No description available.

No description available.

Paleocene-Eocene stratigraphy of the Indus Basin is revised and a modern stratigraphic nomenclature is presented. Forty-five species of larger benthic foraminifera (LBF) are described from newly collected sections. Eight Tethyan foraminiferal biozones (SBZ1-SBZ8) and a stable carbon isotopic stratigraphy spanning the Paleocene to Early Eocene interval are established. The evolution of shallow marine communities (especially LBFs) in the east and comparison with west Tethys is discussed. In contrast to coralgaldominated west Tethys (particularly during the SBZ3 Biozone), the Late Paleocene carbonate biotas in the Indus Basin were dominated by LBFs, and corals are scarce. This difference is interpreted here as a product of local palaeoecological conditions and/or the Tethyan latitudinal temperature gradient. The responses of the shallow marine biota and ecosystem to earliest Eocene environmental changes in the east Tethys were remarkably different from those of west Tethys. The larger foraminifer turnover and rapid radiation of typical Eocene LBFs (e.g. Alveolina, Nummulites, Orbitolites) during this time were not observed in the east Tethys. During the earliest Eocene, inner ramp environments of the Indus Basin were still characterized by typical Late Paleocene LBF assemblages (mainly miscellanids, ranikothalids). Mid ramp settings were occupied by nutrient-tolerant heterotroph-dominated communities (mainly encrusting foraminifera) with very rare or no LBFs. These biotic differences were possibly created by the superimposition of initial India-Asia collision on PETM related stresses at the P-E boundary, generating biogeographical barriers and severe environmental conditions (increased continental run off, elevated temperatures) in the east. High sea temperatures (32°C to 33.5°C) and increased productivity/nutrient levels compared to the west Tethys are suggested by δ18O and δ13C isotope data from wellpreserved carbonates. Later, in the Early Eocene (SBZ7-SBZ8 biozones), oligotrophic LBFs (nummulitids, orthopragminids) started to dominate ramp environments, indicating stable environmental conditions.

In the 1960s Oberhauser and Fuchs (palaeontologists working at the Geologische Bundesanstalt in Vienna) described a range of new taxa from the Triassic of Austria that were thought to be the earliest planktonic foraminifera. The first reactions of the palaeontological community were negative but in the subsequent forty years our knowledge of Jurassic planktonic foraminifera has expanded considerably. A thorough re-evaluation of the Oberhauser and Fuchs collections in Vienna has shown that these species are probably not planktonic and that the first planktonic taxa appeared in the Toarcian. This origination in the centre of Western Tethys was followed by a rapid expansion of planktonic foraminifera throughout Peri-Tethys. This expansion is dominated by the genera Conoglobigerina and Globuligerina and while some believe that their separation is straightforward (based on apertural characters) analysis of large assemblages shows that this differentiation is not reliable and requires further analysis not only of holotypes, paratypes and topotypes but of large assemblages. In Southern Poland, Middle Jurassic limestones in the Pieniny Klippen Belt are described as foraminiferal packstones and represent the first evidence of a foraminiferal ooze on the ocean floor. This indicates that, by the mid-Jurassic, there was an oceanic stratification of the Aragonite and Carbonate Compensation Depths and that the modem ocean system had developed, although the depths of these various layers may have been different to those of the present day. By the Oxfordian a relatively diverse planktonic fauna had expanded throughout Peri- Tethys and, probably, around the globe in the tropics. The fauna expanded further in the early Cretaceous as Gondwana fragmented but data across the important Jurassic to Cretaceous transition is extremely limited and requires further investigation.

No description available.

