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Five varieties of Belgian black marbles are investigated in order to discriminate them. Their age ranges from Frasnian (Golzinne) to Visean (Dinant, Theux, Basècle, Lives). Three methods were used: petrography, magnetic susceptibility and geochemistry of major elements and Rare Earth Elements (REE). The petrographic analyze reveals 16 microfacies reflecting very quiet environments, sporadically perturbed by more energetic phenomena like turbidites or storms. These microfacies are integrated in two depositional models: a quiet offshore setting, below or close to the storm wave base (Salet, Basècles) and a shallow but very restricted zone, protected from waves and currents (Lives and Golzinne). The magnetic susceptibility results show that all the black marbles are characterized by very low, even slightly negative values, except the Golzinne one which shows higher values. Geochemical data allow to discriminate between the Theux black marble (low SiO2 content), and the Basècles samples (low Al2O3, K2O and REE contents). These methods could be useful to determine/refine the origin of archaeological stones, even if all these analyses are destructive. Two archeologic samples were investigated in order to identify their possible origin. [ABSTRACT FROM AUTHOR]

New carbon isotopic data from the Devonian of Ardennes (Belgium) and partly from the Holy Cross Mountains (Poland) highlight an abrupt and high-amplitude negative excursion in the punctata conodont Zone. Published information from Moravia and China suggests that this Middle Frasnian negative excursion, jointly with the preceding large-scale positive shift, should be used as a global chemostratigraphic marker. Causation scenarios for this negative 'punctata Event' are correlated neither with major biota turnover nor major sea-level changes, but may be related to: (1) the Alamo Impact Event, that led to (2) the massive dissociation of methane hydrates and (3) the rapid onset of global warming. [ABSTRACT FROM AUTHOR]