Anomalous Au silicifications in the upper carboniferous of the French Massif Central: timing and temperature constraints by combined geochemical and organic-matter studies

2002 ◽  
Vol 91 (3) ◽  
pp. 459-468 ◽  
Author(s):  
Yoann Copard ◽  
Laurent Bailly ◽  
Jean-François Becq-Giraudon ◽  
Jean-Robert Disnar
Keyword(s):  
Organic Matter ◽  
French Massif Central ◽  
Massif Central ◽  
Upper Carboniferous

Thermal maturation and exhumation of a middle orogenic crust in the Livradois area (French Massif Central)

2011 ◽  
Vol 182 (1) ◽  
pp. 5-24 ◽  
Author(s):  
Véronique Gardien ◽  
Olivier Vanderhaeghe ◽  
Nicolas Arnaud ◽  
Alain Cocherie ◽  
Marion Grange ◽  
...  
Keyword(s):  
Final Stage ◽  
Crustal Melting ◽  
Early Permian ◽  
French Massif Central ◽  
Rapid Cooling ◽  
Massif Central ◽  
Upper Carboniferous ◽  
Peak Metamorphism ◽  
Metamorphic Series ◽  
Granitic Dome

AbstractUpper Carboniferous heating and melting of the middle orogenic crust associated with the emplacement of syntectonic granitoids are documented in the Upper Gneissic Unit of the Livradois area (central part of the French Massif Central). Crustal melting post-dates peak metamorphism conditions (800-625°C, 10-8 kb) dated at 360 ± 4 Ma (U-Th-Pb on monazite). The P-T evolution of the metamorphic series indicates that Barrovian metamorphism was followed by a decompression (from 10 ± 1 kbar to 6 ± 1 kbar) associated with either a decrease in temperature in the southern part of the series or with an increase in temperature (of about 150°C) in the northern part of the series. This evolution records the first step of the exhumation of the series coeval with granitoids intrusion, of which the emplacements were dated at 315 ± 4 and 311 ± 18 Ma (U-Pb on zircon). The final stage of the exhumation is associated with an isobaric cooling of the whole series. Similarity of 40Ar/39Ar ages for biotite in the paragneisses (307-300 Ma) and K-feldspar in the granitoids (306-300 Ma) document rapid cooling for this stage. Moreover dextral reverse mylonites, at the border and the northern part of the metamorphic series indicate north-south compression coeval with the unroofing of the series. Youngest 40Ar-39Ar ages on K-feldspar (274.6 ± 5 Ma) combined with normal shearing in mylonites limiting the Carboniferous Brassac-les-Mines basin document the late Carboniferous-early Permian stage of extension coeval with the upwelling of the Velay granitic dome.

scholarly journals Refining the Sarliève Paleolake (France) Neolithic Chronology by Combining Several Radiocarbon Approaches

Radiocarbon ◽  
2013 ◽  
Vol 55 (2) ◽  
pp. 979-992 ◽  
Author(s):  
Christine Hatté ◽  
Jean-Gabriel Bréhéret ◽  
Jérémy Jacob ◽  
Jacqueline Argant ◽  
Jean-Jacques Macaire
Keyword(s):  
Organic Matter ◽  
Significant Contribution ◽  
French Massif Central ◽  
Massif Central ◽  
Single Level ◽  
The Past ◽  
Radiocarbon Data ◽  
Reservoir Age ◽  
Data Call

Dating sedimentary series spanning the past few tens of thousands of years is often problematic due to the quality of radiocarbon data obtained from organic matter (OM), including bulk OM. This problem recently arose when establishing the chronology of a sediment infill at the Sarliève paleolake (French Massif Central). In the studied section of the cores that covers the Neolithic, Ruppia seeds yielded consistent ages for the lower part (7195 ± 75 to 6050 ± 60 yr BP). A reservoir age of 82 ± 42 14C yr was estimated through the comparison of ages derived from charcoal, Ruppia seeds, and charophyte oogonia sampled on a single level. The upper part of the cores lacks macrofossils and bulk OM dating yields unusable data because of a significant contribution of aged OM derived from the Oligocene substratum in the catchment. We therefore performed dating of lipids extracted from the sediments. The age of the lipids was 2880 ± 30 yr BP near the top of the section, i.e. much younger than the age estimated from previous correlations based on pollen assemblages. These new data call into question previous paleoenvironmental interpretations. The combined dating methodology used for the Neolithic series of Sarliève is a rather uncommon approach that may help to refine chronologies of Holocene sedimentary series.

Evaluating Holocene natural hazards in the French Massif Central from a regional lake sediment approach

2021 ◽  
Author(s):  
E. Chapron ◽  
A. Foucher ◽  
L. Chassiot ◽  
W. Fleurdeus ◽  
V. Arricau ◽  
...  
Keyword(s):  
Natural Hazards ◽  
Lake Sediment ◽  
French Massif Central ◽  
Massif Central

Sellaphora labernardierei (Sellaphoraceae, Bacillariophyta), a new epilithic species from French spring and four new combinations within the genus Sellaphora

Phytotaxa ◽  
2016 ◽  
Vol 260 (3) ◽  
pp. 235 ◽  
Author(s):  
AUDE BEAUGER ◽  
CARLOS E. WETZEL ◽  
OLIVIER VOLDOIRE ◽  
ALEXANDRE GARREAU ◽  
LUC ECTOR
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Central Area ◽  
Mineral Waters ◽  
New Combinations ◽  
French Massif Central ◽  
Small Species ◽  
Massif Central ◽  
Floristic Survey ◽  
Scanning Electron

During a floristic survey of freshwater springs in the French Massif Central region, a new Sellaphora species (Bacillariophyceae) was found and is hereby described: Sellaphora labernardierei sp. nov. This new small species, with linear to linear-elliptical valves, slightly inflated in the middle, is formally described using light and scanning electron microscopy. The species has a single H-shaped chloroplast and striae usually biseriate tending to be uniseriate near the centre of the valve. The valve dimensions, the valve, pole and central area shapes, and the striae density and pattern allow their separation from similar taxa belonging to the genera Eolimna, Naviculadicta and Sellaphora. The ecological preferences of Sellaphora labernardierei are mineral waters with high nitrate concentrations. The examination of similar taxa belonging to the genera Eolimna and Naviculadicta and their characteristics lead to propose four new combinations of Sellaphora species.

scholarly journals Tephras in lacustrine sediments of the Sarliève marsh (French Massif Central): age and preservation

2006 ◽  
Vol 338 (16) ◽  
pp. 1141-1149 ◽  
Author(s):  
Agathe Fourmont ◽  
Jean-Jacques Macaire ◽  
Jean-Gabriel Bréhéret ◽  
Jacqueline Argant ◽  
Béatrice Prat ◽  
...  
Keyword(s):  
Lacustrine Sediments ◽  
French Massif Central ◽  
Massif Central
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