Organic-walled Dinoflagellate Cysts Research Articles

Dinoflagellate cyst zonation for the middle to upper Eocene in the Austral Basin, southwestern Atlantic Ocean: implications for regional and global correlation

AbstractThe well-exposed marine Eocene units from southwestern Patagonia, Argentina, contain useful information for reconstructing regional climate and oceanographic patterns in an area adjacent to the Drake Passage. The aim of this paper is to integrate dinoflagellate cyst data from three sections of the southwestern Austral Basin (Río Turbio Formation) to propose a zonation scheme, which can be applied to other southwestern Atlantic Ocean sites. Assemblages of organic walled dinoflagellate cysts have been analysed in different cropping-out sections and cores, showing the high potential of this fossil group as biostratigraphic markers. Comparison of dinoflagellate cyst events of the upper member of the Río Turbio Formation with calibrated biostratigraphic ranges in the Palaeogene South Pacific Ocean allowed us to date and correlate these sedimentary sections. The resulting zonation consists of four dinoflagellate cyst zones labelled RTF 1 to RTF 4, between the middle Lutetian and late Priabonian. As a final point, we applied dinoflagellate cyst species with importance as palaeoenvironmental markers to assess long-term climatic and oceanographic evolution for the area. This study shows that the endemic–Antarctic dinoflagellate cyst assemblage is dominant during the middle to late Eocene (RTF 1 to RTF 3), while a significant replacement of these taxa by cosmopolitan species characterizes the upper part of the upper member of the Río Turbio Formation (RTF 4). This turnover seems to be a consequence of changes in the ocean circulation patterns forced by deepening of the southern Atlantic gateways (the Drake Passage and the Tasman Gateway).

Biogeography of dinoflagellate cysts in northwest Atlantic estuaries.

Few biogeographic studies of dinoflagellate cysts include the near‐shore estuarine environment. We determine the effect of estuary type, biogeography, and water quality on the spatial distribution of organic‐walled dinoflagellate cysts from the Northeast USA (Maine to Delaware) and Canada (Prince Edward Island). A total of 69 surface sediment samples were collected from 27 estuaries, from sites with surface salinities >20. Dinoflagellate cysts were examined microscopically and compared to environmental parameters using multivariate ordination techniques. The spatial distribution of cyst taxa reflects biogeographic provinces established by other marine organisms, with Cape Cod separating the northern Acadian Province from the southern Virginian Province. Species such as Lingulodinium machaerophorum and Polysphaeridinium zoharyi were found almost exclusively in the Virginian Province, while others such as Dubridinium spp. and Islandinium? cezare were more abundant in the Acadian Province. Tidal range, sea surface temperature (SST), and sea surface salinity (SSS) are statistically significant parameters influencing cyst assemblages. Samples from the same type of estuary cluster together in canonical correspondence analysis when the estuaries are within the same biogeographic province. The large geographic extent of this study, encompassing four main estuary types (riverine, lagoon, coastal embayment, and fjord), allowed us to determine that the type of estuary has an important influence on cyst assemblages. Due to greater seasonal variations in SSTs and SSSs in estuaries compared to the open ocean, cyst assemblages show distinct latitudinal trends. The estuarine context is important for understanding present‐day species distribution, the factors controlling them, and to better predict how they may change in the future.

Organic-walled dinoflagellate cyst records from a prospective Turonian – Coniacian (Upper Cretaceous) GSSP, Słupia Nadbrzeżna, Poland

