Calcareous nannofossil biostratigraphy and petrological analysis of the pre-evaporitic diatomaceous sediments from Gavdos Island, southern Greece

The main goal of this study is the biostratigraphical and petrological anal ysis of the Upper Miocene diatomaceous sediments of Gavdos Island, Greece. The studied sequence is dominated by finely laminated diatomaceous sediment s which are cyclically alternating with marlstone and white limestone beds. The biostratigraphical analysis based on calcareous nannofossils achieved the correlation of the diatomaceous marine sediments of Gavdos Island with Zone CN 9b (OKADA & BUKRY 1980) and with the upper part of the Zone NN 11 ( MARTINI 1971) or with the C. leptoporus Zone (THEODORIDIS 1984), which chro nostratigraphically indicate a Messinian age. The presence of small Gephyro capsa spp. (forms which generally appear in the Lower Pliocene) in the stud ied sediments is reported for the first time from the Greek area. Additiona lly the non-birefringent ceratoliths are well represented including also th e species Amaurolithus tricorniculatus. Moreover the extremely rare occurre nce of birefringent ceratoliths has been shown. On the other hand the appli ed petrological studies demonstrate that the diatom layers are rich in amor phous silica (opal - A) and calcite characteristic of an embryonic silica d iagenesis, whereas huntite, elastic quartz and feldspars are also present.