Polysphaeridium Zoharyi Research Articles

Why cysts of Alexandrium catenella and/or A. pacificum (Gonyaulacales, Dinophyceae) do not remain in sediments as fossils?

The dinoflagellate genus Alexandrium contains a number of species that produce paralytic shellfish toxins and have been the focus of attention as toxic plankton for harmless algal studies. Among Alexandrium species, A. catenella and A. pacificum form ellipsoidal-shaped resting cysts, which are preserved in marine sediments, and have attracted attention as potential seeds for future proliferation after favorable environmental conditions environmental improvement. However, although these cysts are preserved in surface of marine sediments, there is no record of their occurrence from solidified sediments as fossils. In order to clarify the reason for this, we investigated the differences in the chemical composition of cyst walls between colorless cyst of Alexandrium catenella/pacificum and Lingulodinium machaerophorum, Polysphaeridium zoharyi, Spiniferites spp. by measuring the thickness of cyst walls and using Fourier Transform Infrared Spectroscopy (FTIR) and Raman Spectroscopy. The results showed that the cyst wall of A. catenella/pacificum and L. machaerophorum were all composed of cellulosic organic matter. However, A. catenella/pacificum have the higher percentage of α−/β-glucosidic linkages and that the thickness of their cyst walls is about one-third of that of L. machaerophorum. Therefore, these are reasons for the cysts of A. catenella/pacificum being more easily degraded in the sediment.

Tropical Warming and Intensification of the West African Monsoon During the Miocene Climatic Optimum

AbstractStudying monsoon dynamics during past warm time periods such as the Miocene Climatic Optimum (MCO; ∼16.9–14.5 Ma) could greatly aid in better projecting monsoon intensity, in the context of future greenhouse warming. However, studies on regional MCO temperature change and its effect on the monsoons during this time period are lacking. Here, we present the first high‐resolution, low‐latitude record of sea surface temperature (SST) and paleoceanographic change covering the Miocene Climatic Optimum, in the eastern equatorial Atlantic, at Ocean Drilling Program Site 959, based on TEX86 paleothermometry. SSTs were ∼1.5°C warmer at the onset of the MCO (16.9 Ma) relative to the pre‐MCO (∼18.3–17.7 Ma). This warming was accompanied by a transient increase in %total organic carbon. Prior to the MCO, sediment composition, geochemical proxy data as well as dinoflagellate cyst assemblages imply a productive surface ocean at Site 959. Immediately following the MCO onset (∼16.9–16.5 Ma), we record an intensification of the West African Monsoon (WAM) characterized by higher amplitude variability in all proxy records on precession to obliquity timescales. We interpret increased orbital‐scale SST, biogenic Ba and dinocyst assemblage variability to represent intensification of equatorial upwelling, forced by the WAM strength. Furthermore, higher SSTs during eccentricity maxima correlate to increased relative abundances of the warm and stratification‐favoring dinocyst Polysphaeridium zoharyi, during periods of low WAM intensity. Finally, while long‐term SSTs decline toward the middle Miocene, maximum SSTs and Polysphaeridium zoharyi abundances occur during MCO peak warming at ∼15.6 Ma.

Paleocene – Late Oligocene dinoflagellate cysts biostratigraphy, onshore Niger Delta