A river section at Słupia Nadbrzeżna, central Poland, has been proposed as a candidate Turonian – Coniacian (Cretaceous) GSSP, in combination with the Salzgitter-Salder quarry section of Lower Saxony, Germany. Results of a high-resolution (25 cm) palynological study of the boundary interval in the Słupia Nadbrzeżna section are presented. Terrestrial palynomorphs are rare; marine organic-walled dinoflagellate cysts dominate the palynological assemblage. The dinoflagellate cyst assemblage has a low species richness (5–11 per sample; total of 18 species recorded) and diversity (Shannon index H = 0.8–1.4), dominated by four taxa: Circulodinium distinctum subsp. distinctum; Oligosphaeridium complex; Spiniferites ramosus subsp. ramosus; Surculosphaeridium longifurcatum. Declining proportions of O. complex and S. ramosus subsp. ramosus characterise the uppermost Turonian, with an increased dominance of S. longifurcatum in the lower Coniacian. The Turonian – Coniacian boundary interval includes an acme of C. distinctum subsp. distinctum in the upper Mytiloides scupini Zone, a dinoflagellate cyst abundance maximum in the Cremnoceramus walterdorfensis walterdorfensis Zone, and the highest occurrence of Senoniasphaera turonica in the basal Coniacian lower Cremnoceramus deformis erectus Zone. Most previously reported Turonian – Coniacian boundary dinoflagellate cyst marker species are absent; a shallow-water oligotrophic epicontinental depositional setting, remote from terrestrial influence, likely limited species diversity and excluded many taxa of biostratigraphic value.

Steps in the intensification of Benguela upwelling over the Walvis Ridge during Miocene and Pliocene

Upwelling is a significant part of the ocean circulation controlling largely the transport of nutrient-rich cold waters to the surface and therefore influencing ocean productivity and global climate. The Benguela upwelling system (BUS) is one of the major upwelling areas in the world. Previous reconstructions of the BUS mainly focused on the onset and intensification in southern and central parts, but changes of the northern part have been rarely investigated in detail. Using the Late Miocene to Pliocene organic-walled dinoflagellate cyst record of ODP Site 1081, we reconstruct and discuss the early upwelling history over the Walvis Ridge with a special focus on the movement of the Angola-Benguela Front (ABF). We suggest that during the Late Miocene the Angola Current flowed southwards over the Walvis Ridge more frequently than today because the ABF was probably located further south as a result of a weaker meridional temperature gradient. A possible strengthening of the meridional gradient during the latest Miocene to early Pliocene in combination with uplift of south-western Africa intensified the upwelling along the coast and increased the upwelling’s filaments over the Walvis Ridge. An intermediate period from 6.2 to 5.5 Ma is shown by the dominance of Habibacysta tectata, cysts of a cool-tolerant dinoflagellate known from the northern Atlantic, indicating changing oceanic conditions contemporaneous with the Messinian Salinity Crisis. From 4.3 Ma on, the upwelling signal got stronger again and waters were well-mixed and nutrient-rich. Our results indicate a northward migration of the ABF as early as 7 Ma and the initial stepwise intensification of the BUS.

Dinoflagellate cyst distribution in the oligotrophic environments of the Gulf of Aqaba and northern Red Sea

Abstract Oligotrophic environmental systems form a major part of the marine aquatic environments on earth. Compared to mesotrophic and eutrophic environments extremely little information is available about the relationship between the distribution of organic-walled dinoflagellate cysts and physical and biological gradients in the upper water column. Here we present the first comprehensive study of the modern geographic distribution of organic-walled dinoflagellate cysts in the oligotrophic environments of the northern Red Sea and Gulf of Aqaba. We show that sediments of both regions have characteristic dinoflagellate cyst associations consisting of both heterotrophic and phototrophic species of which the latter, including both autotrophic and mixotrophic species, form the major part of the associations in both regions. The upper water environment of the Gulf of Aqaba is characterized by slightly enhanced nutrient concentrations compared to the Red Sea, due to water column mixing in winter. Its phytoplankton composition is dominated by pico- and ultra-plankton and a slight higher amount of eukaryotes compared to northern Red Sea. Its sedimentary cyst associations are characterized by higher relative and absolute abundances of the species Brigantedinium spp., Votadinium calvum, Echinidinium spp., Lingulodinium machaerophorum, Spiniferites spp., Spiniferites bentorii, Spiniferites membranaceus and Spiniferites mirabilis. Sediments of the northern Red Sea are characterized by high relative abundances of Impagidinium aculeatum, Impagidinium sphaericum, Operculodinium israelianum, Operculodinium longispinigerum, Operculodinium centrocarpum, cysts of Pentapharsodinium dalei, and Selenopemphix nephroides. A positive relationship between the distribution of the heterotrophic species Brigantedinium spp., Echinidinium spp. and V. calvum with the occurrence of other eukaryotic groups such as e.g. diatoms is documented. The distribution of S. nephroides cannot be related to the presence of diatom occurrences and it is suggested that the distribution of food sources other than diatoms affects its distribution. We document a positive relationship between the sedimentary distribution of the phototrophic dinoflagellate species L. machaerophorum and Spiniferites species and the abundance of the cyanobacteria Synechococcus in the water column. Since Synechococcus is known to be a potential prey of Lingulodinium polyedrum and members of the Gonyaulax spinifera complex (the motile forms producing these cysts) we suggest a possible cyst distribution–prey relationship of mixotrophic dinoflagellates.

