Beitrag
Calcareous nannofossil biostratigraphy and petrological analysis of the pre-evaporitic diatomaceous sediments from Gavdos Island, southern Greece
Triantaphyllou, M.V.; Tsaparas, N.; Stamatakis, M.; Dermitzakis, M.D.
Neues Jahrbuch für Geologie und Paläontologie - Monatshefte Jg. 1999 Heft 3 (1999), p. 161 - 178
39 Literaturangaben
veröffentlicht: Mar 24, 1999
DOI: 10.1127/njgpm/1999/1999/161
ArtNo. ESP157199903002, Preis: 19.00 €
Abstract
The main goal of this study is the biostratigraphical and petrological analysis of the Upper Miocene diatomaceous sediments of Gavdos Island, Greece. The studied sequence is dominated by finely laminated diatomaceous sediments 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 CN9b (Okada & Bukry 1980) and with the upper part of the Zone NN11 (Martini 1971) or with the C. leptoporus Zone (Theodoridis 1984), which chronostratigraphically indicate a Messinian age. The presence of small Gephyrocapsa spp. (forms which generally appear in the Lower Pliocene) in the studied sediments is reported for the first time from the Greek area. Additionally the non-birefringent ceratoliths are well represented including also the species Amaurolithus tricorniculatus. Moreover the extremely rare occurrence of birefringent ceratoliths has been shown. On the other hand, the applied petrological studies demonstrate that the diatom layers are rich in amorphous silica (opal - A) and calcite characteristic of an embryonic silica diagenesis, whereas huntite, clastic quartz and feldspars are also present.
Kurzfassung
Die Diatomite der Insel Gavdos werden ins Messinien (Nannoplankton Zone CN9b (Okada & Bukry 1980) oder oberer Teil von NN11 (Martini 1971) oder in die C. leptoporus Zone von Theodoridis (1984) gestellt. Bemerkenswert ist, dass in diesen Schichten bereits kleine Gephyrocapsa spp., die im allgemeinen erst im Unterpliocaen erscheinen, vorkommen. Die nicht-doppelbrechenden Ceratolithe sind gut vertreten, unter anderem auch mit der Art Amaurolithus tricorniculatus. Die Diatomeenschichten sind reich an amorpher Kieselsäure (Opal-A) und Kalzit, die für ein sehr frühes Diagenesestadium sprechen. Zusätzlich sind Huntit, klastischer Quarz und Feldspäte vorhanden.
Schlagworte
diatomaceous sediments • marlstone • limestone • nannofossils • marine sediments • birefringent ceratoliths • huntite • clastic quartz • feldspars