Search results for "Planetary Science"
showing 10 items of 4367 documents
Les ammonites traditionnellement regroupées dans la sous-famille des Bouleiceratinae (Hildoceratidae, Toarcien) : aspects phylogénétiques, biogéograp…
2003
Resume Les genres d’ammonites, traditionnellement regroupes dans la sous-famille des Bouleiceratinae, appartiennent en fait a des lignees differentes de la famille des Hildoceratidae. Une approche utilisant des arguments paleogeographiques, stratigraphiques et morphologiques d’une part et une approche cladistique d’autre part ont permis de distinguer 3 groupes se succedant au cours du temps et a repartitions paleogeographiques differentes : • les Bouleiceratinae s.s. (genres Bouleiceras, Nejdia et Kohaticeras) du Toarcien inferieur ; • les Leukadiellinae (genres Leukadiella et Renziceras) du Toarcien moyen ; • et les Paroniceratinae (genres Frechiella, Paroniceras et Oxyparoniceras) du Toar…
Database Dry Grasslands in the Nordic and Baltic Region
2012
The Database Dry Grasslands in the Nordic and Baltic Region (GIVD ID EU-00-002) is an initiative of the respective regional subgroup of the European Dry Grassland Group (EDGG). Its aim is to compile the available published and unpublished vegetation-plot data of dry grasslands and related syntaxa (mainly vegetation classes Koelerio-Corynephoretea, Festuco-Brometea, and Trifolio-Geranietea) from the study region (Denmark, Norway, Sweden, Finland, NW Russia, Belarus, Estonia, Latvia, Lithuania, N Poland, and NE Germany). The only requirement for inclusion is that the plot size is between 1 and 100 m2. The database is managed under Sort 4.0, but shall be transferred to TURBOVEG soon. Presently…
New geo-portal for MODIS/SEVIRI image products with geolocation-based retrieval functionality
2015
A large number of remote sensing data sets have been collected in recent years by Earth observation instruments such as the moderate resolution imaging spectroradiometer (MODIS) aboard the Terra/Aqua satellite and the spinning enhanced visible and infrared imager (SEVIRI) aboard the geostationary platform Meteosat Second Generation. The advanced remote sensing products resulting from the analysis of these data are useful in a wide variety of appli- cations but require significant resources in terms of storage, retrieval, and analysis. Despite the wide availability of these MODIS/SEVIRI products, the data coming from these instruments are spread among different locations and retrieved from d…
A diagenetic control on the Early Triassic Smithian-Spathian carbon isotopic excursions recorded in the marine settings of the Thaynes Group (Utah, U…
2016
17 pages; International audience; n the aftermath of the end-Permian mass extinction, Early Triassic sediments record some of the largest Phanerozoic carbon isotopic excursions. Among them, a global Smithian-negative carbonate carbon isotope excursion has been identified, followed by an abrupt increase across the Smithian–Spathian boundary (SSB; ~250.8 Myr ago). This chemostratigraphic evolution is associated with palaeontological evidence that indicate a major collapse of terrestrial and marine ecosystems during the Late Smithian. It is commonly assumed that Smithian and Spathian isotopic variations are intimately linked to major perturbations in the exogenic carbon reservoir. We present p…
Chronology of early Archaean granite-greenstone evolution in the Barberton Mountain Land, South Africa, based on precise dating by single zircon evap…
1991
We report precise 207Pb/206Pb single zircon evaporation ages for low-grade felsic metavolcanic rocks within the Onverwacht and Fig Tree Groups of the Barberton Greenstone Belt (BGB), South Africa, and from granitoid plutons bordering the belt. Dacitic tuffs of the Hooggenoeg Formation in the upper part of the Onverwacht Group yield ages between 3445 +/- 3 and 3416 +/- 5 Ma and contain older crustal components represented by a 3504 +/- 4 Ma old zircon xenocryst. Fig Tree dacitic tuffs and agglomerates have euhedral zircons between 3259 +/- 5 and 3225 +/- 3 Ma in age which we interpret to reflect the time of crystallization. A surprisingly complex xenocryst population in one sample documents …
Solar and interplanetary triggers of the largest Dst variations of the solar cycle 23
2012
Abstract We present the results of an investigation from the Sun to the Earth of the sequence of events that caused major Dst decreases (Δ Dst ≤ – 100 nT during 1 h) that occurred during 1996–2005. These events are expected to be better related to geomagnetic induced current (GIC) events than those events where any geomagnetic index is far from its quiet time value. At least one full halo CME with a speed on the plane of sky above 900 km/s participates in every studied event. The seven events were triggered by interplanetary signatures, which arise as a consequence of interaction among different solar ejections. The interaction arises at different stages from the solar surface, between segm…
Quantification of volcano deformation caused by volatile accumulation and release
2022
<p>Magma stored in the crust may exsolve a significant amount of volatiles, primarily CO<sub>2</sub>, but also H<sub>2</sub>O and SO<sub>2</sub> if cooling promotes crystallisation and volatile exsolution. These volatiles may, over time, segregate and accumulate into a gas-rich foam at the roof of the magma body. This is the underpinning process to explain the frequently observed ‘excess gas’ produced in explosive eruptions, where the amount of erupted SO<sub>2</sub> is much larger than can be explained by the mass of erupted products and …
Decompression and Fracturing Caused by Magmatically Induced Thermal Stresses
2023
Studies of host rock deformation around magmatic intrusions usually focus on the development of stresses directly related to the intrusion process. This is done either by considering an inflating region that represents the intruding body, or by considering multiphase deformation. Thermal processes, especially volume changes caused by thermal expansion are typically ignored. We show that thermal stresses around upper crustal magma bodies are likely to be significant and sufficient to create an extensive fracture network around the magma body by brittle yielding. At the same time, cooling induces decompression within the intrusion, which can promote the appearance of a volatile phase. Volatil…
Property loss potentials for European midlatitude storms in a changing climate
2007
[1] Winter storms of the midlatitudes are an important factor for property losses caused by natural hazards over Europe. The storm series in early 1990 and late 1999 led to enormous economic damages and insured claims. Although significant trends in North Atlantic/European storm activity have not been identified for the last few decades, recent studies provide evidence that under anthropogenic climate change the number of extreme storms could increase, whereas the total number of cyclones may be slightly reduced. In this study, loss potentials derived from an ensemble of climate models using a simple storm damage model under climate change conditions are shown. For the United Kingdom and Ge…
Intensity and spatial extent of droughts in southern Africa
2005
International audience; The standardized precipitation index allows for monitoring the intensity and spatial extent of droughts at different time scales. We used it to do a retrospective analysis of the spatial extent of droughts in Southern Africa (South of 10°S), from 1901 to 1999. Accordingly, the 8 most severe droughts at the 6-month scale (October–April) for the summer rainfall region of Southern Africa ended in 1916, 1924, 1933, 1949, 1970, 1983, 1992 and 1995. At the 2-year scale, they ended in 1906, 1933, 1983, 1984, 1992, 1993, 1995 and 1996. Areas affected by those droughts ranged from 3.4 to 2 106 km2. Eight of those 12 years are El Niño years. Preliminary data indicates that 200…