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Foraminifera
Kinds of Foraminifera Selected AbstractsBIOEROSIVE STRUCTURES OF SCLEROZOAN FORAMINIFERA FROM THE LOWER PLIOCENE OF SOUTHERN SPAIN: A CONTRIBUTION TO THE PALAEOECOLOGY OF MARINE HARD SUBSTRATE COMMUNITIESPALAEONTOLOGY, Issue 4 2006A. SANTOS Abstract:, A palaeoecological study of sclerozoan foraminifera of the families Saccamminidae (aff. Sagenina), Lituolidae (Placopsilina), Cibicididae (Cibicides, Dyocibicides, Cibicidella) and Planorbulinidae (Planorbulina and Planorbulinella) that colonized epifaunal bivalves (ostreids and pectinids) during the early Pliocene in southern Spain has led to the recognition of two new boring ichnogenera: Camarichnus ichnogen. nov., with two ichnospecies, C. subrectangularis ichnosp. nov. and C. arcuatus ichnosp. nov., and Canalichnus ichnogen. nov., with one ichnospecies, C. tenuis ichnosp. nov. The first two ichnospecies were produced by adnate lituolids and cibicidids, the last by saccamminids. Their recognition is very important when quantifying populations of these organisms. Colonisation took place after death of the host bivalves, when they acted as very stable substrates whose topography probably controlled the initial settlement pattern of the foraminifera. The colonisation sequence started with the foraminifera (lituolids-saccamminids-cibicidids-planorbulinids) and was followed by vermetid gastropods, serpulids, spirorbids, cheilostome bryozoans and/or ostreids. Preferred orientations and overgrowth relationships between cheilostome bryozoans and serpulids have been detected in this material. [source] Molecular evidence for widespread occurrence of Foraminifera in soilsENVIRONMENTAL MICROBIOLOGY, Issue 9 2010Franck Lejzerowicz Summary Environmental SSU rDNA-based surveys are contributing to the dramatic revision of eukaryotic high-level diversity and phylogeny as the number of sequence data increases. This ongoing revolution gives the opportunity to test for the presence of some eukaryotic taxa in environments where they have not been found using classical microscopic observations. Here, we test whether the foraminifera, a group of single-celled eukaryotes, considered generally as typical for the marine ecosystems are present in soil. We performed foraminiferal-specific nested PCR on 20 soil DNA samples collected in contrasted environments. Unexpectedly, we found that the majority of the samples contain foraminiferal SSU rDNA sequences. In total, we obtained 49 sequences from 17 localities. Phylogenetic analysis clusters them in four groups branching among the radiation of early foraminiferal lineages. Three of these groups also include sequences originated from previous freshwater surveys, suggesting that there were up to four independent colonization events of terrestrial and/or freshwater ecosystems by ancestral foraminifera. As shown by our data, foraminifera are a widespread and diverse component of soil microbial communities. Yet, identification of terrestrial foraminiferal species and understanding of their ecological role represent an exciting challenge for future research. [source] A REVIEW OF EOCENE NUMMULITE ACCUMULATIONS: STRUCTURE, FORMATION AND RESERVOIR POTENTIALJOURNAL OF PETROLEUM GEOLOGY, Issue 1 2001A. Racey Eocene nummulite accumulations, also referred to as nummullte "banks", form Important hydrocarbon reservoirs in Tunisia and Libya and may constitute exploration targets in other parts of North Africa, the Mediterranean and the Middle East. Porosities commonly average 10,20% and permeabilities 10,50md. Foraminifera of the genus Nummulites may comprise up to 98% of the bioclasts in these carbonate reservoirs, although only one or two species may be present. The absence of associated fauna is generally taken to indicate an oligotrophic depositional environment. In this paper, the palaeoecology of the genus Nummulites is discussed together with depositional models for two nummulitic carbonate reservoirs , the Middle Eocene Seeb Limestone of Oman and the Early Eocene El Garia/Jdeir Formation of Tunisia and Libya. The El Garia and Seeb Limestone Formations were deposited in ramp settings, and comprise a series of amalgamated sheets or low-relief banks. In the Hasdrubal field offshore Tunisia, where the El Garia Formation constitutes the reservoir rock, most of the nummulites have been redeposited from shallow into deeper waters whilst in the Bourri field (offshore Libya) they occur as an in situ "bank". Nummulite accumulations often show evidence that both physical reworking (scouring, winnowing and imbrication) and biological processes (reproduction strategies and bioturbation) have influenced their formation. A general model is outlined for discriminating between physically and ecologically produced biofabrics, and the implications for reservoir quality are discussed. [source] Sea-surface temperature and salinity changes in the northwest Pacific since the Last Glacial MaximumJOURNAL OF QUATERNARY SCIENCE, Issue 4 2004Tadamichi Oba Abstract The oxygen isotope records of both benthic and planktonic Foraminifera in five piston cores, collected from the region between the Oyashio and Kuroshio Currents near Japan, clearly show the marked latitudinal shifts of these two currents during the past 25,kyr. Under the present hydrographic condition, a clear relationship between the sea-surface temperature (SST) and oxygen isotope differences from benthic to planktonic Foraminifera is observed in this region. Using this relationship, we find decreased SSTs of 12,13°C (maximum 15°C) in the southernmost core site at the Last Glacial Maximum (LGM), indicating the Oyashio Current shifted southward. The SSTs at the southern two core sites abruptly increased more than 10°C at 10,11,ka, suggesting the Kuroshio Current shifted northward over these sites at 10,11,ka. In contrast, the northern two core sites have remained under the influence of the cold Oyashio Current for the past 25,kyr. With the reasonable estimate of bottom-water temperature decrease of 2.5°C at the LGM, the SSTs estimated by this new method give exactly the same SST values calculated from Mg/Ca ratio of planktonic Foraminifera, allowing palaeosea-surface salinities to be reconstructed. The result suggests that the ice volume effect was 1.0,±,0.1, at the LGM. Copyright © 2004 John Wiley & Sons, Ltd. [source] Changing marine productivity off northern Chile during the past 19,000 years: a multivariable approachJOURNAL OF QUATERNARY SCIENCE, Issue 4 2004M. Mohtadi Abstract A multivariable approach utilising bulk sediment, planktonic Foraminifera and siliceous phytoplankton has been used to reconstruct rapid variations in palaeoproductivity in the Peru,Chile Current System off northern Chile for the past 19,000,cal.,yr. During the early deglaciation (19,000,16,000,cal.,yr,BP), our data point to strongest upwelling