Biostratigraphy, mineralogy and geochemistry of the Trabakua Pass and Ermua sections in Spain: Paleocene-Eocene transition

Isotopic, geochemical and bulk mineralogical analyses in the Trabakua and Ermua sections, Basque Basin, reveal major changes across the Paleocene-Eocene transition. Expanded sedimentary records exhibit a gradual decrease of 1.0 parts per thousand in delta(13)C values in the lower part of Zone P5 followed by a more rapid 3 parts per thousand negative excursion. The 3 parts per thousand delta(13)C excursion is associated with an abrupt decrease in carbonate sedimentation, increased detrital flux and decreased grain size which suggest changes in marine/atmospheric currents and/or size and structure of the ocean carbon reservoir. The clays recognized at Trabakua record a deep burial diagenesis as indicated by two generations of chlorite, the presence of mixed-layers chlorite-smectite and illite-smectite, the absence of smectite and the near absence of kaolinite. The very low delta(18)O values (<-3.5 parts per thousand) throughout the Trabakua and Ermua sections reflect diagenetic alteration rather than paleotemperatures. Because of deep burial diagenesis and very poorly preserved microfossils, the Trabakua Pass and Ermua sections are not optimal potential stratotypes for the Paleocene-Eocene boundary.

X-ray microtomography of Larger Foraminifera

X-ray microtomography has become a new tool in earth sciences to obtain non-destructive 3D-image data from geological objects in which variations in mineralogy, chemical composition and/or porosity create sufficient x-ray density contrasts.We present here first, preliminary results of an application to the external and internal morphology of Permian to Recent Larger Foraminifera. We use a SkyScan-1072 high-resolution desk-top micro-CT system. The system has a conical x-ray source with a spot size of about 5µm that runs at 20-100kV, 0-250µA, resulting in a maximal resolution of 5µm. X-ray transmission images are captured by a scintillator coupled via fibre optics to a 1024x1024 pixel 12-bit CCD. The object is placed between the x-ray source and the scintillator on a stub that rotates 360°around its vertical axis in steps as small as 0.24 degrees. Sample size is limited to 2 cm due to the absorption of geologic material for x-rays. The transmission images are back projected using a Feldkamp algorithm into a vertical stack of up to 1000 1Kx1K images that represent horizontal cuts of the object. This calculation takes 2 to several hours on a Double-Processor 2.4GHz PC. The stack of images (.bmp) can be visualized with any 3D-imaging software, used to produce cuts of Larger Foraminifera. Among other applications, the 3D-imaging software furnished by SkyScan can produce 3D-models by defining a threshold density value to distinguish "solid" from "void. Several models with variable threshold values and colors can be imbricated, rotated and cut together. The best results were obtained with microfossils devoid of chamber-filling cements (Permian, Eocene, Recent). However, even slight differences in cement mineralogy/composition can result in surprisingly good x-ray density contrasts.X-ray microtomography may develop into a powerful tool for larger microfossils with a complex internal structure, because it is non-destructive, requires no preparation of the specimens, and produces a true 3D-image data set. We will use these data sets in the future to produce cuts in any direction to compare them with arbitrary cuts of complex microfossils in thin sections. Many groups of benthic and planktonic foraminifera may become more easily determinable in thin section by this way.

Assessing sedimentary evolution by means of Sr-isotope ratios : 3 case studies on the Caribbean plate : (Cretaceous: Nicoya Peninsula, Costa Rica, Tertiary: Hess Rise, and La Désirade, Guadeloupe, France)

