Paleogeographic Interpretation of a Peat Layer at Torson di Sotto (Lagoon of Venice, Italy)

Ein 3,3 m langer Kern aus dem zentralen Bereich der Lagune von Venedig enthielt eine Torflage zwischen 1,3 und 2,0 m unter dem mittleren Meeresspiegel. Pollenanalysen zeigen ein Vorherrschen von Quercus und Alnus und eine transgressive Phase an: der untere Teil des Torfes (nach 14C-Daten 1730±80 v.h.) ist in einem Süßwasser-Environment gebildet worden, der obere Teil (nach 14C-Daten 1140 + 80 v.h.) in einem brackischen. Foraminiferenanalysen zeigen an, daß der Transgression eine Regression vorangegangen ist. Die gesamte Abfolge enthält von unten nach oben (Abb. 3): (1) ein oligohalines bis mesohalines Environment (von —3,3 bis —2,5 m) mit sehr zahlreichen Foraminiferen; (2) ein Süßwasser-Environment (von —2,5 bis —2,0 m); (3) die 0,7 m mächtige Torflage, die fortschreitend brackisch wird; (4) ein mesohalines Environment (oberhalb —1,3 m).Korrelationen mit benachbarten Lokalitäten (Abb. 1) weisen darauf hin, daß vergleichbare Erscheinungen zu gleicher Zeit im Zentralteil der Lagune, aber nicht in ihrem Nordteil, aufgetreten sind. Diese Regressions-Transgressions-Abfolge wird auf eine Periode erhöhter Niederschläge um das Ende der Römerzeit zurückgeführt, die zur Überflutung und zu einer Verlagerung des Laufes zahlreicher Flüsse geführt hat; dabei ist das ökologische Gleichgewicht dieses Marschengebietes zeitweilig verändert worden. Im Verlauf der vergangenen 100 Jahre hat sich die Transgression beschleunigt, überwiegend infolge anthropogener Eingriffe. Die „Barene" werden jetzt erodiert und verschwinden rasch (Abb. 2). Sie werden durch weite Meerwasserbecken eingenommen.researc

The genetic diversity, phylogeography and morphology of Elphidiidae (Foraminifera) in the Northeast Atlantic

Genetic characterisation (SSU rRNA genotyping) and Scanning ElectronMicroscope (SEM) imaging of individualtests were used in tandem to determine the modern species richness of the foraminiferal family Elphidiidae(Elphidium, Haynesina and related genera) across the Northeast Atlantic shelf biomes. Specimens were collectedat 25 locations fromthe High Arctic to Iberia, and a total of 1013 individual specimenswere successfully SEMimagedand genotyped. Phylogenetic analyses were carried out in combination with 28 other elphidiid sequencesfrom GenBank and seventeen distinct elphidiid genetic types were identified within the sample set, sevenbeing sequenced for the first time. Genetic types cluster into sevenmain cladeswhich largely represent their generalmorphologicalcharacter. Differences between genetic types at the genetic, morphological and biogeographiclevels are indicative of species level distinction. Their biogeographic distributions, in combination with elphidiidSSU sequences from GenBank and high resolution images from the literature show that each of them exhibitsspecies-specific rather than clade-specific biogeographies. Due to taxonomic uncertainty and divergent taxonomicconcepts between schools, we believe that morphospecies names should not be placed onto molecularphylogenies unless both the morphology and genetic type have been linked to the formally named holotype,or equivalent. Based on strictmorphological criteria,we advocate using only a three-stage approach to taxonomyfor practical application in micropalaeontological studies. It comprises genotyping, the production of a formalmorphological description of the SEM images associated with the genetic type and then the allocation of themost appropriate taxonomic name by comparison with the formal type description. Using this approach, wewere able to apply taxonomic names to fifteen genetic types. One of the remaining two may be potentially cryptic,and one is undescribed in the literature. In general, the phylogeographic distribution is in agreement with ourknowledge of the ecology and biogeographical distribution of the corresponding morphospecies, highlighting thegenerally robust taxonomic framework of the Elphidiidae in time and space

Interprétation paléogéographique d'une tourbe de Torson di Sotto (Lagune de Venise, Italie)