A new biostratigraphic biozonation for the Paleocene to Late Oligocene succession of the onshore Niger Delta has been developed based on the identification of significant stratigraphic dinoflagellate cyst events. This study is aimed at applying rarely used dinoflagellate cysts events in dating, correlating and inferring the paleoenvironment of penetrated sedimentary successions in the studied area. Palynological processing and analysis were carried out on two hundred and twenty ditch cutting samples recovered from two exploration wells (BN-1 and FJ-1) located in the Greater Ughelli and Northern Depobelts of the onshore Niger Delta respectively. Abundant and diverse dinoflagellate cysts recovered included marker Peridinales species Apectodinium sp., Palaeocystodinium australinum, and Gonyaulacales such as Areosphaeridium arcuatum, Cordosphaeridium gracile, Tuberculodinium vancampoae, Polysphaeridium zoharyi and Hystrichokolpoma rigaudiae. Three dinoflagellate cysts Palynological Zones - DPZ 100 (Early to Late Paleocene), DPZ 200 (Early to Late Eocene) and DPZ 300 (Late Eocene to Late Oligocene) are proposed herein. The biozones were subdivided into ten subzones based on the Top occurrence, Quantitative Tops and Quantitative base as well as ACME events of dinoflagellate cysts marker taxa which are used to date the rock sequence to be Paleocene to Late Oligocene. Abundant and diverse shallow outer neritic to inner neritic dinoflagellate cysts are identified from thick grey soft shales at the lower section of the studied wells. The upper section show significant reduction in dinocysts assemblage dominated by inner (coastal) neritic taxa. This dinocysts occurrence and distribution suggests inner (coastal) neritic paleoenvironment at the upper sections which deepened into shallow outer neritic conditions at the lower intervals of the studied wells. The thick brown to grey shales at the lower section and the medium to fine grained, moderately well sorted sandstone interbeds at the middle section of the studied wells are interpreted to be potential source and reservoir rocks respectively. These datasets are useful for correlating possible hydrocarbon source rocks and potential reservoir carrier beds in the Gulf of Guinea.

The Badenian/Sarmatian (Middle Miocene) boundary in the Central Paratethys (Kreminna, western Ukraine): Foraminiferal and palynological evidence

The Badenian/Sarmatian boundary in the Paratethys basin, that marks the transition from normal marine to restricted semi-marine conditions due to isolation of the basin from the world ocean at the onset of Sarmatian time, is still far from being fully understood. The Kreminna section is located at the northeastern margin of the Carpathian Foreland Basin (Central Paratethys) in the Medobory Hills region. The Miocene deposits that overlie here the Upper Cretaceous substratum comprise the >1 m thick upper Badenian marls and clays passing upwards into ~4 m thick Sarmatian marly limestones with intercalations of marls, clays and limestones, and >2 m thick limestones in the uppermost part of the exposure. Fifty-three species of benthic foraminifera and four species of planktonic foraminifera have been recorded. Six benthic foraminiferal assemblages are composed almost exclusively of calcareous forms; agglutinated taxa are practically lacking. Elphidium spp., miliolids, Lobatula lobatula and Ammonia spp. are the most common calcareous benthic foraminifera in the material studied. Planktonic foraminifera are represented only by species of Globigerina and occur rarely in the lowermost part of the section. A characteristic feature of palynofacies is the very low proportion of land-derived elements – sporomorphs and cuticles, which suggests a sedimentary setting without terrestrial influx, and taxonomical impoverishment of dinoflagellate cyst assemblages, which are either monospecific or consist mainly of two to three species: in a majority of samples, assemblages with Polysphaeridium zoharyi and P. subtile occur. Most δ18O values range from –1.5 to ~+0.5‰ VPDB and most δ13C values are between 0 and +2‰ VPDB. In general, the δ13C curve mirrors the δ18O changes in the section. The Badenian/Sarmatian boundary is placed at the level where the Cibicidoides ungerianus Assemblage is replaced by the Elphidium fichtelianum Assemblage. At the boundary, planktonic foraminifers and most abundant stenohaline benthic foraminifera disappeared. Bottom waters were well-oxygenated both in the latest Badenian and earliest Sarmatian in the Kreminna location.

Palynostratigraphy, biochronology and palaeobathymetry of a section of Awaizombe-1 well, eastern Niger Delta, Nigeria