Palaeoenvironmental reconstruction using foraminifera relies on the assumption that assemblages reflect the ecological conditions at the time of deposition. However, the distribution of taxa can be greatly affected by transport and reworking of tests. This is particularly important in high energy environments such as submarine canyon and fan systems, which are major pathways for sediment transported from the continental shelf to the abyssal plain. Traditionally, these assemblages have been abandoned as hopelessly taphonomically corrupted, but it is possible that these assemblages contain useful hydraulic information. This project aims to develop the fundamental concepts needed to extract this information, via a series of classical particle hydraulics experiments on empty tests in static water and unidirectional currents. Hyaline foraminifera have been selected for these experiments, as they are the most abundant tests found in shelf and upper-slope environments and consequently are most likely taxa to be entrained into gravity flows. Static water experiments have shown that settling velocities are significantly different between taxa, meaning that assemblages are likely to fractionate according to species during transportation. Settling velocities range from 0.01 to 0.06 ms-1 with larger specimens falling faster than smaller ones. Elphidium crispum exhibited the fastest average settling velocity of 0.03 ms-1 while Planorbulina mediterranensis fell with the lowest average settling velocity of 0.01 ms-1. The occurrence of spatial separation of taxa within a single flow is directly tested using a flume where a spatially waning turbidity current is simulated by a saline density flow. Results show that the slowly settling tests such as P. mediterranensis and Cibicides lobatulus remain suspended in the current for longer, and are thus transported further than more rapidly settling taxa such as E. cripsum and Ammonia beccarii. The experiments have shown that there are significant statistical differences in settling velocity of foraminiferal species and this does result in significantly distinct travelling distances between species in a turbidite. This information is related to the oceanic environment in the Gulf of Cadiz. The signal of fractionation is then identified in core data from Trinidad supplied by Ichron showing that useful assemblage data can be extracted to interpret the depositional environment.

Les morpho-espèces de foraminifères planctoniques sont composées d'éco-génotypes parfois différentiables sur la base de la morphologie de leur coquille. Cette découverte récente d'une diversité ainsi qualifiée de « pseudo-cryptique » ouvre des perspectives d'amélioration de la précision des reconstructions paléocéanographiques. Malheureusement, ces génotypes ont été définis de façon subjective et ne sont pas homogènes quant à leur rang taxonomique, ce qui est pourtant un pré-requis pour leur intégration dans les modèles de reconstruction. Grâce à l'application de méthodes quantitatives de délimitation d'unités taxinomiques sur les séquences partielles de la petite sous-unité ribosomale (SSU) disponibles chez l'ensemble des morpho-espèces de foraminifères planctoniques, nous montrons que 49 de ces génotypes sont suffisamment divergents pour constituer d'authentiques espèces. Deux morpho-espèces clefs de la paléocéanographie sont étudiées plus en détail. Chez Neogloboquadrina pachyderma, l'obtention des premières séquences complètes de la SSU et la comparaison morphogénétique de spécimens (sub)polaires permettent de proposer un nouveau scénario évolutif et de montrer que les variations morphologiques sont ici d'origine éco-phénotypique, et donc indépendantes de la diversité génétique. Chez Globigerinoides sacculifer, caractérisé par une forte diversité morphologique, il existe au contraire une seule et unique espèce cosmopolite dans les eaux (sub)tropicales de l'Océan mondial. Ces deux cas particuliers montrent que, contrairement à ce que suggéraient les études précédentes, la spéciation pseudo-cryptique n'a pas valeur de règle chez les foraminifères planctoniques / Morphospecies of planktonic foraminifera are clusters of eco-genotypes that show small but significant shell morphological differences (pseudo-cryptic species).This discovery opens a new perspective for improving the accuracy and resolving power of paleoceanographic reconstructions. Unfortunately, current genetic type delimitations suffer subjectivity, inducing non-homogenous taxonomic status while homogenous taxonomic status is a prerequisite for including genetic types in reconstruction models. By applying quantitative and complementary methods for taxonomic units delimitation to the available dataset of partial sequences of SSU (ribosomal small sub-unit), we delimited 49 genuine (pseudo)cryptic species of planktonic foraminifera. We studied two paleoceanographic key-species. Complete sequencing of the SSU and morpho-genetic comparison within austral (sub)polar genetic types of Neogloboquadrina pachyderma lead to a new phylogeographic hypothesis and showed that morphological variations are the result of ecophenotypic effects and are not related with genetic types. The morphologically diverse Globigerinoides sacculifer is the first case of a planktonic foraminifera morphospecies corresponding to a single genetic type distributed world-wide in (sub) tropical waters. These two cases show that, contrary to previous studies conclusions, pseudo-cryptic speciation is not a rule within planktonicForaminifera