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Dinocyst study at the
| Corradini, D. and Biffi, U. | |
| 1988 | |
| Dinocyst study at the |
Corradini, D. and Biffi, U., 1988; Dinocyst study at the Messinian-Pliocene boundary in the Cava Serredi section, Tuscany, Italy. Bull. Centr. Rech. Expl.-Prod. Elf-Aquitaine 12-1 pp.221-236 pl.5. (in French) Seven samples. taken from the Cava Serredi section at the Messinian/Early Pliocene boundary, have been studied from a palynological point of view, in order to compare the yielded assemblages with the environment of deposition. On the basis of paleontological data (Mollusca. Ostracoda, Foraminifera and Oogons of Charophy- tes) the Messinian sediments resulted to have been deposited in a continental environment with shallow brackish waters: it belonged to a lacustrine basin with very variable salinity. characterized by a typical Late Messinian biofacies, well known in the Mediterranean area as "lago-mare" facies The only assemblage found was dominated by Galeacysta etrusca n. gen et n. sp, a very characteristic gonyaulacoid cyst. The Messinian sediments up to the boundary were devoid of dinoflagellate cysts. The transition between the "lago-mare~ facies and the marine shales of Early Pliocene is pointed out by micropaleontological data. The Foraminiferal assemblages and the Calcareous Nannofossils indicate an inner neritic environment of deposition for the lowermost Pliocene shales. with few conditions favourable for marine organism development; however, the environment quickly becomes deeper and definitely open marine. The dinocyst assemblages seem to follow and to confirm this environmental evolution: thus the basal shales are very rich in Protoperidiniaceae, mainly Selenopemphix spp (inner neritic): the incoming of Impagidinium patulum. Operculodinium spp. with rare Protoperidiniaceae confirms the establishment of open marine conditions (outer neritic environment).