A core extracted near the central part of the lagoon revealed a peat layer between 1.3 m and 2.0 m below mean sea level. Pollen analysis indicates the predominance of Quercus and Alnus and testifies the existence of a transgressive phase : the base of the peat (dated 1730 ± 80 yr BP) is formed by fresh water sediments ; in the upper part (dated 1 140 ± 80 yr BP) sediments are brackish, pollen content decreases, and halophytes increase. According to Foraminifera analysis, transgression has been preceded by a regression. The whole sequence is, from bottom to top (Fig. 2) : (1) an oligohaline to mesohaline environment (from -3.3 m to -2.5 m) with very abundant Foraminifera ; (2) a fresh water environment (from -2.5 to -2.0 m) ; (3) the 70 cm-thick peat layer, becoming gradually brackish ; (4) a mesohaline environment (above -1,3 m). Correlation with neighbouring localities indicates that similar phenomena occurred at the same time in relatively wide coastal areas. This regression-transgression sequence is ascribed to an increased rainfall period, at about the end of Roman times, which would have caused the overflow and a change in the course of several rivers, temporarily modifying the hydrologie equilibrium in this marshy region. Man-made factors, mostly introduced over the past 100 years, increasingly hastened the transgression. The "barene" (local name of the tidal flats) are now eroding, rapidly disappeearing (Fig. 1), and being replaced by wide water basins.Une carotte prélevée dans la partie centrale de la lagune a rencontré une couche de tourbe située entre -1,3 et -2,0 m par rapport au niveau moyen de la mer. Les pollens montrent une prédominance du Chêne et de l'Aune et témoignent de l'existence d'une phase transgressive entre la base (sédiments d'eau douce, datés 1730 ± 80 BP) et le sommet de la tourbe. Les sédiments saumâtres du sommet, datés 1 140 ± 80 BP, se caractérisent par la diminution de la quantité de pollens et par l'augmentation du pourcentage des halophytes. D'après l'étude des Foraminifères, cette transgression a été précédée par une phase régressive. La séquence fait apparaître ainsi, de bas en haut : (1) un milieu oligo à mésohalin (entre -3,3 et -2,5 m), avec des Foraminifères très abondants ; (2) un milieu d'eau douce (entre -2,5 et -2,0 m) ; (3) la tourbe de 70 cm d'épaisseur, de plus en plus saumâtre ; (4) un milieu mésohalin (au-dessus de -1,3 m). Des corrélations avec les localités voisines montrent que des phénomènes analogues se sont produits, à la même époque, dans une zone littorale relativement vaste. Cette oscillation régression-transgression est attribuée à une augmentation de la pluviosité, vers la fin de l'époque Romaine, augmentation qui aurait changé le cours de plusieurs rivières et modifié ainsi, temporairement, l'équilibre hydrologique de cette région marécageuse. Depuis environ un siècle, les travaux effectués par l'homme rendent ici la transgression de plus en plus rapide. Les barênes, démantelées par l'érosion, sont en voie de disparition, remplacées par de vastes bassins d'eau.Pirazzoli Paolo Antonio, Planchais Nadine, Rosset-Moulinier Marie, Thommeret J. Interprétation paléogéographique d'une tourbe de Torson di Sotto (Lagune de Venise, Italie). In: Géologie Méditerranéenne. Tome 8, numéro 3, 1981. Pleistocène. pp. 121-128

Données nouvelles sur Rotalia trochidiformis Lamarck (Foraminiferida). Emendation du genre Rotalia Lamarck 1804

In this work, the authors give a new description of the outer and inner morphology of Rotalia trochidiformis LMK. 1804 which was collected in several lutetian exposures of the Parisian Basin (e.g. Grignon). A detailed study of the internal structure with the scanning electronic microscope reveals the originality of the genus Rotalia concerning the morphology of the paries proximus. Its affinities with Discorbis are pointed out. These observations lead to an emendation of the genus Rotalia.Dans ce travail, il est donné une nouvelle description de la mor¬ phologie externe et interne de Rotalia trochidiformis LMK. 1804 récolté dans plusieurs gisements lutétiens du Bassin de Paris (notamment Grignon). Une étude détaillée, au microscope électronique à balayage, de la structure interne de Rotalia trochidiformis met en évidence, en ce qui concerne la morphologie du paries proximus, l'originalité du genre Rotalia et ses affinités avec Discorbis. Ceci conduit à une émendation du genre Rotalia.Levy Alain, Mathieu R., Poignant Alain-François, Rosset-Moulinier Marie, Rouvillois Armelle. Données nouvelles sur Rotalia trochidiformis Lamarck (Foraminiferida). Emendation du genre Rotalia Lamarck 1804. In: Géologie Méditerranéenne. Tome 9, numéro 1, 1982. pp. 33-41

Recherches sur les foraminifères actuels des côtes françaises de la Manche et de la mer du Nord

National audienc

Marine glacial and interglacial stratigraphy in Vendsyssel, northern Denmark: foraminifera and stable isotopes

The marine Quaternary of Vendsyssel has been studied in a series of new boreholes in the area, and the climatic development is discussed on the basis of foraminiferal assemblages and stable isotopes. The foraminiferal zones are correlated with previously published records from northern Denmark, and the spatial local and regional distribution is discussed in details based on the new evidence. The new data show that the marine sedimentation in Vendsyssel was not continuous from the Late Saalian to the Middle Weichselian, as previously thought. For example, there is indication of a hiatus at our key site, Asted Vest in the central part of Vendsyssel, at the transition between regional foraminiferal zones N4 and N3, i.e. at the Late Saalian (MIS 6) - Eemian (MIS 5e) transition. The hitherto most complete Early Weichselian succession (zone N2) in Vendsyssel is presented from Asted Vest. Deposits from the Early Weichselian sea-level lowstands (MIS 5d and 5b) may, however, be missing in parts of the area. Two major breaks in the marine deposition during the Middle Weichselian represent glacial advances into northern Denmark. The first event occurred just after deposition of the regional foraminiferal zone N2 (late MIS 4), and the second event in the middle part of zone N1 (early MIS 3). Zone N1 is succeeded by a series of non-marine units deposited during the sea-level lowstand of the Weichselian maximum glaciation (late MIS 3 and MIS 2), including deeply incised tunnel valleys, which have been refilled with non-marine sediments during the Late Weichselian. Vendsyssel was inundated by the sea again during the Late Weichselian, at c. 18 kyr BP. Subsequently, the marine conditions were gradually changed by forced regression caused by local isostatic uplift, and around the Weichselian-Holocene transition most of Vendsyssel was above sea level. A continuous deposition across the Late Weichselian-Holocene boundary only occurred at relatively deep sites such as Skagen. The environmental and climatic indications for Vendsyssel are in accordance with the global sea-level curve, and the Quaternary record is correlated with the oxygen isotope record from the NorthGRIP ice core, as well as the marine isotope stages