ABSTRACTDitch cuttings (69 samples) from a section of Awaizombe-1well located in the Northern Depobelt of the eastern Niger Delta Basin were used for this study. The lithology of the studied interval 1373–1812 m (439 m thick) consists of fissile grey shale and mudstone units. The scid method of sample preparation for palynormorphs’ recovery was adopted. Analysis recorded a well-preserved and diverse assemblage of palynomorphs, rich in pollen, spores and dinoflagellate cysts (dinocysts). First and last occurrences of marker and age diagnostic species were used for palynostratigraphic interpretation. Four palynostratigraphic interval range zones were established: Psilatriporites sp.–Racemonocolpites hians Zone; early Oligocene (Rupelian age), Praedapollis africanus–Doualaidites laevigatus Zone; late Eocene (Priabonian age), middle Eocene (Lutetian and Bartonian ages), Doualaidites laevigatus–Praedapollis flexibilies Zone; and early Eocene (Ypresian age), Verrucatosporites usmensis–Retitricolpites ituensis Zone. The first downhole occurrence of D. laevigatus at the 1482 m marks the late Eocene/early Oligocene boundary. Established zones are useful for inter and intra basins correlation. Lithology and age of the studied section are suggestive of the lower Agbada Formation. Palaeoenvironmental interpretations using diagnostic species revealed two environments: brackish and inner neritic to upper bathyal (0–600 m) under relatively warm-water marine condition indicated by thermophilic dinocyst taxa, such as Lingulodinium machaerophorum, Polysphaeridium zoharyi and Homotryblium spp. The lithology and these types of environments are good sites for hydrocarbon generation.

Dinoflagellate cyst distribution in surface sediments of Ambon Bay (eastern Indonesia): Environmental conditions and harmful blooms

The present study aimed to document dinocyst ecological preferences in Ambon Bay, Eastern Indonesia, and to investigate if the bay sediments serve as a seedbank for toxic bloom events. To this end, dinocyst and geochemical analyses of surface sediment samples were performed, along with physicochemical water column parameters. Twentythree dinocyst species were identified, and high dinocyst concentrations (up to ~12,000 cysts g−1 dry sediment) were found in the inner bay. Environmental factors such as surface water temperature and salinity generally played an important role in dinocyst distribution. The concentration of Polysphaeridium zoharyi cysts showed a strong positive correlation with phosphorus. A statistically significant correlation was also found with the concentration of other autotrophic dinocysts in the sediments, and an inverse correlation was observed with the sediment C/N ratio. Cysts may serve as seedbanks for Pyrodinium bahamense blooms in the area.

Dinoflagellate cyst distribution in surface sediments from the South China Sea in relation to hydrographic conditions and primary productivity

The geographical distribution of dinoflagellate cysts was investigated in palynologically treated surface sediments from the South China Sea (SCS) to understand the driving environmental factors associated with specific taxa. The western SCS generally has higher total cyst concentrations (>300 cysts g−1) than the eastern region (<200 cysts g−1). The highest concentrations (>1000 cysts g−1) occur off southern Vietnam, whereas the lowest cyst concentrations are off Luzon. The ratio of heterotrophic to autotrophic taxa has inverse distributional patterns to total cyst concentrations, and is likely to be related to an increase in relative abundances of autotrophic taxa when nutrient inputs increase. Brigantedinium spp., Selenopemphix nephroides, and Stelladinium reidii have their highest relative abundances and concentrations off Borneo. Their concentrations are significantly positively correlated with January sea-surface temperature (SST-Jan). In contrast, concentrations of Selenopemphix undulata, Spiniferites hyperacanthus, Dapsilidinium pastielsii and Operculodinium?longispinigerum are negatively correlated with SST-Jan. Lejeunecysta sabrina, cysts of Protoperidinium spp., Votadinium spp., Quinquecuspis concreta and Selenopemphix quanta are positively correlated with chlorophyll-a (chl-a) concentrations and are found in the high primary productivity regions of the SCS. Total Impagidinium, Impagidinium aculeatum, Impagidinium paradoxum, Impagidinium patulum, Nematosphaeropsis labyrinthus, and Polysphaeridium zoharyi are positively correlated with water depth. Their highest abundances are recorded in the northern slope-deep basin that is influenced by the Kuroshio Current, and this cyst assemblage indicates an open-ocean environment.