The understanding of sedimentary evolution is intimately related to the knowledge of the exact ages of the sediments. When working on carbonate sediments, age dating is commonly based on paleontological observations and established biozonations, which may prove to be relatively imprecise. Dating by means of strontium isotope ratios in marine bioclasts is the probably best method in order to precisely date carbonate successions, provided that the sample reflects original marine geochemical characteristics. This requires a precise study of the samples including its petrography, SEM and cathodoluminescence observations, stable carbon and oxygen isotope geochemistry and finally the strontium isotope measurement itself. On the Nicoya Peninsula (Northwestern Costa Rica) sediments from the Piedras Blancas Formation, Nambi Formation and Quebrada Pavas Formation were dated by the means of strontium isotope ratios measured in Upper Cretaceous Inoceramus shell fragments. Results have shown average 87Sr/86Sr values of 0.707654 (middle late Campanian) for the Piedras Blancas Formation, 0.707322 (Turonian-Coniacian) for the Nambi Formation and 0.707721 (late Campanian-Maastrichtian) for the Quebrada Pavas Formation. Abundant detrital components in the studied formations constitute a difficulty to strontium isotope dating. In fact, the fossil bearing sediments can easily contaminate the target fossil with strontium mobilized form basalts during diagenesis and thus the obtained strontium isotope ratios may be influenced significantly and so will the obtained ages. The new and more precise age assignments allow for more precision in the chronostratigraphic chart of the sedimentary and tectonic evolution of the Nicoya Peninsula, providing a better insight on the evolution of this region. Meteor Cruise M81 dredged shallow water carbonates from the Hess Rise and Hess Escarpment during March 2010. Several of these shallow water carbonates contain abundant Larger Foraminifera that indicates an Eocene-Oligocene age. In this study the strontium isotope values ranging from 0.707847 to 0.708238 can be interpreted as a Rupelian to Chattian age of these sediments. These platform sediments are placed on seamounts, now located at depths reaching 1600 m. Observation of sedimentologic characteristics of these sediments has helped to resolve apparent discrepancies between fossil and strontium isotope ages. Hence, it is possible to show that the subsidence was active during early Miocene times. On La Désirade (Guadeloupe France), the Neogene to Quaternary carbonate cover has been dated by microfossils and some U/Th-ages. Disagreements subsisted in the paleontological ages of the formations. Strontium isotope ratios ranging from 0.709047 to 0.709076 showed the Limestone Table of La Désirade to range from an Early Pliocene to Late Pliocene/early Pleistocene age. A very late Miocene age (87Sr/86Sr =0.709013) can be determined to the Detrital Offshore Limestone. The flat volcanic basement had to be eroded by wave-action during a long-term stable relative sea-level. Sediments of the Table Limestone on La Désirade show both low-stand and high-stand facies that encroach on the igneous basement, implying deposition during a major phase of subsidence creating accommodation space. Subsidence is followed by tectonic uplift documented by fringing reefs and beach rocks that young from the top of the Table Limestone (180 m) towards the present coastline. Strontium isotope ratios from two different fringing reefs (0.707172 and 0.709145) and from a beach rock (0.709163) allow tentative dating, (125ky, ~ 400ky, 945ky) and indicate an uplift rate of about 5cm/ky for this time period of La Désirade Island. The documented subsidence and uplift history calls for a new model of tectonic evolution of the area.

Evolution of a Ladinian (Middle Triassic) intraplatform basin : stratigraphy, microfacies and palaeoecology of the Meride Limestone (Monte San Giorgio, Canton Ticino, Southern Switzerland)

The Monte San Giorgio (Southern Alps, Ticino, Switzerland) is the most important locality in the world for vertebrates dating back to the Middle Triassic. For this reason it was registered in 2003 as a UNESCO World Heritage Site. One of the objectives of this doctoral thesis was to fill some of the cognitive gaps regarding the Ladinian succession, including in particular the San Giorgio Dolomite and the Meride Limestone. In order to achieve this, the entire succession, more than 600 metres thick, was measured and sampled. Biostratigraphic research based on new finds of fossil invertebrates and microfossils and on the palynological analysis of the entire section was integrated with single-zircon U-Pb dating of volcanic ash layers intercalated in the carbonate succession. This enabled a redefinition of the bio-chronostratigraphic and geochronologic framework of the succession, which encompasses a significantly shorter time interval than previously held. The Ladinian section extends from the E. curionii Ammonoid Zone (Early Fassanian) to the P. archelaus Ammonoid Zone (Early Longobardian). The age of the classic fossiliferous levels of the Meride Limestone, rich in organic matter and containing vertebrate fossils which are known all over the world, was defined in both biostratigraphic and geochronologic terms. The presumed stratigraphie significance of the pachypleurosaurid reptiles found in such levels is called into question by new finds. These fossiliferous horizons were found to correspond to the main volcanoclastic intervals of the Buchenstein Formation (Middle and Upper Pietra Verde). Thus, a correlation with the Bagolino Section (Italy) containing the GSSP for the base of the Ladinian was proposed. Bulk sedimentation rates in the studied succession average 200 m/Myr and therefore prove to be 20 times higher than those of the South-Alpine pelagic basins. These values express high carbonate productivity from the surrounding platforms on one hand, and on the other a marked subsidence of the basin. Only in the intervals consisting of laminated limestones did the sedimentation rates drop to average values of around 30 m/Myr. The distribution of organic and inorganic facies appears to be the consequence of relative variations in sea-level. The laminated and organic-matter- rich intervals of the Meride Limestone are linked to a relative sea-level drop which favoured dysoxic to anoxic bottom-water conditions, coupled with an increase in runoff, perhaps due to recurrent explosive volcanic activity. The transient development under dysoxic conditions of monospecific benthic meio-/macrofaunas was documented. Organic matter suggests a predominant origin due to benthic bacterial activity, as can be witnessed in alveolar structures typical of exopolymeric substances secreted by bacteria within microbial mats. A microbial contribution to the carbonate (peloidal) precipitation was documented. The protective effect exerted by these microbial mats is also indicated as the main taphonomic factor contributing to the excellent preservation of vertebrate fossils. A radiolarian assemblage discovered in the lower part of the section (earliest Ladinian, E. curionii Zone) suggests the transient existence of open-marine but not deep-water connections with the tethyan pelagic basins. It shows marked similarities to the faunas typical of the late Anisian, suggesting therefore a low resolution power provided by radiolarian biostratigraphy in recognizing the Anisian/Ladinian boundary. The present thesis describes a new species of conifer (Elatocladus cassinae), a new species of insect (Dasyleptus triassicus) and seven new species of radiolarians (Eptingium danieli, Eptingium neriae, Parentactinosphaera eoladinica, Sepsagon ticinensis, Sepsagon? valporinae, Novamuria wirzi and Pessagnollum? hexaspinosum). In addition, following revision of the type material of already existent taxa, four new genera of radiolarians are introduced: Bernoulliella, Eohexastylus, Ticinosphaera and Lahmosphaera.