A new Triassic-Jurassic section in the southern part of the Holy Cross Mts. (Poland) implications for palaeogeography

Sedimentological, stratigraphical and geophysical studies across a new Triassic-Jurassic transition section in the Holy Cross Mts., Poland have revealed a large sedimentary hiatus embracing the entire latest Triassic–Early Jurassic – earliest Middle Jurassic time interval and yielded new data on the Triassic fluvial system and on Middle Jurassic shallow marine sedimentation. The presence of organic-walled dinoflagellate cysts allowed a precise age assignment of the black clay facies. Regional discussions and comparisons may be made with other areas with a similar depositional environment in Poland. For the first time a counterpart of the “Kościeliskie Beds” lithostratigraphic unit is proposed to exist in the Holy Cross Mts. area

Diachronous evolution of sea surface conditions in the Labrador Sea and Baffin Bay since the last deglaciation

Assessing changes in sea surface conditions due to the effects of past freshwater outflow through Baffin Bay and Davis Strait to the Labrador Sea, hereafter referred to as the Baffin Bay corridor, is relevant in understanding the variability in Labrador Sea Water (LSW) formation. Here, regional changes in oceanographic circulation and sea surface conditions are reconstructed based on organic-walled dinoflagellate cyst (dinocyst) assemblages from four cores collected from deep, central sites of the Baffin Bay corridor. All cores exhibit a major shift in dinocyst assemblages since the late glacial period. This shift consists of a change from a polar–subpolar heterotrophic species assemblage tolerating cold and near permanent ice-covered conditions, to assemblages characterized by a higher diversity and the occurrence of phototrophic taxa associated with mild conditions. Sea surface reconstructions from the modern analogue technique display a shift from harsh, quasi-perennial ice cover to warmer summer sea surface temperatures and a seasonal sea ice. South of the Davis Strait sill, this regime shift occurred at ca. 11.9 cal ka BP due to the influence of North Atlantic waters. Baffin Bay, however, remained densely sea ice covered until about 7.4 cal ka BP, when these warmer waters penetrated into Baffin Bay and mixed with the West Greenland Current (WGC). This mixing was facilitated by the retreat of the Greenland and Laurentide Ice Sheet (LIS) margins. A major change in Labrador Sea surface conditions occurred nearly at about the same time (~7.6 cal ka BP) when the strong stratification of surface waters weakened because of the reduction in meltwater supplies from the LIS that allowed winter convection and the inception of LSW formation. All these new records demonstrate large amplitude fluctuations in sea surface conditions tightly controlled by the relative strengths and shifts of the warmer WGC and colder Baffin Island Current.

A determination key for modern dinoflagellate cysts

The first online modern organic-walled dinoflagellate cyst determination key has been launched at www.marum.de/dinocystkey.html. This key is based on easily recognisable morphological features of dinoflagellate cysts that can be observed using standard transmitted light microscopy. To date, the key includes 96 cyst species that can be found in late Quaternary marine sediments. This key is free of charge to users, and will be continuously updated and improved by the authors. For each individual species of dinoflagellate cyst, the website provides information on its defining morphological characteristics and the cyst–motile stage relationship. It gives a comparison with other morphologically similar taxa, links to publications with original cyst descriptions and outlines their modern global distribution where this information is available. All species descriptions are illustrated by line drawings showing their most distinctive characteristics, and accompanied by high-quality bright-field photomicrographs. The key is compatible with all major computing platforms (including smartphones) and software.