Paleogene-early Neogene paleoenvironmental reconstruction based on palynological analysis of ODP Hole 959A, West Africa

Abstract Five paleoenvironmental intervals (interval 1-interval 5) are established in the late Paleogene-early Neogene of the Ocean Drilling Program (ODP) Site 959 (Hole 959A), Cote d'Ivoire-Ghana Transform Margin in the eastern Equatorial Atlantic. The intervals are based on dinoflagellate cyst and palynofacies analyses of 30 samples covering a 273.3-m interval. We observed an abundance of the Filisphaera group (Filisphaera filifera and Bitectatodinium tepikiense) which is interpreted as an Arctic migration to equatorial regions during a narrow interval in the Early Oligocene (early Rupelian). In addition, we document one hiatus within interval 3 in the Early Miocene (Aquitanian). The dominance of typically restricted marine species of the Polysphaeridium group (Homotryblium plectilum and Polysphaeridium zoharyi) at several horizons in the open-oceanic sediments of ODP Hole 959A appear to be very distinctive events. Upon integrating dinoflagellate cyst data with prior lithologic and microfossil data, we interpret these dominance events as being due to offshore transportation by turbidity currents (intervals 1 and 2), hiatus event (interval 3), or hyperstratification conditions (intervals 3 and 4). In addition, the dominance of Cribroperidinium spp. (C. giuseppei and C. tenuitabulatum) in the upper part of the section within paleoenvironmental interval 5 is suggestive of cold-water masses during a strong upwelling period in the latest Early Miocene (Burdigalian). The general abundance of amorphous organic matter alongside the dinoflagellate cyst assemblage supports an outer neritic-oceanic depositional environment for the studied site. The consistent occurrence of degraded phytoclasts in the sediments also suggests fluvial outflows to this offshore site.

Palynological Study of OSE 1 Well in Offshore Niger Delta Basin: Implications for Age, Paleoclimate and Depositional Paleoenvironment

Palynological study of 45 ditch samples from sedimentary successions penetrated by OSE 1 well located offshore western Niger Delta Basin was undertaken to determine the age of the sediment and reconstruct the paleoclimate and depositional paleoenvironment. All the analyzed samples were composited at 30 ft from stratigraphic depth interval of 6330 to 9010 ft. The lithologic composition comprised mainly of brownish grey or light grey, fine-grained shales with a gypsiferous horizon near the bottom. Palynological slides were prepared following standard palynological preparation procedures of sample maceration with hydrochloric (HCl) and hydrofluoric (HF) acids. The samples yielded moderately well-preserved, low to high diversity palynomorph assemblages of 58 taxa comprising 29 pollen grains, 9 pteridophic spores, 17 dinoflagellates, one acritarch, one freshwater algae and a fungi spore. The stratigraphic distribution of microflora assemblages was highly variable. The assemblage abundance was dominated by pollen and spores. The retrieved pollen grains included Monoporites annulatus, Sapotaceoidaepollenites sp. Psilatricolporites crassus, Psilatricolporites sp., Zonocostites ramonae, Retitricolporites irregularis, Monocolpites marginatus, Monocolpites sp., Pachydermites diederixi, Proxapertites cursus, Verrutricolporites rotundiporus, Striatopollis catatumbus, Retistephanocolpites gracilis, Echiperiporites estalae, Echiperiporites sp. and Inaperturopollenites sp. The retrieved spores included Magnastriatites howardi, Acrostichum aureum, Laevigatosporites sp., Polypodiaceoisporites sp., Verrucatosporites sp., Crassoretitriletes vanraadshooveni and Stereisporites sp. The recorded dinoflagellates included Achomosphaera sp., Andalusiella sp., Polysphaeridium zoharyi, Selenopemphix nephroides and Spiniferites sp. Leiosphaeridia sp. was the only acritarch present in the assemblage. The freshwater algae was Botryococcus braunii. Fungi spore was present but not in significant amount. The stratigraphic interval was dated Early to Late Miocene (Burgidalian-Messinian) based on the occurrence and distribution of some stratigraphic fossil marker species including Magnatriatites howardi, Crassoretitriletes vanraadshooveni and Retistephanocolpites gracilis The abundant occurrence of pollen and spores typical of rain forest and freshwater swamp communities in the assemblage indicated tropical paleoclimatic conditions. The distribution pattern of Monoporites annulatus (Poaceae) and Zonocostites ramonae (Rhizophora) suggested seasonal fluctuations between dryer and wetter climatic conditions. The sediments were deposited in a wide range of environments including brackish lagoons, open salt water swamps, freahwater and nearshore to inner neritic settings.

