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Research Paper |
1 Laboratoire dÉtude des Géo-Environnements Marins, Université de Perpignan, 52, Av. Paul Alduy, 66860 Perpignan, France, and 2 Institute of Geological Sciences, Polish Academy of Sciences, ul. Twarda 51/55, 00-818 Warsaw, Poland
* E-mail: wiewiora{at}twarda.pan.pl
(Received 25 April 2003; revised 10 October 2003)
Two sedimentary profiles, at 18 km and at 125 km from the Rhône River mouth were selected to study the steps of glauconitization inside green (glaucony) grains, in a temperate marine environment. The proximal site is characterized by a greater content of alpine minerals (chlorite, illite) than the distal one. In the proximal site, pellets at a younger level demonstrate a largely inherited mineral composition. In the older level, representing the most advanced stage of glauconitization, there is a mixed-layer glauconite-nontronite (G-N) phase with 20% glauconite-80% nontronite in dark green grains. In the distal site, more evolved glaucony has up to 92% glauconite in the G-N. In spite of this difference, the glauconitization process developed similarly in the two sites. The relatively low Fe content in the mud-matrix does not reflect the concentration of this element inside the grains. During diagenesis, most of the inherited minerals disappear, making way for neoformed mixed-layer glauconite-nontronite.
KEYWORDS: glauconite, nontronite, chlorite, illite, Mediterranean, Gulf of Lions
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