intensity and highest productivity of the past 19,000,cal.,yr. The late deglaciation (16,000,13,000,cal.,yr,BP) is characterised by a major change in the oceanographic setting, warmer water masses and weaker upwelling at the study site. Lowest productivity and weakest upwelling intensity are observed from the early to the middle Holocene (13,000,4000,cal.,yr,BP), and the beginning of the late Holocene (<4000,cal.,yr,BP) is marked by increasing productivity, mainly driven by silicate-producing organisms. Changes in the productivity and upwelling intensity in our record may have resulted from a large-scale compression and/or displacement of the South Pacific subtropical gyre during more productive periods, in line with a northward extension of the Antarctic Circumpolar Current and increased advection of Antarctic water masses with the Peru,Chile Current. The corresponding increase in hemispheric thermal gradient and wind stress induced stronger upwelling. During the periods of lower productivity, this scenario probably reversed. Copyright © 2004 John Wiley & Sons, Ltd. [source] Latitudinal gradient of taxonomic richness: combined outcome of temperature and geographic mid-domains effects?JOURNAL OF ZOOLOGICAL SYSTEMATICS AND EVOLUTIONARY RESEARCH, Issue 3 2005A. Brayard Abstract For several decades, the origin and ecological consequences of large-scale continental and marine Latitudinal Gradients of Taxonomic Richness (LGTR) have been intensively debated. Among the various hypotheses, it has been proposed that a LGTR is the by-product of a geographic mid-domain effect, i.e. the result of a random distribution of ranges of taxa between physical hard boundaries such as the continent/ocean interface. In order to more realistically evaluate the role of the mid-domain effect on the origin and evolution of the LGTR of marine planktonic organisms, we present a 2D model based on a cellular-automaton approach in which sea surface temperatures (SST) and currents are forced in the biogeographic dispersal of a randomly generated clade (a 2D ,geophyletic' model). Sensitivity experiments allow to evaluate the effects of currents, SST and the geographical origin of a clade on the formation and shape of a LGTR for planktonic organisms when coupled with a geographic mid-domain effect. Results are discussed in the light of the empirical LGTR of extant planktonic Foraminifera in the Atlantic Ocean. Independently of any other biotic or abiotic parameter, inclusive of the surface currents and origination/extinction absolute and relative rates, our simulations show that the coupling of the mid-domain effect with two critical parameters, namely the shape and intensity of the SST gradient and the geographic origin of a clade, produces realistic patterns of diversity when compared with the observed LGTR of extant atlantic planktonic foraminifera. The results illustrate a non-linear relation between a unimodal latitudinal SST gradient and a resulting bimodal LGTR characterized by a drop in species richness near the equator. This relation indicates that the SST gradient exerts a mid-domain effect on the LGTR. The latitudinal positions of the modal values of the LGTR are also found to be influenced by the geographic origin of the simulated clade. Résumé Depuis plusieurs décennies, l'origine et l'interprétation écologique des Gradients Latitudinaux de Richesse Taxonomique (LGTR) marins ou continentaux, ont été intensivement débattues. Parmi de nombreuses hypothèses, il a été proposé qu'un LGTR puisse être le sous-produit d'un effet de milieu de domaine géographique, i.e. le résultat d'une distribution aléatoire des répartitions des taxa entre deux limites physiques telles que l'interface continent/océan. Afin d'évaluer plus efficacement le rôle de cet effet sur l'origine et l'évolution des LGTR des organismes planctoniques marins, nous proposons un modèle 2D basé sur une approche de type automate cellulaire dans laquelle les températures des eaux de surface (SST) et les courants régulent la dispersion biogéographique d'une phylogénie générée aléatoirement (un modèle «géophylétique»). Ce modèle permet d'évaluer les effets des courants, des SST et de la dépendance thermique des espèces sur la mise en place et la forme d'un LGTR impliquant des organismes planctoniques. Il permet aussi de discuter des influences respectives de ces paramètres quand ils sont superposés à l'effet de milieu de domaine géographique. Les résultats sont discutés à partir du LGTR empirique des foraminifères planctoniques atlantiques actuels. Indépendamment de tout autre paramètre biotique ou abiotique, y compris les courants ainsi que les taux relatifs et absolus d'apparition et d'extinction, les simulations font apparaître que le couplage de l'effet de milieu de domaine à deux contraintes principales, la forme et l'intensité du gradient de SST ainsi que la localisation géographique de l'origine du clade, produit des représentations réalistes de la diversité comparées au LGTR observé pour les foraminifères planctoniques actuels de l'océan atlantique. Nos résultats indiquent une relation non-linéaire entre la structure globale d'un gradient unimodal de SST et le LGTR bimodal correspondant, montrant une baisse de richesse spécifique au niveau de l'équateur. Cette relation suggère que le gradient de SST exerce un effet de milieu de domaine thermique sur le LGTR. Les positions latitudinales des modes du LGTR sont aussi influencées par le lieu d'origine du clade simulé. [source] Multicellular-like compartmentalization of cytoplast in fossil larger foraminiferaLETHAIA, Issue 2 2002CARLES FERRÀNDEZ-CAÑADELL Foraminifera are usually between 0.1 and 1 mm in size, thus falling within the range of the largest eukaryotic cells. However, some fossil and extant foraminiferal species reach diameters of more than 100 mm. One hypothesis of how these gigantic sizes could have been attained by these unicellular organisms is the temporary compartmentalization of cytoplasm into smaller volumes of effective metabolism, as reported for several recent species. Evidence of this phenomenon is shown in fossil genera of larger foraminifera belonging to five families of Cretaceous to Oligocene age. Alternative interpretations are discussed. [source] Palaeobiology and evolution of the earliest agglutinated Foraminifera: Platysolenites, Spirosolenites and related formsLETHAIA, Issue 1 2001Duncan McIlroy Tubular agglutinated fossils of Platysolenites antiquissimus Eichwald, 1860, P. cooperi n.sp. and Spirosolenites spiralis Glaessner, 1979 are examined from selected lower Cambrian successions in Avalonia (England; Wales; Newfoundland) and Baltica (Russia and Estonia). Platysolenites cooperi n.sp. is shown to extend below the first appearance of P. antiquissimus in the Neoproterozoic-Cambrian boundary stratotype region, SE Newfoundland, and to occur at higher stratigraphic