Low latitude Paleocene to early Eocene radiolarian systematics, biochronology and paleoenvironmental analysis

Highly diverse radiolarian faunas of latest Maastrichtian to early Eocene age have been recovered from the low latitude realm in order to contribute to the clarification of radiolarian taxonomy, construct a zonation based on a discrete sequence of co-existence intervals of species ranging from the late Paleocene to early Eocene and to describe a rich low latitude latest Cretaceous to late Paleocene fauna. 225 samples of late Paleocene to early Eocene age have been collected from ODP Leg 171 B-Hole 1051 A (Blake Nose), DSDP Leg 43-Site 384 (Northwest Atlantic) and DSDP Leg 10-Sites 86, 94, 95, 96. Sequences consist of mainly pelagic oozes and chalks, with some clay and ash layers. A new imaging technique is devised to perform (in particular on topotypic material) both transmitted light microscopy and SEM imaging on individual radiolarian specimens. SEM precedes transmitted light imaging. Radiolarians are adhered to a cover slip (using nail varnish) which is secured to a stub using conductive levers. Specimens are then photographed in low vacuum (40-50Pa; 0.5mbar), which enables charge neutralization by ionized molecules of the chamber atmosphere. Thus gold coating is avoided and subsequently this allows transmitted light imaging to follow. The conductive levers are unscrewed and the cover slip is simply overturned and mounted with Canada balsam. In an attempt towards a post-Haeckelian classification, the initial spicule (Entactinaria), micro- or macrosphere (Spumellaria) and initial spicule and cephalis (Nassellaria) have been studied by slicing Entactinaria and Spumellaria, and by tilting Nassellaria in the SEM chamber. A new genus of the family Coccodiscidae is erected and Spongatractus HAECKEL is re-located to the subfamily Axopruinae. The biochronology has been carried out using the Unitary Association Method (Guex 1977, 1991). A database recording the occurrences of 112 species has been used to establish a succession of 22 Unitary Associations. Each association is correlated to chronostratigraphy via calcareous microfossils that were previously studied by other authors. The 22 UAs have been united into seven Unitary Associations Zones (UAZones) (JP10- JE4). The established zones permit to distinguish supplementary subdivisions within the existing zonation. The low-latitude Paleocene radiolarian zonation established by Sanfilippo and Nigrini (1998a) is incomplete due to the lack of radiolarian-bearing early Paleocene sediments. In order to contribute to the study of sparsely known low latitude early Paleocene faunas, 80 samples were taken from the highly siliceous Guayaquil Formation (Ecuador). The sequence consists of black cherts, shales, siliceous limestones and volcanic ash layers. The carbonate content increases up section. Age control is supplied by sporadic occurrences of silicified planktonic foraminifera casts. One Cretaceous zone and seven Paleocene zones have been identified. The existing zonation for the South Pacific can be applied to the early-early late Paleocene sequence, although certain marker species have significantly shorter ranges (notably Buryella foremanae and B. granulata). Despite missing marker species in the late Paleocene, faunal distribution correlates reasonably to the Low-Latitude zonation. An assemblage highly abundant in Lithomelissa, Lophophaena and Cycladophora in the upper RP6 zone (correlated by the presence of Pterocodon poculum, Circodiscus circularis, Pterocodon? sp. aff. P. tenellus and Stylotrochus nitidus) shows a close affinity to contemporaneous faunas reported from Site 1121, Campbell Plateau. Coupled with a high diatom abundance (notably Aulacodiscus spp. and Arachnoidiscus spp.), these faunas are interpreted as reflecting a period of enhanced biosiliceous productivity during the late Paleocene. The youngest sample is void of radiolarians, diatoms and sponge spicules yet contains many pyritized infaunal benthic foraminifera which are akin to the midway-type fauna. The presence of this fauna suggests deposition in a neritic environment. This is in contrast to the inferred bathyal slope depositional environment of the older Paleocene sediments and suggests a shoaling of the depositional environment which may be related to a coeval major accretionary event. RESUME DE LA THESE Des faunes de radiolaires de basses latitudes très diversifiées d'âge Maastrichtien terminal à Eocène inférieur, ont été étudiées afin de contribuer à la clarification de leur taxonomie, de construire une biozonation basée sur une séquence discrète d'intervalles de coexistence des espèces d'age Paléocène supérieur à Eocène inférieur et de décrire une riche faune de basse latitude allant du Crétacé terminal au Paléocène supérieur. L'étude de cette faune contribue particulièrement à la connaissance des insaisissables radiolaires de basses latitudes du Paléocène inférieur. 