Spiniferites Cruciformis Research Articles

Late Quaternary Ponto-Caspian dinoflagellate cyst assemblages from the Gulf of Corinth, Central Greece (eastern Mediterranean Sea)

We present here the first long Quaternary record of organic-walled dinoflagellate cyst assemblages analysed from sediment cores retrieved during the International Ocean Discovery Program (IODP) Expedition 381 in the Gulf of Corinth. Site M0078A is located in the central part of the Gulf of Corinth (GoC), a semi-isolated marine basin that was repeatedly isolated and reconnected to the Mediterranean Sea during the Quaternary glacial/interglacial cycles. Our results show that dinoflagellate cysts are sorted in two major ecogroups, each group alternating between marine and isolated/brackish conditions. The marine intervals are characterised by high dinocyst diversity whereas the isolated intervals are dominated by taxa thriving in low-salinity conditions such as Spiniferites cruciformis and Pyxidinopsis psilata. In several of these assemblages, S. cruciformis is so prevalent that it forms almost monospecific assemblages. The low salinity dinocyst assemblages are reported for the first time outside the Ponto-Caspian region and they show a close affinity to modern assemblages from the Black Sea, Caspian Sea and Marmara Sea. The alternations between marine and brackish conditions recorded in the Gulf of Corinth reflect changes in surface water salinity (SSS) and temperature (SST), in response to the Quaternary glacial-interglacial cycles. These seem to be in good agreement with regional and global marine isotope and sea-level records. Our findings suggest that the study region sensitively responds to climate forcing at orbital time scales and that local factors most likely drive shifts in dinoflagellate species composition and diversity.

Palynology and sedimentology of the Pliocene Productive Series from eastern Azerbaijan

A palynological study of 239 outcrop samples and their sedimentological context was undertaken on the Pliocene Productive Series in the Kirmaky and Yasamal valleys, eastern Azerbaijan. The Productive Series is primarily a representation of the palaeo-Volga and forms the main hydrocarbon-producing reservoirs in the South Caspian Basin. Most sands are interpreted as fluvial, based on sedimentary characteristics. Mudstone and siltstones often contain freshwater and brackish assemblages interpreted as ‘Caspian lake’ transgressions, indicative of rapid Caspian Sea level change during the Pliocene. Most samples contain rich assemblages including pollen, spores, dinoflagellate cysts, algae and fungal bodies. Common tree pollen elements include Pinus, Alnus, Betula, Carya, Juglans, Pterocarya, Quercus and Ulmus, which all occur in present-day vegetation or pollen records from the Caucasus or Urals. Herbaceous pollen includes Amaranthaceae, Asteraceae (including Artemisia), Ephedra and Poaceae, commonly found in the drier Caspian regions. The dinoflagellate cysts include ‘Peri-paratethyan endemic’ taxa such as Caspidinium rugosum and Spiniferites cruciformis. ‘Pannonian’ species such as Thalassiphora balcanica, Romanodinium areolatum and Spiniferites oblongus confirm the persistence of these taxa into the early Pliocene in Eastern Paratethys, around five million years later than their first documented presence in Central Paratethys. ‘Caspian lake’ influences diminish up-section, as indicated by a progression from brackish to freshwater and sub-aerial conditions. Productive Series deposition was mainly driven by the combined effects of lake level and catchment climate. The principal hydrocarbon reservoir sands were deposited as a result of increased catchment humidity, whereas drying conditions led to reduced coarse clastic input and deposition of alluvial plain mudstones. Productive Series deposition terminated with the onset of the marine-influenced Akchagyl Series, which spans the Plio-Pleistocene boundary. The lowermost sediments of the Akchagyl Series are freshwater in origin and grade up-section into marine beds containing dinoflagellate cysts of Arctic affinity.