levels in Wales and Finnmark. Taphonomic, teleological and ultrastructural studies on well-preserved material are consistent with a similar grade of organization and mode of life for P. antiquissimus and the living astrorhizacean foraminiferid Bathysiphon. However, agglutinated proloculi are here described from both rectilinear P. antiquissimus and coiled S. spiralis, which suggests that neither were typical astrorhizaceans. [source] Habitat heterogeneity and its influence on benthic biodiversity in oxygen minimum zonesMARINE ECOLOGY, Issue 1 2010Andrew J. Gooday Abstract Oxygen minimum zones (OMZs; midwater regions with O2 concentrations <0.5 ml l,1) are mid-water features that intercept continental margins at bathyal depths (100,1000 m). They are particularly well developed in the Eastern Pacific Ocean, the Arabian Sea and the Bay of Bengal. Based on analyses of data from these regions, we consider (i) how benthic habitat heterogeneity is manifested within OMZs, (ii) which aspects of this heterogeneity exert the greatest influence on alpha and beta diversity within particular OMZs and (iii) how heterogeneity associated with OMZs influences regional (gamma) diversity on continental margins. Sources of sea-floor habitat heterogeneity within OMZs include bottom-water oxygen and sulphide gradients, substratum characteristics, bacterial mats, and variations in the organic matter content of the sediment and pH. On some margins, hard grounds, formed of phosphorites, carbonates or biotic substrata, represent distinct subhabitats colonized by encrusting faunas. Most of the heterogeneity associated with OMZs, however, is created by strong sea-floor oxygen gradients, reinforced by changes in sediment characteristics and organic matter content. For the Pakistan margin, combining these parameters revealed clear environmental and faunal differences between the OMZ core and the upper and lower boundary regions. In all Pacific and Arabian Sea OMZs examined, oxygen appears to be the master driver of alpha and beta diversity in all benthic faunal groups for which data exist, as well as macrofaunal assemblage composition, particularly in the OMZ core. However, other factors, notably organic matter quantity and quality and sediment characteristics, come into play as oxygen concentrations begin to rise. The influence of OMZs on meiofaunal, macrofaunal and megafaunal regional (gamma) diversity is difficult to assess. Hypoxia is associated with a reduction in species richness in all benthic faunal groups, but there is also evidence for endemism in OMZ settings. We conclude that, on balance, OMZs probably enhance regional diversity, particularly in taxa such as Foraminifera, which are more tolerant of hypoxia than others. Over evolutionary timescales, they may promote speciation by creating strong gradients in selective pressures and barriers to gene flow. [source] Diversity of algal endosymbionts (zooxanthellae) in octocorals: the roles of geography and host relationshipsMOLECULAR ECOLOGY, Issue 8 2005M. J. H. VAN OPPEN Abstract The presence, genetic identity and diversity of algal endosymbionts (Symbiodinium) in 114 species from 69 genera (20 families) of octocorals from the Great Barrier Reef (GBR), the far eastern Pacific (EP) and the Caribbean was examined, and patterns of the octocoral,algal symbiosis were compared with patterns in the host phylogeny. Genetic analyses of the zooxanthellae were based on ribosomal DNA internal transcribed spacer 1 (ITS1) region. In the GBR samples, Symbiodinium clades A and G were encountered with A and G being rare. Clade B zooxanthellae have been previously reported from a GBR octocoral, but are also rare in octocorals from this region. Symbiodinium G has so far only been found in Foraminifera, but is rare in these organisms. In the Caribbean samples, only Symbiodinium clades B and C are present. Hence, Symbiodinium diversity at the level of phylogenetic clades is lower in octocorals from the Caribbean compared to those from the GBR. However, an unprecedented level of ITS1 diversity was observed within individual colonies of some Caribbean gorgonians, implying either that these simultaneously harbour multiple strains of clade B zooxanthellae, or that ITS1 heterogeneity exists within the genomes of some zooxanthellae. Intracladal diversity based on ITS should therefore be interpreted with caution, especially in cases where no independent evidence exists to support distinctiveness, such as ecological distribution or physiological characteristics. All samples from EP are azooxanthellate. Three unrelated GBR taxa that are described in the literature as azooxanthellate (Junceella fragilis, Euplexaura nuttingi and Stereonephthya sp. 1) contain clade G zooxanthellae, and their symbiotic association with zooxanthellae was confirmed by histology. These corals are pale in colour, whereas related azooxanthellate species are brightly coloured. The evolutionary loss or gain of zooxanthellae may have altered the light sensitivity of the host tissues, requiring the animals to adopt or reduce pigmentation. Finally, we superimposed patterns of the octocoral,algal symbiosis onto a molecular phylogeny of the host. The data show that many losses/gains of endosymbiosis have occurred during the evolution of octocorals. The ancestral state (azooxanthellate or zooxanthellate) in octocorals remains unclear, but the data suggest that on an evolutionary timescale octocorals can switch more easily between mixotrophy and heterotrophy compared to scleractinian corals, which coincides with a low reliance on photosynthetic carbon gain in the former group of organisms. [source] Lower Jurassic Foraminifera and Calcified Microflora from Gibraltar, Western MediterraneanPALAEONTOLOGY, Issue 4 2001M. K. Boudagher-Fadel Benthic foraminifera are described for the first time from the Gibraltar Limestone Formation of the Rock of Gibraltar. The new species Siphovalvulina colomiS. gibraltarensisRiyadhella praeregularis occur with Duotaxis metula Kristan, Everticyclammina praevirguliana Fugagnoli, Siphovalvulina sp.,an atypically early example of Textulariopsis sp., and Nodosaria sp. Microflora are present as the probable cyanobacterium Cayeuxia ?piae Frollo, the alga Palaeodasycladus ?mediterraneus (Pia), and the disputed alga Thaumatoporella ?parvovesiculifera (Raineri). The foraminifera compare most closely with poorly-known taxa from Italy, Spain and Morocco, and are consistent with an Early Jurassic (Sinemurian) age for the upper part of the &62;460-m-thick Gibraltar Limestone. Most are textulariids and more primitive than species well known from the later Early Jurassic (Pliensbachian) of the Mediterranean region, especially Morocco and Italy. The biota as a whole is characteristic of inner carbonate platform environments widespread along the rifted western margins of the Early Jurassic