225 échantillons d'âge Paléocène supérieur à Eocène inférieur provenant des ODP Leg 171B-Site 1051A (Blake Nose), Leg DSDP 43-Site 384 (Atlantique Nord -Ouest) et des DSDP Leg 10 -Sites 86, 94, 95, 96, ont été étudiés. Ces séquences sont constituées principalement de « ooze » et de « chalks »pélagiques ainsi que de quelques niveaux de cendres et d'argiles. Une nouvelle technique d'imagerie a été conçue afin de pouvoir prendre conjointement des images en lumière transmise et au Microscope Electronique à Balayage (MEB) de spécimens individuels. Ceci à été particulièrement appliqué à l'étude des topotypes. L'imagerie MEB précède l'imagerie en lumière transmise. Les radiolaires sont collés sur une lame pour micropaléontologie (au moyen de vernis à ongles) qui est ensuite fixée à un porte-objet à l'aide de bras métalliques conducteurs. Les spécimens sont ensuite photographiés en vide partiel (40-50Pa; 0.5mbar), ce qui permet la neutralisation des charges électrostatiques dues à la présence de molécules ionisées dans l'atmosphère de la chambre d'observation. Ainsi la métallisation de l'échantillon avec de l'or n'est plus nécessaire et ceci permet l'observation ultérieure en lumière transmise. Les bras conducteurs sont ensuite dévissés et la lame est simplement retournée et immergée dans du baume du Canada. Dans une approche de classification post Haeckelienne, le spicule initial (Entactinaires), la micro- ou macro -sphère (Spumellaires) et le spicule initial et cephalis (Nassellaires) ont été étudiés. Ceci a nécessité le sectionnement d'Entactinaires et de Spumellaires, et de pivoter les Nassellaires dans la chambre d'observation du MEB. Un nouveau genre de la Famille des Coccodiscidae a été érigé et Spongatractus HAECKEL à été réassigné à la sous-famille des Axopruninae. L'analyse biostratigraphique à été effectuée à l'aide de la méthode des Associations Unitaires {Guex 1977, 1991). Une base de données enregistrant les présences de 112 espèces à été utilisée poux établir une succession de 22 Associations Unitaires. Chaque association est corrélée à la chronostratigraphie au moyen de microfossiles calcaires précédemment étudiés par d'autres auteurs. Les 22 UAs ont été combinées en sept Zones d'Associations Unitaires (UAZones) (JP10- JE4). Ces Zones permettent d'insérer des subdivisions supplémentaires dans la zonation actuelle. La zonation de basses latitudes du Paléocène établie par Sanfilippo et Nigrini (1998a) est incomplète due au manque de sédiments du Paléocène inférieur contenant des radiolaires. Afin de contribuer à l'étude des faunes peu connues des basses latitudes du Paléocène inférieur, 80 échantillons ont été prélevés d'une section siliceuse de la Formation de Guayaquil (Equateur). La séquence est composée de cherts noirs, de shales, de calcaires siliceux et de couches de cendres volcaniques. La fraction carbonatée augmente vers le haut de la section. Des contraintes chronologiques sont fournies par la présence sporadique de moules de foraminifères planctoniques. Une zone d'intervalles du Crétacé et sept du Paléocène ont été mises en évidence. Bien que certaines espèces marqueur ont des distributions remarquablement plus courtes (notamment Buryella foremanae et B. granulata), la zonation existante pour le Pacifique Sud est applicable à la séquence d'age Paléocène inférieure à Paléocène supérieur basal étudiée. Malgré l'absence d'espèces marqueur du Paléocène supérieur, la succession faunistique se corrèle raisonnablement avec la zonation pour les basses latitudes. Un assemblage contenant d'abondants représentant du genre Lithomelissa, Lophophaena et Cycladophora dans la zone RP6 (correlée par la présence de Pterocodon poculum, Circodiscus circularis, Pterocodon? sp. aff. P. tenellus et Stylotrochus nitidus) montre une grande similitude avec certaines faunes issues des hauts latitudes et d'age semblable décrites par Hollis (2002, Site 1121, Campbell Plateau). Ceci, en plus d'une abondance importante en diatomés (notamment Aulacodiscus spp. et Arachnoidiscus spp.) nous mènent à interpréter