From bi-polar to regional distribution of modern dinoflagellate cysts, an overview of their biogeography

This paper examines the distribution of 91 modern dinoflagellate cyst taxa from 3636 locations across the world's oceans. Patterns of distributions among the taxa included bi-polarity, cosmopolitan, northern versus southern hemispheres, and geographically restricted. Of the 91 taxa, three dominate these 3636 assemblages at the global scale, Brigantedinium species, Operculodinium centrocarpum sensu Wall and Dale 1966 and some species of Spiniferites . Whereas Brigantedinium is a true cosmopolitan taxon, with high abundances in each ocean, Operculodinium centrocarpum sensu Wall and Dale 1966 shows high abundances in polar to temperate regions in the Northern Hemisphere, and in tropical to sub-tropical waters in the Southern Hemisphere. Spiniferites species show highest occurrences in the Southern Hemisphere. This study also highlights three true bi-polar species, Impagidinium pallidum , Islandinium minutum and cyst of Polarella glacialis . Only a few taxa are strictly endemic, either being relics of ancient seas such as the Paratethys ( Spiniferites cruciformis ) or linked to specific environmental conditions. However, recent studies have shown recent worldwide dispersal of these endemic species possibly due to human activities. Overall, this compilation has highlighted the progress made since the early 1970s on our understanding of these important tracers of environmental conditions but also gaps in our knowledge of their distribution in pelagic regions of the Pacific and Indian Oceans as well as under Arctic sea ice. • 3636 assemblages of modern dinoflagellate cysts were compiled to discuss patterns of distribution. • Of the 91 taxa, only three dominate globally, Brigantedinium spp., Operculodinium centrocarpum and Spiniferites species. • Only three taxa are truly bi-polar: Impagidinium pallidum , Islandinium minutum and Polarella glacialis.

Where should we draw the lines between dinocyst “species”? Morphological continua in Black Sea dinocysts

Abstract. The morphology of dinoflagellate cysts (dinocysts) is related not only to the genetics of the motile dinoflagellate from which it derives, but is also dependent on a range of environmental factors including salinity, temperature and nutrient status. Although this knowledge improves our understanding of the drivers behind dinocyst morphological variations, it makes the taxonomy governing their description somewhat complex. In basins such as the Black Sea, where environmental change can be extreme and occurs on relatively short (millennial) timescales, taxonomy becomes particularly challenging. Morphological continua can be observed between described forms, displaying a large range of intermediate phenotypes that do not necessarily correspond to any genetic difference. As these morphological nuances may preserve information about palaeoenvironments, it is important to find a systematic method of characterising morphotypes. Here, we show a dinocyst matrix within which dinocysts are described according to their similarity to (or difference from) described forms based on key descriptive parameters. In the example set out here, cyst shape and degree of process and/or ectophragm development are taken as two key parameters in Pyxidinopsis psilata and Spiniferites cruciformis, and can allow the description of intermediate forms even though the definitions do not overlap. We review some frequently occurring morphotypes and propose that using matrices to show the gradual variation between endmember forms is the most pragmatic approach until cyst–theca studies and genetic sequencing can be used to demonstrate relationships between genotypes and morphotypes. As prior studies propose salinity to be a primary driver of intraspecific variability, the endmembers presented may represent salinity extremes within an overall brackish environment. Although we cannot assign each morphotype to a value or a range of an environmental parameter (e.g. salinity) as the different morphotypes can occur in the same sample, using this matrix allows preservation of information about morphological variability without creating taxonomic categories that are likely to require alteration if genetic evidence becomes available.

MIS 5–1 dinoflagellate cyst analyses and morphometric evaluation of Galeacysta etrusca and Spiniferites cruciformis in southwestern Black Sea

Here we evaluate the changes in dinoflagellate cyst assemblages and intraspecies morphometric variability in dominant Black Sea species during MIS 5−1 in sediment recovered from DSDP Site 380. Twenty-three taxa represent the majority of the 16,000 cysts tabulated. Qualitative assessment of assemblage composition indicates that the taxa are distributed in three ecological assemblages; marine stenohaline, marine euryhaline, and brackish Ponto-Caspian endemic species; the fluctuation of these assemblages provide evidence for changes in environmental conditions from the end of MIS 5e to MIS 1. Although some fluctuations in sea-surface salinity are highlighted by changes in dinoflagellate assemblages, the continuous presence of Pyxidinopsis psilata, Galeacysta etrusca and Spiniferites cruciformis likely indicate brackish conditions for most of the interval sampled at this site. Statistical analysis of measured morphometric changes in Galeacysta etrusca endocyst:ectocyst ratios indicate that the specimens recovered mostly belong to a smaller morphotype forming group ‘b’ of Popescu et al. (2009), interpreted as indicative of brackish–marine conditions after migration to the Mediterranean from the Paratethys. Although not fully conclusive because of sampling constraints and limited chronological control, the lack of sudden, large abundance changes in marine salinity-tolerant species the relatively low species diversity, and the sequence of sapropelic layers relative to banded clastic muds provides evidence against the occurrence of sustained marine flooding between ca. 0.07–0.007 Ma and it is not clear that the last interglacial marine highstand during MIS 5e was fully sampled at this site.