Tethys, notably those recorded from Morocco, Italy and Greece as well as southern Spain. [source] Peroxisome Proliferation in Foraminifera Inhabiting the Chemocline: An Adaptation to Reactive Oxygen Species Exposure?,THE JOURNAL OF EUKARYOTIC MICROBIOLOGY, Issue 3 2008JOAN M. BERNHARD ABSTRACT. Certain foraminiferal species are abundant within the chemocline of marine sediments. Ultrastructurally, most of these species possess numerous peroxisomes complexed with the endoplasmic reticulum (ER); mitochondria are often interspersed among these complexes. In the Santa Barbara Basin, pore-water bathing Foraminifera and co-occurring sulfur-oxidizing microbial mats had micromolar levels of hydrogen peroxide (H2O2), a reactive oxygen species that can be detrimental to biological membranes. Experimental results indicate that adenosine triphosphate concentrations are significantly higher in Foraminifera incubated in 16 ,M H2O2 than in specimens incubated in the absence of H2O2. New ultrastructural and experimental observations, together with published results, lead us to propose that foraminiferans can utilize oxygen derived from the breakdown of environmentally and metabolically produced H2O2. Such a capability could explain foraminiferal adaptation to certain chemically inhospitable environments; it would also force us to reassess the role of protists in biogeochemistry, especially with respect to hydrogen and iron. The ecology of these protists also appears to be tightly linked to the sulfur cycle. Finally, given that some Foraminifera bearing peroxisome,ER complexes belong to evolutionarily basal groups, an early acquisition of the capability to use environmental H2O2 could have facilitated diversification of foraminiferans during the Neoproterozoic. [source] Stratigraphy, sedimentology, age and palaeoenvironment of marine varved clay in the Middle Swedish end-moraine zoneBOREAS, Issue 2 2010MARK D. JOHNSON Johnson, M. D. & Ståhl, Y. 2009: Stratigraphy, sedimentology, age and palaeoenvironment of marine varved clay in the Middle Swedish end-moraine zone. Boreas, 10.1111/j.1502-3885.2009.00124.x. ISSN 0300-9483 Deglaciation of the Middle Swedish end-moraine zone and age of the sediment in and between the moraines have been discussed for about a hundred years. The goal of this project was to determine the stratigraphy and age of the sediment in and between the moraines. Inter-moraine flats are underlain by clay, 10,25 m thick, overlying thin sand and gravel or till on bedrock. The clay is overlain by a few metres of sand and gravel. Much of the clay beneath the flats consists of rhythmites that grade from grey to red and are 2,74 cm thick. Our interpretation of these rhythmites as being varves is supported by grain size and mineralogical and elemental variations. Foraminifera and ostracods show that the clay was deposited in an arctic marine environment, while radiocarbon dating of the microfossils indicates that the clay was deposited 12 150 cal. 14C years ago, during the Younger Dryas chronozone (YD). Most of the optical stimulated luminescence dates on the clay are much older, containing quartz sand that was insufficiently bleached. The stratigraphy indicates that the moraines are composed of YD clay pushed into ridge forms during ice-front oscillations. It is not possible to determine how far north the Scandinavian Ice Sheet retreated prior to the YD advance. We neither support nor reject the suggestion that the ice margin retreated to the northern edge of Mt. Billingen during the Allerød, causing the Baltic Ice Lake to drain. [source] Chalk micropalaeontology and the provenancing of middle pleistocene lowestoft formation till in eastern EnglandEARTH SURFACE PROCESSES AND LANDFORMS, Issue 9 2001P. R. Fish Abstract The distribution and deposits of British and Scandinavian Middle Pleistocene ice sheets in eastern England remain problematic. A new till provenancing technique based on Chalk micropalaeontology is described, with the object of refining understanding of the ice sheet which deposited the Lowestoft Formation till (Anglian/Elsterian) and its relationship to Scandinavian ice sheets. The technique involves extracting foraminifera from Chalk erratics and till matrix obtained from stratigraphically controlled till sections and comparing their micropalaeontology with that of Upper Cretaceous Chalk bedrock. Application to the Lowestoft Formation till of eastern England suggests that current models of ice-flow in this region require revision involving reinstatement of some earlier ideas. Chalk provenance data indicate an initial phase of glaciation, with ice streaming southwards across eastern England before fanning across East Anglia from the position of the Fen basin. This was followed by a later phase in which the main southward trajectory of ice-flow was located further east in the North Sea Basin, but again with ice fanning out across East Anglia. These ice-flow trajectories imply constraint of the British ice sheet by Scandinavian ice. Copyright © 2001 John Wiley & Sons, Ltd. [source] Setting the absolute tempo of biodiversity dynamicsECOLOGY LETTERS, Issue 7 2007Andrew P. Allen Abstract Neutral biodiversity theory has the potential to contribute to our understanding of how macroevolutionary dynamics influence contemporary biodiversity, but there are issues regarding its dynamical predictions that must first be resolved. Here we address these issues by extending the theory in two ways using a novel analytical approach: (1) we set the absolute tempo of biodiversity dynamics by explicitly incorporating population-level stochasticity in abundance; (2) we allow new species to arise with more than one individual. Setting the absolute tempo yields quantitative predictions on biodiversity dynamics that can be tested using contemporary and fossil data. Allowing incipient-species abundances greater than one individual yields predictions on how these dynamics, and the form of the species-abundance distribution, are affected by multiple speciation modes. We apply this new model to contemporary and fossil data that encompass 30 Myr of macroevolution for planktonic foraminifera. By synthesizing the model with these empirical data, we present evidence that dynamical issues with neutral biodiversity theory may be resolved by incorporating the effects of environmental stochasticity and incipient-species abundance on biodiversity dynamics. [source] Molecular evidence for widespread occurrence of Foraminifera in soilsENVIRONMENTAL MICROBIOLOGY, Issue 9 2010Franck Lejzerowicz Summary Environmental SSU rDNA-based surveys are contributing to the dramatic revision of eukaryotic high-level diversity and phylogeny as the number of sequence data increases. This ongoing revolution gives the opportunity to test for the presence of some eukaryotic taxa in environments where they have not been found using classical