cette faune comme témoin d'un épisode de productivité biosiliceuse accrue dans le Paléocène supérieur. L'échantillon le plus jeune, dépourvu de radiolaires, de diatomés et de spicules d'éponge contient de nombreux foraminifères benthiques infaunaux pyritisés. Les espèces identifiées sont caractéristiques d'une faune de type midway. La présence de ces foraminifères suggère un environnement de type néritique. Ceci est en contraste avec l'environnement de pente bathyale caractérisent les sédiments sous-jacent. Cette séquence de diminution de la tranche d'eau peut être associée à un événement d'accrétion majeure. RESUME DE LA THESE (POUR LE GRAND PUBLIC) Les radiolaires constituent le groupe de plancton marin le plus divers et le plus largement répandu de l'enregistrement fossile. Un taux d'évolution rapide et une variation géographique considérable des populations font des radiolaires un outil de recherche sans égal pour la biostratigraphie et la paléocéanographie. Néanmoins, avant de pouvoir les utiliser comme outils de travail, il est essentiel d'établir une solide base taxonomique. L'étude des Radiolaires peut impliquer plusieurs techniques d'extraction, d'observation et d'imagerie qui sont dépendantes du degré d'altération diagénétique des spécimens. Le squelette initial, qu'il s'agisse d'un spicule initial (Entactinaria), d'une micro- ou macro -sphère (Spumellaria) ou d'un spicule initial et d'un cephalis (Nassellaria), est l'élément le plus constant au cours de l'évolution et devrait représenter le fondement de la systématique. Des échantillons provenant de carottes de basses latitudes du Deep Sea Drilling Project et de l' Ocean Drilling ont été étudiés. De nouvelles techniques d'imagerie et de sectionnement ont été développées sur des topotypes de radiolaires préservés en opale, dans le but d'étudier les caractéristiques de leur squelette initial qui n'étaient pas visibles dans leur illustration originale. Ceci aide entre autre à comparer des spécimens recristallisés en quartz, provenant de terrains accrétés, avec les holotypes en opale de la littérature. La distribution des espèces étudiés a fourni des données biostratigraphiques qui ont été compilées à l'aide de la méthode des Associations Unitaires (Guez 1977, 1991). Il s'agit d'un modèle mathématique déterministe conçu pour exploiter la totalité de l'assemblage plutôt que de se confiner à l'utilisation de taxons marqueurs individuels. Une séquence de 22 Associations Unitaires a été établie pour la période allant du Paléocène supérieur à l'Éocène inférieur. Chaque Association Unitaire a été corrélée à l'échelle de temps absolue à l'aide de microfossiles calcaires. Les 22 UAs ont été combinées en sept Zones d'Associations Unitaires (JP10- JE4). Ces Zones permettent d'insérer des subdivisions supplémentaires dans la zonation actuelle. Les radiolaires du Paléocène inférieur à moyen des basses latitudes sont rares. Les meilleures sections connues se trouvent dans les hautes latitudes (Nouvelle Zélande). Quelques assemblages épars ont été mentionnés par le passé en Californie, en Équateur et en Russie. Une séquence siliceuse de 190 mètres dans la Formation de Guayaquil (Équateur), s'étendant du Maastrichtien supérieur au Paléocène supérieur, a fourni des faunes relativement bien préservées. L'étude de ces faunes a permis de mettre en évidence la première séquence complète de radiolaires de basses latitudes dans le Paléocène inférieure. Huit zones allant du Crétacé terminal au Paléocène supérieur ont pu être appliqués et la présence de foraminifères planctoniques a fournie plusieurs points d'attache chronologiques. Dans le Paléocène supérieur, un riche assemblage contenant d'abondants diatomés et radiolaires ayant des similitudes faunistiques marquantes avec des assemblages de hautes latitudes de Nouvelle Zélande, témoigne d'un épisode de productivité biosiliceuse accrue pendant cette période. Étant donné que la pointe du continent sud-américain et l'Antarctique étaient plus proches au cours du Paléocène, ce phénomène peut être expliqué par le transport, le long de la côte ouest de l'Amérique du Sud, d'eaux riches en nutriments en provenance de l'Océan Antarctique. Suite à cet épisode, l'enregistrement en radiolaires est interrompu. Ceci peut être associé à des événements tectoniques régionaux qui ont eu pour effet de diminuer la tranche d'eau relative, rendant l'environnement plus favorable aux foraminifères benthiques qui sont abondamment présents dans l'échantillon le plus jeune de la séquence.

