Bioestratigrafía basada en quistes de dinoflagelados del Eoceno-Mioceno del pozo (YPF) Ombucta x-l, Cuenca del Colorado, Argentina

Abstract

"Sediments between 250 and 850 metres deep from the exploration Ornbucta x-1 borehole, located onshore Colorado Basin, were studied palynologically. Dinoflagellate cysts are present in varying amounts allowing age interpretation for the section. Selected dinoflagellate cyst events, mainly last occurrences, suggest five age intervals: late Miocene to early Pliocene, late Miocene, mid Miocene, Oligocene to early Miocene and Eocene to Oligocene. The comparison of the selected dinoflagellate events with previous studies carried out by other authors indicates that these events are consistent throughout the basin. The composition of the dinoflagellate assemblages, with dominance of gonyaulocoids over peridinioids, reflects poor nutrient oceanic conditions. Low dinocyst/pollen ratios at the end of the Miocene and during the Oligocene suggest relatively nearshore environrnents confirmed by high dorninance of the complex Operculodinium israetianum/centrocarpum. Sediments ranging from mid to early Miocene in age show high dinocyst/pollen ratios associated with oceanic species acmes. "