microscopic observations. Here, we test whether the foraminifera, a group of single-celled eukaryotes, considered generally as typical for the marine ecosystems are present in soil. We performed foraminiferal-specific nested PCR on 20 soil DNA samples collected in contrasted environments. Unexpectedly, we found that the majority of the samples contain foraminiferal SSU rDNA sequences. In total, we obtained 49 sequences from 17 localities. Phylogenetic analysis clusters them in four groups branching among the radiation of early foraminiferal lineages. Three of these groups also include sequences originated from previous freshwater surveys, suggesting that there were up to four independent colonization events of terrestrial and/or freshwater ecosystems by ancestral foraminifera. As shown by our data, foraminifera are a widespread and diverse component of soil microbial communities. Yet, identification of terrestrial foraminiferal species and understanding of their ecological role represent an exciting challenge for future research. [source] Palaeoecology and depositional environments of the Tendaguru Beds (Late Jurassic to Early Cretaceous, Tanzania)FOSSIL RECORD-MITTEILUNGEN AUS DEM MUSEUM FUER NATURKUNDE, Issue 1 2002Martin Aberhan Abstract The Late Jurassic to Early Cretaceous Tendaguru Beds (Tanzania, East Africa) have been well known for nearly a century for their diverse dinosaur assemblages. Here, we present sedimentological and palaeontological data collected by the German-Tanzanian Tendaguru Expedition 2000 in an attempt to reconstruct the palaeo-ecosystems of the Tendaguru Beds at their type locality. Our reconstructions are based on sedimentological data and on a palaeoecological analysis of macroinvertebrates, microvertebrates, plant fossils and microfossils (ostracods, foraminifera, charophytes, palynomorphs). In addition, we included data from previous expeditions, particularly those on the dinosaur assemblages. The environmental model of the Tendaguru Beds presented herein comprises three broad palaeoenvironmental units in a marginal marine setting: (1) Lagoon-like, shallow marine environments above fair weather wave base and with evidence of tides and storms. These formed behind barriers such as ooid bar and siliciclastic sand bar complexes and were generally subject to minor salinity fluctuations. (2) Extended tidal flats and low-relief coastal plains. These include low-energy, brackish coastal lakes and ponds as well as pools and small fluvial channels of coastal plains in which the large dinosaurs were buried. Since these environments apparently were, at best, poorly vegetated, the main feeding grounds of giant sauropods must have been elsewhere. Presumably, tidal flats and coastal plains were visited by dinosaurs primarily during periods of drought. (3) Vegetated hinterland. Vegetation of this environment can only be inferred indirectly from plant material transported into the other depositional environments. Vegetation was dominated by a diverse conifer flora, which apparently formed part of the food source of large herbivorous sauropods. Evidence from various sources suggests a subtropical to tropical palaeoclimate, characterised by seasonal rainfall alternating with a pronounced dry season during the Late Jurassic. In Early Cretaceous times, sedimentological and palaeontological proxies suggest a climatic shift towards more humid conditions. Die Tendaguru-Schichten von Tansania in Ostafrika (Oberjura bis Unterkreide) sind als Lagerstätte oberjurassischer Dinosaurier seit nahezu einem Jahrhundert weltweit bekannt. Anhand von sedimentologischen und paläontologischen Daten, die während der Deutsch-Tansanischen Tendaguru Expedition 2000 im Typus-Gebiet der Tendaguru-Schichten gewonnen wurden, werden Paläo-Ökosysteme rekonstruiert. Grundlage der Rekonstruktionen sind die Auswertung sedimentologischer Daten sowie die paläo-ökologische Analyse von Makroinvertebraten, Mikrovertebraten, pflanzlichen Fossilien und Mikrofossilien (Ostrakoden, Foraminiferen, Charophyten, Palynomorphen). Darüber hinaus werden Informationen über Dinosaurier berücksichtigt, die bei früheren Expeditionen gewonnen wurden. Das hier vorgestellte Ablagerungsmodell der Tendaguru-Schichten umfaßt drei Teilbereiche eines randlich marinen Sedimentationsraumes, die wie folgt gekennzeichnet werden können: (1) Lagunen-artige, marine Flachwasserbereiche, die oberhalb der Schönwetter-Wellenbasis lagen und unter deutlichem Einfluß von Gezeiten und Stürmen standen. Sie waren vom offenen Meer durch Barrieren, wie Ooidbarren und siliziklastischen Sandbarrenkomplexen, getrennt und wiesen einen leicht schwankenden Salzgehalt auf. (2) Ausgedehnte Wattgebiete und flache Küstenebenen. Dort befanden sich niedrig-energetische, brackische Strandseen und Teiche sowie Tümpel und kleinere Flußrinnen, in denen die großen Dinosaurier eingebettet wurden. Da diese Lebensräume bestenfalls dürftig bewachsen waren, müssen die Nahrungsquellen und der eigentliche Lebensraum der riesigen Sauropoden anderswo gelegen haben. Vermutlich wurden die Wattgebiete und Flachküsten von Dinosauriern vorrangig in den Trockenzeiten aufgesucht. (3 ) Bewachsenes Hinterland. Die Vegetation dieses Lebensraumes kann nur indirekt aus Pflanzenresten erschlossen werden, die in die anderen Ablagerungsraume transportiert wurden. Die Vegetation wurde von einer diversen Koniferenflora dominiert, die zumindest teilweise die Nahrungsgrundlage der großen, herbivoren Sauropoden bildete. Sedimentologische und paläontologische Indikatoren sprechen für ein subtropisches bis tropisches Klima wahrend der späten Jurazeit mit einem jahreszeitlichen Wechsel von Regenfällen und ausgeprägten Trockenzeiten. In der frühen Kreidezeit deutet sich ein Wechsel zu starker humiden Bedingungen an. [source] An eastern Tethyan (Tibetan) record of the Early Jurassic (Toarcian) mass extinction eventGEOBIOLOGY, Issue 3 2006P. B. WIGNALL ABSTRACT A record of the Early Jurassic mass extinction event is reported from eastern Tethyan (Tibetan) locations for the first time. In the Mount Everest region a thick Lower Jurassic carbonate formation, here named the Yungjia Formation, is developed within the predominantly clastic Triassic,Jurassic succession. Within the formation a sharp transition from peloidal packstones/grainstones to thin-bedded, pyritic micrite-shales interbeds records a sharp pulse of deepening and development of dysoxic bottom waters. Both the lithiotid bivalves and the lituolid foraminifera are important constituents of the lower Yungjia Formation but they disappear at this flooding surface or a short distance below it. This extinction event is comparable to that seen at the base of the Pliensbachian/Toarcian boundary in western Tethyan platform carbonates but the Tibetan events occurred late in the Toarcian Stage as indicated by nannofossil biostratigraphy and C