Past, present and future - assessing changes in aquatic environments using subfossil diatoms

The deterioration of surface waters is one of the most important issues in the environmental management of the European Union. Thus, the EU Water Framework Directive 2000/60/EC (WFD) requires “good ecological and chemical status” of surface waters by 2015 allowing only a slight departure from ecological reference conditions characterized by the biological communities typical for the conditions of minimal anthropogenic impact. The WFD requires the determination of ecological reference conditions and the present ecological status of surface waters. To meet this legislative demand, sedimentary diatom assemblages were used in these studies with various methods 1) to assess natural and human activity induced environmental changes, 2) to characterize background conditions 3) to evaluate the present ecological status and 4) to predict the future of the water bodies in the light of palaeolimnological data. As the WFD refers to all surface waters, both coastal and inland sites were included. Two long and two short sediment cores from the Archipelago Sea in the northern Baltic Sea were examined for their siliceous microfossils in order to assess (1) the Holocene palaeoenvironmental history and (2) the recent eutrophication of the area. The diatom record was divided into local diatom assemblage zones (LDAZ, long cores) and diatom assemblage zones (DAZ, short cores). Locally weighted weighted averaging regression and calibration (LWWA) was applied for the quantitative reconstruction of past TN concentrations (short cores). An age model for the long cores was constructed by using independent palaeomagnetic and AMS-14C methods. The short cores were dated using radiometric (210Pb, 226Ra and 137Cs) methods. The long cores date back to the early history of the Archipelago Sea, which was freshwater – no salinity increase referable to the brackish phase of the Yoldia Sea is recognized. The nutrient status of the lacustrine phase was slightly higher in the Archipelago Sea than in the Baltic Proper. Initial brackish-water influence is observed at 8 150 ±80 cal. BP (LDAZ4), but fully brackish conditions were established at 7 700 ±80 cal. BP (LDAZ5). The diatom assemblages indicate increasing salinity, warming climate and possible eutrophic conditions during the lacustrine to brackish-water transition. The decreasing abundance of Pseudosolenia calcar-avis (Schultze) Sundström and the increasing abundance of the ice-cover indicator species Pauliella taeniata (Grunow) Round and Basson indicate decreasing salinity and climatic cooling after ca. 5 000 cal. BP. Signs of eutrophication are visible in the most recent diatom assemblage zones of both short cores. Diatom-inferred total nitrogen (DI-TN) reconstructions partially fail to trace the actual measured total nitrogen concentrations especially from the late 1980s to the mid 1990s. This is most likely due to the dominating diatom species Pauliella taeniata, Thalassiosira levanderi Van Goor and Fragilariopsis cylindrus (Grunow) W. Krieger being more influenced by factors such as the length of the ice-season rather than nutrient concentrations. It is concluded that the diatom assemblages of the study sites are principally governed by climate fluctuations, with a slight influence of eutrophication visible in the most recent sediments. There are indications that global warming, with reduced ice cover, could impact the spring blooming diatom species composition in the Archipelago Sea. In addition, increased sediment accumulation in the early 90s coincides with the short ice-seasons suggesting that warming climate with decreasing ice-cover may increase sedimentation in the study area. The diverse diatom assemblages dominated by benthic species (54 %) in DAZ1 in the Käldö Fjärd core can be taken as background diatom assemblages for the Archipelago Sea. Since then turbidity has increased and the diatom assemblages have been dominated by planktonic diatoms from around the mid 1800s onwards. The reconstructed reference conditions for the total nitrogen concentrations fluctuate around 400 μg l-1. Altogether two short sediment cores and eight short cores for top-bottom analysis were retrieved from Lake Orijärvi and Lake Määrjärvi to assess the impact of the acid mine drainage (AMD) derived metals from the Orijärvi mine tailings on the diatom communities of the lakes. The Cu (Pb, Zn) mine of Orijärvi (1757 – 1956) was the first one in Finland where flotation techniques (1911 – 1955) were used to enrich ore and large quantities of tailings were produced. The AMD derived metal impact to the lakes was found to be among the heaviest thus far recorded in Finland. Concentrations of Cu, Pb and Zn in Lake Orijärvi sediments are two to three orders of magnitude higher than background values. The metal inputs have affected Lake Orijärvi and Lake Määrjärvi diatom communities at the community levels through shifts in dominant taxa (both lakes) and at the individual level through alteration in frustule morphology (Lake Orijärvi). At present, lake water still has elevated heavy metal levels, indicating that the impact from the tailings area continues to affect both lakes. Lake Orijärvi diatom assemblages are completely dominated by benthic species and are lacking planktonic diatoms. In Lake Määrjärvi the proportion of benthic and tychoplanktonic diatoms has increased and the planktonic taxa have decreased in abundance. Achnanthidium minutissimum Kützing and Brachysira vitrea (Grun.) R. Ross in Hartley were the most tolerant species to increased metal concentrations. Planktonic diatoms are more sensitive to metal contamination than benthic taxa, especially species in the genus Cyclotella (Kützing) Brébisson. The ecological reference conditions assessed in this study for Lake Orijärvi and Lake Määrjärvi comprise diverse planktonic and benthic communitites typical of circumneutral oligotrophic lakes, where the planktonic diatoms belonging to genera Cyclotella , Aulacoseira Thwaites, Tabellaria Ehrenberg and Asterionella Hassall dominate in relative abundances up to ca. 70%. The benthic communities are more diverse than the planktonic consisting of diatoms belonging to the genera Achnanthes Bory, Fragilaria Lyngbye and Navicula St. Vincent. This study clearly demonstrates that palaeolimnological methods, especially diatom analysis, provide a powerful tool for the EU Water Frame Work Directive for defining reference conditions, natural variability and current status of surface waters. The top/bottom approach is a very useful tool in larger-scale studies needed for management purposes. This “before and after” type of sediment sampling method can provide a very time and cost effective assessment of ecological reference conditions of surface waters.