Reconstructions of deltaic environments from Holocene palynological records in the Volga delta, northern Caspian Sea

New palynological and ostracod data are presented from the Holocene Volga delta, obtained from short cores and surface samples collected in the Damchik region, near Astrakhan, Russian Federation in the northern Caspian Sea. Four phases of delta deposition are recognized and constrained by accelerated mass spectrometry (AMS) radiocarbon ages. Palynological records show that erosive channels, dunes (Baer hills) and inter-dune lakes were present during the period 11,500–8900 cal. BP at the time of the Mangyshlak Caspian lowstand. The period 8900–3770 cal. BP was characterized regionally by extensive steppe vegetation, with forest present at times with warmer, more humid climates, and with halophytic and xerophytic vegetation present at times of drought. The period 3770–2080 cal. BP was a time of active delta deposition, with forest or woodland close to the delta, indicating relatively warm and humid climates and variable Caspian Sea levels. From 2080 cal. BP to the present-day, aquatic pollen is frequent in highstand intervals and herbaceous pollen and fungal hyphae frequent in lowstand intervals. Soils and incised valley sediments are associated with the regional Derbent regression and may be time-equivalent with the ‘Medieval Warm Period’. Fungal spores are an indicator of erosional or aeolian processes, whereas fungal hyphae are associated with soil formation. Freshwater algae, ostracods and dinocysts indicate mainly freshwater conditions during the Holocene with minor brackish influences. Dinocysts present include Spiniferites cruciformis, Caspidinium rugosum, Impagidinium caspienense and Pterocysta cruciformis, the latter a new record for the Caspian Sea. The Holocene Volga delta is a partial analogue for the much larger oil and gas bearing Mio-Pliocene palaeo-Volga delta.

From the Allerød to the mid-Holocene: palynological evidence from the south basin of the Caspian Sea

Pollen and dinoflagellate cysts have been analysed in a core from the south basin of the Caspian Sea, providing a picture of respectively past vegetation and water salinity for the Late Pleistocene to middle Holocene. A relatively sharp lithological change at 0.86 m depth reflects a shift from detrital silts to carbonates-rich fine silts. From this depth upwards, a Holocene chronology is built based on ten radiocarbon dates on ostracod shells and bulk carbonates.From the vegetation point of view, the Late Pleistocene deserts and steppes were partially replaced in the most sheltered areas by an open woodland with Pinus, Juniperus-Hippophae-Elaeagnus and even Alnus-Quercus-Pterocarya and Fraxinus, related to the Allerød palynozone. This was interrupted by the Younger Dryas palynozone when Artemisia reaches a maximum in a first instance followed by a very dry phase with only a slight return of Pinus and Quercus and the rare presence of Ulmus-Zelkova. From 11.5 to 8.4 cal. ka BP, an open landscape dominated by shrubs such as Ephedra and progressively increasing Quercus appeared. The final spread of diverse evergreen and deciduous trees is delayed and occurs after 8.4 cal. ka BP. It is suggested that this delay is caused by an arid climate in the Early Holocene linked to high insolation and perhaps to a lake effect.The dinocyst assemblages fluctuate between slightly brackish (Pyxidinopsis psilata and Spiniferites cruciformis, 7 psu and lower) and more brackish (Impagidinium caspienense, ∼13 psu). In the Lateglacial (Khvalynian highstand), the assemblages remained dominated by relative low salinity taxa. A late and brief increase of salinity occurred prior to 11.2 cal. ka BP associated with the Mangyshlak lowstand. It is suggested that it was caused by a brief drop in meltwater flow from both the north and the southeast (Uzboy) and a likely evaporation increase. This lowstand occurs quasi at the same time as the end of a longer lowstand in the Black Sea. The freshest waters are then inferred as having occurred between 8.4 and ≤4.4 cal. ka BP, linked to a connection with the Amu Darya and the melting glaciers on the Pamir Mountains.The Caspian Sea is a sensitive environment, easily perturbed by global climatic changes, such as the Allerød and Holocene warming, and the Lateglacial and Younger Dryas cooling, as well as by regional changes in its hydrography, such as shifts in the Eurasian meltwater and the Volga and Amu Darya inflows.