isotope chemostratigraphy. The Early Jurassic extinction event (and the associated spread of oxygen-poor waters) was therefore not synchronous throughout the Tethyan region. [source] Pendleian (early Serpukhovian) marine carbonates from SW Spain: sedimentology, biostratigraphy and depositional modelGEOLOGICAL JOURNAL, Issue 1 2004P. Cózar Abstract The San Antonio,La Juliana tectono-sedimentary unit contains the only Namurian marine carbonates in the southwestern part of the Iberian Peninsula. The analysis of this unit is fundamental in understanding the sedimentary evolution and tectonic movements which operated during the Namurian in this area. Using foraminifera the succession has been assigned to two biozones (Zones 17 and 18), both occurring in the Pendleian (early Namurian). Seven stratigraphic sections have been analysed: San Antonio, Burjadillo, Lavadero de la Mina, Cornuda, Lozana, Caridad and Via Crucis. The stratigraphic succession of the San Antonio,La Juliana Unit consists of olistolites in the basal part, with common debris-flow deposits (mainly of carbonates, with minor siliciclastic rocks), and turbidites, all of them embedded in shales. These rocks, interpeted as slope deposits, pass up into shallow-water platform facies, with sediments characteristic of the inner platform and tidal flats. Above these rocks, terrigenous deltaic deposits occur. Thus, the stratigraphic sections show an overall shallowing-upward trend. The isolation of some outcrops, and the duplication and absence of some parts of the stratigraphic succession are explained by tectonic movements. Overall, tectonic factors seem to be the main control rather than glacio-eustatic or autocyclic processes, and sedimentation took place in a strike-slip regime. Copyright © 2004 John Wiley & Sons, Ltd. [source] Constraints on the glacial operation of the atlantic ocean's conveyor circulationISRAEL JOURNAL OF CHEMISTRY, Issue 1 2002Wallace S. BroeckerArticle first published online: 8 MAR 2010 Circulation in the Atlantic Ocean is currently dominated by a northward flow of upper waters balanced by a return flow of deep water (i.e., the conveyor). Paleoproxies tell us that, unlike today, during the glacial age the deep Atlantic was stratified. Rather than being flooded with one nearly homogeneous water mass, there were two distinctly different ones. In this paper, the paleoproxy results are analyzed in an attempt to constrain the sources and ventilation rate of the deeper of these two glacial Atlantic water masses. Taken together, the cadmium and carbon isotope measurements on benthic foraminifera and the radiocarbon measurements on coexisting benthic and planktonic foraminifera appear to require a conveyor-like circulation no weaker than half of today's. This conclusion is at odds with geostrophic reconstructions. This seeming disagreement could be eliminated if, as suggested by Keigwin and Schlegel, the radiocarbon measurements by Broecker et al. significantly underestimate the difference between the 14C to C ratio for glacialage surface water and deep water in the equatorial Atlantic. [source] Imaging the fluorescence of marine invertebrates and their associated floraJOURNAL OF MICROSCOPY, Issue 2 2008T.D. AINSWORTH Summary The cells and tissues of many marine invertebrates and their associated flora contain fluorescent pigments and proteins, many of which have been utilized commercially and provide marker molecules in other systems for fluorescence imaging technology. However, in the study of marine invertebrates and their symbioses these naturally occurring molecules have been seen to limit or confound fluorescence microscopy analyses. Here we demonstrate the endogenous fluorescence associated with two marine invertebrates (coral and foraminifera) and describe how these qualities can be utilized in fluorescence microanalyses. Understanding and imaging the diversity of fluorescent molecules provide insight into how fluorescence microscopy techniques can now be applied to these complex systems. [source] THE RESERVOIR POTENTIAL OF MIOCENE CARBONATE ROCKS IN THE ASKALE AND HINIS-MUS-VAN SUB-BASINS, EAST ANATOLIA, TURKEYJOURNAL OF PETROLEUM GEOLOGY, Issue 2 2003A. G. Büyükutku Lower-middle Miocene limestones in East Anatolia (eastern Turkey) assigned to the Adilcevaz Formation were studied using core and cuttings data from eight wells in the Tertiary Askale and Hinis-Mus-Van sub-basins. Their depositional environment, diagenetic characteristics and reservoir quality are reviewed. The Adilcevaz Formation carbonates are up to 225m thick. Abundant bioclasts are dominated by corals, encrusting red algae, bryozoans, and benthonic and planktonic foraminifera. Reef-core, fore-reef and back-reef facies were recognized. The preservation of primary porosity is generally poor as a result of late calcite cementation. Porosity is mainly present as moulds, vugs and interparticle types, which are best developed in the fore-reef and reef-core facies. However these pores are poorly connected and permeability is generally less than 0.1 mD. In contrast to coeval limestones of similiar facies in Iran, Iraq and other parts of the Middle East, the Adilcevaz Formation has little reservoir potential. [source] Seeking a Holocene drift ice proxy: non-clay mineral variations from the SW to N-central Iceland shelf: trends, regime shifts, and periodicities,JOURNAL OF QUATERNARY SCIENCE, Issue 7 2009John T. Andrews Abstract Quantitative X-ray diffraction analysis of the <2,mm sediment fraction was carried out on 1257 samples (from the seafloor and 16 cores) from the Iceland shelf west of 18° W. All but one core (B997-347PC) were from transects along troughs on the NW to N-central shelf, an area that in modern and historic times has been affected by drift ice. The paper focuses on the non-clay mineralogy of the sediments (excluding calcite and volcanic glass). Quartz and potassium feldspars occupy similar positions in an R-mode principal component analysis, and oligoclase feldspar tracks quartz; these minerals are used as a proxy for ice-rafted detritus (IRD). Accordingly, the sum of these largely foreign minerals (Q&K) (to Icelandic bedrock) is used as a proxy for drift ice. A stacked, equi-spaced 100 a record is developed which shows both low-frequency trends and higher-frequency events. The detrended stacked record compares well with the flux of quartz (mg,cm,2,a,1) at MD99-2269 off N Iceland. The multi-taper method indicated that there are three significant frequencies at the 95% confidence level with periods of ca. 2500, 445 and 304 a. Regime shift analysis pinpoints intervals when there was a statistically significant shift in the average Q&K weight %, and identifies four IRD-rich events separated by intervals with lower inputs. There is some association between peaks of IRD input, less dense surface waters (from ,18O data on planktonic