Record of glaciations off the east greenland coast over the last 400KYR : SM-ND isotopic signature of marine clays

We use Nd isotope signature of the clay-size fractions of sediments from the Southern Greenland rise to track deep current changes over the last climate cycle. Fine particle supplies to the Labrador Sea by Western Boundary UnderCurrent (WBUC) were strongly controlled by proximal ice-margin erosion and thus echoed the glacial stage intensity. In contrast, distal WBUC-controlled inputs from NE Atlantic have been less variable, except for a marked increase in surface-sediments that suggests unique modern conditions

Assembly and concept of a web-based GIS within the paleolimnological project CONTINENT (Lake Baikal, Russia)

Web-based Geographical Information Systems (GIS) are excellent tools within interdisciplinary and multi-national geoscience projects to exchange and visualize project data. The web-based GIS presented in this paper was designed for the paleolimnological project 'High-resolution CONTINENTal paleoclimate record in Lake Baikal' (CONTINENT) (Lake Baikal, Siberia, Russia) to allow the interactive handling of spatial data. The GIS database combines project data (core positions, sample positions, thematic maps) with auxiliary spatial data sets that were downloaded from freely available data sources on the world wide web. The reliability of the external data was evaluated and suitable new spatial datasets were processed according to the scientific questions of the project. GIS analysis of the data was used to assist studies on sediment provenance in Lake Baikal, or to help answer questions such as whether the visualization of present-day vegetation distribution and pollen distribution supports the conclusions derived from palynological analyses. The refined geodata are returned back to the scientific community by using online data publication portals. Data were made citeable by assigning persistent identifiers (DOI) and were published through the German National Library for Science and Technology (TIB Hannover, Hannover, Germany).Continen

Land erosion and associated evolution of clay minerals assemblages in Mediterranean region (Southern Turkey): Amik Lake

Under Mediterranean context, continuous human occupation is attested in the Amik Basin (southern Turkey) since 6000-7000 BC. The Basin also is crossed by The Dead Sea Fault (DSF), a major neotectonic structure in the Middle East extending from the Red Sea in the south to the East Anatolian Fault Zone in the north. The study focuses on the mineralogy and clay mineralogy record of the Amik Lake occupying the central part of the Basin. Our objective is to constrain major mineralogical and clay minerals evolution in the area over the last 4000 years and assess changes that would be related to the different land uses during the different Bronze, Roman, Ottoman and Modern civilizations. Sediments were collected at 1 to 2 cm intervals in core sediments up to a depth of 6 meters in the clay deposits. Geochemistry (XRF), mineralogy (XRD) and clay mineralogy are applied to study the sediment records. The age of the record is constrained combining radionuclide and radiocarbon dating. Chemical and mineralogical composition of sediments is quite diversified reflecting the significant geological variation of drainage basins. Abundant mixed-layer and partly disordered minerals characterize the different sedimentary levels recorded in those cores. Levels relatively rich in chlorite, illite and quartz are interpreted as corresponding to relatively dry periods, while more humid periods lead to more intensive weathering and consequently to the dominance of clay minerals more advanced in the relative stability scale, such as kaolinite. Smectite is taken to indicate a climate with contrasting seasons and a pronounced dry season. The sedimentary record clearly shows two periods indicating strong soil erosion in the Lake catchment. The most recent erosion phase is modern. The oldest one would have started during the late Bronze period and lasted until the late Roman Period. The first and older period is attributed to a strong aggradation linked to major increase in erosion. Our study shows that this episode has specific characteristics: mixed-layer clay mineral, high percent in Ni, Cr and Mg coupled with significant amount of organic matter of terrestrial origin. Ni and Mg most probably come from the Amanos Mountains an ophiolitic belt indicating an intensive upland cultivation and possible exploitation of its mineral resource. The second period is attributed to the modern period. The signature of the increase in erosion is different, because most of the soil cover has already been eroded. Only a patchy thin and unmature soil cover exists since the Late Roman time. Erosion is associated with a marked increase of smectite-illite interstratified clay, goethite and hematite found in deep soil horizons. Moreover, a marked increase in Cr is showed and is probably related to an enhanced exploitation of its mineral resource and to a renew land exploitation of the Amanos Mountain Range

Flaws linked to lime in pottery of Marrakech (Morocco)