Eemian and Holocene sea-surface conditions in the southern Black Sea: Organic-walled dinoflagellate cyst record from core 22-GC3

In order to compare the sea-surface conditions in the Black Sea during the Holocene and Eemian, sapropelic parts of marine core 22-GC3 (42°13.53′N/36°29.55′E, 838 m water depth) were studied for organic-walled dinoflagellate cyst content. The record shows a change from freshwater/brackish assemblages (Pyxidinopsis psilata, Spiniferites cruciformis, and Caspidinium rugosum) to more marine assemblages (Lingulodinium machaerophorum and Spiniferites ramosus complex) during each interglacial, due to the inflow of saline Mediterranean water. The lacustrine–marine transitions in 22-GC3 occurred at ~ 8.3 cal kyr BP during the early Holocene and ~ 128 kyr BP during the early Eemian, slightly later compared to the onset of interglacial conditions on the adjacent land. Dinoflagellate cyst assemblages reveal higher sea-surface salinity (~ 28–30) (e.g. Spiniferites pachydermus, Bitectatodinium tepikiense, and Spiniferites mirabilis) around ~ 126.5–121 kyr BP in comparison to the Holocene (~ 15–20) as well as relatively high sea-surface temperature (e.g. Tuberculodinium vancampoae, S. pachydermus, and S. mirabilis) especially at ~ 127.6–125.3 kyr BP. Establishment of high sea-surface salinity during the Eemian correlates very well with reconstructed relatively high global sea-level and is explained as a combined effect of increased Mediterranean supply and high temperatures at the beginning of the last interglacial. The observed changes in the dinocyst record highlight the importance of nutrients for the composition of the Eemian and Holocene dinocyst assemblages.

First high-resolution marinopalynological stratigraphy of Late Quaternary sediments from the central part of the Bulgarian Black Sea area

Spores, pollen and dinoflagellate cysts of Late Pleistocene and Holocene sediments were analyzed from Giant Gravity Core 18 from the Black Sea continental slope, recovered from a water depth of 971 m. The investigated length of the core is 203.5 cm. It includes 3 lithological units: light grey clay, sapropels and coccolith-bearing ooze. The core was sampled at 5–10 cm intervals. Sampling of the interval 141.5–126 cm was carried out at every cm. AMS radiocarbon dating of bulk organic carbon was performed on 18 selected sediment layers. This chronological data allowed the first high-resolution pollen stratigraphy of Late Quaternary sediments from the western Black Sea area to be presented. The percentage spore–pollen diagram is divided into 6 local pollen assemblage zones. The trends in the vegetation dynamics and climate changes and the early history of migration of the majority of the arboreal taxa that nowadays occur in the Eastern Balkan Range were traced out. The palynological record suggests that open oak forests were spread in the Eastern Balkan Range at the beginning of the Holocene and shows early migration of the major temperate arboreal species such as Quercus, Ulmus, Tilia and Carpinus betulus. This vegetation palaeosuccession continues with the spreading of mixed oak forests from 8950 until 2620 cal. BP (8650 ± 40 until 3120 ± 35 14C BP) followed by destructive changes due to human impact and climate deterioration. A cooling of Holocene climate that is well known in the North Atlantic region as the “8200 yrs cold event” is identified for the first time in marine records from the Bulgarian Black Sea area. The assemblages of dinoflagellate cysts and acritarchs were investigated to provide a reconstruction of surface seawater salinity and surface seawater temperature changes. Two main dinoflagellate cyst assemblages, one dominated by fresh- to brackish water species such as Spiniferites cruciformis and Pyxidinopsis psilata and a subsequent one, that is characterized by euryhaline marine Mediterranean species such as Lingulodinium machaerophorum, Spiniferites belerius, Spiniferites bentorii, Operculodinium centrocarpum and acritarchs Cymatiosphaera globulosa testified a change in SSS from low salinity (<7‰) to present day conditions after 7990 cal. BP. Substantial freshening of Black Sea surface waters at 2570 cal. BP is established and connected with the transition from a relatively dry and warm to relatively cold and wet climate.

