ABSTRACT: Improving varve chronologies using micro-fluorescence core scanners.

CGRG Bibliography of Canadian Geomorphology
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Abstract

New micro-fluorescence core scanners are able to perform continuous chemical analyses with resolutions down to 50 µm. Therefore it is possible to quickly obtain elemental profiles with enough resolution to distinguish and count varves with thicknesses of about 1 mm. In this paper, we applied this technology on two sedimentary sequences containing two kinds of varves: clastic ones from the Canadian High Arctic and calcareous ones from the Sahara desert. In both facies, we showed that it is possible to identify elements or element ratios for the characterization of varve structures and the detection of varve boundaries. Clastic varves are characterized by grain-size sensitive elements, while the calcareous ones can be recognized using the Ca profiles. The varves elemental structures were controlled by a comprehensive SEM-EDS investigation made on thin-sections. Comparisons of counts performed on elemental profiles with counts performed using classical techniques (thin-sections, high-resolution radiographs) were in good agreement. The possibility of having an additional way to quickly count varves provides the possibility to cross-validate counts with an independent technique and hence to improve the quality of varve chronologies. The spatial resolution of micro-fluorescence cores scanners operating at the surface of sediment cores is however not sufficient to provide a reliable varve thickness measurements data set.

Bibliography of Canadian Geomorphology