The dinoflagellate cyst genera <i>Achomosphaera</i> Evitt 1963 and <i>Spiniferites</i> Mantell 1850 in Pliocene to modern sediments: a summary of round table discussions

We present a summary of two round-table discussions held during two subsequent workshops in Montreal (Canada) on 16 April 2014 and Ostend (Belgium) on 8 July 2015. Five species of the genus Achomosphaera Evitt 1963 and 33 of the genus Spiniferites Mantell 1850 emend. Sarjeant 1970 occuring in Pliocene to modern sediments are listed and briefly described along with remarks made by workshop participants. In addition, several holotypes and topotypes are reillustrated. Three species previously assigned to Spiniferites are here considered/accepted as belonging to other genera: Impagidinium inaequalis (Wall and Dale in Wall et al. 1973) Londeix et al. 2009, Spiniferites rubinus (Rossignol 1962 ex Rossignol 1964) Sarjeant 1970, and Thalassiphora balcanica Baltes & 1971. This summary forms the basis for a set of papers that follows, where points raised during the workshops are explored in greater detail

Lipid biomarkers as major source and preservation indicators in SE-Atlantic surface sediments

Surface sediments from the eastern South Atlantic were investigated for their lipid biomarker contents and bulk organic geochemical characteristics to identify sources, transport pathways and preservation processes of organic components. The sediments cover a wide range of depositional settings with large differences in mass accumulation rates. The highest marine organic carbon (OC) contributions are detected along the coast, especially underlying the Benguela upwelling system. Terrigenous OC contributions are highest in the Congo deep-sea fan. Lipid biomarker fluxes are significantly correlated to the extent of oxygen exposure in the sediment. Normalization to total organic carbon (TOC) contents enabled the characterization of regional lipid biomarker production and transport mechanisms. Principal component analyses revealed five distinct groups of characteristic molecular and bulk organic geochemical parameters. Combined with information on lipid sources, the main controlling mechanisms of the spatial lipid distributions in the surface sediments are defined, indicating marine productivity related to river-induced mixing and oceanic upwelling, wind-driven deep upwelling, river-supply of terrigenous organic material, shallow coastal upwelling and eolian supply of plant-waxes

Quantitative analysis of diverse sporomorph-derived sporopollenins

Over the years studies on sporopollenin have reported a wide variety of structures. However, the methods and techniques used to elucidate sporopollenin structures are highly diverse so that much is still unclear with respect to the nature and structural diversity of sporopollenins. In order to investigate the structural diversity in sporopollenin between different taxa, extant sporomorphs of ten different species ranging from a mushroom to a cycad were examined using a relatively simple and fast analytical procedure. Sporomorphs, before and after saponification, were analysed for sporopollenin composition by Thermally assisted Hydrolysis and Methylation (THM) using [13C]tetramethylammonium hydroxide ([13C]TMAH). The sporomorp chemical composition differed markedly between the groups of organisms analysed. Moreover, we not only identified the nature and relative quantities of the well-known sporopollenin constituents p-coumaric acid and ferulic acid but also many other phenolic moieties, such as caffeic acid, which appeared to be the most abundant phenolic constituent in spores of Equisetum palustre, Salvinia molesta, Cyrtomium falcatum and Anemia phyllitidis. Within the two Equisetum species analysed as well as in the closely related Azolla and Salvinia species the same suite of phenolic constituents were observed, but their relative distribution varied largely. We thus demonstrate the existence of a high structural diversity, both qualitatively and quantitatively in sporopollenins enabling future studies related to the evolution, phylogeny and (palaeo)environment of sporopollenin-producing organisms. Furthermore, a better knowledge of sporopollenin and its structural variety is of relevance to the rapidly growing application of spores and pollen as a drug delivery agent in medicine

Marine and terrigenous lipids in southeast atlantic sediments (leg 175) as paleoenvironmental indicators: initial results

Lipid compositions of sediments recovered during Ocean Drilling Program Leg 175 in the eastern South Atlantic reflect a variety of oceanographic and climatological environments. Most of the identified lipids can be ascribed to marine sources, notably haptophytes, eustigmatophytes, dinoflagellates, archaea, and diatoms. Elevated concentrations of cholesterol suggest zooplankton herbivory, characteristic for sites influenced by upwelling. At these sites, sulfurized highly branched isoprenoids from diatoms are also present in high amounts. Sterols, sterol ethers, hopanoids, and midchain hydroxy fatty acids could also be detected. Terrigenous lipids are n-alkanes, fatty acids, n-alcohols, and triterpenoid compounds like taraxerol and β-amyrine. n-Alkanes, fatty acids, and n-alcohols are derived from leaf waxes of higher land plants and transported to the sea by airborne dust or fresh water. Triterpenoid compounds are most probably derived from mangroves and transported solely by rivers. Lipid compositions below the Congo low-salinity plume are strongly influenced by terrigenous material from the Congo River. Elevated organic carbon contents and predominantly marine lipid distributions at the Angola margin may indicate a highly productive plankton population, probably sustained by the Angola Dome. Sedimentary lipids in the Walvis Basin contain an upwelling signal, likely transported by the Benguela Current. Sedimentary lipids off Lüderitz Bay and in the southern Cape Basin are dominated by plankton lipids in high to intermediate amounts, reflecting persistent and seasonal upwelling, respectively

Mechanisms forcing abrupt fluctuations of the Indian Ocean Summer Monsoon during the last deglaciation

A piston core from the Somali upwelling area has been studied at high resolution for its dinoflagellate cyst content. Variations in cyst association are inferred to reflect changes in Indian Ocean summer monsoon intensity. Several abrupt fluctuations in monsoon intensity are detected for the interval between 20 and 10 ka BP. Comparison of these fluctuations with changes in contrast between 30°N and 30°S July insolation and the

Postdepositional oxic degradation of alkenones : implications for the measurement of palaeo sea surface temperatures

Free and "bound" long-chain alkenones in oxidized and unoxidized sections of four organic matter-rich Pliocene and Miocene Madeira Abyssal Plain turbidites (one from Ocean Drilling Program site 951B and three from site 952A) were analyzed to determine the effect of severe post depositional oxidation on the value of Uk37

Taraxerol and Rhizophora pollen as proxies for tracking past Mangrove ecosystems

Angola Basin and Cape Basin (southeast Atlantic) surface sediments and sediment cores show that maxima in the abundance of taraxerol (relative to other land-derived lipids) covary with maxima in the relative abundance of pollen from the mangrove tree genus Rhizophora and that in the surface sediments offshore maxima in the relative abundance of taraxerol occur at latitudes with abundant coastal mangrove forests. Together with the observation that Rhizophora mangle and Rhizophora racemosa leaves are extraordinarily rich in taraxerol, this strongly indicates that taraxerol can be used as a lipid biomarker for mangrove input to the SE Atlantic. The proxy-environment relations for taraxerol and Rhizophora pollen down-core show that increased taraxerol and Rhizophora pollen abundances occur during transgressions and periods with a humid climate. These environmental changes modify the coastal erosion and sedimentation patterns, enhancing the extent of the mangrove ecosystem and/or the transport of mangrove organic matter offshore. Analyses of mid-Pleistocene sediments show that interruption of the pattern of taraxerol maxima during precession minima occurs almost only during periods of low obliquity. This demonstrates the complex environmental response of the interaction between precession-related humidity cycles and obliquity-related sea-level changes on mangrove input