A new genus and two new species of dinoflagellate cysts from lower Eocene marine sediments of the Wilkes Land Margin, Antarctica

Integrated Ocean Drilling Program (IODP) Expedition 318 recovered lower Eocene sediments in Hole U1356A from the continental rise of the Wilkes Land Margin, Antarctica. These sediments yielded a new genus of organic-walled dinoflagellate cysts (Adeliesphaera gen. nov.). We tentatively place this new genus within the suborder Gonyaulacineae, family Areoligeraceae, based on the obligate apical archeopyle, the asymmetric antapical geometry and the left-side offset sulcal notch. We herein describe the type species of Adeliesphaera gen. nov., Adeliesphaera ohanlonii sp. nov., as well as a new species of Turbiosphaera, Turbiosphaera guersteinae sp. nov. The short stratigraphic range of both species (53.7–53.4Ma and 53.1–52.9Ma, respectively) qualifies them as potentially important regional Southern Ocean stratigraphic markers for high-resolution age control.

Implication of methodological uncertainties for mid-Holocene sea surface temperature reconstructions

Abstract. We present and examine a multi-sensor global compilation of mid-Holocene (MH) sea surface temperatures (SST), based on Mg/Ca and alkenone palaeothermometry and reconstructions obtained using planktonic foraminifera and organic-walled dinoflagellate cyst census counts. We assess the uncertainties originating from using different methodologies and evaluate the potential of MH SST reconstructions as a benchmark for climate-model simulations. The comparison between different analytical approaches (time frame, baseline climate) shows the choice of time window for the MH has a negligible effect on the reconstructed SST pattern, but the choice of baseline climate affects both the magnitude and spatial pattern of the reconstructed SSTs. Comparison of the SST reconstructions made using different sensors shows significant discrepancies at a regional scale, with uncertainties often exceeding the reconstructed SST anomaly. Apparent patterns in SST may largely be a reflection of the use of different sensors in different regions. Overall, the uncertainties associated with the SST reconstructions are generally larger than the MH anomalies. Thus, the SST data currently available cannot serve as a target for benchmarking model simulations. Further evaluations of potential subsurface and/or seasonal artifacts that may contribute to obscure the MH SST reconstructions are urgently needed to provide reliable benchmarks for model evaluations.

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.

Geochemical and palaeontological characterization of a new K-Pg Boundary locality from the Northern branch of the Neo-Tethys: Mudurnu – Göynük Basin, NW Turkey

A Cretaceous-Paleogene (K-Pg) succession is studied in detail in the Mudurnu-Göynük basin in northwestern Turkey. To characterize the K-Pg transition in this basin, two stratigraphic sections were measured and sampled at high resolution: the Okçular and the Göynük North sections. These sections were analysed for siderophile trace elements, including Ir and other platinum group elements (PGE: Ru, Rh, Pd, Ir, Pt), bulk stable carbon isotopes, calcareous nannofossils, planktic foraminifera and organic-walled dinoflagellate cysts (dinocysts). In this basin, the upper Maastrichtian consists of monotonous grey mudstones, mostly intercalated with turbidites and the basal Danian is characterised by grey mudstones, that are overlain by a rhythmic alternation of limetones and mudstones. The K-Pg boundary is marked by a thin, reddish ejecta layer, characterized by an enrichment of PGE and an abrupt negative shift in bulk δ13C. This ejecta layer is followed by 15–17 cm of thick darker, clayey mudstone, the so-called boundary clay. The upper Maastrichtian to lower Danian interval displays a succession of biostratigraphic events, such as the globally recognized spike of the dinocyst taxon Manumiella druggii in the Maastrichtian, followed by the extinction of Cretaceous planktic foraminifera at the K-Pg boundary, and a subsequent rapid succession of First Occurrences (FOs) of dinocysts, such as Senoniasphaera inornata, Membranilarnacia? tenella and Damassadinium californicum and planktic foraminifera, including Parvularugoglobigerina eugubina and Subbotina triloculinoides in the lower Danian. Overall the sedimentological and palaeontological data suggest that the studied sites in the Mudurnu-Göynük basin were deposited under normal marine conditions, likely in an outer neritic to upper bathyal environment. Our geochemical and biostratigraphic characterization of the K-Pg boundary transition in the Mudurnu-Göynük basin provides a new K-Pg boundary record in the Northern branch of the Neo-Tethys and allows a detailed comparison with K-Pg boundary sections worldwide.