Palynomorphs of brackish and marine species in cores from the freshwater Lake Sapanca, NW Turkey

Lake Sapanca, which is located on the Sakarya–Sapanca–İzmit corridor in NW Turkey, is a freshwater lake with numerous fish farms in its catchment. Palynological analyses including non-pollen palynomorphs of a short (38.5 cm) and a longer sediment core (586 cm), taken in the centre of the lake and dated in previous investigations, revealed the presence of brackish and marine palynomorphs. The longer sediment sequence shows the occurrence of Brigantedinium sp., Impagidinium caspienense and Spiniferites cruciformis from the base of the core at c. AD 580 years up to 300 cm depth at shortly after c. AD 910. A similar assemblage, but this time with the additional presence of dinoflagellate thecae and the acritarch, Radiosperma corbiferum, was found in the recent core, especially from AD 1986 until the present. Past connections between the Gulf of İzmit and the Black Sea, via the River Sakarya and Lake Sapanca, could be the origin of these two microfossil assemblages. Accidental re-introduction via fish translocation since the Roman times may have been a additional mechanism. The consequences of the survival of brackish and marine forms in a freshwater lake are discussed in terms of wider euryhalinity than has been suggested for those still poorly known organisms.

A Holocene dinocyst record of a two-step transformation of the Neoeuxinian brackish water lake into the Black Sea

An exceptionally high-resolution and species-rich dinoflagellate cyst record from core M02-45 collected from the southwestern Black Sea shelf provides strong evidence of a gradual reconnection between the Black (BS) and Mediterranean (MS) seas at the beginning of the Holocene. Two main assemblages, one dominated by brackish species, Spiniferites cruciformis and Pyxidinopsis psilata, and freshwater algae, and a subsequent one, characterised by euryhaline species ( Lingulodinium machaerophorum, Brigantedinium spp., Protoperidinium ponticum), document a progressive change in sea-surface conditions from low saline (∼7–12 psu) to present-day conditions. A first major pulse of marine waters is recorded at around 8.46 ka BP, with a maximum of L. machaerophorum. The occurrence of this species from the bottom of the core, dated at 9.3 ka BP, supports the hypothesis that water levels were already high on the southwestern shelf by that time. Fully present-day conditions are recorded at around 5.6 ka BP, when brackish species and morphotypes of S. belerius, S. bentorii and L. machaerophorum disappeared. Arrivals of Mediterranean species ( Operculodinium centrocarpum and S. mirabilis) are observed simultaneously in the southwest and southeast region of the BS at around 7 ka BP. Despite a different protocol for palynomorph preparation and presentation of data, previous studies from the northern shelf also document the arrival of euryhaline species at 7 ka BP, and marine influence prior to that time. The history of harmful algal blooms (HABs) shows a correlation with warmer mid-Holocene temperatures, followed by a succession of introductions possibly associated with early Greek exploration, then merchant shipping.

Hydrographic development of the Aral Sea during the last 2000 years based on a quantitative analysis of dinoflagellate cysts

