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Glauconitization processes in the northwestern Mediterranean (Gulf of Lions)

¹ Laboratoire d’Étude 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

View larger version (57K): [in a new window]   FIG. 1. Location map of the studied sites: main current directions, mid-shelf deposition of the fine fraction and sedimentation rate curves, partly from Marin & Giresse (2001).

View larger version (36K): [in a new window]   FIG. 2. Core KL04 and EC3 lithological and textural characters with particular emphasis on the sand fraction and associated features. Arrows indicate the studied layers including green grains (G).

View larger version (137K): [in a new window]   FIG. 3 (facing page). Major habits of the green grains: (a) infilling of Elphidium crispum; (b) infilling of Ammonia beccarii; (c) internal moulds of sea-urchin radiole; (d) internal moulds of channels of perforating algae; (e) internal moulds of sea-urchin wall; (f) internal moulds of vermet gastropods; (g) faecal pellets of mud-eaters. The scale bar is 50 µm long.

View larger version (132K): [in a new window]   FIG. 4. Nano-structures: (a) low packing density of neo-formed nano-structures on inherited support of dodecaedral pyrite. The flakes are ~1 µm long (light green infilling from EC3 20–24 cm); (b) high-magnification of scarce and finely chiselled nano-structures. Note the small dimension (0.5 µm) of the neo-formed flakes (light grey-beige faecal pellets from EC3 1–2 cm); (c) honeycombed or foliated neo-formed flakes (1–2.5 µm long) in dense aggregate of cracked dark green grains (EC3 20–24 cm); (d) high magnification of the same foliated neo-formed flakes of cracked dark green grains.

View larger version (20K): [in a new window]   FIG. 5. Main elements wt.% plots of selected grains representative of the major steps of the glauconitization process of KL04 deposits.

View larger version (22K): [in a new window]   FIG. 6. Main elements wt.% plots of selected grains representative of the major steps of the glauconitization process of EC3 deposits.

View larger version (14K): [in a new window]   FIG. 7. Main elements wt.% plots of selected grains representative of the major steps of the glauconitization process after treatment according to Jackson (1969).

View larger version (32K): [in a new window]   FIG. 8. XRD patterns of mud-matrix fractions in a KL04 core, recorded using Co-K radiation on oriented specimens: (a) 2–20 µm, (b) <2 µm, (b,c) glycolated. Depth is given on figure. Sm – smectite, M – mica, Ch – chlorite, Q – quartz, K – kaolinite, P – plagioclase. Spacings are in Å.

View larger version (30K): [in a new window]   FIG. 9. X-ray reflection patterns of mud matrix fractions in an EC3 core. Abbreviations as in Fig. 8.

View larger version (24K): [in a new window]   FIG. 10. XRDT patterns of beige pellets from a KL04 core 70–80 cm, recorded using Co-K radiation. Ch – chlorite, I – illite, Q – quartz, P – plagioclase, F – K-feldspar. Spacings are in Å .

View larger version (28K): [in a new window]   FIG. 11. XRDT patterns of green grains from the KL04 core depth 220–230 cm and EC3 1–2 cm, recorded using Co-K radiation: (a) light green grains, (b) medium green grains, (c) dark green grains. N – nontronite, I – illite, Ch – chlorite, Q – quartz, P – plagioclase, F – K-feldspar, G – goethite, non-labelled peaks belong to mixed-layer glauconite-smectite. Spacings are in Å .

View larger version (19K): [in a new window]   FIG. 12. XRDT patterns of green grains, a, b, c as in Fig. 11, immersed in ethylene glycol inside a capillary, d – simulated mixed-layer powder pattern for KL04 220–230 cm: 80% glauconite/20% nontronite (glycolated) with Reichweite 1 and for EC3 1–2 cm: 92% glauconite/8% nontronite (glycolated) with Reichweite 3, using Newmod software. Abbreviations as in Fig. 3. Spacings are in Å .

View larger version (33K): [in a new window]   FIG. 13. XRDT patterns of: a – faecal pellets, b – light green grains, from an EC3 20–24 cm sample. Peak labels as in previous figures. Spacings are in Å .