New organic-walled dinoflagellate cysts from recent sediments of central Asian seas

Recent to sub-recent sediments from the Caspian Sea, the Kara-Bogaz-Gol Bay, the Enseli lake and the Aral Sea contain the new organic-walled dinoflagellate cysts Caspidinium, Caspidinium rugosum and Impagidinium caspienense. Caspidinium rugosum has S-type paratabulation, dextral torsion and low relief intratabular ornamentation. Impagidinium caspienense has low intratabular suturo-cavate relief, parasutural septa irregular in height and a high septum at the junction of paraplate 1'''' and the sulcus. The accompanying species consist of Spiniferites cruciformis, Lingulodinium machaerophorum, Pyxidinopsis psilata, cysts of Pentapharsodinium dalei and Brigantedinium spp. Spiniferites cruciformis varies from specimens with a cruciform body with a well-developed postero-lateral membranous flange to specimens with a pear-shaped body, reduced processes and no flange. Sea-surface data from these Central Asian seas suggests that the two new taxa Caspidinium rugosum and Impagidinium caspienense are probably related to low salinity conditions (12-13)

Late Pleistocene and Holocene palaeoenvironments in and around the middle Caspian basin as reconstructed from a deep-sea core

This article has been made available through Open Access by the Brunel Open Access Publishing Fund.Late Pleistocene and/or Holocene high-resolution palynological studies are available for the south basin of the Caspian Sea (CS), the world's largest lake. However, the north and middle basins have not been the object of high-resolution palynological reconstructions. This new study presents the pollen, spores and dinoflagellate cysts records obtained from a 10m-long sediment core recovered in the middle basin, which currently has brackish waters and is surrounded by arid and semi-arid vegetation.An age-depth model built based on six radiocarbon dates on ostracod shells indicates that the sequence spans the period from 14.47 to 2.43cal.kaBP. The present palaeoenvironmental study focuses on the top 666cm, or from 12.44 to 2.43cal.kaBP.At the vegetation level, the Younger Dryas is characterised by an open landscape dominated by desert vegetation composed by Amaranthaceae with shrubs and salt-tolerant plants. However, although the Early Holocene is also characterised by desert vegetation, it is enriched in various shrubs such as Ephedra and Calligonum, but tree expansion is not important at the Holocene onset. After a major shift at 8.19cal.kaBP, the Middle Holocene displays now both the character of desert and of steppe, although some trees such as Quercus and Corylus slightly spread. The Late Holocene records steppe vegetation as dominant, with more tree diversity.Regarding the lacustrine signal, the dinocyst assemblage record fluctuates between slightly brackish conditions highlighted by Pyxidinopsis psilata and Spiniferites cruciformis, and more brackish ones - similar to the present day - with the dominance of Impagidinium caspienense. The Late Pleistocene is characterised by low salinities, related to the Khvalynian highstand. From 11.56cal.kaBP, slightly more saline waters are reconstructed with an increase of I.caspienense for a period of 1000 years, which could be attributed to the Mangyshlak lowstand. From 10.55cal.kaBP, low salinity conditions return with remains such as Anabaena and Botryococcus abundant until 8.83cal.kaBP, followed by a slow, progressive decrease of P. psilata and S. cruciformis until 4.11cal.kaBP, which is the main assemblage change at lacustrine scale. Since then, higher salinities, similar to the present one, are reconstructed. Finally, Lingulodinium machaerophorum starts its development only at 2.75cal.kaBP, in the Late Holocene.The present research revealed fundamental differences from previously published sea-level curves, in that a 6000yr-long highstand suggested by low salinities is shown between 10.55 and 4.11cal.kaBP. Amongst other arguments, using a comparison to a similar palynological regard but in the south basin, a N-S salinity gradient that is the reverse of the present one across the CS, suggests that the Amu Darya was flowing in the CS. Hence the CS levels during the Late Pleistocene and Holocene were influenced by a combination of precipitation over the high European latitudes and the indirect influence of the Indian summer monsoon over the Pamirs. © 2014.This study has been conducted within the European Contract INCO-Copernicus “Understanding the Caspian Sea erratic fluctuations” n IC15-CT96-0112. This was funded by the Centre National de la Recherche Scientifique within the framework of the INSUDYTEC (DYnamique de la Terre et du Climat) Program (France)

Hydrologie et géochimie isotopique

Cet ouvrage rassemble des travaux récents dans les domaines de l'hydrologie et de la géochimie isotopique. La première partie explore le cycle des eaux naturelles, depuis les précipitations jusqu'aux aquifères profonds, par l'analyse des variations de la composition isotopique de l'hydrogène, de l'oxygène et du carbone. Des types régionaux sont présentés, sous diverses latitudes : Spitzberg, Bassin parisien, bassin soudano-sahélien du Niger. L'intérêt de l'approche isotopique dans l'étude du changement global est illustrée en deuxième partie. Les variations hydro-climatiques de types régionaux, en Afrique essentiellement, sont retracées par l'analyse multidisciplinaire d'enregistrements sédimentaires, dont la géochimie isotopique constitue la clé essentielle. L'homogénéité du refroidissement, aux moyennes et basses latitudes, lors du dernier maximum glaciaire est démontrée par l'analyse isotopique des gaz nobles dans les eaux souterraines. La mise en évidence de l'origine organique du carbone de carbonates sédimentaires remet en question l'interprétation de certaines analyses isotopiques. La troisième partie fait référence aux isotopes d'origine cosmique et à la production in situ de radionucléides. Il est rappelé que la datation par 14C a contribué à la compréhension des mécanismes des changements du climat au cours du dernier maximum glaciaire et depuis lors. Les limites de cette méthode et ses progrès récents font l'objet d'une synthèse amplement documentée. Par l'apport de données isotopiques, la géochimie s'avère fonder la modélisation des conditions de stabilité du réacteur de fission nucléaire fossile d'Oklo. (Résumé d'auteur

Extracranial guiding structures for navigation to specific topographical sectors of the equine neopallium: an anatomical investigation performing three-dimensional distance measurements in adult warm-blooded horses

This basically anatomical study focuses on two items; firstly, the establishment of a system for the cartographic subdivision of the neopallium; secondly, the topographical correlation of extracranial landmarks and intracranial sites on the neopallium. The surface of the neopallium was subdivided into 15 Sectors with reference to a newly introduced pattern of Primary Sulci. The topographical link between extracranial landmarks and certain intracranial sites (i.e., neopallium Sectors) was elaborated by using a simple stereotactic device and a computer-assisted measurement device. Measurements were performed between points on the head´s outer surface and on the isolated brain. The introduction of an anatomical three-dimensional Coordinate System was an essential key issue for this investigation. This setting facilitated the measurements and calculations of the so-called Indirect Distances that were characterized by their alignment along the three orthogonal axes (x, y, z) of the anatomical Coordinate System. The inter-individual comparison (16 adult horses [Equus caballus]) of the Indirect Distances revealed that each Sector Center lay within a distinct morphometric Residence Area. The measured and calculated data also showed that each Sector Center could be assigned to its proper extracranial landmark that – in comparison with other landmarks – was best suited for the optimal allocation of the Sector Center Point