The Aral Sea Basin is a critical area for studying the influence of climate and anthropogenic impact on the development of hydrographic conditions in an endorheic basin. We present organic-walled dinoflagellate cyst analyses with a sampling resolution of 15 to 20 years from a core retrieved at Chernyshov Bay in the NW Large Aral Sea (Kazakhstan). Cysts are present throughout, but species richness is low (seven taxa). The dominant morphotypes are Lingulodinium machaerophorum with varied process length and Impagidinium caspienense, a species recently described from the Caspian Sea. Subordinate species are Caspidinium rugosum, Romanodinium areolatum, Spiniferites cruciformis, cysts of Pentapharsodinium dalei, and round brownish protoperidiniacean cysts. The chlorococcalean algae Botryococcus and Pediastrum are taken to represent freshwater inflow into the Aral Sea. The data are used to reconstruct salinity as expressed in lake level changes during the past 2000 years. We quantify and date for the first time prominent salinity variations from the northern part of the Large Aral Sea. During high lake levels, I. caspienense, representing brackish conditions with salinities of about 10–15 g kg − 1 or less, prevails. Assemblages dominated by L. machaerophorum document lake lowstands during approximately 0–425 AD (or 100? BC–425 AD), 920–1230 AD, 1500 AD, 1600–1650 AD, 1800 AD and since the 1960s. Because salinity in the Aral Sea is mostly controlled by meltwater discharges from the Syr Darya and Amu Darya rivers, we interpret changes in salinity levels as a proxy for temperature fluctuations in the Tien Shan Mountains that control snow melt. Significant erosion of marine Palaeogene and Neogene deposits in the hinterland, evidenced between 1230 AD and 1400 AD, is regarded as sheet-wash from shore. This is controlled by the low pressure system that develops over the Eastern Mediterranean and brings moist air to the Middle East and Central Asia during late spring and summer. We propose that the recorded environmental changes are related primarily to climate, but perhaps to a lesser extent by human-controlled irrigation activities. Our results documenting climate change in western Central Asia are fairly consistent with reports elsewhere from Central Asia.

Dinoflagellate cysts, freshwater algae and fungal spores as salinity indicators in Late Quaternary cores from Marmara and Black seas

Seismic profiles and mollusks have been used to suggest that from ∼12 500 to 7000 yr BP, the Black Sea was an isolated freshwater lake containing potable water and implying a surface salinity of <1. According to Ryan and Pitman (1999), these circumstances encouraged Neolithic settlement and farming on the shore of the Black Sea. This model conflicts with previous studies of dinoflagellate cysts and seismic profiles from the Marmara Sea. Here we investigate Ryan and Pittman’s model using palynological studies of organic-walled dinoflagellate cysts, acritarchs, freshwater algae, microforaminifera, and fungal remains as tracers of changes in surface salinity for seven cores of pleniglacial to Holocene sediments from the Marmara and Black seas. Core-top data from 16 sites along a salinity gradient from 39.5 in the Aegean Sea to ∼17 in the Black Sea show that the dinocyst species Impagidinium aculeatum, Impagidinium patulum, Operculodinium israelianum, Polysphaeridium zoharyi and Nematosphaeropsis labyrinthus are markers of Mediterranean Sea water and summer surface salinity >24, and that Spiniferites cruciformis, Spiniferites inaequalis, Peridinium ponticum, Polykrikos spp. and Quinquecuspis concreta characterize the lower salinity of the Marmara and/or Black seas. The core-top data and correlatable down-core assemblage changes in time-equivalent sapropelic and brown muds show that there is no evidence for differential aerobic decay of dinocysts in the study area. The main acritarchs are Sigmopollis psilatum, Concentricystes cf. C. rubinus and cf. Acritarch-8 of Traverse (1978), all of which are absent from the Aegean Sea and decrease in abundance with increasing salinity; the first two taxa have been reported previously as freshwater species. Fungal remains show a similar distribution pattern to the freshwater acritarchs, indicating their origin from terrestrial environments. Freshwater Chlorococcales are almost confined to the Black Sea but they have rare occurrences in the Aegean, indicating long-distance transport. Microforaminiferal linings are abundant in the Marmara Sea but are absent in deep water of the Black Sea. In the Marmara Sea, mid–late Holocene assemblages (<7 ka) are dominated by Lingulodinium machaerophorum, Operculodinium centrocarpum and halophilic Mediterranean Spiniferites spp. ( S. mirabilis, S. hyperacanthus, S. bentorii), and a diversity of heterotrophic protoperidinioid and Polykrikos species are present in both sapropels and brown lutites. In contrast, the early Holocene interval (including sapropels) has fewer halophilic Spiniferites spp. and other Mediterranean taxa ( O. israelianum, Polysphaeridium zoharyi) and more low salinity indicators ( P. ponticum, Pyxidinopsis psilata and S. cruciformis), suggesting that the overflow of Black Sea water was greater than now. The time-equivalent early Holocene unit in the Black Sea has a higher percentage of taxa found in freshwater environments (including S. cruciformis forms 1–3; Gonyaulax apiculata, fungal remains and freshwater acritarchs) but the continued presence of Spiniferites morphotypes and other taxa associated with brackish (∼7–18) to saline surface water indicates that there was some Mediterranean water present at this time. The late glacial and Pleniglacial sediments in the Marmara Sea contain a lower diversity of dinoflagellates, dominated by S. cruciformis and P. psilata, as in early Holocene sediments of the Black Sea but including the short-spine morphotypes of S. cruciformis which are not found in freshwater lakes. We conclude that although the glacial stages were marked by much lower sea-surface temperatures, there was either some periodic marine influence or the marine dinocysts were living in a brackish water environment (∼7–18) with the freshwater species being transported from glacial lakes. Overall, there is no palynological evidence that the surface salinity of the Black or Marmara seas was ever as low as a freshwater lake. This finding is consistent with models that estimate the time required to desalinate the Black Sea after closing of the Marmara–Bosphorus gateway.