foraminifera) and intervals of moraine building. Copyright © 2009 John Wiley & Sons, Ltd. [source] Recognising subtidal foraminiferal assemblages: implications for quantitative sea-level reconstructions using a foraminifera-based transfer function,JOURNAL OF QUATERNARY SCIENCE, Issue 3 2009Sarah A. Woodroffe Abstract Microfossil-based transfer function models are increasingly used to provide decimeter-scale sea-level change reconstructions. In this paper I demonstrate that in the tropical location of northern Australia problems arise in selecting the appropriate elevation range for the modern training set used to calibrate fossil calcareous foraminiferal assemblages. Most calcareous foraminiferal species found in cores occur in both modern intertidal and shallow subtidal environments. A lack of independent measures to indicate whether fossil assemblages come from intertidal environments forces use of a training set that includes intertidal and subtidal environments. This results in decreased precision compared to using a training set solely from intertidal environments. The widely used method of assessing model fit to fossil assemblages (modern analogue technique) often fails to discriminate between acceptable and unacceptable reconstructions. It is important to investigate a number of different measures including modern analogue technique, canonical correspondence analysis and changing bootstrapped sample specific transfer function errors to fully understand the level of similarity between modern and fossil foraminiferal samples, to judge the reliability of transfer function-predicted sea-level reconstructions. Copyright © 2008 John Wiley & Sons, Ltd. [source] Relative sea-level observations in western Scotland since the Last Glacial Maximum for testing models of glacial isostatic land movements and ice-sheet reconstructions,JOURNAL OF QUATERNARY SCIENCE, Issue 6 2006Ian Shennan Abstract Observations of relative sea-level change and local deglaciation in western Scotland provide critical constraints for modelling glacio-isostatic rebound in northern Britain over the last 18,000 years. The longest records come from Skye, Arisaig and Knapdale with a shorter, Holocene, record from Kintail. Biostratigraphic (diatom, pollen, dinoflagellate, foraminifera and thecamoebian), lithological and radiocarbon analyses provide age and elevation parameters for each sea-level index point. All four sites reveal relative sea-level change that is highly non-monotonic in time as the local vertical component of glacio-isostatic rebound and eustasy (or global meltwater influx) dominate at different periods. Copyright © 2006 John Wiley & Sons, Ltd. [source] Late Quaternary upwelling off tropical NW Africa: new micropalaeontological evidence from ODP Hole 658C,JOURNAL OF QUATERNARY SCIENCE, Issue 3 2006Simon K. Haslett Abstract Planktonic foraminifera and radiolaria have been analysed in a Late Quaternary (40,0,ka) sediment sequence from Ocean Drilling Program (ODP) Hole 658C located under a coastal upwelling system near Cap Blanc, offshore northwest Africa, in order to document the palaeoceanographic history of the area. Temporal variations in species abundance and faunal assemblage analysis reveal a tripartite phased sequence of palaeoceanographic change through the Late Quaternary. Phase 1 spans 40,14.5,ka and is characterised by moderate upwelling, but Heinrich event 2 is distinguished as a brief episode of strengthened upwelling. Phase 2 begins with a change in a number of variables at ca. 14.5,ka and extends to ca. 5.5,ka. This phase is characterised by a general strengthening of upwelling, but may be subdivided into three minor phases including (a) the recognition of the Younger Dryas, marked by a temporary reduction in upwelling strength, followed by (b) an intensification of upwelling, and (c) upwelling and high productivity between 8 and 5.5,ka. This phase of upwelling corresponds with maximum Holocene cooling, possibly triggered by the collapse of the Laurentide ice sheet. Phase 3 extends from 5.5 to 0,ka and is characterised by weak upwelling and significant calcite dissolution. These phases are related to climatic events, particularly the African Humid Period (AHP), which is coincident with Phase 2. The AHP is characterised by increased precipitation, linked to an intensification of the African monsoon that enhances North East Trade Wind-driven coastal upwelling and is associated with the expansion of continental vegetation across North Africa. Copyright © 2006 John Wiley & Sons, Ltd. [source] Modern distribution of saltmarsh testate amoebae: regional variability of zonation and response to environmental variablesJOURNAL OF QUATERNARY SCIENCE, Issue 5-6 2002Dan J. Charman Abstract Sea-level reconstruction from biological indicators in saltmarsh sediments requires an understanding of the modern ecology of the organisms concerned. Previous work suggested that testate amoebae are a potential new group of organisms to use for sea-level reconstruction, especially combined with diatoms and foraminifera. This paper analyses data from three saltmarshes on the Taf estuary, South Wales, the River Erme, Devon, and at Brancaster, Norfolk (UK) to (i) test for the presence and zonation of testate amoebae in relation to elevation; (ii) examine the similarity of zonation patterns between marshes; and (iii) explore the relationship between assemblage composition and a wider range of environmental variables. In addition we provide an update on the identification of testate amoebae on saltmarshes. Our results confirm that at all sites the primary environmental gradient is tidal inundation. Major changes in taxa along the tidal gradient are similar except for the lowest elevations, where different taxa become dominant at different sites. Canonical correspondence analysis (CCA) shows that assemblage composition is also strongly related to other variables, independent of the tidal position. Salinity, particle size and organic matter content are particularly important, and there is a statistically significant geographical effect on assemblages. Relationships between sea-level and assemblage composition are often stronger for individual sites, suggesting that local data sets should be used for quantitative sea-level reconstructions. However, the combined data set would provide more robust estimates of past sea-level change from fossil data. Other environmental variables explain as much of the variability in species assemblages as tidal parameters and should be considered more often in sea-level reconstructions based on microfossil indicators. Copyright © 2002 John Wiley & Sons, Ltd. [source] Latitudinal gradient of taxonomic richness: combined outcome of temperature and geographic mid-domains effects?JOURNAL OF ZOOLOGICAL SYSTEMATICS AND EVOLUTIONARY RESEARCH, Issue 3 2005A. Brayard Abstract For several decades, the