Environmental forcing on the flux of organic-walled dinoflagellate cysts in recent sediments from a subtropical lagoon in the Gulf of California

To evaluate the relationship of changes in organic-walled dinoflagellate cyst (dinocyst) fluxes to sediments with environmental variables (air and sea surface temperatures, El Niño conditions, rainfall, and terrigenous index), cyst assemblages were analyzed in a 210Pb-dated sediment core (~100years) from the pristine San José Lagoon (San José Island, SW Gulf of California). The dinocyst abundance ranged from 3784 to 25,108cystsg−1 and fluxes were of the order of 103–104cystscm−2yr−1. Lingulodinium machaerophorum, Polysphaeridium zoharyi and Spiniferites taxa accounted for 96% of the total dinocyst assemblages, and the abundances of these species increased towards the core surface. P. zoharyi fluxes increased from about 1965 onwards. Redundancy analyses, showed that mean minimum air temperature and terrigenous index were the key factors governing dinocyst fluxes. In this study, dinocyst fluxes of dominant taxa had responded to changes in climate-dependent environmental variables during the past ~20years; this may also be the case in other subtropical coastal lagoons.

Effect of nutrient pollution on dinoflagellate cyst assemblages across estuaries of the NW Atlantic

We analyzed surface sediments from 23 northeast USA estuaries, from Maine to Delaware, and nine estuaries from Prince Edward Island (PEI, Canada), to determine how dinoflagellate cyst assemblages varied with nutrient loading. Overall the abundance of cysts of heterotrophic dinoflagellates correlates with modeled nitrogen loading, but there were also regional signals. On PEI cysts of Gymnodinium microreticulatum characterized estuaries with high nitrogen loading while the sediments of eutrophic Boston Harbor were characterized by high abundances of Spiniferites spp. In Delaware Bay and the Delaware Inland Bays Polysphaeridium zoharyi correlated with higher temperatures and nutrient loading. This is the first study to document the dinoflagellate cyst eutrophication signal at such a large geographic scale in estuaries, thus confirming their value as indicators of water quality change and anthropogenic impact.

Investigating the impact of land use and the potential for harmful algal blooms in a tropical lagoon of the Gulf of Mexico

Palynological and geochemical analyses were carried out on a sediment core collected in the shallow Alvarado lagoon (Veracruz, Southwestern Gulf of Mexico) in order to evaluate the impact of the significant decline in the surrounding native coastal vegetation on phytoplankton assemblages. The sedimentary sequence encompasses the last millennium and provides information on pre-industrial phytoplankton assemblages. Results highlight a recent increase of freshwater-sourced organic matter relative to marine organic matter in line with reduced total concentrations of cyst-producing dinoflagellates. These changes appear to be synchronous to the extensive conversion of wetlands into agricultural areas, with consequences on the stability and water retention capacity of the soils bordering the lagoon system. The data also show that Polysphaeridium zoharyi, a cyst produced by the potentially toxic dinoflagellate Pyrodinium bahamense, is present in high abundance in the dinoflagellate population of the lagoon. Consequently, the modern cyst bank of P. bahamense in sediment has the potential to initiate harmful blooms since surface sediments are prone to resuspension events related to strong seasonal winds and human activities.

Long-term hydrological changes in the northeastern Gulf of Mexico (ODP-625B) during the Holocene and late Pleistocene inferred from organic-walled dinoflagellate cysts

Palynological analyses are used in conjunction with oxygen isotopes and Mg/Ca ratios in foraminifers in order to document the response of dinoflagellate cysts (dinocysts) assemblages to changing climate conditions in the northeastern Gulf of Mexico over the Holocene and late Pleistocene. During MIS 6, but also during the cooler phases of MIS 5, Impagidinium species and Operculodinium centrocarpum were dominating the assemblages. By contrast, during the last interglacial (LIG) and the Holocene, assemblages were mainly composed of Spiniferites taxa and characterized by high relative abundance of Spiniferites mirabilis-hyperacanthus, Operculodinium israelianum and/or Polysphaeridium zoharyi. These two periods exhibit ~1-2°C difference in temperature as inferred from Mg/Ca ratios and show significantly distinct assemblages, with higher percentages of S. mirabilis during the LIG and higher percentages of P. zoharyi during the Holocene. This likely denotes important differences in the hydrogeographical conditions (e.g. surface circulation, bathymetric configuration) between the present and last interglacial. The importance of environmental parameters other than temperature and salinity for dinocyst assemblage dynamics is furthermore illustrated.