A short-term cooling event, 4.205 million years ago, in the Ptolemais Basin, northern Greece

A distinct clay-rich layer in the otherwise regular succession of alternating lignites and marls of the early Pliocene Ptolemais Formation reveals an equally distinct palynomorph assemblage; only in this layer (fresh water) dinoflagellate cysts, Spiniferites cruciformis and Gonyaulax apiculata, are encountered. These co-occurring dinoflagellate species may be taken to indicate that surface water temperatures must have been remarkably low for early Pliocene mid-latitudes, contrasting other indications that overall warm humid climates prevailed at this time. A multi-component study of this so-called ‘dinolayer’ with an astrochronologically derived age of 4.205±0.01 Ma was undertaken to further investigate the apparently contrasting climatic signals. Integrated sedimentological, micropaleontological, palynological and geochemical data indicate that the dinolayer was deposited in a shallow fresh water lake. The pollen record points to slightly cooler conditions during deposition of the dinolayer in comparison with conditions just below and above. An anomalously low winter temperature is proposed as a possible cause for the recorded phenomena.

Spiniferites cruciformis: a fresh water dinoflagellate cyst?

Palynological studies of cored lacustrine sediments from the late Quaternary of Lake Kastoria, northern Greece, revealed a Late Glacial interval with abundant dinoflagellate cysts. Cyst assemblages include two identifiable species, Spiniferites cruciformis and Gonyaulax apiculata. The presence of the fresh water species G. apiculata is consistent with the lacustrine setting of these deposits, but that of S. cruciformis is anomalous. Previously, this species has only been recorded in abundance from presumed brackish marine sediments from the Black Sea and Marmara Sea sediments where geochemical data clearly record brackish salinities. Therefore, it has been regarded as a low salinity cyst type with a wide range of morphological variation that some workers have suggested to reflect salinity fluctuations. Specimens from Greece display only part of the range of morphological variability previously described from these (brackish) marine settings. Encountered morphological variation includes ellipsoidal/pentameral and cruciform endocyst shapes with rare intermediate shapes, and highly variable septa development. Specimens characterized by extremely reduced ornamentation known from (brackish) marine environments have not been recorded. Our records of S. cruciformis indicate that: (1) it could thrive in fresh water conditions; and (2) that apparently most of the strong morphological variations of the cysts are an intrinsic phenomenon for this taxon, and may only partly be linked to salinity variations as suggested earlier. We suggest that S. cruciformis essentially is a fresh water taxon, and that its records in (brackish) marine environments, with the exception of specimens with strongly reduced ornamentation, may be due to transportation, to short-lived fresh water surface conditions in such environments, or to tolerance of the species to brackish conditions.

Paleosalinity relationships of dinoflagellates in the late quaternary of the black sea—a summary

Abstract Dinoflagellates in Late Quaternary sediments from deepwater cores in the Black Sea appear to fall into two ecological categories that are dependent upon paleosalinity relationships. Sediments deposited there during the last 7,000 years contain cosmopolitan, euryhaline species of common marine genera and represent the brackish‐water Old Black Sea Stage of Soviet authors. Older sediments whose ages did not exceed 23,000 years in our cores contain a unique assemblage that comprises essentially two species, Tectatodinium psilatum Wall and Dale and Spiniferites cruciformis Wall and Dale. These dinoflagellates apparently lived in the almost freshwater “lake‐sea” of the New Euxinic Stage and were displaced abruptly 7,000 years ago when saline water from the Mediterranean began to flow into the Black Sea.