Marine connections of Amazonia: Evidence from foraminifera and dinoflagellate cysts (early to middle Miocene, Colombia/Peru)

Species composition in the present-day Amazonian heartland has an imprint of past marine influence. The exact nature, timing and extent of this marine influence, however, are largely unresolved. Here we use calcareous tests of foraminifera and marine palynomorphs from Miocene sediments in northwestern Amazonia to extend on current estimates for salinity ranges, paleoenvironments and paleogeography. Our samples mostly contain tests and/or organic linings of euryhaline (tolerant to a wide range of salinity) foraminifera of the genera Ammonia, Trochammina and Elphidium, with Ammonia being by far the dominant genus at all locations. Organic-walled dinoflagellate cysts (dinocysts), such as Spiniferites, Brigantedinium and Tuberculodinium vancampoae, are also common at a number of sites. This association of foraminifera and dinocyst taxa points at varying salinities, with aberrant forms of Ammonia indicating lower limits of 0–10psu (practical salinity units) whereas dinocyst associations suggest more marine conditions. Such regional heterogeneity is common at the interface of shallow marine to freshwater environments, like estuaries. We conclude that during the early and middle Miocene marginal marine conditions reached at least 2000km inland from the Caribbean portal. Global high sea level and fast subsidence in the sub-Andean zone are thought to be the controlling mechanisms of the marine incursions. Lowering of global sea level and a change in tectonic regime terminated the incursions in the course of the Plio-Pleistocene.

Organic-walled dinoflagellate cysts from the Upper Cretaceous–lower Paleocene succession in the western External Rif, Morocco: New species and new biostratigraphic results

Palynological investigation of the Upper Cretaceous–lower Paleocene succession from the Tahar section near Arba Ayacha in northwestern Morocco (westernmost External Rif Chain) reveals the presence of rich, diverse and well-preserved dinoflagellate cyst assemblages. For the first time in the study region, biostratigraphic interpretations based on the dinoflagellate cyst assemblages from the studied interval allow the recognition of the upper Maastrichtian and Danian. Relevant upper Maastrichtian–Danian global dinoflagellate cyst events include: the First Appearance Datum of the upper Maastrichtian species Disphaerogena carposphaeropsis, Glaphyrocysta perforata, and Manumiella seelandica; the Last Appearance Datum of the Cretaceous taxa Dinogymnium spp., Isabelidinium cooksoniae, and Pterodinium cretaceum; and the First Appearance Datum of the earliest Danian markers Carpatella cornuta, Damassadinium californicum, Membranilarnacia? tenella, and Senoniasphaera inornata. We formally describe the biostratigraphical range and potential of two new dinoflagellate cyst species, namely Nematosphaeropsis silsila Guédé and Slimani nov. sp., and Pterodinium ayachensis Guédé and Slimani nov. sp. Both species are found in the westernmost External Rif Chain and are restricted to the upper Maastrichtian.

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.

Shapes of organic walled dinoflagellate cysts in early diagenetic concretions—markers for mechanical compaction

Two species of organic walled dinoflagellate cysts: Pareodinia ceratophora Eisenack 1938 (Jurassic) and Deflandrea phosphoritica Deflandre 1947 (Palaeogene) are proposed as markers for determining the mechanical compaction ratio of fine-grained rocks. The near original shapes of these species are obtained from specimens preserved in siderite and calcareous concretions occurring in mudstone host rocks of various ages. An efficient and simple light microscopy examination method of the dinoflagellate cyst height along the microscope optical axis is presented and quantitatively tested on the available material. The differences of the cyst height measurements between specimens preserved in concretions and specimens preserved in the host rock deposits reflect the compression of dinoflagellate cysts most likely due to mechanical compaction of the rocks studied. The mechanical compaction ratios revealed are about 67% for Jurassic mudstones and about 64% for Palaeogene mudstones. Further marker investigations of samples from different outcrops and strata of different ages are recommended.