origin and ecological consequences of large-scale continental and marine Latitudinal Gradients of Taxonomic Richness (LGTR) have been intensively debated. Among the various hypotheses, it has been proposed that a LGTR is the by-product of a geographic mid-domain effect, i.e. the result of a random distribution of ranges of taxa between physical hard boundaries such as the continent/ocean interface. In order to more realistically evaluate the role of the mid-domain effect on the origin and evolution of the LGTR of marine planktonic organisms, we present a 2D model based on a cellular-automaton approach in which sea surface temperatures (SST) and currents are forced in the biogeographic dispersal of a randomly generated clade (a 2D ,geophyletic' model). Sensitivity experiments allow to evaluate the effects of currents, SST and the geographical origin of a clade on the formation and shape of a LGTR for planktonic organisms when coupled with a geographic mid-domain effect. Results are discussed in the light of the empirical LGTR of extant planktonic Foraminifera in the Atlantic Ocean. Independently of any other biotic or abiotic parameter, inclusive of the surface currents and origination/extinction absolute and relative rates, our simulations show that the coupling of the mid-domain effect with two critical parameters, namely the shape and intensity of the SST gradient and the geographic origin of a clade, produces realistic patterns of diversity when compared with the observed LGTR of extant atlantic planktonic foraminifera. The results illustrate a non-linear relation between a unimodal latitudinal SST gradient and a resulting bimodal LGTR characterized by a drop in species richness near the equator. This relation indicates that the SST gradient exerts a mid-domain effect on the LGTR. The latitudinal positions of the modal values of the LGTR are also found to be influenced by the geographic origin of the simulated clade. Résumé Depuis plusieurs décennies, l'origine et l'interprétation écologique des Gradients Latitudinaux de Richesse Taxonomique (LGTR) marins ou continentaux, ont été intensivement débattues. Parmi de nombreuses hypothèses, il a été proposé qu'un LGTR puisse être le sous-produit d'un effet de milieu de domaine géographique, i.e. le résultat d'une distribution aléatoire des répartitions des taxa entre deux limites physiques telles que l'interface continent/océan. Afin d'évaluer plus efficacement le rôle de cet effet sur l'origine et l'évolution des LGTR des organismes planctoniques marins, nous proposons un modèle 2D basé sur une approche de type automate cellulaire dans laquelle les températures des eaux de surface (SST) et les courants régulent la dispersion biogéographique d'une phylogénie générée aléatoirement (un modèle «géophylétique»). Ce modèle permet d'évaluer les effets des courants, des SST et de la dépendance thermique des espèces sur la mise en place et la forme d'un LGTR impliquant des organismes planctoniques. Il permet aussi de discuter des influences respectives de ces paramètres quand ils sont superposés à l'effet de milieu de domaine géographique. Les résultats sont discutés à partir du LGTR empirique des foraminifères planctoniques atlantiques actuels. Indépendamment de tout autre paramètre biotique ou abiotique, y compris les courants ainsi que les taux relatifs et absolus d'apparition et d'extinction, les simulations font apparaître que le couplage de l'effet de milieu de domaine à deux contraintes principales, la forme et l'intensité du gradient de SST ainsi que la localisation géographique de l'origine du clade, produit des représentations réalistes de la diversité comparées au LGTR observé pour les foraminifères planctoniques actuels de l'océan atlantique. Nos résultats indiquent une relation non-linéaire entre la structure globale d'un gradient unimodal de SST et le LGTR bimodal correspondant, montrant une baisse de richesse spécifique au niveau de l'équateur. Cette relation suggère que le gradient de SST exerce un effet de milieu de domaine thermique sur le LGTR. Les positions latitudinales des modes du LGTR sont aussi influencées par le lieu d'origine du clade simulé. [source] Palaeontologic and biogeochemical characterization of the Cyrtograptus lundgreni event in the black shales of eastern Mid-Sardinia, ItalyLETHAIA, Issue 2 2006Paola Pittau A succession of biotic and geochemical changes that occurred during the Cyrtograptus lundgreni Event (Late Wenlock) have been recorded from the ,pelagic' black-shales in the Goni section, eastern mid-Sardinia, Italy. The studied interval encompasses the Cyrtograptus rigidus to Pristiograptus dubius-Gothograptus nassa zones. The fossil association includes graptolites, chitinozoans and microplankton i.e. probable linings of agglutinated foraminifera and radiolaria capsular membranes. Analysis of the chitinozoan distribution revealed a succession of several chitinozoan associations with low species diversity and dominated by opportunistic species. Three chitinozoan faunal turnovers and three extinction events have been recorded. Two of them coincide with graptolite extinctions whereas one probably is of local significance. Disappearance of the chitinozoan and microplankton associations occurred during four consecutive graptolite zones. Geochemical data (trace elements analysis) showed significantly higher (up to c. 100%) values for Co and Cd in the sedimentary organic matter (SOM) than in the whole rock samples. Possible relationships between peaks of metal enrichment, the major faunal changes among chitinozoans, extinction events among chitinozoans and graptolites and, to a certain extent, oceanic events may be inferred. The first extinction datum is older that those occurring in Gotland, Sweden and Thüringen, Germany and is so far considered to be of local significance. The second extinction datum of Sardinia can be matched with Datum 1 of Gotland and Thüringen. A close correlation between the third extinction datum of Sardinia and Datum 2 of Thüringen and Gotland reinforces the importance of these events at global scale. [source] Multicellular-like compartmentalization of cytoplast in fossil larger foraminiferaLETHAIA, Issue 2 2002CARLES FERRÀNDEZ-CAÑADELL Foraminifera are usually between 0.1 and 1 mm in size, thus falling within the range of the largest eukaryotic cells. However, some fossil and extant foraminiferal species reach diameters of more than 100 mm. One hypothesis of how these gigantic sizes could have been attained by these unicellular organisms is the temporary compartmentalization of cytoplasm into smaller volumes of effective metabolism, as reported for several recent species. Evidence of this phenomenon is shown in fossil genera of larger foraminifera belonging to five families of Cretaceous to Oligocene age. Alternative interpretations are discussed. [source] | |||||||||||||