Microfacies analysis of the lower paleocene beda formation in Western Concession 59 and Block 59F, Sirte Basin, Libya /

The rock sequence of the Tertiary Beda Formation of S. W. concession 59 and 59F block in Sirte Basin of Libya has been subdivided into twelve platformal carbonate microfacies. These microfacies are dominated by muddy carbonates, such as skeletal mudstones, wackestones, and packstones with dolomites and anhydrite. Rock textures, faunal assemblages and sedimentary structures suggest shallow, clear, warm waters and low to moderate energy conditions within the depositional shelf environment. The Beda Formation represents a shallowing-upward sequence typical of lagoonal and tidal flat environments marked at the top by sabkha and brackish-water sediments. Microfossils include benthonic foraminifera, such as miliolids, Nummulites, - oerculina and other smaller benthonics, in addition to dasycladacean algae, ostracods, molluscs, echinoderms, bryozoans and charophytes. Fecal pellets and pelloids, along with the biotic allochems, contributed greatly to the composition of the various microfacies. Dolomite, where present, is finely crystalline and an early replacement product. Anhydrite occurs as nodular, chickenwire and massive textures indicating supratidal sabkha deposition. Compaction, micr it i zat ion , dolomit izat ion , recrystallization, cementation, and dissolution resulted in alteration and obliteration of primary sedimentary structures of the Beda Formation microfacies. The study area is located in the Gerad Trough which developed as a NE-SW trending extensional graben. The Gerad trough was characterized by deep-shallow water conditions throughout the deposition of the Beda Formation sediments. The study area is marked by several horsts and grabens; as a result of extent ional tectonism. The area was tectonically active throughout the Tertiary period. Primary porosity is intergranular and intragranular, and secondary processes are characterized by dissolution, intercrystalline, fracture and fenestral features. Diagenesis, through solution leaching and dolomitization, contributed greatly to porosity development. Reservoir traps of the Beda Formation are characterized by normal fault blocks and the general reservoir characteristics/properties appear to be facies controlled.

Dinocyst biochronology and palynofacies : inferred systems tract character of Miocene sequences from New Jersey mid-Atlantic transect (ODP legs 174A and 174AX) /

One of the main objectives of the mid-Atlantic transect is to improve dating resolution of sequences and unconfonnity surfaces. Dinoflagellate cysts from two Ocean Drilling Program boreholes, the onshore Leg 174AX Ocean View Site and Leg 174A continental shelf Site 1071, are used to provide age estimates for sequences and unconfonnities fonned on the New Jersey continental margin during the Miocene epoch. Despite the occasional lack of dinocysts in barren and oxidized sections, dinocyst biochronology still offers greater age control than that provided by other microfossils in marginal marine environments. An early Miocene to late Miocene chronology based on ages detennined for the two study sites is presented. In addition, .palynofacies are used to unravel the systems tract character of the Miocene sequences and provide insight into the effects of taphonomy and preservation of palynomorphs in marginal marine and shelf environments under different ~ea level conditions. More precise placement of maximum flooding surfaces is possible through the identification of condensed sections and palynofacies shifts can also reveal subaerially exposed sections and surfaces not apparent in seismic or lithological analyses. The problems with the application of the pollen record in the interpretation of Miocene climate are also discussed. Palynomorphs provide evidence for a second-order lowering of sea level during the Miocene, onto which higher order sea level fluctuations are super-imposed. Correlation of sequences and unconfonnities is attempted between onshore boreholes and from the onshore Ocean View borehole to offshore Site 1071.

Non-pollen palynomorphs and thecamoebians as proxies of environmental and anthropogenic change: a case study from Lake Simcoe, Ontario, Canada

The distribution of aquatic microfossils and pollen in the long core from Lake Simcoe (LS07PC5) shows synchronous response since deglaciation, highlighting the potential of little-known non-pollen palynomorphs (NPP) as paleolimnological indicators. Upcore variations in NPP, thecamoebians and pollen reflect hydrological and climatic variations: onset of the Main Lake Algonquin, the draining of Lake Algonquin, the early Holocene drought, the midto late Holocene climate shifts including mid-Holocene drought and the Little Ice Age, and human settlement. The distribution of microfossils in the short cores (CB1 and SB1) shows the level of eutrophication decreasing gradually from Cook’s Bay to the Atherley Narrows outflow due to differences in the extent of anthropogenic impact and cumulative retention of phosphorous within sediments. Changes in assemblages and concentration of NPP within the cores reflect the history of settlement within Lake Simcoe basin, recording temporal differences in eutrophication.

Provenance of chalk tesserae from Brading Roman Villa, Isle of Wight, UK

Thin section petrographical analysis of chalk tesserae at Brading Roman Villa, Isle of Wight, England, identifies a range of planktonic foraminifera and the calcareous algal cyst Pithonella that identify the Late Cenomanian Rotalipora cushmani Biozone (BGS Foraminiferal Biozones 4iii to 7). The local chalk crop to the north of the villa includes rocks of R. cushmani Biozone age, and indicates a likely local, rather than long distance, source for the tesserae. Microfossils provide a powerful tool for identifying the provenance of artefacts in Roman Britain.