Brackish to Freshwater Dinoflagellate Cyst Assemblages from the la Colonia Formation (Paleocene?), Northeastern Patagonia, Argentina

A palynological analysis of the section of La Colonia Formation exposed at Estancia San Miguel yielded conspicuous assemblages of organic-walled dinoflagellate cysts (dinocysts) and green algae. The monotypic palaeoperidinioid dinocyst assemblage of ?Ginginodinium sp. in the basal beds of this section indicates low-salinity water conditions in a restricted shallow marine paleoenvironment. The green-algaedominated assemblages together with specimens of ?Morkallacysta spp., Dinocysts type P and ?Vesperopsis sp. recorded in the middle and upper part of the San Miguel section indicate brackish to freshwater and freshwater depositional conditions, respectively. The changes in the composition of the palynological assemblages, in agreement with the analysis of the sedimentary facies, reflect a salinity-drop in the water bodies and a progressive upward-shallowing trend. The occurrence of specimens of the neritic open marine Cribroperidinium spp., Apteodinium sp., Circulodinium sp. and Areoligera sp. cf. A. circumsenonensis Fensome et al. is here considered as reflecting contemporaneous transported material from the adjacent shelf. The marine part of the La Colonia Formation is associated to Late Cretaceous and Paleocene ages. Nevertheless, palynomorphs together with a stratigraphical criterion suggest an age non older than Paleocene for the deposits of the unit at the San Miguel section.

Characterising the middle Miocene Mi-events in the Eastern North Atlantic realm: A first high-resolution marine palynological record from the Porcupine Basin

The warm climate of the Miocene peaked during the middle Miocene Climatic Optimum (MMCO; 17–14.5Ma). After the MMCO, global climate went through several short-lived cooling events: the Mi-events (Miocene isotope events). One of the more severe Mi-events is Mi-3, associated with East Antarctic Ice Sheet growth, species turnover in terrestrial and marine realms, Northern Hemisphere and mid-latitude aridification and Antarctic sea-surface temperature cooling. CO2 reconstructions, as well as the aforementioned observations, suggest that a drawdown of CO2 and/or changes in ocean circulation led to the changes surrounding Mi-3. A combination of eccentricity and obliquity amplitude modulation minima, favourable conditions for ice growth, has also been suggested as a possible triggering mechanism. However, an exact cause cannot be pinpointed yet. High-resolution records necessary to investigate the exact order of events surrounding Mi-3 and the possible role of orbital forcing, a very likely trigger, are sparse.Integrated Ocean Drilling Program (IODP) Leg 307 recovered such a high resolution record from the middle Miocene at the Porcupine Basin (offshore south-western Ireland). Well-preserved palynomorphs, mainly organic-walled dinoflagellate cysts, acritarchs and some pollen were extracted from Site U1318, and relative and absolute abundance changes were determined. Using dinocysts and calcareous nannoplankton the age model for the record was improved. Based on the palynology, the Mi-3a, Mi-3b and Mi-4 events were successfully identified and concomitant palaeoenvironmental change was observed. These events, although different in magnitude, can be associated with a decrease in sea-surface temperature, as well as with a likely fall in sea-level. Furthermore, possible palaeoenvironmental preferences of 5 dinocyst taxa were determined, based on observations from the record and multivariate statistics.

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.

Spiniferites multisphaerus, a new dinoflagellate cyst from the Late Quaternary of the Guaymas Basin, Gulf of California, Mexico

A new organic-walled dinoflagellate cyst species, Spiniferites multisphaerus sp. nov., is described from Late Quaternary sediments of Guaymas Basin, Gulf of California (Mexico). This species is characterized by a pronounced apical protuberance and bubble-like elements that comprise the central body wall, sutural septae and processes. The central body wall is ∼1.0–2.1 μm thick and appears pseudoreticulate in transmitted light microscopy. Processes are generally stubby and have blunt or furcated tips. Tabulation is expressed by low to moderate sutural septae, and is typical of the genus. Spiniferites multisphaerus sp. nov. has been found in low abundances throughout the Late Quaternary in Guaymas Basin with maximum abundances of 6% or 1670 cysts g–1, and is rare in the Holocene, including modern sediments.