The studied clayey materials come from soil of Marrakech Haouz Plain. We discussed the influence of grain size, mineralogical and chemical composition of these raw materials on the lime behaviour in pottery shards. In this paper we propose some recommendations to inhibit lime blowing and the efflorescences responsible for flaws. The application of such recommendations will improve the quality of produced pottery and the income of potters in the region.Peer reviewe

Suitability of Foumban Clays (West Cameroon) for Production of Bricks and Tiles

peer reviewe

Diagenèse osseuse et genèse de nodules phosphatés, associés aux sédiments fluvio-lacustres de sites à hominidés miocène (Kenya)

audience: researche

Cambios ambientales del último milenio en sedimentos lacustres del Lago Thompson, Patagonia Chilena Norte

Este estudio se enfoca en un análisis multiproxy de un testigo sedimentario del Lago Thompson (area 1 km2; 751 masl ; 45°38’S 72°47’W) obtenido en 2008 (LT08-E, 130 cm), con el objetivo de documentar la variabilidad climática durante el último milenio en la Patagonia Chilena Norte y su impacto sobre el ambiente. El modelo de datación se basó en cinco fechados de 14C. Los resultados de 210Pb y 137 Cs no permitieron estimar la tasa de sedimentación para la parte superficial del núcleo. El lago Thompson esta caracterizado por una pequeña cuenca de suaves pendientes y sus sedimentos están dominados por limo arcilloso y partículas amorfas (principalmente diatomeas). Esto último es sustentado por la relación atómica de carbono/nitrógeno (C/N) que indica el origen fitoplanctónico del sedimento (8-10). Los perfiles de rayos –X, susceptibilidad magnética y LOI 550ºC evidencian dos depósitos volcánicos en 1410-1440 y 1780-1790 AD. Los perfiles de C/N y sílice biogénica (SiB) sugieren una alta productividad durante un periodo equivalente a la Pequeña Edad del Hielo (1650-1850 AD), con una máxima intensidad durante ~1800 AD. Desde 1850 AD hasta la actualidad, los perfiles de LOI 550ºC y SiB evidencian una reciente eutrofización y aumento del nivel del lago (asociado con aumento de temperaturas y humedad). Además, los perfiles de SiB presentan una correlación inversa con las temperaturas reconstruidas por anillos de árboles en la Patagonia. El contenido de diatomeas es dominado por especies planctónicas (Aulacoseira sp. y Cyclotella sp.), mientras que taxa bentónicos no muestran una buena diversificación en comparación a otros lagos de la Patagonia. La abundancia de diatomeas muestra respuestas específicas a los depósitos volcánicos con una disminución de Aulacoseira sp.. La relación planctónica/bentónica permite identificar dos periodos de alto y bajo nivel del lago coincidiendo con fases húmedas y secas de la Pequeña Edad de Hielo (1200-1650 y 1650-1850 AD). La realización de análisis sedimentológicos, geoquímicos y de microfósiles permitiría una mejor caracterización de los modelos de depositación del sedimento (impregnación del núcleo sedimentario) y de la interacción entre depósitos volcánicos y diatomeas. Agradecimientos a Fondecyt Nº1070508, FNRS 1360 2007-2010 y ULg CFRA 1060 2009-2010

EVALUATION DES INDICES D'ALTERATION CHIMIQUE SUR UN PROFIL KAOLINISE CAS : TAMAZERT (NE ALGERIE) ASSESSMENT OF CHEMICAL WEATHERING INDICES IN KAOLINISED PROFIL CASE: TAMAZERT (NE ALGERIA)

peer reviewedLes indices d'altération chimique sont couramment utilisés pour caractériser les profils d'altération développés sur des roches mères hétérogènes ou homogènes. Parmi les indices d'altération évalués dans cette étude, l'indice de Parker (WIP), l'indice chimique d'altération (CIA), l'indice de météorisation chimique (CIW), l'indice d'altération des plagioclases (PIA), Ruxton ratio (R). L'objectif principal de cette étude est d'examiné l'étendue de l'altération chimique affectée les différentes roches surtout gneissiques dans la zone de Tamazert et de tester l'aptitude d'application des indices d'altération chimique pour des profils d'altération hétérogènes. La pétrographie et la géochimie des éléments majeurs de la roche mère et du produit d'altération ont été discuté dans ce travail