Driving factors behind the distribution of dinocyst composition and abundance in surface sediments in a western Mediterranean coastal lagoon: Report from a high resolution mapping study

Species composition and abundance of dinocysts in relation to environmental factors were studied at 123 stations of surface sediment in Bizerte Lagoon. Forty-eight dinocyst types were identified, mainly dominated by Brigantidinium simplex, Votadinum spinosum, Alexandrium pseudogonyaulax, Alexandrium catenella, and Lingulodinum machaerophorum along with many round brown cysts and spiny round brown cysts. Cysts ranged from 1276 to 20126cystsg−1dry weight sediment. Significant differences in cyst distribution pattern were recorded among the zones, with a higher cyst abundance occurring in the lagoon’s inner areas. Redundancy analyses showed two distinct associations of dinocysts according to location and environmental variables. Ballast water discharges are potential introducers of non-indigenous species, especially harmful ones such as A. catenella and Polysphaeridium zoharyi, with currents playing a pivotal role in cyst distribution. Findings concerning harmful cyst species indicate potential seedbeds for initiation of future blooms and outbreaks of potentially toxic species in the lagoon.

The Middle–Upper Pleistocene Fronte Section (Taranto, Italy): An exceptionally preserved marine record of the Last Interglacial

The Fronte Section, a well-exposed stratigraphic succession from southern Italy (Taranto area), provides an uninterrupted marine sedimentary record of MIS 5e. At this location, a highly expanded (8.5m thick) stratigraphic succession, unconformably overlying Middle Pleistocene marine clay deposits, provides evidence for sea-level fluctuations during the Last Interglacial. An integrated study of Fronte Section, including facies analysis, detailed macrofaunal and meiofaunal characterization, and sequence stratigraphy, is presented. The occurrence of Persististrombus latus (=Strombus bubonius) and other warm-water indicators (“Senegalaise” – “Senegalian” – guests of Gignoux, 1913), together with the presence of the dinocyst Polysphaeridium zoharyi and ten U-series dates on Cladocora caespitosa samples, permit an unequivocal MIS 5e age assignment to the upper part of the study succession. Above a stratigraphic unconformity marked by the boring coastal-lagoonal bivalve Pholas dactylus, the MIS 5e succession displays a first transgressive suite of brackish to shallow-marine deposits. These latter include highly fossiliferous muds rich in C. caespitosa, overlain by a fossil-rich calcarenite, 2m-thick, yielding warm-water “Senegalian” mollusks. Above this prominent stratigraphic marker (regionally called panchina), which is interpreted to represent a short-lived phase of sea-level stillstand or gentle fall during MIS 5e, renewed transgression took place, leading to the accumulation of middle-outer shelf muds, about 5m thick. The maximum flooding zone is clearly identified on the basis of the turnaround from a deepening-up to a shallowing-up trend. The upper part of Fronte Section records a second fossil-rich, sublittoral calcarenite containing warm-water mollusks, which is interpreted to reflect the subsequent phase of sea-level highstand, likely correlative with the MIS 5e plateau.

