microfossil calibration, organic-walled dinoflagellate cysts (dinocysts) are increasingly successful in the stratigraphic analysis and calibration of the marginal-marine North Sea Basin successions. Here we present a high-resolution Oligocene dinocyst biostratigraphic zonation scheme for the southern North Sea Basin based on previously published and new dinocyst studies from Belgium, northern Germany and The Netherlands. Eight (southern) North Sea Oligocene (NSO) dinocyst zones (biozones) and four subzones are here defined. Their application on a regional and inter-regional scale is discussed. The stratigraphic important Late Oligocene dinocyst taxon Triphragmadinium demaniae gen. and sp. nov. is formally described.