Formation et chronologie palynologique des tufs calcaires du Luxembourg belgo-grand-ducal

Abstract

Alors que la majorité des auteurs rattachent la précipitation du tuf calcaire aux périodes chaudes, le contraire avait été affirmé récemment pour les tufs de Gaume. L'analyse pollinique prouve que l'optimum de formation se situe dans les périodes d'optimum climatique. Seul un tuf lacustre à Characées à Echternach est déposé en période froide en conditions particulières. Deux affirmations se trouvent pratiquement dans toutes les publications sur les tufs : les eaux de source seraient sursaturées en carbonates et la photosynthèse favoriserait la formation des dépôts. Les mesures effectuées prouvent que les eaux des sources incrustantes sont encore agressives et que la photosynthèse ne joue aucun rôle.

The origin of closed depressions in Northeastern France: A new assessment

“…Due to the digging in Bisping, we were able to show that 16 cm of the early blue-grey sediment covered 300 to 400 years. Natural processes, and especially periglacial features/processes (Slotboom, 1963) or rock dissolution (Coûteaux, 1969) and soil collapse, should have created either older or younger sediment structures, which we did not find. Our data agree with findings of some previous studies.…”

“…The origins of these structures are still debated. The most commonly accepted hypothesis in Lorraine (Barth et al, 2001) is that CDs formed through soil collapse caused by the dissolution of salt or gypsum lenses deep below the structures (Delafosse, 1948;Coûteaux, 1969). Alternatively, CDs could be attributed to other natural phenomena like periglacial features/ processes (Slotboom, 1963;Pissart, 2003), karstic sinkholes (Van Den Eeckhaut et al, 2007;Galve et al, 2009), morainic kettle holes (Booth et al, 2004;Frielinghaus and Vahrson, 1998;Lamentowicz et al, 2008) and human activities around archaeological settlements (Wichmann, 1903;Grenier, 1906;Welter, 1908;Linckenheld, 1927), water ponds or small quarries for clay (Härbele, 1938), iron nodules (Wingert, 1996) or lime (Gillijns et al, 2005;Vanwalleghem et al, 2007).…”

New stratigraphic and geochemical data on the Holocene environment and climate from a tufa deposit at Direndall (Mamer Valley, Luxembourg)

“…At Direndall, the tufa is overlain by fluvial deposits of late Glacial/early Holocene age according to the C14 dating, and malacological data demonstrate that the tufa deposits did not start until the beginning of the Holocene (Figure 2). This is strongly consistent with other studies in Europe, especially in the Northwest, including the London-Paris Basin, which show a very similar tufa onset around 10,000-9500 yr BP according to radiocarbon data (Garnett, 2004;Pentecost, 1993Pentecost, , 2005; the few of them that have also provided environmental data thus do not record the late-Glacial/Holocene transition (Couteaux, 1969;Limondin-Lozouet and Preece, 2004;Žák et al, 2002).…”

Searching for ancient forests: A 2000 year history of land use in northeastern French forests deduced from the pollen compositions of closed depressions

“…In these small (10–30 m in diameter) closed wetlands, mostly supplied by rainwater, pollen grains are trapped in the sediment perfectly preserved (Etienne et al, 2010; Hannon et al, 2000; Lindbladh and Bradshaw, 1995; Ruffaldi et al, 2007). Surprisingly, closed depressions have not been often used as environmental archives in the region until now (however, see Blouet and Klag, 1987; Coûteaux, 1969; Daubigney and Richard, 1986). In a previous paper, we examined the origin of CDs in central Lorraine using morphological, archaeological and palaeo-environmental investigations (Etienne et al, 2011).…”