Organic-walled dinoflagellate cyst distribution in the Gulf of Mexico

In order to document the distribution of organic-walled dinoflagellate cysts (dinocysts) and their relationship with sea-surface parameters (temperature, salinity, primary productivity), palynological analyses were performed on 44 surface sediment samples from the Gulf of Mexico (17°N to 29°N). Samples display low to moderate concentrations with values ranging from 78 to 3576 dinocysts·g − 1 dry weight sediment. Assemblages are dominated by either Brigantedinium spp. or Polysphaeridium zoharyi along with the phototrophic taxa Spiniferites spp. and Operculodinium spp. Redundancy analyses (RDA) identified the distance to the coast and/or water depth and annual temperature as being the most important factors that control cyst distribution in the Gulf of Mexico. The first two axes explain respectively 44.7% and 20% of the total variance. The inshore to offshore trend in cyst distribution emphasized by the RDA involves changes in associations of species with the presence of Impagidinium spp. in more oceanic assemblages and higher representation of P. zoharyi nearshore. This latter species, produced by the potentially toxic dinoflagellate Pyrodinium bahamense , reaches very high abundances notably on the west Florida shelf and in the Mexican lagoons. Additionally, Melitasphaeridium choanophorum , which was considered to have gone extinct by the end of the Pleistocene, appears as a modern component of marine sediment from the north and southwestern Gulf. Our results thus demonstrate a biostratigraphical range extending to the present, at least in the study area. This palynological investigation highlights the importance of the Gulf of Mexico as potential refuge for late Cenozoic species thought to be extinct. • Gulf of Mexico as potential refuge for late Cenozoic species thought to be extinct. • Melitasphaeridium choanophorum appears as a modern component of marine sediment. • The distance to the coast and/or water depth are the main parameters that control assemblages.

Middle and Late Miocene palynological biozonation of the south-western part of Central Paratethys (Croatia)

Middle and Late Miocene palynological biozonation of the south-western parts of Central Paratethys (Croatia) is presented based on organic-walled phytoplankton. Nine characteristic palynozones of regional palynostratigraphic range are recognized, e.g. Early Badenian (Langhian) Cribroperidinium tenuitabulatum (Cte), Badenian (Late Langhian – Earliest Serravallian) Unipontidinium aquaeductum (Uaq), Late Badenian (Early Serravallian) Cleistosphaeridium placacanthum (Cpl), Sarmatian (Middle and Late Serravallian) Polysphaeridium zoharyi – Lingulodinium machaerophorum (Pzo-Lma), early Early Pannonian s.l. Mecsekia ultima – Spiniferites bentorii pannonicus (MulSpa), middle Early Pannonian s.l. Spiniferites bentorii oblongus (Sob), late Early Pannonian s.l. Pontiadinium pecsvaradensis (Ppe), early Late Pannonian s.l. Spiniferites validus (Sva), and late Late Pannonian s.l. Galeacysta etrusca (Get). As inferred from the regional palynostratigraphic correlation, the signals of two transgressions after the isolation of Paratethys during the Sarmatian are recognised: the first one in the late Early Pannonian, when Mediterranean dinoflagellates migrated into the Pannonian Basin, and the second one in the Late Pannonian, when endemic Paratethyan taxa migrated into the Mediterranean.

Lower and Middle Miocene biostratigraphy, Gulf of Suez, Egypt based on dinoflagellate cysts and calcareous nannofossils

This is the first detailed stratigraphic correlation of Lower and Middle Miocene deposits in the Gulf of Suez, Egypt using dinoflagellate cysts. The correlation is based on 273 ditch-cutting samples from five onshore boreholes located along the southwestern margin of the Gulf of Suez. The interval studied is represented by the Nukhul, Rudeis and Kareem formations of the Gharandal Group, and the lower part of the Belayim Formation of the Ras Malaab Group. These Miocene deposits unconformably overlie the Lower or lower Middle Eocene. The dinoflagellate cyst record is more diverse than previously reported and many taxa are documented for the first time in Egypt. Five biozones are established and tied to a chronostratigraphic framework by calibration to calcareous nannofossils (NN biozones) obtained from the same set of samples: (1) Lingulodinium machaerophorum Assemblage Biozone (GOS1), Aquitanian through mid-Burdigalian; (2) Exochosphaeridium insigne Taxon-range Biozone (GOS2), lower through mid-Burdigalian; (3) Apteodinium spiridoides Interval Biozone (GOS3), mid-Burdigalian through lower Langhian; (4) Cleistosphaeridium placacanthum Interval Biozone (GOS4), upper Burdigalian, Langhian, and lower Serravallian?); and (5) Polysphaeridium zoharyi Assemblage Biozone (GOS5), upper Langhian and Serravallian? Comparison with other Miocene biozonations from the Mediterranean, Central Paratethys, North Atlantic region, and eastern USA indicate that the highest occurrences of Apteodinium spiridoides, Cordosphaeridium cantharellus, Distatodinium paradoxum, Exochosphaeridium insigne and Cleistosphaeridium placacanthum, and the lowest occurrences of Exochosphaeridium insigne and Sumatradinium soucouyantiae are important datums, whereas the lowest occurrences of Hystrichosphaeropsis obscura, Labyrinthodinium truncatum, and Operculodinium? borgerholtense provide useful supporting age control.