Evaluating microfossil content of dental calculus from Brazilian sambaquis

To date, limited numbers of dental calculus samples have been analyzed by researchers in diverse parts of the world. The combined analyses of these have provided some general guidelines for the analysis of calculus that is non-destructive to archaeological teeth. There is still a need for a quantitative study of large numbers of calculus samples to establish protocols, assess the level of contamination, evaluate the quantity of microfossils in dental calculus, and to compare analysis results with the literature concerning the biology of calculus formation. We analyzed dental calculus from 53 teeth from four Brazilian sambaquis. Sambaquis are the shell-mounds that were established prehistorically along the Brazilian coast. The analysis of sambaqui dental calculi shows that there are relatively high concentrations of microfossils (phytoliths and starch), mineral fragments, and charcoal in dental calculus. Mineral fragments and charcoal are possibly contaminants. The largest dental calculi have the lowest concentrations of microfossils. Biologically, this is explained by individual variation in calculus formation between people. Importantly, starch is ubiquitous in dental calculus. The starch and phytoliths show that certainly Dioscorea (yam) and Araucaria angustifolia (Parana pine) were eaten by sambaqui people. Araceae (arum family), Ipomoea batatas (sweet potato) and Zea mays (maize) were probably in their diet. (C) 2009 Elsevier Ltd. All rights reserved.

Permian stromatolites associated with bivalve coquina beds-Angatuba, SP, Brazil (Teresina Formation, Parana Basin)

Silicified stromatolites have been described in the Permian Teresina Formation, Passa Dois Group, of the Parana Basin. These stromatolites occur as blocks in the Fazenda Monte Alegre area at the headwaters of the creek known as Corrego Catanduva in the municipality of Angatuba. These blocks originate from the Serra de Angatuba region and were recognized in a road that was cut in the midst of sandstones and siltites. The stromatolites are isolated bioherms that are domed to subspherical with a flat base in profile and a rounded to lenticular shape in plan view. The stromatolites exhibit a reddish coloration and are composed of microcrystalline quartz. Lamination is continuous, non-columnar, and anastomosed, showing parallel to divergent growth; however, divergent columns also occur, especially at the tops of the bioherms. The lamination is fine and well preserved, with alternating light and dark laminas. Microfossils of filamentous cyanobacteria are preserved and were related to the genera Microcoleus and Rivularia. Silicified bivalves occur in association with the stromatolites and are preserved in the form of coquina beds and rare isolated specimens within the bioherms. The described specimens belong to the Pinzonella illusa biozone, with representatives of the species Pinzonella illusa, Angatubia cowperesioides, and Houldausiella elongata. The formation environment of these stromatolites is associated with tidal plains of shallow, brackish, relatively calm, warm waters of good luminosity with the presence of weak currents. There was likely a low level of predation, and the environment may have been hypersaline. The coquina beds associated with the stromatolites indicate a probable proximal tempestite, i.e., they were formed near the coastline. The stromatolites were originally composed of carbonates, although these were replaced by silica during early diagenesis.

Braquiópodes (Rhynchonelliformea, Bouchardioidea) neógenos da bacia de Pelotas (RS) e seu significado paleoambiental

The occurrence of brachiopods in Cenozoic rocks of the Pelotas Basin is known since 1862. In spite of that, detailed systematic and taphonomic studies are still missing. Investigations made a half century ago, have suggested that these brachiopods could belong to Bouchardia cf. zitteli, a species found in the San Julian Formation, Late Oligocene, Argentina. Our data suggest that those brachiopods may resemble Bouchardia transplatina. In the Uruguayan portion of the Pelotas Basin B. transplatina is known in rocks of the Camacho Formation, Miocene. In addition, small recrystallized shells of brachiopods were also recovered from three Petrobras boreholes (2PJ-1-RS, 2PN-1-RS, and 2GA-1-RS) from the Pelotas Basin. Brachiopods come from the interval of 130 to 150 meters within the Miocene Henryhowella evax Zone. Despite the degree of taphonomic modiication of those brachiopod shells they indubitably belong to Bouchardia sp. This is noteworthy for various reasons: 1- Bouchardia is a brachiopod with warm water afinities. Presently, extant members of this genus are unknown in latitudes up to 34[degree]S, with the main records at 23[degree]S. 2- Although occurring in depths down to 200 meters, the living member (Bouchardia rosea) of this genus is most abundant in shallow platformal, nutrient-rich waters. 3- The occurrence of Bouchardia in the Miocene of the Pelotas Basin indicates that, at least to the interval of Henryhowella evax Zone, warm waters of the Brazilian currents prevail. This interpretation is in strong accordance with other paleoeoceanographic and paleoclimatic data offered by various groups of co-occurring microfossils, such as ostracodes and foraminifers.