Gelatinous laminae were observed in three out of ten cores recovered in Bacino Bannock and in both dredges carried out on its flanks during cruise BAN 84 by R/V Bannock in the Eastern Mediterranean. Bacino Bannock is a depression 3.520 m deep, characterized by present partially anoxic sedimentation and gypsum precipitation. The millimetric laminae, dark grey and greenish in color, are always included in very dark sediments that are Quaternary in age. These gelatinous laminae have been investigated by optical, scanning and transmission electron microscope in order to decipher their nature. We observed abundant skeletal remains of siliceous and calcareous planktonic organisms (Radiolarians, Diatoms, Silicoflagellates, Foraminifers and calcareous Nannofossils) entrapped within amorphous organic matter. Gelatinous laminae including these vegetal and animal remains do not show any cellular structure; they do not react with HCl and are completely destroyed by $H_{2} 0_{2}$. Flash pyrolysis-gas chromatography and flash pyrolysis-gas chromatography-mass spectrometry were carried out to determine the organic matter laminae compounds. We suggest that gelatinous laminae are bacterial in origin and grew at the brine/sea water interface located at — 3.200 m in Bacino Bannock. The floating laminae entrapped biogenic and non biogenic particles and sank to the basin floor after load increasing.
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Con il contributo del Ministero per i Beni e le Attività Culturali