Palynological records of climate and oceanic conditions in the late Pleistocene and Holocene of the Nile Cone, Southeastern Mediterranean, Egypt

Variations in palynomorph concentrations and relative abundances, including pollen and spores, organic‐walled dinoflagellate cysts, and amorphous organic matter (AOM), were studied in sediment core NC Core 2 from the upper slope (1,030 m water depth) of the Nile Cone, southeastern Mediterranean, Egypt. Each sample represents palynomorph deposition for intervals of around 500–1,000 years, and this study provides the first detailed palynological record for the Nile Cone. The dinoflagellate cyst assemblages and AOM production reflect changes in surface water temperature and river discharge in response to climate forcing as marked by variations in pollen and spore indicators of semi‐desert vegetation and tropical Monsoon intensity. The basal sediments (approximately 14,600–9400 yr before present [BP]) contain high concentrations and relative abundances of Polysphaeridium zoharyi, Polysphaeridium spp., Spiniferites elongatus, and Spiniferites spp. during the transition from postglacial to interglacial conditions. Variations in these taxa and total Impagidinium spp. suggest a gradual temperature increase, interrupted by a pre‐Holocene cool interval around 11,000 yr BP. The high African monsoon index for this pre‐Holocene time corresponds with pollen evidence of relatively high Nile discharge. The organic‐rich S1 sapropel sediments, dated as around 9,500–6,270 yrBP, were deposited several thousand years later, during a time of lower Monsoonindex, wanner surface water, and increased dinoflagellate cyst production. This was accompanied by moderate Nile flooding and oxygen‐deficient or anoxic bottom water on the upper Nile Cone, mainly supporting the increased production and carbon import hypothesis for eastern Mediterranean S1 formation. Dinoflagellate cyst assemblages in the Nile Cone S1 differ from those of the deeper, more northern Levantine and Cretan basins in the near absence of heterotrophic protoperidinioid cysts, despite the uniformly high organic S1 carbon content. The prevailing climate during the formation of sapropelic sediments in the southeastern Mediterranean was tropical to subtropical, but was interrupted by an early cooler interval with reduced humidity, as marked by re‐appearance of Spiniferites elongatus and increased Ephedra pollen. The carbonate‐rich surface layers were probably deposited under warm dry climatic conditions with minimum Nile input, but evidence of oxidation prevents detailed interpretation.

Holocene paleoenvironmental change in inner continental shelf sediments, Southeastern Mediterranean, Egypt

The palynology of marine sediments from CS Core taken on the inner continental shelf offshore Nile Delta, Southeastern Mediterranean, has been used to reconstruct the regional paleoenvironment during the past 5380 yr BP. This includes detailing the relative abundances of dinoflagellate cysts, acritarchs, prasinophytes and other algal spores, microforaminiferal linings, crustacean eggs, and fungal hyphae. The composition and ecological interpretation of the dinoflagellate cyst assemblages, acritarchs and other non-pollen palynomorphs is discussed. Concentrations of dinoflagellate cysts range from 5926 to 416 specimens per gram of sediment, and the most common taxa were Lingulodinium machaerophorum, Operculodinium centrocarpum, Operculodinium israelianum, Polysphaeridium zoharyi, Spiniferites ramosus, Spiniferites mirabilis, Echinidinium transparantum and Protoperidinum nudum. The assemblages are like those on the Tunisian Shelf, but with more protoperidinioid cysts. It is concluded that the shelf sediments were deposited under suboxic bottom water conditions. A high nutrient supply to the area during the deposition of the CS Core sediments is evidenced by the strong significant correlation ( R-values) between the nutrient-demanding species, L. machaerophorum and P. zoharyi, toxic species, total phosphorous percent (TP%) and total organic carbon percent (TOC%). These data suggest that Nile discharge from the Damietta Channel increased during the past 5830 yr BP and was accompanied by increases in fresh or brackish water algae and fungal hyphae.