Search results for "Tufa"

Fossiliferous Holocene tufa of Mende (Lozère, southern France): implication for the Atlantic vegetation of the Causses Basin

2016

International audience; Tufas bearing plant macroremains are uncommon in the Causses Basin (southern France). Here, we report anew fossiliferous tufa deposits at Mende, in Lozère. This palaeontological site is the first Quaternary tufa from thenorthern part of the Causses Basin that yields such an abundance of plant macroremains. The radiocarbon dating showsthat these Holocene deposits are related to the Atlantic period. Geomorphology and mineralogy show that theplant-bearing deposit is a calcareous tufa only composed by calcite, deposited near to an outlet of cool water, linked tothe karstic hydrological system of the Causse de Mende. The flora exposed in this article is dominated by angio…

A multi-proxy long-term ecological investigation into the development of a late Holocene calcareous spring-fed fen ecosystem (Raganu Mire) and boreal…

2021

Abstract The calcareous substrate of spring-fed fens makes them unique islands of biodiversity, hosting endangered, vulnerable, and protected vascular plants. Hence, spring-fed fens ecosystems require special conservation attention because many of them are destroyed (e.g. drained, forested) and it is extremely difficult or even impossible to restore the unique hydrogeological and geochemical conditions enabling their function. The long-term perspective of paleoecological studies allows indication of former wetland ecosystem states and provides understanding of their development over millennia. To examine the late Holocene dynamics of a calcareous spring-fed fen (Raganu Mire) ecosystem on th…

Calcitic radial palisadic fabric in freshwater stromatolites: diagenetic and recrystallized feature or physicochemical sinter crust?

1999

Abstract When favorable conditions occur for carbonate precipitation (physicochemical processes) in tufas and travertines, organisms intervene either directly (the framework created by organisms acts as a crystal support) or indirectly (organic products influencing the mineralogy, nucleation, growth and habit of primary crystals). In the literature, fluvial and travertine crystalline sparite crusts with palisadic or prismatic crystals are generally interpreted as the result of early recrystallization of micrite in algal buildups (mostly composed of Schizothrix). Therefore, biological mediation is essential for the construction of continental bioherms and biostromes, even if organic remains …

Textural features and isotope geochemistry of the Scillato travertine (north-central Sicily): genetic implications.

2015

The travertine deposit, outcropping near the Scillato town (north-central Sicily), was originated by precipitation of calcium carbonate from the Scillato springs, documented as bicarbonate-enriched waters due to dissolution of the Madonie mountains carbonate rocks. This deposit is today well represented by the Travertine Cave, essentially constituted by stalactites and stalagmites in which travertine typically appears laminated with alternation of light and dark laminae. Mineralogical analysis have revealed the almost exclusive presence of calcite and observation under the polarized-light microscope showed different textural features, like presence of debris and porous portions, micritic po…

Dépôts carbonatés microbiens en domaine lacustre et fluviatile : fabriques et facteurs de contrôle

2020

The non-marine carbonates related to microbial activity display a large range of morphologies and compositions and accumulate in various settings (freshwater, alkaline, and saline lakes, fluvial environments, thermal and freshwater springs, …). The variety of non-marine microbial carbonates and their particularity led to propose numerous and complex terminologies and classifications, making their use complicated and restrictive for the interpretation of depositional settings. Mineralization of these carbonates results from the interaction between biotic factors (intrinsic) and environmental factors (extrinsic and external) at multi-scales. The first aim of this work was to characterize morp…

STOP 3: Late-glacial and early postglacial environmental processes and the history of the River Triečupīte valley and surroundings, in the foreland o…

2014

Laminated carbonate deposits in Roman aqueducts: Origin, processes and implications

2013

Carbonate deposits in Roman aqueducts of Patara and Aspendos (southern Turkey) were studied to analyse the nature of their regular layering. Optical microscopy and electron-backscattered diffraction results show an alternation of dense, coarsely crystalline, translucent laminae composed of bundles and fans of elongate calcite crystals with their c-axes parallel to the long axis, and porous, fine-grained laminae with crystals at near-random orientation. The ?18O and ?13C data show a strong cyclicity and anti-correlation, whereby high and low ?18O values correspond to dense columnar and porous fine-grained laminae, respectively. Geochemical analyses show similar cyclic changes in carbonate co…

Aegopinella bourdieri nov. sp. (Gastropoda: Zonitidae),une espèce nouvelle du Pléistocène normand (France)

1989

St Pierre-les-Elbeuf (Normandy, NE France) is a reference site for the middle and the upper Pleistocene of NW France. In the eastern part of the quarry, the paleosoils Elbeuf III and IV are truncated, white sands and a small tufa lay on Elbeuf IV. Similar deposits have been recognized at Vernon (Seine valley) and at Arrest (northern France). They are probably contemporaneous (Holsteinian) and each of them has yielded an interglacial malacological fauna. The faunal communities are interesting because they are composed by species living up to now in this country, by emigrated species and by fossil species. Among them, A. bourdieri is a new fossil taxa, endemic of Holsteinian tufas of Normandy…

Anthropogenic travertine between History, Archaeology and Environment: a geoarchaeological study of the Roman site of Jebel Oust, Tunisia.

2013

Travertine, known as lapis tiburtinus during Roman times, are continental limestones precipitated in calcareous environments from thermal waters of hot springs (travertine) or cool waters of karstic springs (calcareous tufa). This phenomenon is well-known during Classical Antiquity and had been described by several ancient authors (Strabo, Pliny the Elder, Vitruvius) who depicted a stone that forms extremely rapidly, a stone that outlines the landscape and which is largely used for construction (e.g. The Colosseum in Roma, the Greek temple at Segesta in Sicily). These deposits are widespread on Earth’s surface showing various morphologies and are great sedimentary records of climatic and hy…

La figure de la maîtresse d'école dans l’œuvre de femmes écrivains

2015

International audience; L’article porte sur la représentation de la figure de la maîtresse d’école dans l’œuvre de trois femmes écrivains. Le corpus comprend "Scuola normale femminile" (1886) de Matilde Serao, "La maestra" (1887) de Clarice Tartufari et "Annuzza la maestrina. Vecchia storia … inverosimile" (1907) d’Elvira Mancuso. Ces textes montrent les contradictions du travail des maîtresses d’école entre la fin du XIXe et le début du XXe siècle. Les femmes - qui s’orientent vers ce métier dans un espoir d’ascension sociale et d’accès au travail intellectuel - doivent faire face à des obstacles comme la misère, le harcèlement sexuel et les mentalités contraires à l’indépendance des femme…